GB2603942A

GB2603942A - Completion string assembly and method of completing a well

Info

Publication number: GB2603942A
Application number: GB2102436.9A
Authority: GB
Inventors: Eidem Morten
Original assignee: Equinor Energy AS
Current assignee: Equinor Energy AS
Priority date: 2021-02-22
Filing date: 2021-02-22
Publication date: 2022-08-24
Anticipated expiration: 2041-02-22
Also published as: GB2603942B; GB202102436D0

Abstract

A completion string assembly is connected at a proximal end to a landing string 2 and at a distal end to a BHA 5. The assembly includes an inner string 3 within a completion string 4 that may include a sand screen, the inner string 3 including a thruster sub 6 or preferably a plurality of thruster subs. An inner string co-operation potion and completion string co-operation portion may take the form of abutment portions 10 and cooperate with each other to limit the relative axial movement of the distal ends of the inner and completion strings. A swivel joint (8, Figs 2&3) or centraliser may be present to decouple rotational movement of the landing string 2 from the completion string 4. The inner string 3 may or may not be arranged for rotational movement and the distal ends of the inner and completion strings may or may not be fixedly connected to allow for relative rotational movement between the strings. There is also a method of completing a well.

Description

COMPLETION STRING ASSEMBLY AND METHOD OF COMPLETING A WELL

FIELD

The invention relates to completion string assemblies and methods for installing borehole completions and, in particular, installing a completion screen, for example sand screen tubulars.

BACKGROUND

A well completion process typically takes place after the well has been drilled and prepares the well for production or injection. The well may be completed by setting a liner or a casing inside the well to support the structural integrity of the well. The liner or casing may be cemented against the formation. The use of a cemented liner or casing can be avoided in open-hole completion. The production zone may be left bare in open-hole completion, but usually sand control is required by way of a sand screen or slotted liner to avoid inflow of sand into the production tubing. A gravel pack may be used to prevent sand entering the well. A pump such as an electrical submersible pump may also be placed in the production zone to create artificial left if the well pressure is not sufficiently high for production.

The use of mechanical thrusters is known in downhole drilling. Thrusters generate weight-on-bit by using drilling fluid hydraulics. The pump-open behaviour of thrusters decouples the lower part of the bottom hole assembly from the remainder of the drillstring, and in so doing provides a constant, controllable weight-on-bit (WOB) that dampens out axial vibrations and shocks. WO-A-9701693 discloses an hydraulic thruster for use in a drill string for generating a thrust force to a drill bit located at the lower end of a drill string. The thruster comprises a first member connectable to an upper part of the drill string and a second member connectable to a lower part of the drill string, said members being telescopingly arranged relative to each other and being capable of transmitting torque between the upper and lower part of the drill string during drilling. A fluid passage for passing through said members for drilling fluid flowing through the drill string towards the drill bit and means for generating an inward telescoping reaction of said members upon transmission of torque between the upper and lower part of the drill string during drilling are provided.

Thus thrusters are known for connecting two drilling strings and are used for length adjustment, effectively allowing the drill string to telescope, and for damping or absorbing shocks (reducing vibration).

GB-A-2546997 discloses a method of completing a well which has a longitudinal axis along a direction with a horizontal component, the method comprising rotating a first string and moving the first string into the well along the longitudinal axis of the well, providing a swivel joint rotatably connecting the first string to a second string, moving the second string along the longitudinal axis of the well into the well, wherein the second string comprises completion equipment, moving the completion equipment into the well along the longitudinal axis of the well. The second string may not rotate and the swivel joint may comprise a thrust washer or a ball bearing. There may be a pusher sub on the first string with wheels for advancing the first string into the well as the string rotates. The pusher sub is arranged such that a rotational motion of the drill string causes the drill string to be pulled into the well. The pusher sub will cause movement in the longitudinal direction of the well. The pulling function of the pusher sub at the end of the drill string which is located at the furthest position in the well will reduce compressive forces on the drill string, whilst advancing the drill string. Basically, the pusher sub converts rotational movement of the string into an axial pulling force, in this case, by the use of projecting wheels which are at an angle between 0 and 90 degrees with respect to the place perpendicular to the longitudinal axis of the drill string and pusher sub (analogous to a screw thread). According to GB-2546997, In directional drilling applications, using downhole drilling motors or rotary steerable tools it will often be necessary to selectively engage or disengage the main drill string with drill bit to allow rotation independent of the main drill string at times, and rotation with the drill string at others.

Alternatively, as described in WO-A-2015104389, a swivel sub is used for example in a method of running a string in a wellbore, wherein the bottom of the string comprises fragile elements that are not suitable to rotate. Such elements can be for example a liner, a screen or a gravel pack assembly. Therefore, the string including such elements is deployed into the wellbore in a first step wherein the portion of the string upper the swivel sub is rotated while the portion of the string under the swivel sub is not rotated. Rotation of the string breaks the friction between the string portion upper the swivel and the wall of the wellbore, allowing the string to be deployed in deeper areas without damaging the fragile elements under the swivel sub. When it is needed to rotate the string section under the swivel sub, a pressure differential is applied between the bore of the swivel sub and the annulus for moving the sliding sleeve to its second position.

US-A-2016312586 describes a system for liner drilling in a wellbore that includes a drill bit, a mud motor, a reamer, a drill pipe work string including an expandable liner hanger running tool, and a thruster coupled to an expandable liner hanger and liner. A release pin may be provided in the expandable liner hanger running tool that can be sheared to de-couple the expandable liner hanger from the expandable liner hanger running tool allowing the drill pipe work string to be removed from the borehole while the liner remains in place. A latch coupling is also provided for coupling the expandable liner hanger running tool to the expandable liner hanger when the drill pipe work string is tripped back into the borehole so the liner drilling can be performed using the thruster until the thruster is at full stroke. The thruster is used to "drill out the hole", when tripping the drill bit during drilling.

Similarly, EP-A-1006260 discloses a drilling liner having a core bit at its bottom end is carried along with a pilot bit on an inner bottom hole assembly driven by a downhole mud motor. In one embodiment, the motor is powered by mud carried by an inner string. Alternatively, the inner string may be omitted and the flow of mud through the liner powers the motor: this requires a locking tool for locking the motor assembly to the outer assembly. Once an abnormally (high or low) pressured zone has been traversed, the liner is set as a casing, the inner assembly is pulled out, and drilling may be resumed using a conventional tool. Directional drilling is accomplished by having an MWD device for providing directional information and having directional devices on the inner and outer assembly. These include retractable steering pads. Expandable bits, under-reamers and jetting nozzles may also be used in the drilling process. One embodiment of the invention has a bottom thruster between the mud motor and the drill bits that makes it possible to continue drilling for a limited distance even if the upper portion of the casing is stuck.

US-A-2001045300 discloses a bottom hole assembly that contains a thruster for applying an axial force on the drill bit during drilling of the wellbore. The bottom hole assembly includes at least one sensor which provides measurements for determining a parameter of interest relating to the drilling of the wellbore. A power unit supplies power to the thruster to move a member toward the drill bit to apply the force on the drill bit. A processor operatively coupled to the thruster controls the magnitude of the force generated by the thruster in response to one or more parameters interest.

These drill strings with thrusters can be used in simultaneous drilling and lining or casing methods. However, in completion methods, using completion strings subsequent to drilling, for example where the completion tubulars are less robust (such as sand screens), there is a problem that it is sometimes not possible to transfer sufficient weight from the landing string to the bottom of the completion string because, for instance, the string cannot be rotated, which also makes it hard to determine how much weight is actually transferred from the landing string to the completion string. Consequently, under these circumstances (e.g. using non-rotatable completion strings), there can be limited force that can be used to push the completion string through tight portions or obstructions in the well.

SUMMARY

The invention provides a completion string assembly having a proximal end for connection to a landing string and a distal end for supporting a BHA, the completion string assembly comprising, a completion string for forming at least part of a well bore completion and including a completion string co-operation portion; and an inner string arranged within the completion string and including at least one thruster sub and an inner string co-operation portion, wherein the inner string co-operation portion and the completion string cooperation portions cooperate with each other to at least limit relative axial movement of the distal end of the inner string relative to the distal end of the completion string.

The at least one thruster sub may comprise a plurality of thruster subs.

The completion string may comprise a sand screen.

The assembly may comprise a swivel joint or centralizer for decoupling rotational movement of the landing string from at least the completion string.

The inner string and completion string may be fixedly connected to each other at their distal ends.

The inner string may be arranged for rotational movement and the distal ends of the inner string and completion string are not fixedly connected but arranged for relative rotational movement between the inner string and completion string.

The inner string may comprise at least one thruster sub located axially between the proximal end and the axial location of the completion string co-operation portion.

In another aspect the invention provides a method of completing a well, the method comprising, connecting to a landing string, a completion string assembly having a proximal end for connection to the landing string and a distal end for supporting a BHA, the completion string assembly comprising, a completion string for forming at least part of a well bore completion and including a completion string co-operation portion, and an inner string arranged within the completion string and including at least one thruster sub and an inner string co-operation portion, wherein the inner string co-operation portion and the completion string cooperation portions cooperate with each other to at least limit relative axial movement of the distal end of the inner string relative to the distal end of the completion string; and inserting the completion string assembly on the landing string into a well bore.

The method may further comprise: monitoring the forces applied to at least one of the inner string, the completion string, and a bottom hole assembly on the distal end or the inner string; and activating the at least one thruster sub when it is determined that at least one threshold has been met during monitoring.

In the method the at least one thruster sub may comprise a plurality of thruster subs.

In the method the completion string may comprise a sand screen.

In the method the completion string assembly may comprise a swivel joint or centralizer for decoupling rotational movement of the landing string from at least the completion string and the method comprises rotating the landing string.

In the method the inner string and completion string may be fixedly connected to each other at their distal ends.

In the method the inner string may be arranged for rotational movement with the landing string, and the distal ends of the inner string and completion string are not fixedly connected but arranged for relative rotational movement between the inner string and completion string.

In the method the inner string may comprise at least one thruster sub located axially between the proximal end and the axial location of the completion string cooperation portion.

In a further aspect the invention provides the use of the completion assembly of the invention in a well bore completion method.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a completion string assembly according to an embodiment; Figure 2 is a schematic side view of a completion string assembly according to an embodiment and including a swivel joint; Figure 3 is a schematic side view of a completion string assembly according to an embodiment and including a swivel joint; Figure 4 is a flow diagram of a method according to an embodiment

DETAILED DESCRIPTION

During completion of an oil or gas well, sand control screens or liners, for example, may be located in the wellbore. Typically the screens and liners are lowered into the wellbore on a workstring, but there is often insufficient workstring down weight available to the driller to put the screens into the well without rotating the string to break the friction. Applying too much downhole weight can over-compress the pipe below, thereby causing damage, such as buckling of the drill pipe of screen section. It is advantageous to rotate the workstring attached to the screens or liners when inserting in high angle/ERD (extended reach drilling) or tortuous wells due to the fact that the associated drag of the friction is reduced in the workstring, making it easier to observe and apply the necessary measured down weight to aid getting sand screens or liners to the planned depth. However, it is often not desirable to rotate the screens or liners (perhaps with delicate accessories) for fear of damage. For example, if the screen or liner sticks, buckling can occur as a result of the applied torque, such completion strings (such as sand screens) can be considered "unrotatable" completion screens.

In the present invention a completion string assembly includes an inner string within a completion string (for example a screen such as a sand screen). The inner and completion strings are securely connected at their proximal (proximate the landing string) and distal (proximal the Bottom Hole Assembly (BHA)) ends. The inner string includes at least one thruster sub, for instance a thruster sub of the type disclosed in US-A2001045300 In an embodiment, as shown in figure 1, there are plural thruster subs 6 (three are shown). Figure 1 shows schematically a portion of a completions string assembly in a wellbore 1. The assembly includes an inner string 3 located within a completion string 4 -the chain lines indicating an unrotatable completion string (a sand screen in this embodiment). The inner string 3 is terminated at the BHA 5 which, in an embodiment, includes a bumper-sub and guide shoe. The assembly is connected to a landing string 2 via a liner running tool 7, which connect the landing string 2 to the completion string assembly.

The inner string 3 of the assembly of Figure 1 includes a plurality of thruster subs 6 between the subs making up the inner string (three thruster subs 6 are shown in the portion of the inner string 3 shown in figure 1). The completion string 4 is connected to the inner string 3 at, or proximal, both ends. Specifically, the distal end of the completion string 4 includes an abutment plate or other portion that cooperates with an abutment portion of, for example, the end of the inner string 3, the bumper sub or guide shoe, that prevents the end of the inner string 3 extending in an axial direction relative to the end of the completion string 4. The abutment portions are indicated generally by reference numeral 10 in figure 1. When the thruster subs 6 are activated, the inner string 3 is prevented from extending by the connection with the completion string 4, whereby the completion string 4 is held in tension which serves to counteract compressive and frictional forces acting on the completion string 4, which may be particularly delicate or fragile. The thruster subs 6 ensure weight is transferred from the landing string 2 to the bottom of the completion string 4 and the BHA 5.

The means for connecting the completion string 4 to the inner string 3 or BHA 5 is not limited. Any of these components can be provided with a bottom plate or no-go profile preventing relative movement of the end of the inner string 3 relative to the end of the end of the completion string 4, or preventing the BHA 5 from protruding from the landing profile, i.e. a fixed limit to the relative axial movement of the end of the inner string 3 relative to the completion string 4 -any further expansion of the inner string 3 due to the expansion of the thruster subs 6 acts upon both the BHA 5 and the completion string 4. Of course the end of the completion string 4 may be rigidly connected to the end of the inner string 3 or BHA 5 preventing movement axially in either direction (proximally or distally) and also preventing rotational movement.

The use of multiple thruster subs 6, for example evenly distributed along the inner string 3, allows an even distribution of compression forces along the inner string 3.

As shown in figure 1, the use of the thruster subs 6 enables transfer of weight from the landing string 2 to the BHA 5 and, therefore, the bottom of the completion string 4. For example, a compressive force of over 10 tons (over 9 tonnes). In figure 1, since the completion string is considered unrotatable, the landing string 2 does not rotate.

In figure 2, the arrangement is the same as for figure 1, except that the landing string 2 is connected to the liner running tool 7 via a swivel joint 8. By using a swivel joint 8 on top of liner running tool 7 and completion string 4 allows rotation of landing string 2, whilst decoupling the rotation from the completion string and inner string. Rotation of the landing string allows a much more precise knowledge of how much weight is set down on top of the completion string. A suitable swivel joint is know from GB-A-2546997.

The arrangement of figure 3, differs from that of figure 2 in that a swivel joint 8 is used between liner running tool 7 and completion string 4 instead of above the liner running tool. The landing string 2 can be rotated and the rotation can be transferred to the inner string 3, but the landing string 2 is decoupled from the completion string 4 which does not rotate, which might cause buckling or damage to any fragile components such as sand screens. Alternatively, instead of swivel joint 8, the inner string 3 could have one or more centralizers to decouple the inner string from the completion string.

In the case of the embodiment of figure 3, the connection between the ends of the completion string 4 and the inner string 3 or BHA 5 will also have to allow rotation of the inner string 3 relative to the completion string 4 whilst preventing relative axial movement. Such a connection is required in order to ensure that weight is transferred from the landing string 2 to the bottom of the completion string 4, whilst allowing the inner string 3 to rotate freely within the non-rotating completion string 4. In the case of a rotating inner string 3, the inner string 3 may be centred within the completion string using centralisers within which the inner string 3 (rotates). In figure 3 the most distal thruster sub 6 of figure 2 is shown replaced by a centraliser 9.

In the arrangements of figures 1 to 3 it is envisaged that a thruster sub such as that disclosed in WO-A-9701693 is used, for example, one that is activated by circulating fluid. Of course a thruster sub activated by any convenient means could be used and the invention is not limited to a fluid activated thruster sub.

The use of the inner string 3 of the present invention allows circulation of fluid to the bottom to assist in washing through any restrictions. As a consequence a low cost sacrificial motor may be used downhole in the BHA 5.

The string assembly is shown as straight in the figures, however, obviously, the invention is not so limited and the invention is applicable to directional boreholes, including those having horizontal portions.

In a method using either arrangement from figure 1, 2 or 3, the completion string assembly is set down in a well bore 1 using a landing string 2 to force the completion string assembly down the well bore 1. The weight applied to the bottom of the inner string 3 is measured and, as a threshold is approached fluids are circulated using the inner string thereby activating the thruster sub(s) 6. The compression forces generated in the inner string 3 caused by expansion of the thruster sub(s) 6, increases the force applied to any obstruction by the BHA 5. In other words, the forces applied to the inner string 3, the BHA 5 and/ or the completion string 4 are monitored and at a threshold below a predetermined maximum for the system to prevent damage to the components (particularly the completion string 4) the thrusters 6 are activated, for example by circulation of fluid through the inner string. As well as increasing the weight transferred to the bottom of the string assembly, the compression forces are distributed along the inner string 3.

Claims

CLAIMS: 1. A completion string assembly having a proximal end for connection to a landing string and a distal end for supporting a BHA, the completion string assembly comprising: a completion string for forming at least part of a well bore completion and including a completion string co-operation portion; and an inner string arranged within the completion string and including at least one thruster sub and an inner string co-operation portion, wherein the inner string co-operation portion and the completion string cooperation portions cooperate with each other to at least limit relative axial movement of the distal end of the inner string relative to the distal end of the completion string.
2. The completion string assembly as claimed in claim 1, wherein the at least one thruster sub comprises a plurality of thruster subs.
3. The completion string assembly as claimed in claim 1 or 2, wherein the completion string comprises a sand screen.
4. The completion string assembly as claimed in claim 1, 2 or 3, wherein the completion string assembly comprises a swivel joint or centralizer for decoupling rotational movement of the landing string from at least the completion string.
5. The completion string assembly as claimed in any one preceding claim, wherein the inner string and completion string are fixedly connected to each other at their distal ends.
6. The completion string assembly as claimed in claim 4, wherein the inner string is arranged for rotational movement and the distal ends of the inner string and completion string are not fixedly connected but arranged for relative rotational movement between the inner string and completion string.
7. The completion string assembly as claimed in any one preceding claim, wherein the inner string comprises at least one thruster sub located axially between the proximal end and the axial location of the completion string co-operation portion.
8. A method of completing a well, the method comprising: connecting to a landing string, a completion string assembly having a proximal end for connection to the landing string and a distal end for supporting a BHA, the completion string assembly comprising, a completion string for forming at least part of a well bore completion and including a completion string co-operation portion, and an inner string arranged within the completion string and including at least one thruster sub and an inner string co-operation portion, wherein the inner string co-operation portion and the completion string cooperation portions cooperate with each other to at least limit relative axial movement of the distal end of the inner string relative to the distal end of the completion string; and inserting the completion string assembly on the landing string into a well bore.
9. The method of claim 8, further comprising: monitoring the forces applied to at least one of the inner string, the completion string, and a bottom hole assembly on the distal end or the inner string; and activating the at least one thruster sub when it is determined that at least one threshold has been met during monitoring.
10. The method as claimed in claim 8 or 9, wherein the at least one thruster sub comprises a plurality of thruster subs.
11. The method as claimed in claim 8, 9 or 10, wherein the completion string comprises a sand screen.
12. The method as claimed in any one of claims 8 to 11, wherein the completion string assembly comprises a swivel joint or centralizer for decoupling rotational movement of the landing string from at least the completion string and the method comprises rotating the landing string.
13. The method as claimed in any of claims 8 to 12, wherein the inner string and completion string are fixedly connected to each other at their distal ends.
14. The method as claimed in any one of claims 8 to 11, wherein the inner string is arranged for rotational movement with the landing string, and the distal ends of the inner string and completion string are not fixedly connected but arranged for relative rotational movement between the inner string and completion string.
15. The method as claimed in any one of claims 8 to 14, wherein the inner string comprises at least one thruster sub located axially between the proximal end and the axial location of the completion string co-operation portion.
16. Use of a completion assembly as claimed in any one of claims 1 to 7 in a well bore completion method.