NO313563B1 - Inflatable liner packing and method of using the liner packing in a lined borehole - Google Patents

Description

This invention relates generally to an inflatable packing for use in well bores, and in particular to an inflatable packing having a hybrid elastomer element construction which provides sealing capability and anchoring support for use in lined holes. More specifically, but not by way of limitation, this invention relates to an inflatable pack where the sealing element acts independently of the anchoring element.

Production for oil and gas reserves has brought the industry to remote locations on land and at sea. Moreover, hydrocarbon production in remote locations has become "the norm". For example production in deviant and multi-sided well bores has now become very common. Consequently, new and peculiar problems have arisen, particularly in the completion phases. Historically, the costs of developing and maintaining hydrocarbon production have been very high in remote locations. And as production continues in these remote areas, costs have also risen due to the special problems that arise when producing oil and gas in hard-to-reach areas and/or producing hydrocarbons through many zones. Consequently, production techniques in these remote areas require creative solutions to unique problems that do not occur in conventional well drilling.

As one skilled in the industry will understand, hydrocarbon production rates directly affect the profitability of a well drilling. During the productive life of these wells, the well must be maintained so that hydrocarbon production and withdrawal is carried out in the most efficient way and at maximum capacity. Well operators want maximum recovery from productive zones, and to maximize production, proper testing, completion and management of the well is necessary.

When constructing a wellbore, four factors enter into any wellbore design phase: (1) the completion method best suited for a particular well, (2) the required fluid flow paths, (3) the completion system selected to bring the fluids to the wellhead , and (4) the completion costs in relation to the production potential. The completion method chosen is an important element, and this invention relates to proper zone isolation and the most effective and efficient means of accomplishing this. More specifically, it applies to zone isolation in lined wellbores. As would be expected in the industry today, multi-sided wellbores require lined wellbores for efficient drainage through multiple zones and/or reservoirs. In addition, many operations that are conventionally performed at the surface are now performed downhole. Consequently, operations in lined holes have become a necessity for many well drilling completions.

Thus, different tools are required for each of two completion methods: (1) completion of unlined holes and (2) completions of lined

or perforated holes. In an unlined wellbore completion, a relatively large inner diameter is encountered and the open hole shape is always skewed. The open hole is irregular (not completely cylindrical) as the hole is drilled into the soil formation. Therefore, the outer casing packing becomes an ideally suited tool for isolating zones during production or cementing operations due to its high inflation and sealing capacity. In such completion methods, the outer casing seal is part of the casing string and forms a seal and an anchor against the wall of the lined hole when an elastomer element in the inflatable tool is inflated. The anchorage in the lined hole is formed when the gasket's elastomer element is inflated and follows the shape of the lined hole, thereby preventing axial movement in the wellbore. The flexible elastomer elements' unusual expansion and sealing properties mean that these tools can handle conditions that would be impossible for conventional packing tools. When the packing element is inflated, it conforms to almost any irregularity in the lined completed well bores. Although no packing element can withstand all conditions, the inflatable packing elements have been found to be very tolerant of unlined completions.

On the other hand, unlined wellbores encounter a different set of criteria and problems for completing and overhauling a wellbore. A problem that has recently been encountered is to isolate a special zone that is located under completion equipment that is already placed in the wellbore. Such zones are normally very difficult to isolate, as only limited access or penetration in existing well drilling equipment is available to the underlying zone. Conventionally, such completion equipment has provided relatively narrow access to an underlying section. In such wellbores, there is therefore a need for zone isolation gaskets that can be installed under any existing equipment. It is clear that conventional packing equipment cannot be used in such well drilling, since it largely includes equipment with a larger diameter. Such equipment cannot therefore pass through the narrowed, accessible access.

Also, conventional pump service and production injection packing techniques are also inadequate in these applications, as they do not and cannot provide adequate sealing capability in larger diameter casing using a blow-up medium operating under a phase change condition. Examples of a phase change medium include cement or epoxy. Phase change of a swelling medium occurs after the swelling medium solidifies. A blowing medium solidifies when it maintains a permanent phase. E.g. a phase change occurs when the cement or epoxy hardens. After such hardening, however, another phase change takes place, so that the cement or epoxy shrinks somewhat.

In these limited access wellbores, conventional production injection packings and pump service techniques using phase change inflation media cannot be inflated to reach the outside diameter of the lined wellbore (wall) for effective sealing of a zone, for reasons that will be discussed below. There is thus a great need for a new zone isolation tool for isolating certain zones in the lined wellbore.

One concept is to use conventional external casing packing techniques, which are now used in large diameter open hole completions, for anchoring and sealing (isolation) of a particular zone, particularly as they have a relatively small "through" outer diameter and thus are able to pass through the limited access of existing equipment. Examples of these conventional packing techniques include "production injection packers" (English: production injection packers) and "pump service packs" (English: thru-tubing packers). However, even with improved elastomer technology, these conventional packings have proven to be relatively ineffective in applications requiring inflation in a lined wellbore with a phase change medium.

In order to understand why this is so, it is first necessary to review the construction of these (inflatable) seals. Inflatable gaskets have long used a construction that includes the use of various elastomeric elements combined with metal rods or ribs as inflatable elements. Such inflatable tools comprise an elastomeric sleeve member which is mounted around a tubular body. To protect the elastomer sleeve member, a number of elastic splines or ribs are circumferentially connected to the elastomer sleeve member. The middle part of the elastomer sleeve is further surrounded by, and can be connected to, an outer ring-shaped elastomer sleeve element or "cover" of considerable thickness. These known external casing seals thus use a "full coverage" construction. Upper and lower assemblies connect the ends of the packing element sleeves to the central pipe section in a secure and sealing manner. A phase change inflation medium under pressure is sent to the pipe part and then through radial channels on this to the interior of the elastomer sleeve element for inflation of the packing elements, which thereby lie radially sealing against the wellbore wall.

A conventional external casing packing (with or without a phase change medium) is ineffective in lined wellbores because the contour of the casing is sufficiently cylindrical and consequently prevents a satisfactory anchorage between the external casing packing and the casing wall. One reason why a satisfactory anchoring is not obtained is that the coefficient of friction between the elastomer element and the steel casing in a moist medium environment is very low. The pressure difference in the wellbore between places above and below the packing will thus force it to move.

Moreover, the conventional external casing packing is designed to provide benefits only in terms of anti-squeezing. E.g. the ribs are placed only on the elastomer element's attached end (fixing assemblies) and thus only provide limited anchoring advantages. As such, the elastomeric member tends to "roll over" or overlap the attached end when a sufficient axial force is applied to the ribs. On the other hand, if a modification is carried out and the elastomer elements are fully provided with ribs, another disadvantage arises. In the latter case, an elastomer element with full-length ribs, in combination with the elastomer element, is a gasket with a much larger outer diameter. Therefore, a new construction requires a thinner casing to overcome the limited access available through existing downhole equipment.

However, when a thinner casing is introduced in the new construction, another significant problem arises when phase change inflation media is used to inflate the inflatable packing in the lined wellbore. This new problem occurs when the inflation medium changes phases (hardens and contracts) and this leads to a loss of available radial force against the casing wall. A person skilled in the art will understand that a relatively thicker elastomer element will normally compensate for this difference in radial force. However, when a thinner element is used, the radial force loss cannot be compensated or "evened out". The degree of compensation that an elastomer element can "compensate" is thus a function of its thickness. In other words, the elastomer element's energy storage capacity available to sealing systems is a function of its thickness. When a relatively thicker elastomer element is used, there will thus be a relatively greater energy storage potential. This greater, stored energy potential is available to act in the event of sealing against the wall of the lined wellbore, thereby compensating for any shrinkage in the inflation medium. In a lined wellbore, a relatively thick elastomer element is therefore necessary to achieve satisfactory sealing performance. There is thus a need for a new zone isolation tool that is not affected by all these limitations.

There are various known external casing packing devices, but none provide a solution for isolating a zone under existing equipment that has limited access in the vicinity of a cased wellbore. E.g. US Patent No. 5,143,154 discloses an inflatable packing element for an inflatable packing with a special rib connection construction to the mandrel.

US Patent No. 5,101,908 relates to an inflatable packing device and a sealing method. The device has upper and lower elastomeric members surrounding a tubular mandrel. However, this device is also not aimed at the problems discussed here.

US patent no. 4,869,325 shows a method and device for setting, loosening and withdrawing a packing or a bridge plug from a well, where the packing can pass through small diameter pipes. Nor is this publication aimed at the particular problems discussed here.

There is therefore a need for a device and method for an inflatable tool that provides a solution for isolating a zone through completion equipment with limited access in a lined wellbore, which provides both sealing and anchoring.

This need is satisfied by an inflatable downhole seal as well as a method for sealing a lined borehole, as stated in the subsequent patent claims.

The present invention is directed to a new and improved wellbore packing device for use when isolating zones in a wellbore and a method for using the packing device in a lined hole. The present invention is directed to a new and improved inflatable or external casing pack (UFP) for use in lined wellbores. A hybrid inflatable packing element construction in a UFP is shown which has in a single unit anchoring and sealing sections for use in lined wellbores using a phase change inflation medium such as cement or epoxy or the like. The present invention overcomes the limitations of existing prior UFPs as these known UFPs are unable to provide both sealing and anchor packing elements in a single unitary construction in well bores of limited size and access.

The inflatable elements comprise a sealing section using a discontinuous, reinforced elastomeric element with anti-extrusion ribs at its ends. When the elastomer element is filled with the inflatable medium, a radial frictional force will bring the elastomer element into sealing contact with the casing wall. There is also an anchoring section which uses a continuous ribbed elastomer bellows element. The steel ribs on the surface of the elastomer element are in metallic contact with the casing wall when the inflation medium exerts a radial frictional force. Any trapped well drilling fluid between the sections escapes via the path between the ribs. A procedure for using the hybrid UFP is also shown. More specifically, a method for using the hybrid inflatable pack in a lined hole environment with a phase change inflation medium is shown.

In the following, the invention will be explained in more detail with reference to the drawing where: Fig. 1A is a combination of a section and a perspective view of a known external casing seal, and shows an inflatable element of the continuous ribbed type, Fig. 1B is a combination of a section and a perspective view of a known external casing packing, showing an inflatable element of a non-continuous type, Fig. 2 is a section through a hybrid external casing packing according to the preferred embodiment, showing a sealing section with an inflatable element and an anchoring section with an inflatable element, as it would look in the run-in-operations phase, and

Fig. 3 is a section through a hybrid external casing seal according to the preferred embodiment, showing a sealing section with an inflatable element and an anchoring section with an inflatable element, as it would appear in the inflation-operating phase.

The present invention can best be described and understood in connection with its application and known constructions of external casing seals (see fig. 1A and 1B).

Pump service overhaul and completion techniques have significant advantages, particularly because they provide isolation in restricted access zones. Certain operating and construction limitations still occur with such techniques. For example pump service techniques are dimensioned smaller and therefore have limited application in well bores with larger diameters. In drilled wellbores, significant pressure differences occur in the wellbore when flowing wellbore fluids are present, and as a result unintentional displacement of settable or inflatable tools occurs. Flow in one direction or the other usually occurs in a wellbore when a producing zone is in hydraulic connection with a consumer zone and such interzone "crossflow" can occur in a wellbore, regardless of whether flow is directed towards the surface.

Inflatable well drilling tools can operate in several modes, such as the "run-in" mode of operation, an "expansion or inflation" mode of operation, and a "set" mode of operation. The inflatable tool is held in an insertion state during insertion of the tool into the wellbore with a reduced radial dimension, so that the tool can pass through limited access areas. Once the inflatable tool has passed the narrowed access area and is located in a desired area, inflation pressure is applied to the tool with an inflation medium to force it in a radially outward direction in an inflated state. Such radial expansion will, at least partially, prevent the flow of wellbore fluid in the lined wellbore.

The obstruction created by the inflatable tool often creates a pressure difference across the inflatable tool. Typically this occurs when the inflatable tool is placed over a producing zone. Wellbore fluids, such as oil, gas and water, will continue to flow in the wellbore due to a pressure difference between the formation and the wellbore, as well as a pressure difference between zones. Wellbore fluid flow can thus force the inflatable tool to move, rotate, twist and/or slide, particularly in wet environments in a lined wellbore. The inadvertent, and often harmful, displacement of the inflatable tool often occurs because the currently available known pump service techniques do not provide satisfactory anchoring means. Such anchoring means are traditionally found in tools with "grabbing teeth", such as those found in the more conventional metallic packing devices. Thus, e.g. coiled-tube suspended inflatable tools do not have adequate anchoring means to prevent displacement and are not often used in such applications. The mechanical seals are clearly simply not suitable for use where there is limited access.

Also, if a pressure differential is created across the inflatable tool, the pressure differential may act to disconnect the inflatable tool from the suspension tool or means. E.g. in a cable line-suspended tool, a large pressure difference can thus act to detach the well drilling tool from the cable. Alternatively, a high pressure sensitive or tension sensitive disconnect device used in conjunction with a coiled tubing or production string operation can readily activate and disconnect the packing device from the coiled tubing or production string.

With regard to known constructions, such as inflatable packing devices for unlined holes, an outer lining packing (UFP) 20 of the continuous ribbed type, shown in fig. 1A and a UFP of the non-continuous ribbed type is shown in FIG. 1B. The continuous rib type UFP 20 forms a long dynamic hydromechanical seal that utilizes an elastomeric element 14 combined with continuous stainless steel ribs 16 to protect the inflatable elements 12, 14 from the enormous multidimensional stresses that exist in non-uniform well bores. The steel ribs 16 are used to provide strength, flexibility and long-term reliability against tearing of the inner elastomer element 12. These inflatable elements 12, 14 are mounted on the mandrel or the inflatable tool 10 using attachment units 18 on each end. This UFP 20 is particularly useful for short or long sealing applications that require secure seals in highly differential, irregular, or elliptical, unlined well bores. The continuously finned UFP uses various inflation media, including water, drilling fluids and/or cement.

The non-continuous ribbed UFP 30 is, on the other hand, used as an additional gasket for the continuous ribbed UFP 20 in special applications that require longer sealing elements and use cement, mud, fluid or epoxy as inflation medium. It may include a valve collar 38 which exhibits an increased inflation flow capacity and a flow control which reduces erosion of the valve seats 35, seals (not shown) and the inflation channel 39. The ribs 31 are located only on the attached ends 36 of the elastomeric member and thus provide only limited anchoring advantages . As previously mentioned, the ribs 31 provide strength at the end hole area 36 and also where the ribs abut 33 against the wellbore wall 11. The non-reinforced middle or center part creates a flexible expansion area that easily molds to irregularities 12 in the lined hole , thereby providing a satisfactory seal.

When completing an unlined well bore as shown in fig. 1, a relatively large diameter is encountered in the well bore, and the open hole wall 11 is always slanted or irregular 12 (not perfectly cylindrical) as the hole is drilled in the soil formation 13. Therefore, the conventional UFP, as described above, became an ideally suited well drilling tool for isolating zones in such environments during production or overhaul operations, due to the inflatable elastomer element's great inflating ability. In such operations in an unlined borehole, the UFP forms part of the casing string and forms a "sealing" anchorage against the irregular wall 12 in the unlined (open) borehole or well bore.

The "sealing" anchorage in the lined wellbore is formed when the gasket's elastomer element 14 is inflated and assumes the shape of the open hole 12, thereby preventing axial movement in the wellbore. Axial movement is prevented because multidimensional forces act radially against the wellbore wall 11. Moreover, these known UFPs use a "full coverage" elastomer element construction. A full coverage construction encloses the full length of the inner elastomer element 12, 29 with an outer elastomer element 14, 32. Alternatively, the non-continuous metal ribs 31 (Fig. 1B) can be produced inside the elastomer cover 32 and connected to the end sleeves 36, thereby forming reinforcements against extortion when the element 32 is inflated. The flexible elastomer element's unusual expansion capability thus allows the use of these UFP tools under conditions that would otherwise be impossible for conventional (mechanical) packing tools.

As previously mentioned, however, these known UFPs 20, 30 have limited use in operations in open holes. For applications in lined well bores, these known UFPs 20, 30 are inappropriate, because the contour 55 of the casing 54 is sufficiently cylindrical. The uniform cylindrical shape of the casing wall 54 prevents a proper or suitable anchoring between a conventional UFP 20, 30 and the casing wall 54.

One reason why proper anchoring is not achieved using the conventional UFPs 20, 30 is that the coefficient of friction between the elastomer element 14, 32 and the steel casing 54 in a wetted medium is very low. The pressure difference in the wellbore between places above and below the packing therefore leads to movement or displacement of the packing, which usually leads to major damage to the well, particularly loss of production and consequent financial damage.

Also, the conventional, non-continuous, ribbed type UFP 30 is constructed so that the ribs 31 are only located on the attached ends 36 of the elastomeric member 32, and consequently provide only limited anchoring and/or anti-pressing action. As such, the elastomeric member 32 tends to "roll over" or overlap the attached end 36 near the end sleeves 33 when a sufficient axial force is applied to the ribs 30. On the other hand, if a modification is made so that the elastomeric member 32 is fully ribbed, another problem. An elastomer element 14 provided with ribs over its entire length, as shown in fig. 1A, becomes a much larger diameter inflatable element 14 and therefore requires a thinner elastomer cover 14, so that the UFP 20 can pass through existing equipment (not shown), with only limited or constricted access to the underlying zone.

When a thinner elastomer cover 14 is used, however, a significant disadvantage occurs with regard to satisfactory seal protection. It should therefore be understood that the inflatable tool is used for lined well bores, using a phase change medium for inflating the element. Thus, when the phase change inflation medium hardens, a loss of available radial force against the casing wall occurs when the inflation medium changes phase, i.e. the inflation medium contracts or shrinks as it hardens, leading to a loss of available radial force or energy against the wellbore wall. It will be clear to a person skilled in the art that the elastomer element normally compensates for the difference in radial force loss through the elasticity of a relatively thick elastomer cover, i.e. the relatively thick elastomer cover stores a certain amount of radial force energy during the expansion of the inflatable medium and releases this stored energy to compensate for any phase changes in the inflation medium, such as shrinkage or contraction. The amount of energy storage available to compensate for shrink force loss is clearly a function of the elastomer's thickness. In a lined wellbore, it is therefore necessary to have a relatively thick elastomer cover to achieve the correct sealing ability. The necessity of this thicker cover construction, however, comes into conflict with the fact that there is only limited access through the downhole equipment in lined wellbores. There is thus a need for a new, inflatable zone isolation tool that overcomes all these limitations.

In fig. 2 and 3, there is shown a new, inflatable tool construction which overcomes many of the limitations mentioned above. In the preferred embodiment, the new inflatable tool construction uses a sectional element construction to provide two of the most important requirements for use in cased wellbore applications using phase change inflation media: (1) sealing capability, and (2) anchoring capability.

In the preferred embodiment, the sealing layer 40 is provided with a full-covering elastomer construction 45 which has a relatively large thickness 41, while the anchoring layer 42 is provided with an exposed, continuous rib-equipped construction 62, i.e. provided with ribs over its entire length, which form a metallic structure 63 against the casing wall 54. The full-coverage elastomer construction 45 of the sealing element section 40 provides the necessary elastomer thickness 41 to compensate for phase change losses in radial sealing force. On the other hand, the fully exposed rib element section 42 provides a metallic attachment 63 between the anchoring element 62 and the casing wall 54, thereby creating sufficient anchoring force in the lined wellbore.

The two sections 40, 42 are separated by end sleeves 44 which connect each element 40, 42 to the inflatable tool's tubular main part 58. The method of connecting each element 40, 42 is known in the art and is shown in US patent no. 5 143 154, to which reference is hereby made. In addition, the features of the valve device (not shown) for correct inflation of the elastomer elements are known in the art. See e.g. US Patent No. 4,708,208, US Patent No. 4,805,699 and US Patent Application No. 138,197, to which reference is hereby made. The end sleeves 44 are mechanically connected to the pipe part 58 using conventional techniques such as threaded sleeves (not shown).

In fig. 2, an embodiment of the invention, there is shown a hybrid inflatable tool in the lowered state. The sealing section 40 comprises elastomer element 48 supported by non-continuous, extrusion-preventing ribs 46. The sealing section 40 is preferably located in a direction away from the transport device (not shown), while the anchoring section 42 is located close to the transport device. However, this in no way implies any limitation on the present invention.

Opposite ends 45 of the sealing element 48 are connected 47 to the pipe part 58 by means of end sleeves 44.

The extrusion-preventing ribs 46 are mechanically connected to the end sleeve 44 in accordance with conventional methods known in the art and to which reference is hereby made. The non-continuous, non-reinforced rib construction of the seal member 40 provides the necessary thickness 41 to compensate for radial force loss from phase change in the inflation medium 56. Nevertheless, the thickness 41 of the seal member 48 provided overcomes any access and size limitations of existing equipment already placed downhole, as can be seen from the following.

The inflatable tool element 48 in the sealing section 40 is not reinforced in the middle portion 49 of the elastomer element 48, and as such does not have ribs 46 extending from end to end. Such a construction clearly compensates for an elastomer element 48 with a relatively large thickness 41, because the ribs 46 are looped in the middle part 49. The ribs 46 are only arranged at the ends 45 where the sealing element 48 is connected to the pipe mandrel 58 to absorb the end load. The middle part 49 is simply made of elastomer, and therefore a thicker 41 elastomer can be arranged. However, anchoring is not possible in lined wellbores under such circumstances. In an open hole, the anchoring is due to the uneven, non-continuous surface of the wellbore, while the casing has a smooth surface 55 with the result that no firm grip occurs. However, anchorage is provided by means of a separate but related section 42.

In the preferred embodiment, the anchoring element section 42 comprises an inner tube or bellows 52 which is inflated, the anchoring ribs 62 and an elastomer stiffening band 60 for even distribution of the ribs 46 along the inner tube 52 circumference can be added. The ribs 62 are made of steel and are exposed so that they come into metallic contact 63 against the wellbore casing 55. The ribs 62 are mechanically connected with a ring (not shown) and mounted inside the end sleeves 44. The exposed steel ribs 62 can be introduced into surroundings with a high pressure difference and still maintain metallic friction 63 for a strong anchoring relationship. In certain applications, such as short length packs, the bands 60 are not necessary.

The hybrid construction of the present invention shown here constitutes an inflatable tool that overcomes the limitations of traditional lined well bores, and still exhibits an inflatable, unitary element construction that provides sealing and anchoring, and which are in pressure connection with each other. The combined construction thus has two elements 40, 42 which provide independent functions, but which are inflated in relation to each other. The anchoring element 42 only acts as an anchoring, while the sealing element 40 only acts as a seal.

In the preferred embodiment, the elastomeric compositions 48, 52 included in the cover construction include materials that have good memory for returning to their original size and are designed for use in sub-zero surface conditions to avoid impact damage to the element surface during handling. at the workplace. The temperature range for the elastomer elements extends from ambient temperature to more than 260°C depending on the type of elastomer used. However, it should be noted that the present invention does not depend on which type of elastomer is used. New elastomer technology with large temperature tolerances can just as well be incorporated here. The temperature ranges discussed here are representative of today's available elastomer technology.

Each of the sealing and anchoring elements 40, 42 may be inflated with a phase change inflation medium 56 such as cement, epoxy or other such media. With today's expanding cement technology, there will thus be some contraction or shrinkage in the inflating medium 56 during the curing or phase change step. The present invention overcomes this limitation even by using phase change inflation medium 56 which can be subjected to radial force loss such as cement which undergoes contraction during the setting step.

In fig. 3, one of the embodiments, the present invention is shown as an expansion or inflation mode of operation and a set mode of operation. In the sealing element section 40, the inflatable elastomer element is fully expanded, and exerts a radial force against the casing wall 55. The radial force from the pressurized inflation medium 56 creates a sealing system 64 between the elastomer element 48 and the casing wall 55. Consequently, wellbore fluids are prevented from having cross-flow, and the area above and below the inflatable tool is isolated from each other. The pressure force or frictional engagement 64 between the elastomer element 48 and the casing wall 55 ensures a fluid-tight seal.

The extrusion-preventing ribs 45 in the sealing element section 40 protect the elastomer element 48 from rolling over when the element 48 is inflated under a relatively large compressive force. In addition, the ribs 45 protect the elastomer element 48 against tearing and malfunction.

The anchoring element section 42 of the preferred embodiment is also shown in the inflated position in fig. 3. The ribs 62 of steel or other suitable metal provide a strong anchoring against rotation, axial movement, twisting action, or any other form of displacement. Such movement is prevented because a large radial force acting on the ribs 62 from the inflation medium 56 pushes it into frictional contact 63 with the casing wall 55. The exposed anchoring section 42 comprises a continuous rib element 62. In other words, the ribs run over the entire length of the elastomer element and are connected at the ends 47 with the end sleeves 44. The end sleeves 44 are in turn mechanically connected to the tube mandrel 58 by means of conventional means known in the art, such as threaded sleeves (not shown here). The inner tube or bellows 52 is mounted under the ribs 62 which are likewise connected to the end sleeves 44. The inner tube 52 acts as a containment element for the inflation medium 56. The inner sleeve 44 which is not connected to the sealing section is displaceable relative to the tube mandrel 58. It should be understood that the elastomer band 60 in the anchoring section 42 is arranged so that the ribs 62 are evenly distributed among themselves, and it is not intended to provide sealing ability. In fact, the band 60, although abutting the casing wall 54, need not form a pressure seal, as its primary function is to create a path (between the ribs 62) for the escaping fluids in the annulus 65 between the inflatable tool and the casing wall 54. The stiffening rings 60 are typically in number from zero to ten depending on the size of the gasket.

It should be understood that the preferred embodiment of the hybrid inflatable tool inflates gradually, with the sealing section 40 being inflated first and then the anchoring section 42, due to the differences in stiffness between the elements in each section. This provides an important advantage in that fluid will not be trapped between the two sections in the annulus 65 near the mechanical joint 44 during the inflation operation. Fluid entrapment is further prevented because the anchoring section 42 with its exposed ribs 62 forms a path for any trapped fluid that may escape through the channels between the ribs 62.

The elements 40, 42 can be inflated in a conventional manner. The inflation medium 56 is injected through a receiving port 50 which communicates with the inflatable elements 40, 42. The inflation medium 56 will flow into the port 50, preferably at the upper end of the gasket, and inflate the first component (preferably the sealing element 40) and then the inflation medium 56 will flow around the end sleeves 44 and gradually inflate the second component (preferably the anchoring element 42) of the tool. In the preferred embodiment, there are several ports or paths 50 for inflating the elastomer elements 40, 42. The inflation fluid 56 flows into these ports 50 and simultaneously inflates the elements 40, 42 in relation to each other. However, the inflatable sections 40, 42 may operate independently of each other. However, they can be inflated during a single unitary operation. The inflation features of the present invention may further include the conventional construction where the flow paths approach the inflatable tool in a "valve collar up" inflation mode (not shown), i.e. the inflation medium path begins at the valve collar from the transport side. In such an inflation mode design, the inflation ports are located at the top of the inflatable tool, ie the valve collar is located at a distance from the free or floating end and close to the coupled end or conveying end. Inflation will thus take place from the vein-collar side. However, it should be noted that an unconventional construction of "valve collar down" works just as well, depending on well drilling conditions and requirements.

The location of the anchoring and sealing sections 42, 40 in relation to the transport device can be made interchangeable, i.e. the sealing element 40 can be close to or at a distance from the transport device. The decision to place the sealing element close to the transport device (on top) is dependent on many factors and wellbore requirements including the ease with which inflation can occur. Preferably, the anchoring section 42 is placed near the "floating" end. In the preferred embodiment, the sealing element 42 is placed close to a mechanical "tie-in" or transport device (pipe string on the upper side or similar) because the floating end "pulls" up when the anchoring element is inflated. When inflation occurs, the axial length of the anchoring element 42 will thus be shortened to compensate for the radial inflation. The bottom end, including the anchoring element and the bottom end sleeve 44 will thus be displaced when the anchoring element is inflated and pulled up and finally come into an anchoring engagement 63.

In the case where the sealing section 40 is on the bottom, the anchoring section 42 will pull "down" and catch 63 when it is inflated provided that compensation is provided so that the anchoring section can be shifted axially. In this case, the sealing element 40 is inflated relatively in front of the anchoring element 42 and the pull-down takes place during this time due to the stiffer anchoring element 42 (with the ribs 62) and is consequently inflated more slowly than the sealing element 40.

A number of inflation tools in series cannot be easily inflated. E.g. shows a Selective Inflation Packer System (English: Selective Inflation Packer Sys-tem) SC IPSO (not shown) shows complementary tools that cooperate with the present invention for lowering, activating or inflating and setting the hybrid inflatable tool shown here. The SCIPSO tool is designed for use in horizontal or vertical wellbore applications requiring selective cement or epoxy inflation of inflatable tools. Uncontaminated cement is injected into the inflatable tool for inflation purposes. The SCIPSO tool allows selective inflation and movement between staggered inflatable tools located in slotted extension tubes, pre-drilled extension tubes or strainers without loss of inflation medium during repositioning. The SCIPSO tool can be lowered together with the inflatable tool or by itself on a second lowering after the casing or extension pipe string has been lowered. In addition, all remaining, unused cement can be circulated in the opposite direction. When the elements are inflated, both the sealing and anchoring element gradually expand to the casing wall as a volume change occurs in the cement.

By using a sectional element construction for the preferred embodiment, i.e. the sealing and anchoring element sections, which are mechanically connected and in constant pressure connection, the present invention can achieve the advantages of both sealing and anchoring in a single, inflatable tool unit when used in a lined wellbore and a phase change inflation medium is used, thus creating significant savings for the operator.

The method by which the present invention is used in cased well drilling does not differ significantly from existing and common methods. The inflatable tool of the present invention may be immersed in the lined wellbore using any number of conventional methods such as cable, coiled tubing, production tubing, and the like. The only limitation is that the inflatable tool must have access to and get past existing downhole equipment. Such a limitation is overcome by the present invention, which is aimed at overcoming this limitation. The present invention presupposes a relatively small outer diameter operation and is therefore able to be submerged under such conditions to the correct place in the lined wellbore. When the inflatable tool is correctly positioned, it can be inflated to seal anchor engagement with the liner wall. Such inflation is achieved as described above. The inflation media may vary depending on the expected use, but in the present invention it is intended to be a phase change fluid which can solidify and may involve slight shrinkage.

Claims (14)

1. Inflatable downhole packing for sealing against the wall (54) of a lined or unlined wellbore, comprising: a tubular part (58), a movable sealing section (40) which is inflatablely operable between a lowering position and a set position where the sealing is located against the wall (54), at least one movable anchoring section (42) which is inflatablely operable between a lowering position and a set position where it bears against the wall to support the pipe part (58), characterized in that the sealing section (40) is arranged at a distance from the anchoring section (42). 2. Gasket according to claim 1, characterized in that the sealing section (40) comprises a first elastic element (48), that the anchoring section (42) comprises a second elastic element (52), and that the first elastic element (48) is thicker than the second elastic element (52). 3. Gasket according to claim 2, characterized in that the first elastic element (48) comprises ribs (46) which are located adjacent to at least one of the opposite ends and which do not extend continuously over its entire length. 4. Gasket according to claim 3, characterized in that the second elastic element (52) comprises continuous ribs (62) which extend over most of the distance from end to end. 5. Gasket according to claim 4, characterized in that the second elastic element (52) further comprises at least one band (60) which is mounted over the ribs (62). 6. Gasket according to claim 2, characterized in that the first elastic element (48) has sufficient thickness to maintain the sealing system against the wall (54) if an inflation medium (56) undergoes shrinkage when it hardens. 7. Gasket according to claim 3, characterized in that the first elastic element (48) comprises an outer surface that rests against the wall (54) and that the ribs (46) are arranged below the outer surface, so that they do not rest against the wall in said set score. 8. Gasket according to claim 4, characterized in that the ribs (62) in the second elastic element (52) extend from end to end of the element and are exposed for abutment against the wall (54) in said set position. 9. Method for sealing a lined borehole, where an inflatable gasket is arranged on a part (58) with a first inflatable element (48) for sealing and a second, inflatable element (62) for anchoring, the part (58) is lowered into position, and both elements are inflated, characterized in that the sealing element (48) is arranged at a distance from the anchoring element (52). 10. Method according to claim 9, characterized in that an inflating material is used which shrinks when it hardens. 11. Method according to claim 10, characterized in that the inflatable sealing element (48) is designed with a greater thickness (41) than the anchoring element (52), and that said greater thickness (41) is used to compensate for the shrinkage. 12. Method according to claim 11, characterized in that the anchoring element (52) is reinforced with ribs (62) that extend over at least most of its length, and that the ribs (62) on the anchoring element are exposed so that they come into contact with the lining drill holes. 13. Method according to claim 12, characterized in that ribs (46) are arranged on the sealing element (48) which extend from at least one end and almost to the center of the sealing element. 14. Method according to claim 13, characterized in that the ribs (46) are placed on the sealing element (48) while they are stretched from each end to leave a large middle section of the element without ribs.