NO335372B1 - Extension pipe hanger, set tool, and method - Google Patents

Description

Related applications

The present application requires priority from:

US Provisional Patent Application Serial No. 60/292,049, filed May 18, 2001 (Attorney's Reference: 108-P); US Provisional Patent Application Serial No. 60/316,572, filed August 31, 2001 (Attorney's Reference 108-1); US Provisional Patent Application Serial No. 60/316,459, filed Aug. 31, 2001 (Attorney's Reference: 111); US patent application serial no. 09/943,854, filed August 31, 2001 (Attorney's Reference: 118); US patent application serial no. 09/943,701, filed August 31, 2001 (Attorney's Reference: 119); US patent application serial no. 09/981,487, filed October 17, 2001 (attorney's reference: 123); US patent application serial no. 10/083,320, filed Oct. 19, 2001 (Attorney's Reference: 111-1); US patent application serial no. 10/004,945, filed Dec. 4, 2001 (Attorney's Reference: 106); US patent application serial no. 10/004,588, filed Dec. 4, 2001 (Attorney's Reference: 124); US patent application serial no. 10/136,992, filed May 2, 2002, entitled Apparatus for Use In Cementing An Inner Pipe Within An Outer Pipe Within A Wellbore (Attorney's Reference: 116); US patent application serial no. 10/136,969, filed May 2, 2002, entitled Slip Assembly For Hanging An Elongate Member Within A Wellbore (Attorney's Reference: 117).

Background for the invention

When drilling a well, a borehole is typically drilled from the earth's surface to a selected depth, and a string of casing is suspended and then cemented into place into the borehole. A drill bit is then passed through the initially lined borehole and used to drill a smaller diameter borehole to an even greater depth. A smaller diameter casing is then suspended and cemented into place inside the new borehole. This is conventionally repeated until a plurality of concentric casing is suspended and cemented inside the well to a depth that causes the well to extend through one or more hydrocarbon-producing formations.

Instead of suspending a concentric casing from the bottom of the borehole to the surface, a casing is often suspended at the lower end of the previously suspended casing, or from a previously suspended and cemented casing, to allow the casing to extend from the previously set the casing or liner to the bottom of the new borehole. A liner is defined as a casing that does not go to the surface. A casing hanger is used to suspend the casing inside the lower end of the previously set casing or casing. The casing hanger typically has the ability to receive a tie back tool to connect the casing to a string of casing extending from the casing hanger to the surface.

A driving and setting tool provided on the lower end of a work string may be releasably connected to the casing hanger, which is attached to the top of the casing. The work string lowers the casing hanger and casing into the open borehole so that the casing extends below the lower end of the previously set casing or casing. The borehole is filled with fluid, such as a selected drilling mud, which flows around the casing and casing hanger as the casing is driven into the borehole. The assembly is driven into the well until the casing hanger is adjacent to the lower end of the previously set casing or casing, with the lower end of the casing typically slightly above the bottom of the open borehole.

When the drilling reaches the desired location relative to the bottom of the open borehole and the previously set casing or casing, a setting mechanism is conventionally actuated to move retaining wedges on the casing hanger from a retracted position to an extended position and into engagement with the previously set the casing or liner. Then, when lowering weight is applied to the hanger's retaining wedges, the retaining wedges are set to hold the liner.

The typical casing hanger can be actuated either hydraulically or mechanically. The liner hanger can have a hydraulically operated setting mechanism for setting the hanger's holding wedges or a mechanically operated setting mechanism for setting the holding wedges. A hydraulically operated setting mechanism typically uses a hydraulic cylinder that is actuated by fluid pressure in the bore in the casing, which is connected to the bore in the working string. When mechanically setting the casing hanger, it is usually necessary to perform relative downhole rotation of the parts between the setting tool and the casing hanger to release the hanger's retaining wedges. The hanger's retaining wedges typically work one way, in that the hanger and casing can be raised or lifted upwards, but a downward movement of the casing sets the retaining wedges to keep the hanger and casing inside the well.

To release the driving tool from the set casing hanger, the setting tool can be lowered relative to the casing hanger and rotated to release a drive nut on the setting tool from the casing hanger. Cement is then pumped down the bore into the workstring and casing and up the annulus formed by the casing and the open borehole. Before the cement sets, the setting tool and work string are removed from the borehole. In the case of a poor cementing job, it may be necessary to attach a casing packing and a casing packing setting tool to the work string and lower these back into the borehole.

The gasket is set using a gasket setting tool. Gaskets for liners are often referred to as "liner insulation" gaskets. A typical liner insulation packing system includes a packing element mounted on a spindle and a sealing nipple disposed below the packing. The sealing nipple plugs into the tie back receptacle above or below the previously set and cemented casing hanger. A liner isolation gasket can be used, as explained above, to seal the liner in the event of a poor cement job. The casing insulation gasket is typically set down onto the hanger after the hanger is attached to the outer pipe, and the gasket is set by the setting tool to seal the annulus between the liner and the previously set casing or liner.

In general, the deeper a well is drilled, the higher the temperature and pressure encountered. It is thus desirable to have casing seals that will ensure quality cementation of the casing in order to provide a high safety factor with regard to preventing gas from the formation from migrating up the annulus between the casing and the outer casing pipe.

During the cementing operation, fluid, such as drilling mud, in the annulus between the casing and the outer casing is displaced by cement as the cement is pumped down the flow bore in the work string. First the drilling mud and then the cement flows around the lower end of the casing and up the annulus. If there is a significant restriction to flow in the annulus, the rate of cement flow is reduced and a good cementing job cannot be done. Any reduction in the speed during cementing in the annulus means that the gas in the formation has time to travel up the annulus and through the cement to prevent a good cementing job.

Drive tool release mechanism

For practical reasons, the driving tool for calling the casing must include a release mechanism so that, once the casing is reliably seated at the lower end of the casing, the driving tool can be released from the casing hanger and retrieved to the surface. Conventional casing trailer drive tool release mechanisms include hydraulically actuated mechanisms, and release mechanisms operated by left-handed rotation of the drive string. However, the left-handed rotation of the drive string is generally considered undesirable, as it may result in an inadvertent loosening of one of the pipe lengths in the drive string, causing separation of the drive string and a fishing operation to retrieve the drive tool, which may have been damaged by the accidental the detachment. For various reasons, the operation of hydraulically operated drive tool release mechanisms can fail, or they can prematurely release the drive tool from the casing hanger.

Improvements in release mechanisms are therefore desirable, which will reliably release the drive tool from the set liner only when intended, particularly when retrieval is easy to perform, and premature release of the drive tool from the liner is highly unlikely.

Sealing bushing

A sealing bushing for a casing hanger conventionally seals between the casing hanger and the driving tool, and consequently between the casing and the driving string or work string, which conventionally may be drill pipe. A sealing bushing is particularly necessary during cementing operations, so that fluid pumped through the drill pipe continues to the bottom of the well and then back up into the annulus between the wellbore and the casing to cement the casing in place. During cementing operations, the sealing body is placed in the sealing bushing in the annulus between the casing hanger and the driving tool, and includes on its outer diameter seals for sealing engagement with the casing hanger, and on its inner diameter seals for sealing engagement with the driving tool. Sealing bushings can preferably be picked up together with the driving tool to prevent having to drill out the bushings after the cementing operation has been completed. Furthermore, a sealing sleeve is preferably lockable to the liner hanger by means of locking within a profile to prevent the sleeve from moving axially in relation to the liner hanger. If the sealing bushing is not lockable to the profile in the liner hanger, the bushing can be "pumped out" through the top of the holder, so that a cementing job is lost.

A conventional retrievable and lockable seal bushing includes metal hooks or lugs that are locked into engagement with the liner hanger to prevent the seal bushing from moving axially during the cementing operation. The sealing bushing can be retrieved with the driving tool, thus eliminating the need to drill out the bushing after the cementing operation is complete. Depending on the manufacturer, retrievable sealing bushings are also referred to as retrievable sealing spindles or retrievable cementing bushings. Regardless of the terminology used, the retrievable and lockable seal bushing seals the annulus between the travel string and the top of the casing and can be locked into a profile in the casing hanger using the slip joint to prevent the bushing from being pumped out of the casing hanger.

Mating surfaces on the casing travel adapter, the smooth joint on the travel tool, and the seal body on the seal bushing connect the bushing axially to the casing hanger during driving of the casing hanger into the well. These mating surfaces can be unlocked to release the driving tool from the liner hanger and allow axial handling of the driving tool and the slip joint relative to the seal bushing. The smooth joint thus seals against the sealing bushing during axial movement of the driving tool. Once the mating surfaces are unlocked from each other, shoulders of the seal bushing and driving tool engage after a predetermined amount of axial movement between the driving tool and the sealing body, so that the seal bushing can be retrieved to the surface together with the driving tool after the cementing operations are completed. A conventional sealing bush is described in US Patent 4,281,711.

A significant limitation on sealing bushings according to the known technique concerns their desired retrievability together with the driving tool, when this is coupled with the desire to take the driving tool up in relation to the sealing bushing before the cementing operation. An operator will typically want to pick up the driving tools after release from the liner hanger, to ensure that these tools are detached. The length of the driving tool's smooth joint determines the maximum length that the driving tool should be taken up after release from the liner hanger. When the seal bushing is withdrawn from the liner hanger, the hooks or lugs conventionally drilled from the seal bushing are allowed to move radially inward, preventing the retrievable seal bush from being pushed back into and locked into the liner hanger. Conventional casing hanger driving tools do not allow the seal bushing to be "re-inserted" into the casing hanger and thus re-establish pressure integrity between the casing hanger and the driving tool. In many applications, it is difficult for the operator to determine the exact extent to which the driving tool must be taken up, particularly during operations in deep wells or wells with large deviations. If the operator takes the driving tool up an axial distance not allowed by the length of a smooth joint, the seal bushing will be pulled up with the driving tool and will become detached from the casing hanger, which can cause a cementing failure, costing the operator millions of dollars in lost time and money. Consequently, the consequences of accidentally detaching the sealing bush from the liner hanger and not being able to reinsert and lock it to the liner hanger can be serious.

The smooth joint used with the liner hanger driving tool has a polished surface on its outside diameter that seals against the seal on the inside diameter of the seal body in the seal bushing. The surface of the outside diameter of the smooth joint may be scratched or damaged during handling, causing a cement leakage during the cementing operation. Since the driving tool is designed to move axially over significant distances relative to the seal bushing, the internal seals of the sealing body can wear out during the cementing process due to the reciprocating movement of the driving tool's smooth joint. This problem is exacerbated when the quality of the polished surface of the butt joint has deteriorated. Axially long smooth joints are expensive to manufacture and maintain.

Another problem with sealing bushings according to the prior art relates to the limited load capacity of the lugs that lock the sealing bushing to the liner hanger. Conventional seal bushings use multiple lugs that protrude from the seal body, which increases the complexity and cost of the seal bushing. The limited size of these lugs nevertheless limits or delimits the cementing pressure capacity of the sealing bushing.

Gasket set assembly

A conventional casing trailer drive tool includes a gasket set assembly, which allows actuation and sealing of the stool's top gasket. Conventional packing set assemblies incorporate multiple spring-loaded hooks or lugs that can be compressed into a reduced-diameter position by being inserted into the packing set sleeve when the casing hanger is driven into the well, and by cementing the casing inside the casing. When the packing set assembly is lifted out of the packing set sleeve, the hooks or lugs expand to a diameter greater than the inside diameter at the upper end of the set sleeve, which is also the holder for the liner extension for the liner hanger. When the prongs engage the top of the set sleeve, a setting force can be transferred from the drive string through the prongs and to the packing set sleeve as the weight of the drive string is released to set the packing element.

Certain packing set assemblies according to the prior art include an axial bearing to enable rotation of the working string during setting of the packing element. Other packing set assemblies include both a bearing and a shear indicator to provide visual confirmation that the correct set load was applied to the packing, and/or an unlocking feature that allows the packing set assembly to be pulled out of the packing set sleeve once without exposing the set tabs. This latter tool allows reinsertion of the gasket set assembly into the gasket set sleeve once, which activates the set tabs so that they are ready to expand the second time the tabs are withdrawn from the set sleeve.

A primary problem with prior art package assembly assemblies is poor reliability. In some well environments, the packing set hooks in conventional packing set assemblies retract and re-enter the set sleeve without setting the packing element. Manufacturers have provided more hooks or lugs to remedy this problem, and/or have provided heavier springs to bias the hooks radially outward. These changes have had little, if any, effect on achieving higher reliability.

US 4,757,860 describes a downhole tool in which casing hangers are connected to the upper ends of smaller diameter casing strings and are adapted to be lowered into and landed within the bore of a casing head.

The disadvantages of the known technique are overcome with the present invention according to the patent claims. It will be described hereafter i.a. an improved driving tool for a casing trailer that includes improvements in a driving tool release mechanism, a retrievable seal bushing, and a packing set assembly. In addition, the improved packing set assembly can be used in operations that do not involve a casing trailer driving tool.

Summary of the Invention

The main features of the present invention appear from the independent patent claims. Further features of the invention are indicated in the independent claims.

A preferred embodiment of a driving tool for a liner trailer according to the present invention includes improvements to one or more of the driving tool release mechanism, the retrievable seal bushing and the packing set assembly. The driving tool can be used for positioning a casing in a casing in a wellbore and subsequently cementing the casing in place, then retrieving the driving tool to the surface with the seal bushing and packing set assembly. The packing kit assembly can be used in other downhole packing kit applications.

Drive tool release mechanism

The drive tool release mechanism for the casing trailer preferably includes a hydraulically actuated mechanism for releasing the drive tool from the set casing hanger in response to fluid pressure within the drive tool, and also a mechanical clockwise release mechanism that, if necessary, allows the drive tool to be mechanically released from the casing hanger by clockwise rotation of the work string. The combination of the hydraulic release mechanism and the higher directed release mechanism greatly improves the reliability of the driving tool.

It is an object of the present invention to provide an improved driving tool release mechanism for releasing a driving tool from a set liner hanger. The driving tool can be released hydraulically, but can also be released by clockwise rotation of the driving string. A first piston is used for hydraulic release. Another piston is used to bring a coupling out of engagement, allowing a nut to move downward along the right-handed threads of the drive tool spindle due to right-handed rotation of the drive string. Once the nut has moved axially down the spindle, the work string can be taken up to bring the driving tool out of engagement with the liner hanger.

Yet another feature of the invention is that, after the coupling has been brought out of engagement to allow right-hand release of the driving tool, fluid pressure may be used to reengage the coupling to allow rotation of the casing during a cementing operation.

Yet another feature of the invention is that fluid within the drive tool that transmits fluid pressure to the piston for hydraulic release of the drive tool can be isolated by a sleeve, so that the sleeve moves downward to expose a port and allow hydraulic fluid to release the drive tool.

An essential feature of the release mechanism for the driving tool is that the release mechanism can be actuated both hydraulically and by clockwise rotation of the driving string or the working string.

A related feature of the drive tool release mechanism is that the reliability of the release operation is greatly improved with little, if any, cost increase.

Sealing bushing

During the cementing operation, the seal bushing serves its function of providing a seal between the casing hanger and the driveline. The seal bushing may be axially secured to the casing hanger during the cementing operation with a C-shaped locking ring, which is held locked in a groove in the casing hanger by a piston responsive to fluid pressure. The sealing bushing is designed so that it can be re-inserted into the liner hanger when the sealing bushing together with the drive string is raised in relation to the installed liner hanger. The cost of the smooth joint can therefore be avoided. The sealing bushing for the casing hanger can thus be removed from the casing hanger when the operator picks up the driving tool to check for release of the driving tool from the casing hanger, and to verify that the casing is correctly inserted into the casing pipe. When the driving tool is eased back into the casing hanger before pumping cement, the packing bushing can be reinserted into and resealed against the casing hanger. When pressure is then applied to the travel string during a cementing operation, the seal bushing will be locked to the casing hanger by the fluid pressure to prevent movement out of the casing hanger. Fluid pressure therefore keeps the sealing bushing locked to the liner hanger, while the absence of pressure in the drive string makes it possible to pick up the sealing bushing, out of the liner hanger, and then reinsert it into the liner hanger. Accordingly, the casing hanger driving tool includes a sealing bushing that can be repeatedly "re-sucked" back into the casing hanger, as desired by the operator, to re-establish pressure integrity between the driving tool and the casing hanger.

By providing a reinsertable sealing bush, the operator has much more flexibility when picking up to check for drive tool release. By providing a seal bushing that can be repeatedly reinserted into the casing hanger, so that a seal can be repeatedly established between the stringer and the casing hanger, the operator avoids much of the danger of a poor cementing job, and the considerable loss of time and money to correct a bad cementing job. The reinsertable seal bushing can be used on a driving tool with or without a casing hanger gasket to seal between the casing and the casing hanger.

The sealing sleeve is preferably designed with a C-shaped locking ring to increase the sealing sleeve's capacity with regard to cementing pressure. Compared to sealing bushings according to prior art, the locking ring avoids the use of several lugs and springs that increase the length and complexity of the sealing bushing without significantly increasing the capacity of the sealing bushing in terms of cementing pressure when it is locked to the casing hanger.

It is a purpose of the present invention to provide a driving tool for a liner hanger together with the sealing bushing, which can be inserted repeatedly into the top of the liner.

A feature of this invention is that the seal bushing incorporates a C-shaped snap ring in one part, which effectively locks the seal bushing to the liner hanger in response to fluid pressure acting on a piston to hold the snap ring in the locked position. The absence of fluid pressure allows the snap ring to contract, allowing the reinsertion of the seal bushing into the top of the liner hanger. The C-shaped snap ring may include radially external or internal grooves to enable expansion and contraction of the snap ring.

The seal bushing includes a radially outer shoulder for engagement with a radially inner shoulder on the liner hanger when the snap ring is aligned with the groove in the liner hanger so that settling weight can be applied to the liner hanger. The sealing bushing also includes a radially inner shoulder, so that the sealing bushing is brought up to the surface together with the tool. In addition to the seal bushing, the drive tool may include a packing set assembly for actuating the packing member to seal between the casing and the casing hanger.

It is a feature of the invention that the vehicle may include a retrievable sealing bush which can be re-inserted or "re-inserted" into the liner trailer numerous times. A related feature of the invention is that the cost of a smooth joint can be avoided.

It is a further feature of the present invention to provide an improved seal bushing for a liner hanger driving tool wherein fluid pressure keeps the seal bushing locked to the liner hanger, while the absence of fluid pressure allows the seal bushing to be picked up, out of the liner, and then reinserted it into the lining. A related feature of the driving tool with the improved seal bushing is the reduced risk of a poor cementing job.

Gasket set assembly

The gasket set assembly can be used with the casing hanger driving tool to set the casing head gasket after the casing hanger has been set and after the casing hanger driving tool has been released from the casing hanger. The packing assembly assembly may be positioned on the drive tool in a desired location, which may be axially between the release assembly for the liner hanger and the assembly for setting the retaining wedges at the lower end of the drive string or work string. Thus, when the driving tool is assembled at the surface, the packing set assembly is inside the liner extension holder or set sleeve in the liner hanger assembly.

The packing set load is preferably transferred to the packing set sleeve through a C-shaped setting in one part. The C-ring design makes it possible to reduce more weight on the set sleeve than with the variety of hooks used in the prior art. A locking function keeps the set ring in weight-transmitting engagement with the set sleeve, so that the set ring will not prematurely slip radially inwards towards the gasket set housing before the gasket is set. Seals on both the inside diameter and outside diameter of the gasket set assembly also help seat the gasket. Once the initial load has been placed on the liner hanger, the inner diameter seal, which seals against the driving tool spindle, and the outer diameter seal, which seals against the set sleeve, act as a piston responsive to pressure applied to the annulus to assist in seating the packing element. This fluid pressure helps, together with the lowering weight, to achieve the correct seating force on the liner's top packing element. By using annulus pressure to assist in setting the packing element, a significant additional hydraulic force supplements the lowering weight to reliably set the casing hanger packing element.

A preferred packing set assembly includes an unlocking feature that allows the assembly to be withdrawn from the packing set sleeve once without releasing a set. By reinserting the assembly into the set sleeve, the gasket set ring is activated, and is ready to expand the second time the gasket set assembly is pulled out of the set sleeve. An adjustable shear indicator may be included to provide immediate visual confirmation, when the driving tool is brought up to the surface, that the appropriate application force was applied to the liner head gasket. A bearing assembly in the packing setter tool allows rotation and slackening of the drive string without damaging the packing setter sleeve or the setter ring. Rotation also breaks the static friction between the driveline and the casing, which reduces distortion and ensures maximum transfer of settling force to the casing packing element.

It is an object of the present invention to provide a gasket set assembly that uses an expandable and contractible C-ring in one part to reduce weight on a gasket element. The gasket set assembly also includes seals on its outside diameter and seals on its inside diameter so that fluid pressure can be used to increase the seating force applied to the gasket element.

It is a feature of the gasket set assembly according to the present invention that the C-ring can be locked in a contracted position by a locking mechanism, to prevent the C-ring from moving to its extended position. This allows the gasket set assembly to be pulled out of the liner extension holder once without releasing the C-ring and allows the locking mechanism to engage the top of the liner extension holder to reduce weight. The next time the packing assembly is pulled out of the liner extension holder, the C-ring is allowed to expand radially outward to engage the top of the liner extension holder.

It is also a feature of the present invention that the gasket set assembly has several uses. The packing kit assembly can be used as part of a casing trailer driving tool, although the packing kit assembly can also be used in other applications where an operator wishes to set a downhole packing radially.

It is a feature of the invention that the packing set assembly transfers the packing set load to the packing set sleeve through a C-shaped tether.

A related feature is that seals on both the inside diameter and outside diameter of the gasket set assembly can help seat the gasket.

Yet another feature of the packing set assembly is that the set ring can be easily and reliably locked to prevent premature actuation.

Yet another feature of the packing set assembly is that it may include an unlocking feature so that the assembly can be pulled out of the packing set sleeve once without releasing the packing ring.

An advantage of the improvements to each of the drive tool release mechanisms, the retrievable packing bushing, and the packing set assembly is that these mechanisms are based on components that have been found to be highly reliable in the oilfield service industry. The complexity of the driving tool with one or more of these features has not been significantly increased, and in many cases has become simpler. The tool's reliability has been increased to perform the desired downhole operations.

Brief description of the drawings

Figures 1A-1J illustrate sequential lower portions of a setting tool for a casing trailer driven into a well. Figure 1A shows how the tool is connected to a work string. Figure 1B shows the assembly for setting the liner hanger's retaining wedges. Figure 1C shows the gasket set assembly. Figure 1D shows the liner hanger release assembly. Figure 1E shows the retrievable cementing sleeve. Figure 1F shows the packing element. Figure 1G shows the hanger retaining wedge assembly. Figure 1H shows the lower end of the driving tool spindle. Figure 11 shows the ball deflector. Figure 1J shows the liner scraper plug. Figure 2A shows the holder for the liner extension raised to set the retaining wedges.

Figure 2B shows the retaining wedges in set position.

Figure 3A shows the upper seat after releasing the bullet. Figure 3B shows the bullet landing on the lower seat. Figure 3C shows the lower seat moved downward to open ports and to allow the snap ring in the release assembly to retract. Figure 4A shows the ball released from the lower seat and released into the deflector.

Figure 4B is a cross section through Figure 4A.

Figure 5A shows the pump down plug landed on the scraper plug. Figure 5B shows the casing scraper plug and pump down plug released. Figure 5C shows the plug set landed within a landing collar. Figure 6A shows the tool positioned to emphasize the packing element.

Figure 6B shows the packing element in the set position.

Figure 7A shows the drive tool seal bush unlocked from the liner hanger. Figures 8A and 8B show the lower end of the driving tool released from and pulled upwardly from the set liner hanger, with the upper portion of the set liner hanger shown in Figures 8C and 8D. Figure 8E shows an embodiment of a retaining wedge element raised into engagement with the casing; Figure 9A shows the packing elements and another embodiment of the retaining wedge assembly in the run-in position. Figure 9B shows the components moved to set the retaining wedge assembly. Figure 9C shows the retaining wedge assembly in engagement with the casing and the packing element moved to seal against the casing. Figures 10A and 10B show components in the driving tool for a hydraulic release when driving into the well. Figure 10C shows the components after pressure is increased to move the ball seat, which frees the drive tool and disengages a coupling. Figure 10D shows fluid pressure acting on the second piston, so that the coupling can again engage with the liner hanger. Figures 11A and 11B show sequential components of the driving tool during a mechanical release from the casing hanger. Figure 11C shows the components with the ball seat moved to release the drive tool and disengage the coupling. Figure 11D shows the second piston activated for engagement with the clutch, with the driving tool released. Figure 12A is a cross-sectional view of a preferred retrievable sealing bush according to the present invention, which can be positioned below an assembly for setting a liner hanger seal and above the ball deflector. Figure 12B is a cross-sectional view of the retrievable seal bush shown in Figure 12A. Figure 13 is a cross-sectional view of a preferred embodiment of a packing set assembly on a driving tool for a liner trailer according to the present invention. Figure A1 is a vertical cross-sectional view through the head itself;

Figures A1A and 1B are a top view and a cross-sectional view,

Figure A1C is a bottom view of the head of Figure A1, and Figure A1D is a side view of a portion of the head; and Figure A2 is another enlarged vertical sectional view of the head installed between a cementing swivel and a lower indicator pipe piece connected to the working string, showing the balls and plugs in the passages in position to be released. Figures B1A and B1B are respectively a side view, partially in section, and an end view of the C-ring in its fully contracted position where its side edges engage each other; the outside of the C-ring having vertical grooves to enable the passage of fluid between the casing and the outer casing in the well when the retaining wedges are expanded. Figures B2A and B2B are corresponding views of the C-ring in the fully extended position. Figures B3A and B3B are vertical cross-sectional views of the retaining wedge assembly, wherein the contracted C-ring is shown in Figure B3A arranged around the liner with its lower end received within the recess in the liner, and in Figure B3B, raised from the recess and expanded to a position where the liner can be raised to move its outer face upwardly over the truncated conical surface of the casing to cause its teeth to engage the well casing; and Figure B3C is an enlarged detailed view of a portion of Figure 3B, to illustrate the controlled friction teeth on the inner slide of the C-ring. Figures B4, B5 and B6 are enlarged vertical sectional views of the assembly, showing the C-ring as it is moved by the liner, from the retracted to the extended position, the C-ring being shown in the retracted position in Figure 4, raised out of the recess by by means of the tension rod in Figure 5, to release it for outward expansion for engagement with the casing, and, in Figure 5, the tension rod has raised the truncated conical surface of the liner above the inner surface of the C-ring, to cause C- the retaining wedge is moved outwards, into engagement with the casing in the well. Figures B3AA and B3BB are detailed sectional views as shown in Figures B3A and B3B. Figure C1 is a vertical sectional view of the outer length of casing having a bore designed to engage a hanger mounted on an inner casing or liner when lowered into the outer casing. Figure C2 is a view of the casing with the hanger mounted thereon, for landing inside the profiles in the outer casing; Figure C3 is a view corresponding to Figure C2, but showing the liner and its hanger as they are lowered into the outer casing; and Figure C4 is another similar view, but with the liner lowered further to cause its hanger to engage the profile of the outer casing and then lowered to a position to lock the hanger in place. Figure D1 is a half sectional view of the sealing element according to the present invention, positioned at the lower end of a casing extension holder for downward movement along a cone and for sealing against a casing pipe. Figure D2 is an enlarged view of a sealing element shown in Figure 1, positioned when the sealing element initially engages the casing. Figure D3 is a cross-sectional view of the sealing element in its final set position for sealing engagement between the cone and casing. Figure E1 is a vertical sectional view of the diverter including the pipe section from which the cementing assembly is suspended. Figure E2 is a diagram corresponding to Figure E1, with a ball landed in the diverter pocket. Figure E3 is a cross-sectional view of the deflector, taken along broken lines 3-3 of Figure E2, but on a larger scale, to show the "U" shaped groove formed in the ramp on one side of the deflector ball to allow passage of a pump down plug. Figure E4 is another vertical sectional view of the casing below the diverter, showing the pump down plug after passage through the slot in the ramp and into a landed position in the casing scraper plug in the cementing equipment; and Figure E5 is a further vertical sectional view, but where the connection to the scraper plug has been severed from the lower end of the tubular element below the ball deflector. Figure F1 is a cross-sectional view of a plug holder pipe piece according to the present invention, showing the position of components for attachment to the casing scraper plug on the left side of the center line, and which are positioned for releasing the casing scraper plug from the plug holder pipe piece on the right side of the center line. Figure F2 is a cross-sectional view of a lower portion of the plug holder tubing shown in Figure F1, showing the upper portion of a casing scraper plug attached to the plug holder tubing on the left side of the centerline and released on the right side of the centerline.

Detailed description of preferred designs

Figure 1-9 driving tool

To suspend the casing, the driving tool 120 may be initially attached to the lower end of a work string WS and releasably connected to the casing hanger, from which the casing is suspended to be lowered into the borehole below the previously set casing or casing C. The assembly can be easily driven in by a speed that does not adversely affect the well formations or the driving tool.

A holder 130 for a casing extension, as shown in Figure 1B, is held around the driving tool 120, with its upper end having the assembly 140 for setting the casing hanger slide wedges. The upper end of the casing extension holder 130 provides, upon removal of the driving tool, a means by which a casing extension (not shown) can then extend from its upper end to the surface. As shown in Figures 1A-1I, tool 120 includes a central spindle 132, which may include multiple composite sections.

The lower end of the holder 130 for the liner extension is connected to the sliding sleeve 148 for the packing element, as shown in Figure 1 F, the function of which will be described in connection with the setting of the packing element 150 around an upper cone 152, as well as the setting of an alternative embodiment of the retaining wedge 142A around a lower cone 144A (see Figure 1G) below the packing member 140. The driving tool 120 includes a cementing bushing 160 (see Figure 1E) from which a tubular body 162 is suspended to hold the ball deflector 280 (see Figure 11) and the casing scraper plug 180 (see figure 1J) at the lower end of the driving tool. The retrievable cementing bushing 160 provides a retrievable seal between the driving tool 120 and the casing hanger assembly for fluid circulation purposes. By incorporating an axially movable slip joint, the driving tool can be moved without breaking the seal provided by the seal bushing.

The assembly 140 for setting the liner hanger retaining wedge, as shown in Figure 1B, includes a sleeve 212 which is arranged within and is axially movable relative to a portion 210 of the driving tool spindle 132. The piston sleeve 212 is held in its upper position by shear pins 222 in the spindle portion 210. A tubular ball seat 232 is held at the lower end of the sleeve 212. The lower end of the ball seat has a neck portion 234 which is reduced in diameter and thinner, for a purpose which will be described below. A ball 240 is released from the surface, into the bore 126 of the driving tool, and onto the seat 232. An increase in fluid pressure inside the spindle 132 will shear the pins 222 and lower the ball seat to a landed position in the bore in the driving tool, for example against the stop shoulder 236.

Ball bearing head

This invention also relates to an improved apparatus for dropping a ball as mentioned above, which includes a head suspended from a top-driven rotary system for use in sequentially dropping balls and plugs into a liner suspended from the head. More specifically, it relates to the use of such equipment in cementing the casing within the outer casing, where the one or more balls are to be dropped onto a seat inside the casing to actuate certain parts for the purpose of suspending the casing in the outer casing, followed of dropping pump-down plugs through the casing to pump cement beneath them, into the annulus between the casing and the outer casing.

In earlier heads of this type, the balls and scraper plugs were mounted in individual manifolds that each had an opening into a bore leading to the equipment to be actuated. As will be appreciated, this greatly increased the vertical height of the equipment below the top-drive rotary system, making it much more inaccessible, not only during the insertion and release of the balls and blowdown plugs, but also when it came to gaining visual access to the interior of each manifold where the plugs and balls were located.

US Patents 6,182,752 and 6,206,095 claim to solve this excessive height problem by means of heads having such a construction as to allow the balls and plugs to be mounted and to be released from substantially the same vertical location below the top-driven rotary system. Nevertheless, their construction is complicated and requires large internal rotating parts, which increased the possibility of leakage and other need for repair.

It is therefore another object of this invention to provide such a head where the balls and plugs are mounted at generally the same level, but which does not include the large rotating parts and other mechanisms which increase the danger of repair and replacement.

These and other objects are achieved in accordance with the illustrated embodiments of this invention by means of a housing having an inlet adapted to fluidly connect in-line with the lower end of a top-driven rotary system, an outlet generally aligned with the inlet and passageways extending downward into the housing at locations spaced along the perimeter. Each passage has an upper end opening to the side for the inlet and a lower end connected to the outlet, and lateral passages in the housing connect each inlet to a passage. A shut-off member is removably mounted at the upper end of each passage to permit a ball or plug to be installed therein, and plug valves are mounted in the housing, each for opening and closing a passage below the lateral passage connected thereto, to hold the ball or plug when closed, and allow it to pass through when open. Circulating fluid can pass downward through an open passage when a ball or plug is not in the passage.

Reference should now be made to the details of figures A1 and A2, where the head A10 comprises a housing A11 which has a vertical opening A12 at its upper end and a vertical opening A13 at its opposite lower end, the openings being generally vertically aligned. The upper opening is threaded to a tubular member A14 whose upper end is threaded for connection with a top-driven rotation system.

Between the upper and lower ends of the element A14, a Kelly valve A16 is installed for opening or closing its bore A15. When closed, the valve allows cement to be supplied to the bore A15 through one or more side openings A16 in the element A14 below the Kelly valve. The element A14 is installed on a swivel A20 which has through openings which are aligned with openings A16 in pipe fittings A17 leading to the bore A15 in the element. As is well known in the art, this allows relative rotation between the swivel and the tubular element, so that the tubular element and the cementing truck are fluidly connected during relative rotation.

The lower end opening A13 in the head is threaded to the upper end of a piece of pipe A21 having a through bore A22 which is adapted to connect with the liner or other tubular element suspended therefrom. A "flag" A23 is mounted on a rod A24 which is rotatable in the tube piece to show the passage of a

bullet or plug through it.

As shown, the housing is of a generally truncated conical shape, and has four passages P1, P2, P3 and P4 extending downwardly and inwardly through it to connect with the opening A13 at its lower ends. More specifically, these passages are spaced at an equal distance from each other around the center line of the housing, and consequently the opening A12, to connect at their lower ends with a common opening A21A at the upper end of the pipe piece A21.

The upper end of each passage is adapted to receive a closure member 25, the threaded connection between each closure member and its passage making it possible to selectively remove or install the closure member. The housing also has a side-directed opening A26 which connects the lower end of its upper opening A12 with one of the passages Pi, P2, P3 and P4 below its closing element.

Each passage Pi, P2, P3 and P4 is in turn opened and closed by means of plug valves PV1, PV2, PV3 and PV4 with through-bore which are installed in the housing below the lateral openings A26, and are vertically offset to accommodate the valves. These valves, of course, regulate the passage of a plug or ball as well as the circulation of fluid through the top-driven rotary system, the head and into the liner below it. Accordingly, with the valves controlled in the manner that will be described, the circulation of the fluid may be continuous through at least one passage, even though the individual passages are closed to contain balls or scraper plugs.

As shown, each plug valve comprises a body having a through opening A30 which, upon rotation of the body between its alternate positions, is adapted to align with or across a passage. These valve bodies can of course be rotated in any suitable manner, and are held in place by a mounting plate MP which is screwed to the outside of the housing.

As shown in figure A2, one of the passages can receive a ball B between the upper closing element and the valve, while another passage can receive a pump-down plug PDP. One of the other passages can be used to receive a ball or a plug, depending on the use of the balls and plugs in the system where the head is installed. The fourth passage may remain open to allow fluid to circulate freely downward therethrough on a continuous basis.

A plug or ball can be installed in a passage by removing the closure member 25, which provides easy visual access to the passage to determine if the ball or plug is in place or has been dropped downward. Each ball falls freely by its own weight when the plug valve in its passage is opened. However, the pump-down plug has scraper blades which are in flexible engagement with the passage, so that the downward movement of the scraper blade into the liner can be assisted by the passage of fluid through the ports connected to the passage. The fourth passage can receive either a plug or a ball, depending on the needs of the system where the head is installed or remains open for free downward flow of the circulating fluid.

As will be understood, the only parts in the head that require movement, and thus bearings and seals, are the plug valves PV for the individual passages. Closing the plug valve in the three passages can allow downward pressure through the fourth passage when its plug valve is open, forcing the ball or plug downward into the casing.

As shown, each plug valve is mounted for rotation within its passage by means of a mounting plate MP which is screwed onto a recessed portion of the outside of the head and engages with an annular shoulder around the plug valve element.

Driving tools

Continuing a description of the driving tool 120 previously described, the piston sleeve 220 is disposed around and is axially movable relative to the portion 210. An upper sealing ring 214 is disposed around a smaller outside diameter of the driving tool spindle than the lower sealing ring 216, to form an annular pressure chamber 218 between them to lift the holder 130 for the liner extension from the position shown in Figure 1B to the upper position, which will be described in connection with the setting of the retaining wedges 142. Ports 242 formed in the driving tool spindle 132 connects the driving tool bore with the surrounding pressure chamber 218 once the sleeve 212 is lowered. An increase in pressure through the ports 242 will raise the piston sleeve 220. Upward movement of the sleeve 220 causes the upper end 312 of the piston sleeve 220 to overcome the resistance of the split ring 244, as shown in Figure 1A, to raise the liner extension holder 130, as shown in figure 2A, thereby raising the retaining wedges 142A, as shown in figure 2B. The sleeve 245, as shown in Figure 1D, can move downward to expose ports 260, which raises the piston 252 to release the ring 244 which was connected to the top of the holder 130 for the liner extension. A further increase in pressure will force the ball through the reduced neck in the seat 232 to pump the ball to a closed position on a lower seat 246 (see Figure 1D), which corresponds to the upper seat 232.

A problem with a conventional retaining wedge assembly is the need to coordinate the setting of the individual retaining wedges so that their teeth engage the outer casing substantially simultaneously. Furthermore, it is of course expensive to machine several wedge surfaces around the liner, as well as to provide several retaining wedge elements, and the main purpose of this invention is to provide a retaining wedge assembly for this purpose which only requires a single retaining wedge element which can interact with only a single wedge surface in the liner or a other elongated element.

Accordingly, in the embodiment of Figures 9A-9C, and which is also shown and described in the above-mentioned provisional application 60/292,099, the retaining wedge assembly includes retaining wedge segments 141 which are raised by means of a tension rod above the outer conical surface of a cone 143 to cause the teeth to 142 around the retaining wedges grips the casing C. In a preferred embodiment of the invention, the truncated conical surfaces of the element and the retaining wedge extend downwards and inwards, the lower end of the retaining wedge being received in an upwardly facing recess in the element, and the teeth of the C-ring facing downwards in position to grip the wellbore, when the C-ring is raised above the surface of the element, whereby the element can be suspended inside the wellbore. The means for raising the lower end of the C-ring from the recess into a position to slide along the tapered surface of the member comprises at least one tension rod extending vertically through the member for controlled reciprocating movement relative thereto. More specifically, the inside of the C-ring and the lower end of the tension rod have mating parts which allow the lower end of the C-ring to be raised out of the recess, but which cannot be disengaged when the rod is raised to allow for the ring to expand into engagement with the wellbore.

Preferably, and as shown, the internal truncated conical surface of the C-ring has relatively blunt teeth around its truncated conical surface for engagement with the truncated conical surface of the member, to control the friction between them, and consequently control the force applied to the casing.

As shown and described, the elongate member is a liner, and the recess for receiving the end of the retaining wedge is annular.

C-ring retaining wedge

With reference to the drawings described above, and as can best be seen from figures B3A and B3B, the liner B20 has a downwardly and inwardly extending truncated conical surface B22 thereabouts, above an upwardly facing annular recess B23. The casing has been lowered on a suitable driving tool (not shown) to a position in the outer well casing where the casing is to be suspended.

As will be described in more detail below, the C-ring C is initially expanded to enable it to be disposed around the conical wedge face of the liner. It can then be pulled together and pressed downwards to cause its lower end B26 to move into the recess B23. When installed in this manner, the C-ring retaining wedge is held in the retracted position in a shape somewhat larger than its fully contracted shape shown in Figures B1A and B1B.

When the C-ring has been pulled upwardly to remove its lower end from the recess B23, it expands toward its fully extended position in Figures B2A and B2B, whereby the downward-facing teeth B22 around its outside engage the outer well casing, as shown in Figure B3B, in a somewhat less than fully extended position. Then, when the C-holding wedge is raised, the inner surface of the C-ring will slide over the wedge face B22 to push it outward to cause its teeth to cut into the outer well casing, thus enabling the weight of the casing and its associated parts to be suspended up on the casing.

As shown in Figures B3A and B3B and detail in Figures B3AA and B3BB, the inner truncated conical surface of the C-ring retaining wedge has blunt teeth CF which, as is well known in the art of retaining wedges, regulate the frictional engagement with the liner and consequently the outwardly directed force applied to the casing. Accordingly, when the teeth initially cut into the casing, the blunt teeth on the inside of the retaining wedge will begin to bite the wedge surface of the liner to regulate the extent to which the teeth cut into the casing. The force applied in this way to the casing and liner can be regulated by the relationship of the inner and outer teeth to each other. Although teeth CF are preferred, the inner surface of the C-ring may be smooth.

Referring to Figures B4 to B6, one or more tension rods B30 extend downwardly through a groove B40 in the liner for controlled reciprocating movement relative thereto. The lower end of each tension rod is connected to the upper end of the retaining wedge to raise its lower end out of the recess. Accordingly, as shown in Figures B4-B6, the lower end of each tie rod 30 has a flange 50 which is received in a groove B36 around the inner diameter of the C-ring, the C-ring being initially fitted in the recess.

When the tension rod is raised to lift the C-ring out of the recess B23, the flange B50 on its lower end moves out of the groove B36 to release the C-ring therefrom, as shown in Figure B5. At this point, of course, the weight of the casing can be relaxed on the outer truncated conical surface of the C-ring to push the teeth of the C-ring outwards into gripping engagement with the outer casing, as shown in Figure B6.

As an alternative to retaining wedge assemblies, as previously described, other devices for this purpose - i.e., suspending an inner casing within an outer casing, have locking elements adapted to expand into corresponding locking grooves formed in the outer casing . In some cases, the locking elements are adapted to be spring biased into corresponding grooves formed in the outer casing. However, these springs are susceptible to breakage or other malfunctions. This is particularly the case since the hanger 8 comprises a large number of intricate parts which are expensive to replace, and which require a delay in the overall well operations. In still other cases, the hangers only have a single locking part for fitting within a single track, limiting its load-carrying capacity. Another object of this invention is to provide a casing hanger system which overcomes these and other problems inherent in known hangers for such systems.

These and other purposes are achieved in accordance with the illustrated embodiment of this invention by means of a casing hanger system comprising a length of casing adapted to be inserted as part of an outer casing installed within a wellbore, and a casing which is adapted to be lowered and landed inside the outer casing. The bore in the casing length has a polished bore and vertically spaced upwardly spaced landing surfaces formed in the polished bore, and the liner includes a tubular body having a recess formed around its body. And a hanger element comprising a circumferentially expandable and contractible C-ring arranged in the recess. The ring has teeth on its outer diameter for landing on the landing surfaces of the casing length when in its extended position and, by relative vertical movement relative to the casing, expands outwards towards the polished bore. With continued relative movement of the liner and ring, the teeth will move into a position where they extend further outwards into landed positions on the landing surfaces to enable the liner to be suspended from there.

Lining hanger

Reference will now be made to Figure C1, where the length of tubing C10 of the outer casing section is threaded at its upper and lower ends to allow it to be inserted as part of the outer casing installed in the wellbore, as with the casing hanger systems the is shown above. The polished bore in the casing section has an annular recess C11 in its lower part, and a series of upwardly facing landing shoulders C12 which are arranged at a vertical distance above the recess C11, and which are separated from this by an annular restriction C14. There is another annular recess C15 which is formed in the bore above and is separated from the landing surfaces C12 by means of an upper restriction C16 above an annular recess C13. The restrictions and landing shoulder are substantially the same diameter as the polished bore above them.

Figure C2 shows that the hanger C17 is drilled within a recessed portion 18 around the casing L. The hanger C17 is a C-ring which is split around its circumference in a position to be pressed along the circumference outwardly to engage the inside diameter of the casing when expanded , but, as shown, is held in its contracted position when the casing is driven into the outer casing. In this position, its lower end C20 is adapted to be received in a groove C19 in the upper end of a part C21 of the liner with an enlarged outer diameter.

The upper end of the hanger has teeth C22 formed around it with a mutual vertical distance corresponding to the landing surfaces C12 of the casing, and which fit into the recess C18 around the casing. The toothed section and lower end of the ring are connected by an outwardly enlarged cylindrical portion C35 having an inner surface which engages with the outer surface of the extension C25 around the bushing.

As will be described and shown in Figure C3, the hanger is adapted to be raised relative to the casing to free it for outward expansion into engagement with the polished bore of the outer casing. Accordingly, the casing hanger system includes a suitable mechanism for raising the hanger out of its restrained position, to release its lower end from the slot C19. This can be accomplished by raising the hanger by means of tension rods C30 which are connected at their upper ends to a conical C cover which a packing element is adapted to lower to seat it against the outer casing. The tension rods extend through vertical grooves in the recessed part of the liner, and have an outer flange C31 which is releasably inserted in a groove C32 around a lower extension of the cone C.

From a comparison of Figures C2 and C3, it will therefore be seen that raising the packing cone will raise the lower end of the hanger free of the retaining groove C19, and consequently allow the hanger to extend outwards to the position of Figure C3. This then allows the rib C61 on the lower end of the tension rod to disengage from the groove 62 in the lower end of the hanger and disengages the tension rods from the hanger as it moves into its upper relative position to the liner. This relative vertical movement between the liner and the packing element cone is a result of shearing off the pin C33 releasably connecting them in the position of Figure C2. This can of course be achieved by raising the packing cone in relation to the casing, before lowering the hanger into a position opposite the grooves which form landing surfaces in the bore in the outer casing.

On lowering the hanger with the liner from the position of Figure C2 to the position of Figure C3, the lower radially expanded section C35 of the hanger, which extends over the outer extension 25 of the liner, is free to move outwards, into the recess C11 in the outer casing. Accordingly, when lowered to a position opposite the landing surfaces C12 within the outer casing, the teeth C22 around the upper end of the hanger move outwards onto the landing surfaces, forming multiple shoulders upon which the load from the liner within the outer casing can be carried. This outward expansion of the hanger element has occurred after it has been lowered below the expansion in the bore in the outer casing when the casing is lowered from its position in Figure C3 to its position in Figure C4.

When the hanger has sprung outward to the position of Figure C4, continued lowering of the liner will move the extension C25 around it into the lower end of the hanger on which the teeth are formed, continuing to hold it in its outer hanging position, as shown in Figure C4 . A downward facing shoulder C51 is formed on the outer diameter of the liner above the outwardly directed extension C50, to land on the upper end of the hanger, as shown in Figure C4. The outwardly directed extension is moved into the inner diameter of the hanger, as shown in Figure C4, by means of a conical shoulder C50B formed on its upper end and capable of sliding over an inwardly and downwardly directed conical shoulder surface C50A on the liner.

As the hanger moves into the landed position, the extension C35 around it, below its teeth, fits snugly into the recess C16 in the outer casing bore, to limit outward expansion of the hanger member as soon as it is moved into the hanging position.

An inwardly directed extended portion C60 on the lower end of the hanger, below its outwardly directed extended portion C35, is moved across the outside diameter of the lower end of the liner, thereby cooperating with the extension C50 to hold the hanger member in its outward hanging position.

Driving tools

Reference should again be made to the driving procedure, as the annular packing element 150 (see Figure 1 F) is arranged around a downwardly extended upper cone 152 below the push sleeve 148. The packing element 150 originally has a circumference where its outer diameter is reduced and consequently has a distance from the casing C. However, the packing element 150 can be expanded so that it can be moved downward, over the cone 152, to seal against the casing.

The packing member 150 is adapted to be seated by means including spring-loaded tabs 328 which, when moved upwardly out of the liner extension holder 130, will be urged into an extended position, as shown in Figure 6A, for engagement with the top of the liner extension holder. When weight is lowered, the extended lugs 328 transmit this downward force through to the push sleeve 148 and the packing member 150. A body lock ring 270 (see Figure 1F) is provided between the liner extension connector 130 and the push sleeve 148 and allows the packing member 150 to be pushed down, over the upper cone 154, when lowering the liner extension connector. Upward movement of the set packing element is prevented.

The packing member 150 may be of a construction described in US Patent No. 4,757,860, which comprises an inner metal body to slide over the cone and annular flanges or ribs extending outward from the body for engagement with the casing. Rings of resilient sealing material can be fitted between such ribs. The sealing bodies can be formed from a material that has a significant elasticity to span the annulus between the casing hanger and the casing C.

Gasket for radial setting

The present invention also relates to an improved radial setting gasket for sealing against a casing or other downhole cylindrical surface which is configured with a primary seal and a back-up seal, and which may be part of a downhole tool which includes a transport tube and a conical wedge ring, and which can therefore be used for reliable sealing engagement between a casing hanger and a casing string.

The packing element or packings which are set radially by axial movement of the packing element in relation to a conical wedge ring have been used for sealing in underground well holes. A transport tube is conventionally provided for positioning the packing element at the desired position inside the wellbore, and an actuator causes the packing element to move axially in relation to a conical wedge ring and thereby expand into sealing engagement with the cylindrical surface to be sealed.

US Patents 4,757,860 (previously mentioned) and 5,076,356 describe packing elements for radial setting that can be used in various applications, including a subsea wellhead. In a typical wellhead application, it may be that the packing element needs to be expanded in diameter approx. 0.76 mm to achieve a reliable seal with the polished bore. US Patents 5,511,620 and 5,333,692 describe packing elements intended to seal between a casing hanger and a casing. More specifically, a conical member is moved axially relative to the packing member to expand the packing member into engagement with a casing. The expansion can be significantly greater than the expansion of a packing element in a wellhead application, which is due to the difference in diameter of the casing, from the operating inside diameter (minimum allowable inside diameter for a particular size casing) to the maximum inside diameter allowed by API for a casing of this size. The difference between this internal operating diameter and the maximum internal diameter for a casing of a certain size can thus be 7.6 mm or more.

There are several problems with the packing elements described in the '620 patent. Because the sealing member is stationary relative to a movable conical member, the radially extending flanges or ribs of the sealing member may not be extended as desired into portions of the casing string of non-uniform diameter to achieve a reliable metal engagement. -anti-metal sealing. Furthermore, the packing element does not always form a reliable metal-to-metal seal against the conical wedge ring, and the conical wedge ring similarly does not always form a reliable metal-to-metal seal against the spindle of the tool. Furthermore, the elastomeric sealing portions of the sealing member are not allowed to thermally expand in response to high temperature downhole conditions and consequently exert uncontrollable forces on the spaced apart metallic radial flanges or ribs.

Other problems with sealing elements according to the prior art relate to poor sealing reliability under conditions of high pressure. It may be that the metal ribs do not reliably seal against the cylindrical surface, and that the elastomeric part of the sealing assembly does not reliably seal over long periods of time. Certain packing elements function sufficiently well when high pressure is applied to one side of the packing element, but do not function well when high fluid pressure is applied to the other side of the packing element.

The disadvantages of the prior art are overcome by the present invention, and an improved packing element and a tool incorporating the improved packing element will now be described for reliable sealing between the packing spindle and a downhole cylindrical surface.

The annular packing element for radial setting according to the present invention is positioned downhole by means of a transport tube. The packing element may be moved by means of a setting tool from a reduced diameter run-in position to an expanded diameter set position so that the packing element engages a casing, a holder for a casing extension, or another downhole cylindrical surface in a well. If the cylindrical surface is a casing or other element which may have an irregular surface, the packing element is preferably moved axially in relation to a conical wedge ring or a cone during the setting operation. The sealing element is particularly well suited for reliable sealing against high pressure either from above or from below the element, and includes a primary elastomeric seal and a secondary elastomeric seal, and a primary metallic seal and a secondary metallic seal. The metal ribs in the packing element are angled so that the primary elastomeric seal is pressed against a rib angled towards the high pressure, and the secondary elastomeric seal is correspondingly pressed against a rib angled towards the high pressure. The secondary elastomeric sealing body acts on the primary rib to prevent the primary rib from standing perpendicular to the sealing surface, thereby increasing the reliability of the seal.

It is an object of the present invention to provide an improved packing element which can be used in downhole applications for reliable sealing against a cylindrical surface. It is a feature of the present invention that the packing element is particularly well suited to seal between a casing hanger and a casing under conditions where the casing can become considerably larger in response to thermal expansion and/or pressure expansion during downhole operations.

It is a related object of the invention to provide a downhole tool which includes a transport tube, a conical wedge ring and an annular seal assembly or packing element according to the present invention.

It is a feature of the present invention that each of the primary metallic ribs and the metallic reserve ribs in the sealing element are angled at least 15° in relation to a plane which is angled on a central axis in the sealing element.

Another feature of the invention is that metallic protrusions which are arranged at a mutually axial distance provide a reliable metal-to-metal seal between the packing element and the cone, and also preferably between the cone and the spindle or the interior of the body in the cone.

Yet another feature of the invention is that the elastomeric sealing bodies in the packing element include specifically designed volumetric cavities, so that, after the sealing bodies come into engagement with the surface, the elastomeric sealing bodies will be compressed until the ends of the ribs come into engagement with the sealing surface. At this stage, the now smaller cavities in the sealing bodies allow for thermal expansion of each sealing body between the metallic ribs to minimize unwanted tension force on the ribs.

Sealing element

Figure D1 shows an annular packing element D10 according to the present invention, positioned at the lower end of a push sleeve D12, at the lower end of a casing extension holder prior to sealing engagement with a casing C. Conventional slots or threads D28 or equivalent connectors may be used for to connect the packing member to the holder for the liner extension. Axial movement of the packing sleeve D12, and consequently the packing element D10, in response to the operation of setting the packing, pushes the packing element downward relative to the tapered cone D14, to expand the sealing element into sealing engagement with the casing. The cone D14 is in turn held on a liner hanger body D16. In an environment where the packing element is not the upper casing hanger seal, the packing element D10 can be held on the end of a seal actuator that replaces the slide sleeve D12, and the casing hanger body D16 can be a packing spindle or other transport tube for positioning the packing element in the well. In the embodiment in figure D1, the body D16 is consequently part of the transport pipe which

positions the packing element in a selected position inside the wellbore. The slide sleeve in the liner extension holder shown in Figure D1 represents a lower portion of an actuator sleeve which urges the packing member from a run-in position with

reduced diameter to an activated or closed position with expanded diameter. Accordingly, the actuator sleeve can apply a selected axial force to the packing member to seat the packing. The actuator can be selectively actuated by various mechanisms, including lowering weight or other manipulation of the transport tube, and can include axial

movement of a piston in response to fluid pressure, either by or by not releasing plugs or balls to increase fluid pressure. Additional details regarding the use of the packing element in a liner hanger application are described in US Provisional Patent Application Serial No. 60/292,049, filed May 18, 2001.

The packing element shown in Figure D1 is in its original configuration where the outside diameter has been reduced before it has been sealed against the casing. The packing element D10 is extended so that it is moved downwardly over the stationary cone D14 to seal against the casing, as discussed below, and as shown in Figure D3. It is a feature of the invention that the packing element D10 is moved into reliable sealing engagement with the casing by a setting operation which includes moving the packing element D10 axially in relation to the packing cone D14, instead of moving the cone in relation to the stationary packing element. This setting operation forms a more reliable seal against the casing by allowing the ribs D20 during the setting operation to bend or deform to the shape of the casing.

Referring to Figures D1 and D2, the packing member D10 comprises an inner metal body or base D12 for sliding over the conical wedge ring or cone D14, and annular flanges or ribs D20 extending radially outward from the base D18 for engagement with the casing. The base D18 is relatively thin to allow for radial expansion. The base D18 and the ribs D20 form a metal framework to support the preferably elastomeric sealing bodies of rubber or other resilient material. Rings of resilient sealing bodies D22, D24 and D26 are arranged between the ribs D20, and the upper and lower sides of each sealing body are preferably engaged with the respective rib. The body D18 and the ribs D20 are formed from a material that has sufficient ductility to expand into the annulus between the casing and the casing hanger. The metal part of the packing element, namely the base D18 and the radially projecting ribs D20, are thus formed of a material which is relatively soft compared to metals usually associated with downhole tools. This means that the packing element can reliably expand into sealing engagement with the casing at a reduced settling load.

Each of the radially projecting ribs D20 in the packing element is mainly angled in relation to a plane which is angled on a central axis in the packing element. More specifically, the center line of each rib is angled more than 15°, and preferably approx. 30°, in relation to the plane D38 which is perpendicular to the central axis of the packing element. Although the ribs may be slightly tapered to become thinner upon radially outward movement, the ribs preferably have a substantially uniform axial thickness. The rib D32 is shown in Figure D2 at an angle D33 between the center line of the rib and the plane D38. This feature causes each of the ribs D20 to expand significantly as the diameter of the casing varies or "grows", whether in response to internal pressure and/or thermal expansion. Due to the end of the angled ribs D20 being bent, reliable metal-to-metal contact is maintained between the ends of the ribs and the casing, as shown in Figure D3.

A particular feature of the invention is that the sealing element D10 inherently forms both a primary seal against the casing and a secondary seal against the casing, where the secondary seal depends on the direction of the pressure. The sealing element can further include both a primary elastomeric seal and a reserve elastomeric seal, and a primary metallic seal and a reserve metallic seal. Referring to Figure D3, it will be understood that the downward inclination of the ribs D30 and D32 is such that relatively high fluid pressure above the packing element can pass these ribs and the annular elastomeric upper sealing body D22, so that the inner sealing body D24, which constitutes a main part of the elastomeric seal area, forms the primary elastomeric seal against fluid flow. The term "fluid" as used herein includes gas, liquids and combinations of gas and liquid. The sealing body D24 preferably engages the ribs D32, D34 and the base D18, and mainly fills the annular cavity between these surfaces. When fluid pressure is above the sealing element D10, the lower sealing body D26 positioned between the ribs D34 and D36 forms a backup secondary elastomeric seal in the event that the primary elastomeric seal should leak. Similarly, when high fluid pressure is below the packing element, high pressure fluid is likely to flow past the ribs D36 and D34, so that the sealing body D24 is the primary sealing element. The sealing body D22 between the ribs D30 and D32 thus becomes the secondary elastomeric sealing element. Accordingly, the primary elastomeric sealing element is pressed in an axial direction (generally along the central axis of either the transport pipe body or the casing) in response to pressurized fluid, against an inclined rib angled towards the high pressure, and the secondary elastomeric sealing element is retained between two ribs which each is angled towards the high pressure side, so that the secondary sealing element is also pressed in an axial direction against a rib which is angled in the direction of the high pressure. The most important thing is that the spare seal, regardless of whether it is a sealing body D22 or D26, is held between two ribs and thus minimizes the probability that the axially innermost rib D32 or D34 will bend outwards to align with the plane D38, i.e. perpendicular to the wall in the casing. The material of the sealing body D22 or D26 thus acts as a biasing force which tends to hold the rib D32 or D34 at a desired angle, which then holds the primary sealing body D24 and prevents the rib D32 or D34 from standing perpendicular to the wall of the casing C. If should the ribs be bent past the point where they are perpendicular to the casing wall, it is likely that the packing element will lose its sealing integrity with the casing. The radial ribs D20 are consequently located at a vertical distance from each other and act independently in relation to upward and downward pressure forces.

The packing element D10 also includes several metal sealing surfaces, namely the ends of each of the ribs D20, so that annular metal-to-metal seals are formed against the casing. More specifically, these angled ribs are designed to maintain a constant metal-to-metal seal against the casing even though the packing element may be subjected to variable fluid pressure and temperature cycling. Under high pressure, the two ribs adjacent to the high pressure may be bent towards the base D18, and consequently not maintain seal integrity. A primary metal seal is nevertheless formed by one of the axially innermost ribs D32 or D34 on the downstream side of the elastomeric packing body D24, and a spare metal-to-metal seal is formed by the axially outermost rib D30 or D36 located in an axial distance farthest from the high pressure. High fluid pressure forces both the primary and secondary reserve ribs to decrease the angle D33, forming a tighter seal engagement with the casing. The redundant or backup elastomeric seal D22 or D26 exerts a biasing force which tends to prevent the primary metal seal D32 or D34 from moving past the position where it is perpendicular to the wall of the casing.

Reference should again be made to figure D2, where each of the elastomeric sealing bodies D22 or D24 and D26 is provided with a substantial cavity area D23, D25 and/or D27 to allow compression of the elastomeric body, and for thermal expansion, so that the rubber-like material, both during the final setting operation and during downhole use, is not squeezed outward past the ends of the ribs, or squeezed to exert significant forces on the ribs, which would alter the bending of the ribs. The cavity area between the ends of the ribs and the base of the sealing element is preferably such that at least approx. 5% to 10% thermal expansion of the elastomeric material. This void area of 5% to 10% consequently allows for thermal expansion of each elastomeric resilient seal, thus avoiding the generation of additional forces acting on the ribs D20. Accordingly, each of the elastomeric sealing bodies preferably includes cavities which allow each resilient sealing body to be compressed between the metal ribs without overloading or breaking the ribs. Consequently, these cavities will be filled mainly due to compression of the resilient sealing material, and will be mainly filled, as shown in Figure 3, due to compression of the sealing bodies and thermal expansion of the resilient sealing bodies. The stress level on each of the elastomeric seals can therefore remain substantially constant with varying thermal cycles in the wellbore.

As shown in Figure D3, the elastomeric sealing bodies have been compressed to reduce the void area, leaving only a small void volume for further thermal expansion. The cavity area is preferably designed to be from 5% to 10% of the volume of the resilient sealing bodies once each sealing body is in its compressed position where the ends of the ribs engage the casing, but before thermal expansion.

Figure D3 shows the sealing element D10 according to the present invention in tight engagement with the casing C, and at a temperature where the elastomeric material has already expanded so that it fills most of the above-mentioned cavity area. Figure D3 also shows the flexing or bending of these ribs from the run-in position, as shown by dashed lines, to the sealing position, as shown by solid lines. The inclination of the ribs, i.e. the angle D33 shown in figure D2, is thus increased during the operation of setting the gasket. The ribs D30 and D32 at the upper end of the packing element D10 are angled inwards, and the ribs

D34 and D36 at the lower end of the packing element are angled upwards. As explained above, the center line of each rib is angled at least 15° in relation to plane D38 which is perpendicular to the central axis of the element 10 before setting, i.e. when it has a reduced diameter, as shown in figure D1.

The base D18 of the gasket seal includes a plurality of inwardly projecting protrusions D40. These annular projections or beads on the packing element provide an engagement with a reliable metal-to-metal seal with the packing cone D14. These protrusions provide points of high stress to form a reliable metal-to-metal seal. Corresponding projection D42 on the packing spindle D16 provides an engagement with a metal-to-metal seal between the packing spindle D16 and the packing cone D14. The seal according to the present invention therefore operates together with the gasket's cone to achieve a complete metal-to-metal seal between the gasket's spindle and the gasket's cone, between the gasket's cone and the sealing element, and between the sealing element and the casing. The multiple sealing protrusions or beads D40 form metal-to-metal seals with a mutual axial distance between the base D18 of the sealing element D10 and the tapered cone D14, while protrusion D42 seals between the cone D14 and the packing body or another transport tube D16. These metal-to-metal seals are activated when the gasket seal is set, and preferably include several redundant annular metal-to-metal seals. One of or both of the radially inner and intermediate metal-to-metal seals can alternatively be formed by annular projections on the gasket's cone for sealing with one of or both of the gasket element's base D18 and the gasket's spindle D16.

The resilient elastomeric seals D48 on the inside diameter of the seal bore D18 may be backup seals, since the spaced apart metal protrusions D40 form the metal-to-metal seal between the packing element and the cone once the packing element is fully seated. Another elastomeric seal, such as a V-seal D15, provides an elastomeric back-up seal between the cone D14 and the body D16. These metal projections D40 on the inner diameter of the element D10 are axially in-line with (laterally substantially opposite) the area where the ribs D20 seal against the casing. The interface between the casing and the metal ribs D20 of the packing element D10 consequently forces the metallic sealing protrusions D40 into tight metal-to-metal sealing contact with the cone D14. The projections D42 on the body D16 are correspondingly axially in-line with the element D10. The metal-to-metal seals between the packing element and the cone are preferably arranged on the packing element, since its axial position in relation to the cone, when in the set position, can vary with the well conditions.

With the desired seating force applied to the packing element D10, the packing element will be pushed down the ramp of a cone D14 so that the ribs D20 come into metal-to-metal engagement with the casing. Metallic sealing protrusions D40 and D42 between the sealing element D10 and the cone D14 and between the body D16 and the cone D14 are in contact, but have not been activated. When the setting pressure is increased, the ribs on the packing element can be bent inwards to a position in solid lines in figure D3. This high seating force will compress the sealing bodies between the ribs and cause the outside diameter of each sealing body to come into sealing engagement with the casing. This high seating force will also cause the metal protrusions D40 along the inner diameter of the sealing element D10 and the metal protrusions D42 along the outer diameter of the spindle D16 to form a reliable metal-to-metal seal with the cone D14. Under this load, these metal protrusions form high local stress at the point where the protrusions engage the cone to achieve a reliable metal-to-metal seal. The metal projections which provide the desired metal-to-metal seals between the body or spindle D16 and the cone D14 may be provided either on the outer generally cylindrical surface of the body D16 or on the inner generally cylindrical surface of the cone D14. A reliable fluid pressure-tight barrier, which can be both a liquid barrier and a gas barrier, is consequently formed with high reliability under different temperatures, pressures and conditions with a long service life for the seal, which is due to the combination of the elastomeric seals and metal seals. After the packing element contacts the casing, the BOP shutoffs can be closed around the drill pipe (or other transport pipe) and fluid pressure can be applied to the annulus to pressure assist the setting of the packing element.

The sealing element according to the present invention is suitable for use in a casing hanger for sealing between the packing spindle in the casing hanger and the casing pipe. The initial settling weight on the sealing element D10 will consequently push the sealing element down the cone D14 and into contact with the casing C. The sealing material located radially outside the ends of the ribs D20 will initially be compressed to occupy much of the cavity area in the sealing bodies. Once the elastomeric seals have been deformed so that the ends of the ribs engage the casing, the remaining void area may be from 5% to 10% of the volume of each seal body, assuming that there has been no significant expansion of the seal bodies on due to thermal expansion. If the sealing bodies experience high thermal expansion before a setting operation, the cavity area will be reduced by compression of the sealing body.

During well operations, the pressure may cause the casing to expand in diameter, and this expansion will cause the ribs to expand with the casing, so that the position of the ribs relative to the expanded casing may return to the configuration shown by dashed lines in Figure 3. The ribs ability to "grow" in diameter with the expanding casing keeps the ends of the ribs in reliable metal-to-metal contact with the casing as the well cycles through pressure and temperature cycles. When pressure is released and the casing shrinks, the ribs can return to the configuration shown by the solid line in Figure 3.

Thus, the sealing element D10 according to the present invention is ideally suited for applications where high pressure can be applied from both directions to the sealing element, since the sealing element inherently provides both a primary seal and a secondary seal, each elastomeric seal being supported in one direction to resist axial movement in response to the high pressure, which is done with a rib that is angled in the direction of the high pressure, and which allows bending to fit the casing. The rib on either side of the primary seal body is held by the secondary seal body, which biases the rib against the high pressure.

In the case of a liner trailer, the driving tool for the liner trailer conventionally includes the actuator which provides the compressive force on the packing element D10 to set the packing. In other applications where the sealing member is used, an actuator may be used to apply the compressive force to move the seal from an engaged position or radially reduced position to a sealing position or radially expanded position. The actuator may be hydraulically driven, or may use mechanical setting operation. Then, after the driving tool is returned to the surface, a retainer holds the sealing element in sealing contact with the casing by preventing or limiting axial movement of the sealing element when fluid pressure is applied.

The sealing element according to the present invention can be used in various applications in a wellbore where a pipe is arranged, where a packing spindle or another transport pipe is positioned inside the wellbore to position the packing element in a selected location. The packing element is arranged around the transport pipe and includes a plurality of elastomeric sealing bodies for sealing engagement with the wellbore pipe, and a plurality of metal ribs that separate the elastomeric sealing bodies, where the rib ends are intended for sealing metal-to-metal engagement with the pipe. The packing element can be driven into the well in a configuration corresponding to that shown in Figure D1, where the sealing element has a reduced diameter, and the packing element deforms radially outward into sealing engagement with the wellbore tubing as it moves relative to a conical wedge ring, until the packing element reaches the final set position, as shown in figure D3. The sealing element for radial setting according to the present invention can thus be used for different types of downhole tools. Further spare secondary metal ribs may be provided, as well as further spare elastomeric bodies which engage these further ribs.

Different types of transport pipe can be used for positioning the packing element at a selected location below the surface of the well. The generally conical key ring or cone may have various constructions with a generally outer conical surface configured to radially expand the annular seal assembly or packing upon axial movement of the packing member relative to the key ring, either due to axial movement of the packing element in relation to the stationary wedge ring or axial movement of the wedge ring in relation to the stationary packing element. In a preferred embodiment, the sealing assembly includes an upper elastomeric sealing body, a primary elastomeric sealing body, and a lower elastomeric sealing body. Although each of the upper and lower seal bodies ideally provides backup elastomeric seals in the event that the primary elastomeric seal should leak, an important function of the upper seal body D22 and the lower seal body D26 is to provide a desired biasing force against the respective rib D32 or D34 . These elastomeric sealing bodies therefore function as biasing elements between the axially outermost rib and the adjacent inner rib to exert a force which prevents the inner rib from bending beyond a predetermined degree. For example, the lower seal body D26 engages both the inner rib D34 and the outer rib D36 and exerts an upward biasing force to prevent the rib D34 from moving downward past a position where it is perpendicular to the wall of the casing. At the same time, the lower seal body D26 exerts a downward biasing force which tends to increase the downward bending of the outer rib D36 as the inner rib D34 is bent downward in response to high pressure across the packing member.

In addition to the primary metal-to-metal seal, the secondary metal-to-metal seal, the primary elastomeric seal and the secondary elastomeric seal, additional sets of metal-to-metal seals and elastomeric seals may be provided in the packing element. Elastomeric bodies which are configured differently than shown here can therefore be used for this purpose. Different types of plastic materials in different configurations can provide the desired biasing force, and ideally also a secondary resilient seal. Alternatively, a wave-shaped spring or other biasing element of a metallic material can be used instead of or in cooperation with the elastomeric bodies D22 and D26.

Each of the metal ribs in the packing element described herein are preferably annular elements where the outermost surface of each rib, when in the drive-in position, has substantially the same radial distance from a central axis in the tool, for reliable sealing engagement with the surface to be sealed.

In other embodiments, one or more of the ribs may include radial notches, so that the ribs will not form a complete annular metal-to-metal seal, which may then be provided by the elastomeric seal, even if the complete annular metal seal then will not be achieved. In a preferably of protrusions with a mutual axial distance is preferably provided for engagement with metal-to-metal sealing between the packing element and the cone, and between the cone and the transport tube. In other applications, a single annular projection may be sufficient to provide the desired metal-to-metal sealing function.

Ball seats

With a continued description of the overall system, the lower ball seat 246 (see Figure 1D) is mounted inside the bore of the driving tool by means of shear pins 248 which are opposite the pressure chamber 256. The sleeve 245 therefore holds the seat 246. The lower end of the ball seat has a reduced thinner section or throat 258. Furthermore, one or more ports 260 formed in the driving tool are positioned to be uncovered to allow fluid pressure in the driving tool to be admitted into the pressure chamber 256 upon lowering the seat 246. When the ball 240 is released from the upper seat 232 it will land on the second seat 246, whereby pressure inside the driving tool above the ball will move the seat 246 downwards by shearing off the pins 248, to open the ports 260 leading to the pressure chamber 256.

Accordingly, the ball 240 can pass through the first seat 232 to be placed on the reduced diameter 258 in the second seat 246, so that additional pressure can be applied through the ports 260 to raise the outer piston sleeve 252. This in turn allows the split ring 264, having external teeth which engage the casing hanger 110, moves into a position opposite a lower end 268 of the reduced diameter sleeve 252, and consequently out of gripping engagement with the casing hanger, thereby releasing the driving tool from the casing hanger.

At this stage, the operator will increase the pressure to cause the ball to pass through the seat 246, so that the drop in pressure will indicate that the ball 240 has passed through the ball seat 246, allowing circulation through the drive string to continue and the ball to be pumped downward into the ball deflector 280 (see figure 11). Fluids are then circulated through the tool pending cement displacement. The cement is then injected into the driving tool and pumped down, and the pump down plug 182 follows the cement into the casing scraper plug 180 (see Figures 1J, 5A and 5B). This then forms a barrier against the previously displaced cement and the displacement fluid.

The lower end of the driving tool spindle 132 extends downward below the retaining wedge assembly, and has an extended body 145 (see Figure 11) which is adapted to move back and forth within the liner 146. This extended body 145 has an upwardly facing shoulder 147 which can is raised into engagement with a downward facing shoulder to allow the driving tool to be raised out of the set liner hanger, which will be described.

As previously described, generally in connection with Figures 1, 4A and 4B, for improvements in devices of this type where the cementing operation requires the sequential lowering of balls and pumping plugs into the inner tube, where, in a preferred and illustrated embodiment, the inner tube is a casing having an upper end installed inside an outer casing by means of a column of cement pumped out the lower end of the casing into the annulus between it and the outer casing.

As described above, in a system of this type, a ball is dropped on a seat in the bore of the casing to allow circulating fluid to be directed into a portion thereof for hydraulic actuation of a portion of the system outside the bore of the casing, and an opening which the ball is placed on can be driven circumferentially, by the application of higher circulating pressure, to cause the ball to pass through it and out the lower end of the liner. The ball can then be followed by a pump-down plug to force cement down, through the lower end of the casing, and into the annulus between it and the outer casing.

In the system shown and described in the above provisional application, the ball is relatively large, and in any case larger than the bore in the liner wiper plugs (LWP) into which the pump down plugs (PDP) are to be installed. Unless, bore through the scraper plug is as small as possible, the inside diameter of the liner to be cemented in the outer hanger is necessarily enlarged to accommodate the scraper plugs held around it. It is therefore the purpose of this invention to provide a device for such a system where the balls can be significantly larger than the pump-down plugs, and consequently larger than the bore through the scraper plugs in which the pump-down plugs are to be landed.

These and other purposes are achieved by devices including the previously described diverter 280 which comprises a tubular member such as a piece of tubing having an upper end connected to a well pipe to be lowered into a casing in the well to allow the is lowered therein, and which has a bore with an upper part with a relatively large diameter and a lower part with a relatively smaller diameter. The larger portion allows one or more balls to be lowered through, but the LWP in the smaller diameter portion prevents the passage of the balls while allowing the passage of the pump down plugs into the casing plug.

For this purpose, a piece of pipe installed below the larger part has a pocket on one side of its bore, into which the ball, or at least part of it, is diverted, thereby allowing the blowdown plug to pass between the ball and that side of the piece of pipe located opposite the pocket, whereby the pump down plug can continue down to enter the casing scraper plug. The barrel also includes a ramp which extends over the bore in the barrel and slopes down towards the pocket so that, when the ball is released, it will land on the ramp and thus be guided into the slot. More specifically, the ramp has a U-shaped groove that is too narrow for a bullet to pass, but wide enough for a plug to pass down between its closed end and the inside of the diverted bullet.

Bullet deflector

Reference will now be made to the details of the above-described drawings, each of Figures E1, E2 and E4 showing in vertical cross-sections a tubular element E10 which is suspended inside a casing L which is installed inside an outer casing C inside a wellbore, its purpose being to circulate cement downward through the lower portion of the tubular member and into the annulus between the liner and the casing to cement the liner into the casing. As also shown in Figures E4 and E5, a casing scraper plug LWP is suspended from the tubular member with a pump down plug installed therein.

The ball deflector BD comprises a tube piece installed between the upper and lower portions of the tubular member, and has a pocket P formed in the side of the tube piece to receive a portion of a ball B adapted to pass downwardly through it tubular element. A ramp R fitted to the pipe has an upper face which slopes downward from its upper end to its lower end to terminate opposite the pocket P. A slot S in the ramp is narrower than the ball so that when the ball is passed through the driving tool and into the upper end of the tubular element in the cementing tool, it will be guided into the pocket.

As shown in Figure A3, the opening between the inner end of the slot allows the lips of the pump down plug to be bent inwards, so that the pump down plug is free to continue downward to a position where it is positioned against the seat of the casing scraper plug LWP, as shown in Figure A4 . That is to say, after dropping the ball into the pocket, the deflation plug, under the influence of downwardly circulating fluid, will pass between the ball and the closed end of the slot in the ramp. The pump-down plug continues to be lowered until it lands in the casing scraper plug, as shown in Figure A4, which closes the lower end of the bore through the tubular member, all in a manner well known in the art.

Increased pressure in the circulating fluid shears off the pin P holding the casing scraper plug in place to allow the casing scraper plug to be moved down the casing, as shown in Figure A5. Accordingly, the released plug assembly will continue to force the cement down through the casing and then up into the annulus between the casing and into the outer casing, whereby the casing can be cemented into the casing, all in a manner well known in the art.

Driving tools

Again, continuing with the general rights, Figure 2-8 shows movement of components in the tool 120 in the process of setting the liner. As soon as the casing is sunk to the desired depth, fluids are circulated through the wellbore "from the bottom up". After conditioning the wellbore, the ball 240 is released from handling equipment at the surface and allowed either to fall freely or at a desired rate to be pumped to the upper seat 232. By applying pressure to the ball located on the seat, pins 222 between the seat and the liner hanger seat assembly is cut to allow the ball and seat to move downward to a position which exposes ports 242 in the body of the assembly 140 for setting the retaining wedge. The further application of fluid pressure will cause the surrounding piston sleeve 220 to move upwards. As a result, the casing extension holder 130, actuator retaining wedge rod 149, and retaining wedges 142 are pulled upward until the circumferentially spaced retaining wedges engage the casing C. Accordingly, as shown in Figure 2A, the piston sleeve 220 in the assembly 240 for setting the retaining wedge surrounding the driving tool spindle 132 has been moved upwards due to the increase in pressure over the ball 240. The piston sleeve 220 is moved upwards until the upper end 312 of the piston sleeve 220 engages and releases the split locking ring 244. This causes the holder 130 for the liner extension can continue to move upwards.

On the other hand, raising the liner extension holder 130 raises the cone 144A, the retaining wedge arm 149 and the retaining wedge 142A to the set position, as shown in Figure 2B. At this point, the load on the casing can be relaxed on the retaining wedges, whereby the weight of the casing is "hung" in the casing. Consequently, while the pressure is kept constant in the drill pipe to keep the retaining wedges in contact with the casing, the casing hanger can be relaxed on the retaining wedges. To ensure that the entire casing load is relaxed on the casing hanger assembly 110, additional pipe weight can be applied to check if the hanger is moving. Once it is determined that the retaining wedges have been hung, the fluid pressure can be re-applied, to a higher predetermined level, to the ball 240 located on the seat, so that the ball can be pumped to the lower seat 246 of the assembly 250 to release the liner. the trailer. With the ball positioned on the seat in this manner, a predetermined pressure can be applied to move the ball seat 246 and sleeve 245 downward to expose the ports 260 in the liner hanger release assembly. Higher fluid pressure can then be applied to cause the piston sleeve 252 to move upward, causing the liner hanger release ring 264 to contract within the reduced diameter lower end 268 of the sleeve 252, releasing the driving tool from the liner hanger. If the hydraulic release is not operable to move the ring 264 to disengage the driving tool, the operator may resort to a mechanical release mode. The function of the ball in releasing the driving tool from the set liner hanger is discussed below.

The further increase in pressure on the ball 240 and the lower seat 246 will release the ball from the lower seat, so that circulation through the drive string can continue while the ball 240 is pumped downward, into the ball deflector 280. Fluids can then be circulated through the tool pending cement displacement. The cement and displacement fluid are then injected into the driving tool and pumped down. Once the cement has been pumped, the pump-down plug sealing against the drill pipe is released from surface handling equipment to land on a seat in the casing scraper plug, forming a barrier between the previously displaced cement and the displacement fluid. A calculated amount of displacement fluid is required to pump the drill pipe plug down to the lower casing scraper plug. The operator observes the increase in pressure as the pump-down plug 182 locks into the casing scraper plug 180. The pump-down plug 182 (see Figure 5A) consequently follows the cement into the casing scraper plug 180. As the pump-down plug gets close to the driving tool, the pump rate can be reduced, to reduce the risk of malfunction between the locking and sealing of the lower scraper plug and the pump down plug. This enables observation of the increase in pump pressure when the pump-down plug 182 has landed in the lower scraper plug 180, as shown in Figure 5A.

A calculated amount of displacement fluid is required to push the cement to the desired height in the annulus between the casing and the casing. The drill string can be pressurized to a predetermined level to cut across the pins 186 (see Figure 5A) connecting the plug set to the driving tool. When the casing scraper plug is released as shown in Figure 5B, displacement fluids move the plug set down the casing 146 to the landing collar 370. The plug set therefore forms a barrier between the cement and the displacement fluid, preventing the displacement fluid from contaminating the cement fluids. A calculated amount of displacement fluid can be used to press the cement to the desired height in the annulus between the casing and the casing.

The operator continues to pump displacement fluid until the casing scraper plug and pump down plug assembly locks into the landing collar 370 (see Figure 5C) located in a lower portion of the casing. When landed in this manner, seals 372 seal around the plug set inside the upper reduced bore of the landing collar 370, and retaining wedges 374 with serrated surfaces engage the opening in the landing collar to prevent upward movement of the landed plug due to any downhole Print. At this point, the driving tool pressure can be increased to a level significantly above the circulating pressure to ensure that the scraper plug is properly landed and held down, and that the seals between the plug set and the landing collar are effective. The plug can then be tested by draining pressure to ensure that float equipment below the landing collar 370 is permanent.

Plug holder tube piece

As mentioned above, conventional casing trailer driving tools include a plug holder tube piece adapted to hold a casing scraper plug on the driving tool during a cementing operation. The plug holder pipe piece is conventionally locked to the drive string, and the casing scraper plug is attached to the plug holder pipe piece with a shear connection. Unfortunately, these shear connections are often prematurely weakened, or sheared either due to handling of the driving tool or due to the impact of the blowdown plug landing and seating on the casing scraper plug.

Some manufacturers have included a plug holder tube piece that has a locking lug and a displacement sleeve. The plug cannot be released until the pump-down plug displaces the sleeve to allow the locking lugs to be relieved, thereby allowing the plug set to be separated from the driving tool. US Patents 4,624,312 and 4,934,452 describe plug holder pipe pieces that use a collet instead of a locking lug. US Patent 5,036,922 describes a driving tool that uses a piston that is moved to release the plug set.

Although the above systems may prevent premature release of the plug set due to travel tool movement or handling, they do not prevent premature release of the plug set due to the impact of the blowdown plug and the plume of fluid behind this plug as it lands and settles on the casing scraper. the plug. In many applications, this landing force or "hammering" force will cause the plug set to release so quickly that the operator cannot detect the release, and therefore cannot correctly calculate the fluid displacements. This "hammering" effect of the pump down plug hitting the casing scraper plug and the effect of prematurely releasing the plug set can screw up a cementing job. The prior art has not solved the problem of premature release of the plug set due to this hammering effect of the pump down plug hitting the casing scraper plug. As a result, the operator may not be able to calculate the fluid displacement after the pump down plug has sealed against and locked into the casing scraper plug.

The disadvantages of the prior art are overcome by the present invention, and an improved downhole plug holder and method of holding a casing scraper plug which increases the reliability of cementing operations will now be described.

The plug holder pipe piece according to the present invention can be used for positioning a scraper plug that can be released from a driving tool for a casing hanger or the end of a pipe string during a cementing operation. The plug holder tube piece can be releasably positioned on the lower end of the casing hanger travel tool, and is sized to allow a pump down plug to pass, which lands in the casing scraper plug held on the travel tool by the plug holder tube piece. The casing scraper plug is connected to the plug holder tubing in a manner that prevents premature release of the plug assembly from the driving tool, either by handling the driving tool or due to the hammering effect of the blowdown plug entering and locking into the casing scraper plug. Once the pump down plug is tightly seated and locked into the bore of the casing scraper plug, fluid pressure acts on a piston which is moved to unlock the plug set from the driving tool, releasing the plug set and allowing it to be pumped to the landing collar.

The piston that unlocks the plug set from the driving tool acts on a fluid-filled chamber that is vented to the annulus through an opening. When the pump-down plug is sealed inside the bore in the casing scraper plug, increased fluid pressure acts on the piston. The type and volume of fluid being vented, as well as the size of the orifice, determine the time it takes to move the piston to a plug release position. This time is important to enable the operator to determine the correct displacement of cement volumes for cementing the casing in the well.

The plug holder tube allows the driving tool to be handled without any adverse effects on the casing scraper plug. The pump down plug can be pumped to the casing scraper plug at any desired rate, and sealed and locked. The hammering effect of landing the pump down plug on the casing scraper plug will not prematurely release the plug set. After the deflation plug has been seated and locked, the operator can increase pressure on the drive tool, confirming to the operator that the plug has been seated in the liner scraper plug. The operator can calculate the exact amount of displacement fluid required to cement the casing in the well. The fluid pressure can then be increased, causing the piston to start moving to the plug release position. The pump down plug and the casing scraper plug will consequently be released as a set after a predetermined time, which again is important for the operator to be able to determine the correct displacement volumes for cementing the waste in the well.

It is an object of the present invention to provide a plug holder tube piece for releasing a casing scraper plug in response to high fluid pressure acting against a piston, which in turn drives fluid from a chamber through a metering nozzle.

It is a further object of the invention to provide an improved method of releasing a casing scraper plug in response to fluid pressure such that fluid pressure moves a piston from a holding position to a release position. The time it takes for high pressure to drive fluid out through a metering nozzle is monitored to increase reliability in the correct release of the casing scraper plug during the cementing operation.

It is a feature of the present invention that a C-shaped retainer can be used to attach the casing scraper plug to a tubular body, where movement of a piston to a release position releases the C-shaped retainer to release the casing scraper plug.

It is a further feature of the invention that the C-shaped ring can have threads or other internal gripping elements for gripping engagement with the liner scraper plug. A dosing nozzle may also have external threads for threaded engagement with the tubular body.

It is an advantage of the present invention that the plug holder pipe piece is very reliable and relatively cheap.

These and other purposes, features and advantages of the present invention will be apparent from the following detailed description, where reference is made to the figures in the accompanying drawings.

Figure 1 shows a plug holder pipe piece F110 for holding a conventional casing scraper plug. The tube piece F110 includes a body F112 which is attached to the lower end of the driving tool spindle. Before the driving tool and casing are lowered into the well, the casing scraper plug engages the snap ring F114, which is held between the body F112 and the lower body F116 by means of the piston F134. The locking ring F114 includes grooves or threads F115 or other suitable elements for gripping engagement with the liner scraper plug. The seal F120 on the lower body F116 seals the plug holder tube against the liner scraper plug. Threads F128 connect the body F112 to the lower body F116, and the seal F122 seals between these connected bodies.

The body F112 includes a passage F128 which is open to the annular space around the driving tool. A hole nozzle F130 with a relatively sized hole is positioned along this port, and preferably includes threads for engagement with the threaded port F126. The fluid containing chamber F132 is pressurized by the piston F134, which includes a seal F136 on the outside diameter and a seal F138 on the inside diameter.

When the pump down plug lands inside the casing scraper plug, the increased pressure inside the driving tool acts on the piston F134, which in turn is pushed upwards to drive fluid out of the chamber F132. The quantity flow of fluid out of the chamber will be determined by the properties of the fluid inside the chamber F132, and the size of a selected hole in the nozzle F130 which is positioned downstream of the chamber. The left side view in figure F1 shows a pin F131 sealing off a drip port to the chamber F132. Pin F131 has a small port for slow release of pressurized fluid to the annulus. The pin F131 can be fixed inside the drip port by means of a drop forging operation, and is another form of dosing nozzle. The right side shows a nozzle F130 for thread attachment to the body F112.

A significant advantage of the plug holder pipe piece according to the present invention is that the increase in fluid pressure is not the primary factor that determines the release of the plug set. The speed of upward movement of the piston to drive fluid out of the chamber is primarily a function of a particular size of the nozzle and the type of fluid in the chamber. Accordingly, the operator will see an increase in pressure when the blowdown plug is landed on the casing scraper plug, and will then, within selected limits, know that a predetermined period of time should elapse from this increase in pressure until the plug set is released. As the piston F134 moves upward to reduce or eliminate the volume inside the chamber F132, the C-shaped snap ring F114 is free to move radially outward, freeing the liner scraper plug and pump down plug. The C-shaped snap ring F114 may be biased outward, but generally held radially inward by the piston F134, or it may be biased inward and moved outward for release by the downward force of the liner scraper plug.

Plugs are conventionally run in a well in pairs, and the plug holder tubing shown in Figure F1 is suitable for holding a pair of casing scraper plugs. In some applications, one pair of plugs is preferably used before the cement fluid, and another set of scraper plugs is used after the cement fluid and before the displacement fluid. For this latter application, each of the plug sets can be released separately in response to an increase in fluid pressure, which moves a respective piston to drive fluid out of the chamber and thereby release the plug set. A piston which is responsive to a low-pressure fluid can consequently be arranged on the holder pipe, this piston releasing the first plug set. At a higher fluid pressure, another piston may be moved in response to fluid pressure to release the second plug set. Each piston can push fluid through a selective hole in a nozzle. If desired, the second piston and/or both the first and second piston can be fixed with shear pins, so that no movement occurs until a selected pressure level is reached. If desired, the first plug set can alternatively isolate the port for the second plug set, so that pressure cannot act on the second plug set until the first plug set is released.

Figure F2 shows the piston F134 in its holding position, with the C-shaped retaining member F114 held radially inward so that its threads engage with corresponding threads F152 on the liner scraper plug F154. The through-passage in the casing scraper plug F154 is provided with a seat F156 for sealing with a conventional blowdown plug, as discussed above. The casing scraper plug F154 conventionally includes at least one and preferably two cup-shaped elastomeric sealing elements F158 on its exterior so that high fluid pressure behind the casing scraper plug pushes the casing scrapers outward into sealing engagement with the casing. An annular body F159 with o-rings F160 and locking rings F161 can be provided for sealing and locking the plug set against the landing collar.

The spacer and cement fluids can be mixed during circulation of fluids for cement displacement. Once the cement has been pumped, the pump down plug can be released from the surface, forming a barrier between the previously displaced cement and the displacement fluid. A calculated amount of displacement fluid can therefore be used to pump the pump down plug to the casing scraper plug. When the pump-down plug comes close to the driving tool, the fluid pressure can be reduced, for example to approx. 3.45 MPa, and this pressure will increase when the blowdown plug lands in the casing scraper plug, as discussed above.

Once the pump down plug is locked into the casing scraper plug, the work string can be pressurized upwards and after a selected period of time, the casing scraper plug and pump down plug will be released from the plug holder pipe. Increased fluid pressure consequently moves a piston to release a snap ring, which releases the casing scraper plug from the plug holder tube.

The piston inside the plug holder pipe piece preferably acts on a fluid with a known viscosity at the downhole temperature in the plug holder pipe piece. Fluid flow through an orifice of predetermined size will take a predetermined period of time to release the casing scraper plug. This time can be used by the operator to calculate an actual displacement of fluid volumes. A calculated amount of displacement fluid will consequently force the cement to the desired height in the annulus between the casing and the casing. Fluid will therefore be pumped until the set of casing scraper plug and pump-down plug is locked into the landing collar, at which point pressure can be increased to, for example, 6.90 MPa above the circulating pressure to complete locking of the plugs and check that the seals between the plugs and the landing collar hold. Pressure can then be drained off and checked for bleed-back to ensure that the float equipment is holding pressure.

Different types of dosing nozzles can be used for selective dosing of fluid from chamber F132. Substantial restrictions may be formed within the passage F128 to form an effective dosing nozzle. Fluid in the chamber F132 will be at a known viscosity for the downhole conditions, and with a metering nozzle of selected size, the operator will know with acceptable accuracy the time it will take for the piston F134 to move from the hold position to the release position.

Other forms of retaining elements may be used to connect the tubular body F116 to the casing scraper plug. A preferred retaining element has a C-shaped design with internal grooves or teeth for attachment to the casing scraper plug. The inner surface of the piston F134 thus prevents the retaining element from moving to the release position until the piston moves axially to its release position, as shown on the right side of Figure 1.

As discussed above, the casing scraper plug can be used at the lower end of the casing hanger driving tool. The plug holder pipe piece according to the present invention can more generally be used at the lower end of any transport pipe, such as the transport pipe F140 which is generally shown in figure F1. The transport pipe F140 can therefore be used to both transfer fluid pressure to the interior of the plug holder pipe piece, and also to position the plug holder pipe piece at a selected location inside the well. The plug holder pipe according to the present invention can therefore be used at the lower end of various types of tools, including a driving tool for a casing hanger, or at the lower end of the pipe string used in a cementing operation, to reliably release the scraper plug from the plug holder pipe during the cementing operation. As soon as the scraper plug is freed, it can seal against the casing or against another downhole pipe.

Driving tools

Continuing with the description of the overall system, conventional cementing equipment can be used below the diverter, including the plug set described above which forms a barrier against various fluids flowing down the casing. A pump down plug F182 as shown in Figure F5A may include upwardly facing cups 183 for cleaning the drill string so that increased pressure in the travel string, when the plug 182 seals against the casing scraper plug 120, releases both plugs (set) from the lower end of the casing hanger. The casing scraper plug 180 has corresponding cups 181, and lands on the collar 186 to tightly lock in place and shut off the lower end of the casing.

The released driving tool 120 can be picked up until the packing set assembly 380 (see Figure 1C) is removed from the top of the liner extension holder 130, whereby the spring-loaded lugs 328 are raised to a position above the top of the liner extension holder, at which time they are extended outward. With the packing set assembly 380 in the extended position, weight can be relieved by bringing the lugs 328 into engagement with the top of the liner extension holder to cause the packing member 150 to begin its downward sealing sequence. This weight also activates a sealing ring 384 between the packing set assembly 380 and the liner extension holder, to aid in further seating of the packing element with the assistance of annulus pressure. With the packing member 150 engaged with the casing, shut-offs on the BOP at the surface can be closed against the drill pipe to form a pressure vessel between the shut-offs and the expanded packing. The cross-sectional area between the casing and the drill pipe is known, and the load required to fully seat the packing element 150 is known, so that the operator can apply predetermined fluid pressure to the annulus to cause the casing extension holder to move downward, applying a predetermined additional axial load on the packing element.

Downward movement of the slide sleeve 148 to seat the packing element 150 will disengage the internal threads 386 (see Figure 6B) in the slide sleeve from the holder 130 for the liner extension. The push sleeve 148 thus moves radially outward as the push sleeve moves down the cone 152. The push sleeve 148 may be split along its circumference in such a way that in its normal, contracted position, its internal threads 386 will engage the external threads 131 of the holder. 130 for the liner extension. Other types of sliding sleeves can be used.

The spindle 132 in the released driving tool 120 can then be used to raise the cementing bushing 160 to cause the bushing lugs 392 to engage and unlock from the casing hanger 110. After pulling the lower end of the driving tool to a predetermined position at the upper end of the casing, the operator can circulate fluid through the driving tool to the pump and excess cement to the surface. Circulation effectively reduces the amount of cement that will need to be drilled out before the top of the casing is driven in again, and enables the operator to check for fluid flow and/or fluid loss.

After the driving tool is raised to a predetermined position above the top of the casing, the operator circulates through the drill string to pump any overshoot cement to the surface, reducing the amount of cement that will need to be drilled out before the top of the casing is re-entered. Figure 8A shows the released driving tool 120 raised from the liner. When checking for fluid flow and/or fluid loss, the operator pulls the driving tool out of the hole. As soon as the tool reaches the surface, the operator can check the running tool for damage, wash the fluid off the tool, and flush the tool's inside diameter before returning the tool to the shop. Figure 9C also shows what remains in the casing C, namely the set gasket 150 and the set retaining wedges 142.

The liner hanger release assembly 250 shown in Figures 1D and 1E can be replaced with the release assembly shown in Figures 10 and 11. The liner hanger release assembly shown in Figures 10 and 11 may still be located below the packing set assembly 380, as described above, or the packing set assembly 52 which is described below, and includes an inner piston sleeve 340 which is sealingly arranged around the driving tool spindle 132, and another piston sleeve 342 which is arranged around the inner piston sleeve. Piston sleeve 340 forms a pressure chamber corresponding to sleeve 252 shown in Figure 1D for releasing the liner hanger. The liner hanger release assembly shown in Figures 10 and 11 releases the snap ring 326 which is provided with external grooves for engagement with the grooves on the inside diameter of the liner hanger 110 at the upper end of the liner 146. The snap ring 326 is held in the locking position by the extended upper outer diameter of piston sleeve 340, which, as shown in Figure 10A, is in its lower position. At this time, the coupling 316 shown in Figure 1D is pushed downward by springs 318 for engagement with the liner hanger 110, which is threaded for engagement with right-hand threads 324 on the driving tool spindle 132. The nut 322 has lugs 326 which are pushed outward by springs 327, into vertical grooves formed in the casing hanger 110 to prevent relative rotation between the spindle 132 and the casing hanger.

Upon raising the inner piston 340, the snap ring 326 is free for inward contact around the lower reduced outer diameter 368 of the piston sleeve 340, thereby freeing the driving tool to be raised after setting the retaining wedges but before setting the packing, allowing circulation of cement down through the tool and up into the annulus between the tool and the casing.

In the event that the locking ring 326 is not released for some reason, such as by frictional engagement between the inner diameter of the locking ring 326 and the outer diameter of the piston 340 (see Figure 11 A), the operator has the option of mechanically releasing the driving tool, as shown in Figure 11. As shown in Figure 11C, lowering the ball 240 to open the port 260 in the driving tool spindle will allow pressurized fluid to pass through the port 262 in the inner piston 340 to act on the outer piston 342 and cause the outer piston to be moved upward by cutting off the pin 358 (see Figure 11 A) between the inner and outer pistons. This causes the outer piston 342, which is connected to the coupling 316 with a shear pin 360, to raise the coupling 316 and disconnect it from the casing hanger.

Once the coupling 316 is released, the operator can rotate the tool to the right so that with the right-hand threads between the threaded nut 322 and the drive tool spindle 132, he can lower the nut onto the spindle 132, as shown in Figure 11C. As soon as the threaded nut 322 is lowered, the driving tool can be picked up the distance the nut 322 is moved downward, which releases the locking ring 326 and thus detaches the driving tool from the liner hanger. As shown in Figure 11D, the snap ring 326 has contracted on the reduced outer diameter 341 of the inner piston 340.

Accordingly, the driving tool 120 can be lowered to bring its coupling into engagement with the coupling on the liner hanger. The coupling 316 is pressed down the springs 318, so that the lower teeth 317 (see Figure 8C) at the upper end of the casing hanger 110 engage with corresponding teeth at the lower end of the coupling 316 to maintain rotational engagement between the driving tool and the casing hanger. As shown in Figure 1D, the upper end 332 of the coupling 316 may be splined to the outside diameter of the driving tool spindle 132, to allow relative axial movement relative thereto during the compression of the spring 318. When the coupling 316 is engaged, rotation of the working string that the casing hanger rotates. When the coupling is disengaged, rotation of the work string causes the driving tool spindle 132 to rotate to move the nut 322 relative to the threads 324, as described below.

Accordingly, Figure 11 A-C shows a release assembly for a casing hanger which enables the operator to release mechanically by upward rotation, in the event he is unable to release hydraulically. As shown in Figures 11A and 11B, the driving tool spindle 132 is surrounded by a pair of inner and outer sleeve stamps 340 and 342. The inner piston 340 has a shoulder 272 for engagement with the shoulder 274 of the driving tool spindle 132. Intermediate sealing rings above and below the ports 260 are exposed. by lowering the ball 240 on the ball seat 246 to the lower position, as shown in figure 11C. The outer sleeve piston 342 surrounds the inner piston 340 and, when in the position shown in Figure 11A, is held on the inner piston 340 by engagement with an outer shoulder 340 on the inner piston with the generally opposite shoulder on the outer piston 342. More specifically, this shoulder 348 is generally aligned with the port 262 in the inner sleeve 340 and between the upper and lower sealing rings 346 between the inner and outer sleeves. A ring 350 forms a stop shoulder at the upper end of the inner piston 340 to limit upward movement of the outer piston 342 relative to the inner piston. The inner piston 340 is stopped in an upward direction by a downward facing shoulder 344 on the driving tool.

In the initial position of the assembly shown in Figure 11A, prior to lowering the lower ball seat 246 and opening the port 260 from the bore in the driving tool, the locking ring 326 is held in a locked position between a portion of the inner piston 340 with a enlarged diameter and the internal diameter of the liner hanger 110. The nut 322 as shown in Figure 11B is positioned below the portion 341 of the reduced diameter internal piston 340, with the internal threads 352 in engagement with the threads 324 around the driving tool spindle 132. So in the previous described embodiment, the threaded nut 322 is prevented from rotating relative to the liner hanger assembly by means of spring-loaded cams 326 in vertical slots in the liner hanger 110. If the driving tool is not released hydraulically by opening the ports 260 to raise the inner piston 340 and release the lock ring 326 , the driving tool can be released mechanically with another hydraulic release operation, as discussed above.

If the operator wishes to rotate the liner during cementing, then higher fluid pressure is applied to the outer piston 342 to shear pins 360 between the outer piston 342 and the coupling 316, at which point the spring 318 will reengage the coupling. The operator can then rotate the driving tool spindle 132, which rotates the casing hanger. Additional fluid pressure can then be applied to the ball 240 to force it through the reduced thinner diameter of the seat 246.

Figure 12 packing bushing

Reference should now be made to figure 12A, where a preferred embodiment of a sealing bushing 10 is shown for sealing between a radially outwardly directed liner set adapter on the liner hanger and a radially inwardly directed driving tool spindle. The seal bushing 10 is axially retained on the drive tool spindle or tubular body 12. The compact design of the seal bushing and its limited axial movement on the drive tool body 12 enables reinsertion of the seal bushing into the liner hanger, as explained below. The upper end 14 of the body 12 includes threads 16 and a seal 18 for tight engagement with the lower end of the liner hanger release assembly in the driving tool. The lower end 20 of the body 12 includes corresponding threads 22 for connection with a sleeve extending downwardly to a ball diverter. The body or pipe piece 12 is thus part of the spindle in the driving tool, and a smooth joint is not necessary.

As shown in Figure 12A, an internal seal 24 and an external seal 28 are provided on the locking pistons 26. The seal 24, which may be a V-packing seal, consequently seals between the locking piston 26 and the body 12, and the seal 28, which may also be a V-pack seal, seals between the piston 26 and the drive adapter in the liner hanger 48. The holder 30 is threaded to the piston 26 to hold the seals 24 and 28 in place.

The retaining member 32 is threadedly connected to the top cap 34 so that the C-ring 36 is partially positioned between the top cap 34 and the piston 26. The retaining member 32 includes a shoulder 38 to bring the shoulder 40 into engagement with the body 12. The lower flange portion 33 in the holding element 32 and the upper end 27 of the piston 26 are each provided with splines, so that the spline fingers engage each other along the circumference around the sealing bushing. Flange parts 33 consequently retain the locking ring 36 axially when the piston 26 is pressed upwards. The locking ring 36 is a uniform C-shaped ring having a circumference greater than 200°, and usually less than about 350°, and which is intended for engagement with and axial locking to the liner hanger. A preferred snap ring 36 may have a circumference of from 300 to 340°, providing substantially full contact with the liner hanger along the circumference, while allowing radial expansion and contraction of the snap ring. The relaxed diameter of the locking ring 36 is substantially as shown in Figure 12A. The gasket holder 30 usually has an axial distance which is a small distance above the stop surface 44 on the body 12 for locking and unlocking the bushing.

As fluid is pumped downward through the casing hanger driving tool, the lower end of the piston 26 is subjected to high pressure, which moves the piston 26 away from the stop surface 44, as shown in Figure 12A, so that the locking surface 46 on the end of the piston 26 holds the C-ring 36 radially outwards and into locking engagement with the liner hanger for axial locking of the seal bushing to the liner hanger. The lock ring 36 thus prevents the seal bush from moving axially when pressure is increased during the cementing operation, while the seals 24 and 28 maintain fluid integrity between the driving tool and the casing hanger.

Since the top cap 34 is axially secured to the body 12, the load shoulder 44 on the top cap 34 provides a means of transmitting forces downward to the casing hanger during the run-in and cementing operation. The shoulder 44 will thus come into engagement with the shoulder 45 of the travel adapter 48 in the liner hanger when a lowering weight is applied to the liner hanger, so that the liner hanger is "hung". A bearing 46 may be provided to allow the drive tool body 12 to rotate relative to a seated seal bushing during an emergency release operation. Thus, the seal bushing can be reliably held in the locked position, with the piston 26 up and the C-ring 36 expanded, as shown in Figure 12A, when fluid pressure is applied to the seal bushing. Those skilled in the art should appreciate that engagement shoulders 38 and 40 allow the seal bushing assembly 10 to be retrieved to the surface along with the driving tool after the cementing operation. The retrievable sealing bushing 10 shown in Figure 12A thus replaces the bushing shown in Figure 1.

Use of the C-ring 36 instead of circumferentially spaced tabs allows high cementing pressure forces to be applied to the seal bushing without "pumping out" of the seal bushing. As shown in Figure 12A, an annular groove 47 in the drive adapter 48 of the liner hanger receives the snap ring 36 to lock the sealing bush to the liner hanger when fluid pressure is applied to the piston 26. Thus, without fluid pressure, the C-ring 36 retracts radially inward toward the retainer member 32 when the snap ring 36 comes in engagement with the upper surface of the groove 47 when the bushing is withdrawn from the liner hanger. When the bushing is again inserted into the liner hanger, the C-ring 36 is pulled radially back inwards, for example when the locking ring 36 engages with the load shoulder 45 on the liner hanger. Consequently, during upward movement of the driving tool relative to the liner hanger, the C-ring 36 can move radially inward when engaged, and it can also move radially inward when the seal bushing is re-stretched back into the liner hanger. The C-ring design greatly increases the reliability of the tool of the present invention, and reduces both the complexity and cost of known tools that use multiple lugs or hooks. Figure 12B shows the elements 27 of the piston 26 which are provided with splines, and the elements 33 of the retaining element 32 which are provided with splines, and the C-shape of the locking ring 36. External grooves 37 which are arranged with a mutual distance along the circumference around the C-ring 36 enables expansion and contraction of the C-ring.

The casing hanger driving tool with the sealing sleeve described here can be used on different types of casing collection operations. The sealing sleeve can be used with or without a packing set assembly and a packing element for sealing between the casing hanger and the casing. Although the sealing bushing described herein is positioned axially between the casing hanger release assembly and the retaining wedge assembly, the sealing bushing may be located elsewhere in the casing hanger driving tool.

The gasket set assembly in Figure 13

Figure 13 shows a preferred embodiment of a gasket set assembly 52, which will allow activation and sealing of the liner's top gasket. The packing set assembly is arranged on the sleeve-shaped body or tube piece 54 which is part of the spindle in the driving tool, and includes lower threads 55 for engagement with a lower tube piece in the spindle. The packing assembly 52 includes a housing 56 that holds a V-packing seal 58. Other conventional elastomeric seals may replace the V-packing 58. A flow groove 53 in the body 54 ensures fluid communication with splines or ribs 57 on the body 54, allowing the housing 56 to move axially along these splines without trapping the fluid pressure. The gasket holder 60 and the clamping ring 62 hold the V-gasket in place. A seal-setting or power-transmitting C-ring 64 is positioned on the housing 56, and includes an internal sleeve portion 66. A C-shaped release ring or detent 70 is positioned between the locking sleeve 68 and the retaining cap 72. The locking sleeve 68 engages with the sleeve portion 66 to retain C -ring 64 in the compressed position, as shown in figure 13, so that the C-ring 64 will slip out when it is released. A housing extension 74 is held with threads to the housing 56, and a bearing 80 allows the body 54 to rotate in relation to the housing 56. The bearing sleeve 78 is connected to the pipe piece 54 with a cutting element 82. The sleeve part 84 of the bearing sleeve 78 is engaged with the body 54, as shown in Figure 13, although sealing between the body 54 and the bearing sleeve 78 is not necessary. The sealing element 86 on the body 54 is discussed below.

The first time the packing set assembly is moved out of the polished bore holder 90 (which is the same as the holder 130 discussed in connection with the driving tool of Figures 1-9), the release ring 70, which was positioned inside the polished bore holder, will slip a radially outward facing position, as shown in Figure 13, due to the natural bias of the C-shaped release ring. When the gasket set assembly is then reinserted into the polished bore holder, the release ring 70 will engage the top of the polished bore holder 90, as shown in Figure 13, and the gasket setting C-ring 64 is positioned inside the polished bore holder drilling. When lowering force is applied, the housing 56 will move downwards relative to the locking sleeve 68, and the release ring 70 will move radially inwards due to camming. Accordingly, the entire packing set assembly can be lowered to flatten on a lower portion of the travel adapter prior to initiation of the cementing operation. The next time the packing set assembly is lifted out of the polished bore holder, the radially outward biasing force from the C-ring 64 will cause the C-ring to engage the top of the polished bore holder in the liner hanger. More specifically, the shoulder 65 will engage the top of the polished bore holder 90, since the natural or released diameter of the C-ring 64 approaches the outside diameter of the holder 90. The flat surface 65 of the C-ring 64 thus engages with the upper surface of the holder 90 for the liner extension. In this position, the conical surface 73 at the lower end of the retainer cap 72 engages the corresponding conical surface 63 on the upper end of the C-ring 64, and the set weight consequently results in a radially outward force applied to the C-ring 64 to effectively locking the C-ring in the weight transfer position, so that the C-ring will not prematurely slip radially inward before the gasket is set. As soon as the C-ring 64 is set against the liner hanger, the body 54 can be moved downwards relative to the housing 56, which cuts off the elements 82.

The packing set assembly 52 has high reliability, since a significant downward set weight can be transferred through the C-ring 64 to the casing extension holder, and since the mechanical setting pressure is assisted by fluid pressure between the inside diameter of the casing and the outside diameter of the driving tool or drill pipe. After elements 82 are cut across and the body 54 moves downwards relative to the housing 56, the radially inwardly directed surface of the projection 88 on the housing 56 is held on the surface 90 of the larger diameter pipe piece 54, as packing elements 86 seal against the housing 56. A collar or similar stop on body 54 engages the top of bearing sleeve 78 to limit downward movement of the spindle. The seal 58 remains sealed to the liner extension holder. After the packing set assembly 52 is set, the increase in pressure in the annulus between the casing and the driving tool allows the housing 56 to act as a piston that is pushed down in response to the annulus pressure, providing increased downward force to reliably seat the casing hanger packing as the packing is pushed radially outward when it is pushed down the packing set cone.

A complete driving procedure for driving, setting and releasing the liner-hanger system according to the present invention will now be discussed. The setting tool is conventionally attached to the lower end of a work string, typically a drill pipe, and is releasably connected to a casing hanger, which is attached to the top of the casing. The work string lowers the casing into the borehole to a position above the lower end of the previously set casing or casing. With the casing at a desired depth, the wellbore fluids are circulated "from the bottom up" to clean the hole. A setter ball may initially be dropped from a cementing manifold at the surface. The ball can either free fall or it can be pumped to the liner hanger retaining wedge seating assembly, where the ball will rest on the expandable ball seat. Fluid pressure can then be increased to a selected value, for example 3.45 MPa, which exerts a force on the shear screws acting between the ball seat and the spindle in the set assembly for the retaining wedge. When this force exceeds design limits, the screws will shear to release the ball and seat to a position that exposes hydraulic ports in the spindle. Continued pumping of fluid will then push the ball through the seat, making it possible to pump the ball to the other ball seat in the release tool.

Fluid pressure is then increased to cut over screws between the piston and the spindle in the liner hanger kit assembly. The piston, which was subjected to pressure within the drive string when the ball was first released, is responsive to fluid pressure and moves upward, forcing the retaining wedges to release and contact the casing. The load on the lining can then be relaxed on the set retaining wedges. As soon as the retaining wedges bear the weight of the stool, the liner is "hung up".

With the load on the liner relaxed on the hanger's retaining wedges, additional slack or "set-down weight" can be applied to the hanger to check for any movement of the hanger. The lowering weight will be transferred through the driving tool to the casing hanger, which is carried by the casing hanger's holding wedges. This lowering weight can, for example, be transferred through the driving tool's spindle to the sealing bushing, and then from the load shoulder on the sealing bushing to the liner hanger. A ball can then be landed, and the ball seat moved to expose fluid ports. Pressure can then be increased to a selected value, for example 8.27 MPa, if transmitted through ports in the spindle in the liner hanger release assembly. This increased pressure cuts across screws on the primary piston, which moves the piston to allow the liner hanger release ring to contract and release the drive ring from the liner hanger. At this stage, the casing trailer driving tool is released from the casing trailer. Since the clutch that wedges the driving tool to the liner hanger is attached to the release piston with shear pins, it is moved from the engaged position to a disengaged position as the piston moves upward to release the driving ring. The driving tool is preferably released by means of the increase in fluid pressure acting on the primary piston. If the driving tool is still engaged with the casing hanger after upward pressurization of the primary release piston, the operator can continue to pressurize the drill string to the maximum allowable pressure, to check for release in small pressure increments up to the shear pressure of the secondary piston. If the primary piston does not release the driving tool from the liner hanger, continued pressure will shear the secondary piston from the primary piston and the secondary piston will move axially up to release the coupling in the driving tool from the coupling on the liner hanger. With the clutch released, the driving tool can be rotated 5-6 turns to the right to disengage the driving tool from the liner hanger.

At this stage, the operator can pick up the driving string and note the loss of casing weight on a ring weight indicator, indicating that the driving tool has been released from the casing hanger. This pick-up operation will also release the sealing bushing from the liner hanger travel adapter or liner extension holder. As previously stated, the sealing bushing is designed to be reinserted, so that the operator can pull the driving tool and sealing bushing upwards as desired to check that the driving tool has been released from the liner hanger. After it has been confirmed that the driving tool has been released, the sealing bushing will be inserted again when the driving tool is loosened back into the liner hanger. When there is pressure below the sealing bushing, the bushing is locked to the liner hanger.

A selected fluid pressure, for example 17.24 MPa, can then be used to shear the secondary piston from the coupling to enable the coupling to reengage the liner hanger. Once the liner hanger driving tool is freed from the liner, pressure can be applied to the ball and seat. At a predetermined pressure, for example 20.68 MPa, the ball will pass through the port isolation ball seat, expanding the diameter of the seat. The ball is forced through the seat to permanently deform the ball seat. The drop in pressure and the return of fluid circulation will then indicate that the ball's passage through the ball seat has been successful. The ball is then allowed to fall freely, or it is pumped to the ball diverter.

The spacer and cement fluids can be mixed while circulating fluids for cement displacement. Once the cement has been pumped, the pump down plug can be released from the surface, so that a barrier is formed between the previously displaced cement and the displacement fluid. A calculated amount of displacement fluid can therefore be used to pump the pump down plug to the casing scraper plug. When the pump-down plug comes close to the driving tool, the fluid pressure can be reduced, for example to approx. 3.45 MPa, and this pressure will increase when the pump down plug locks into the casing scraper plug. Once the pump-down plug is locked into the casing scraper plug, the work string can be pressurized and after a selected period of time, the casing scraper plug and pump-down plug will be freed from the plug holder pipe piece. Increased fluid pressure consequently moves a piston to release a ring, which releases the casing scraper plug from the plug holder tube. The piston inside the plug holder tube piece acts on a fluid of a known viscosity, and by means of fluid flow through a hole of a predetermined size, it will take a predetermined period of time to release the casing scraper plug. This time can be used by the operator for a specific calculation of volumes of displacement fluid. A calculated amount of displacement fluid will consequently push the cement to the desired height in the annulus between the casing and the casing. Fluid will therefore be pumped until the set of liner scraper plug and pump-down plug is locked into the landing collar, at which point the pressure can be increased to, for example, 6.90 MPa above the circulation pressure to complete plug locking and check that the seals between the plugs and the landing collar are durable. Pressure can then be drained off, and it can be checked for backflow to ensure that the float equipment maintains pressure.

It should be noted that the packing set assembly incorporates an unlocking feature that allows the packing set assembly to be withdrawn from the liner hanger's liner extension container once without unlocking the packing setting ring. Upon reinsertion of the assembly into the liner extension holder, the gasket setting ring is activated, and is ready to expand the second time the gasket set assembly is withdrawn from the liner extension holder. Accordingly, the driving tool can be retracted until the packing set assembly is removed from the liner extension holder, allowing the release ring to expand and engage the top of the liner extension holder. Slack and the drive string causes the release ring to contract, allowing it to re-enter the holder for the liner extension, and moves a locking sleeve out of contact with the ring for setting the gasket. Since the C-ring for setting the gasket is compressed but now released from the locking sleeve, the gasket set assembly is ready to be activated the next time it is pulled from the liner extension holder. Accordingly, the driving tool can be raised sufficiently to expose the gasket set assembly, then lowering weight is used to seat the gasket element.

As soon as the packing setting ring is in its extended position, drill pipe weight can be released on top of the casing extension holder. This downward force through the packing set assembly and into the liner extension holder initiates the packing setting sequence. This action will cut across screws and allow the set load to be transferred to the packing element. As a load increases, the outer diameter of the packing element will expand as it moves down the cone, pushing the expanding packing element out into engagement with the casing.

With the packing element in engagement with the casing, the rig stoppers can be closed around the drill pipe, creating a pressure vessel between the casing and the driving tool and between the packing element and the seals in the surface stopper. Since it is known how much load is required to correctly seat the packing element, a known fluid pressure can be applied to the annulus to cause the holder for the liner extension to move downward, which applies a greater and known load to the packing element. A desired settling load on the packing element can therefore be applied through a combination of settling weight and fluid pressure.

After pulling the setter to a predetermined position above the top of the casing, fluid can be circulated through the drill string to circulate any excess cement to the surface, reducing the need for drilling. Once excess cement has been circulated out of the well, the operator can withdraw the setting tool from the well. Once at the surface, the tool can be checked for damage and serviced.

The tools discussed above function as an assembly for a specific application, i.e. for driving and releasing the casing hanger, the cementing of the casing into the wellbore and the setting of the packing element. One can drive a liner trailer without a packing element, and the driving tool will therefore not require the packing kit assembly. Furthermore, a packing element can be driven into a wellbore without a casing hanger retaining wedge mechanism, and the assembly for releasing the retaining wedge will therefore not be necessary in the driving tool. Various combinations of the described tools can be assembled to run a variety of downhole tools.

Although preferred embodiments of the present invention have been shown in detail, it is obvious that modifications and adaptations of the preferred embodiments will be apparent to those skilled in the art. However, it should be clearly understood that such modifications and adaptations are within the idea and framework of the present invention, as indicated in the following claims.

Claims (21)

1. A downhole tool for use in an underground well to seal against a generally cylindrical internal surface of a pipe or other downhole tool, the tool comprising: a transport pipe for positioning the tool at a selected location below the surface of the well, and an annular seal assembly arranged around the transport pipe, characterized in that a wedge ring (D14) has a substantially conical outer surface which is configured to radially expand the annular seal assembly upon axial movement of the annular seal assembly relative to the wedge ring (D14), so that the seal assembly expands from its run-in position to its extended sealing position, wherein the sealing assembly is in sealing engagement with the generally cylindrical interior surface, and that the annular sealing assembly has a reduced diameter run-in position and an extended sealing position, and includes a metal framework having a row overall inner annular base (D18) and a plurality of metal ribs (D20) each extending radially outwardly from the base (D18), the metal framework including an upper downwardly angled primary seal metal rib (D32) for sealing pressure below the seal assembly, a lower upwardly angled primary seal metal rib ( D34) for sealing pressure above the seal assembly, a primary elastomeric seal (D24) in a cavity radially outside the base (D18) and axially between the upper primary seal metal rib (D32) and the lower primary seal metal rib (D34), an upper downward-angled secondary seal metal rib ( D30) at an axial distance above the upper primary sealing metal rib (D32), and a lower upwardly angled secondary sealing metal rib (D36) at an axial distance below the lower primary sealing metal rib (D34). 2. Downhole tool as set forth in claim 1, further comprising: an upper biasing member (D22) between the upper primary sealing metal rib (D32) and the upper secondary sealing metal rib (D30) for exerting a downward biasing force on the upper primary sealing metal rib (D32) in response of high fluid pressure below the seal assembly, and a lower biasing member (D26) spaced between the lower primary seal metal rib (D34) and the lower secondary seal metal rib (D36) to exert an upward force on the lower primary seal metal rib (D34) which response to high fluid pressure across the seal assembly. 3. A downhole tool as set forth in claim 1, wherein an outer surface of each of the upper primary sealing metal rib (D32), the lower primary sealing metal rib (D34), the upper secondary sealing metal rib (D30) and the lower secondary metal rib (D36) is configured to form an annular metal-to-metal seal with a generally cylindrical inner surface. 4. A downhole tool as set forth in claim 1, wherein the transport tube (D16) holds the key ring (D14) generally stationary, while the seal assembly moves axially relative to the stationary key ring (D14). 5. Downhole tool as set forth in claim 1, wherein the transport pipe (D16) holds the seal assembly generally stationary, while the key ring (D14) moves axially relative to the stationary seal assembly. 6. A downhole tool as set forth in claim 1, wherein the sealing assembly seals against an internal surface of a downhole pipe. 7. A downhole tool as set forth in claim 1, wherein the primary elastomeric seal (D24) includes a cavity region (D25) when the primary elastomeric seal (D24) is moved into sealing engagement with the cylindrical surface, such that the primary elastomeric seal (D24) can be thermally expanded to fill at least a portion of the cavity region (D25) in response to elevated downhole temperatures. 8. A downhole tool as set forth in claim 1, wherein each of the downwardly angled primary seal metal rib (D32) and the upwardly angled primary seal metal rib (D34), when in the run-in position, is inclined at an angle of at least 15° to a plane that is perpendicular on a central axis for the cylindrical inner surface. 9. A downhole tool as set forth in claim 8, wherein each of the downwardly angled secondary seal metal rib (D30) and the upwardly angled secondary seal metal rib (D36), when in the run-in position, is inclined at an angle of at least 15° to the plane perpendicular to the central axis of the cylindrical inner surface. 10. Downhole tool as set forth in claim 1, further comprising: one or more protrusions (D40) with a mutually axial distance on a radially inner surface of the annular base (D18) of the metal framework, each of which is for sealing metal-to- metal engagement with the conical outer surface of the key ring (D14). 11. A downhole tool as set forth in claim 10, further comprising: one or more annular elastomeric sealing elements (D48) for sealing between the base (D18) of the metal framework and the conical outer surface of the wedge ring (D14). 12. A downhole tool as set forth in claim 10, further comprising: one or more annular metal protrusions (D42) on one of an outer surface of the transport tube (D16) and an inner surface of the key ring (D14) to form a metal-to-metal -seal between the wedge ring (D14) and the transport tube (D16). 13. Downhole tool as set forth in claim 12, further comprising: one or more annular elastomeric sealing elements (D48) carried by one of the conical wedge ring (D14) and the transport tube (D16) to form an elastomeric seal between the transport tube (D16) and the wedge ring (D14). 14. Method for forming a downhole seal against a generally cylindrical internal surface of a pipe or other downhole tool, which method is characterized by the following steps: providing an annular seal assembly arranged around a transport pipe (D16), the seal assembly having a run-in position of reduced diameter and an extended position, wherein the seal assembly includes a metal framework having a radially inwardly directed annular base (D18) and a plurality of metal ribs (D20) each extending radially outwardly from the base (D18), wherein the metal framework includes an upper downwardly angled primary seal metal rib (D32) for sealing pressure below the seal assembly, a lower upwardly angled primary seal metal rib (D34) for sealing pressure above the seal assembly, a primary elastomeric seal (D24) in a cavity radially outside the base (D18) and axially between the upper primary seal metal rib (D32) and the lower primary sealing metal rib (D34), an upper downwardly angled secondary sealing metal rib (D30) at an axial distance above the upper primary sealing metal rib (D32), and a lower upwardly angled secondary sealing metal rib (D36) at an axial distance below the lower primary sealing metal ribs (D34); providing a key ring (D14) having a substantially conical outer surface; and axial movement of the annular seal assembly relative to the key ring (D14), such that the seal assembly expands from its run-in position to its extended position, where the seal assembly is in sealing engagement with the generally cylindrical inner surface. 15. Method as set forth in claim 14, further comprising the following step: providing an upper biasing member (D22) between the upper primary sealing metal rib (D32) and the upper secondary sealing metal rib (D30) for exerting a downward biasing force on the upper primary sealing metal rib ( D32) in response to high fluid pressure below the seal assembly; and providing a lower bias member (D26) spaced between the lower primary seal metal rib (D34) and the lower secondary seal metal rib (D36) for exerting an upward force on the lower primary seal metal rib (D34) in response to high fluid pressure above the seal assembly. 16. Method as set forth in claim 14 or 15, wherein an outer surface of each of the upper primary sealing metal rib (D32), the lower primary sealing metal rib (D34), the upper secondary sealing metal rib (D30) and the lower secondary sealing metal rib (D36), is configured to form an annular metal-to-metal seal against a generally cylindrical interior surface. 17. Method as stated in claim 14 or 15, where the wedge ring (D14) is generally stationary, while the sealing assembly moves axially in relation to the stationary wedge ring (D14). 18. Method as stated in claim 17, where a lowering weight which is transferred to the sealing assembly through the transport tube (D16) moves the sealing assembly axially in relation to the stationary wedge ring (D14). 19. A method as set forth in claim 14 or 15, further comprising: providing one or more protrusions (D40), with a mutually axial distance, on a radially inner surface of the annular base (D18) of the metal framework, each of which is for sealing metal-to-metal engagement with the conical outer surface of the key ring (D14). 20. Method as set forth in claim 19, further comprising: providing one or more annular elastomeric sealing elements (D48) for sealing between the base (D18) of the metal framework and the conical outer surface of the wedge ring (D14). 21. Method as set forth in claim 19, further comprising: providing one or more annular metal protrusions (D42) on one of an outer surface of the transport tube (D16) and an inner surface of the wedge ring (D14) to form a metal counter - metal seal between the wedge ring (D14) and the transport tube (D16).