DOWNHOLE APPARATUS AND METHODS

Abstract

A well construction method in which a drilled bore is lined with a plurality of successively smaller diameter sections of bore-lining tubing including casing sections a liner section is provided. A liner is provided with an inner string extending to a distal end of the liner. The liner and the inner string are run into a distal section of a drilled bore. Settable material is pumped from surface through the inner string and through the distal end of the liner to partially fill an outer annulus surrounding the liner. Fluid displaced from the outer annulus and a portion of the settable material is permitted to flow from the outer annulus through a port in the liner and into an inner annulus between the inner string and the liner.

Claims

1. A well construction method in which a drilled bore is lined with a plurality of successively smaller diameter sections of bore-lining tubing including at least one casing and at least one liner, the well construction method comprising: providing a liner and an inner string extending to a distal end of the liner; running the liner and the inner string into a distal section of a drilled bore; pumping a settable material from surface, through the inner string, and through the distal end of the liner to at least partially fill an outer annulus surrounding the liner, and permitting at least one of fluid displaced from the outer annulus and a portion of the settable material to flow from the outer annulus through a port in the liner and into an inner annulus between the inner string and the liner.

2. The method of claim 1, further comprising: locating the port in the liner such that when the liner is run into the bore the port is located below a section of overlap between the distal end of a previous casing and the proximal end of the liner; and opening or closing the port.

3. The method of claim 1, comprising mounting a port-operating tool on the inner string and translating the tool relative to the port to reconfigure the port.

4. The method of claim 1, further comprising closing the port following the filling of the outer annulus with the settable material.

5. The method of claim 1, further comprising providing a telescopic section in the inner string and reconfiguring the telescopic section between extended and retracted configurations, in one of the configurations the telescopic section being capable of transferring torque and in the other of the configurations the telescopic section permitting independent rotation of portions of the inner string above and below the telescopic section.

6. The method of claim 1, further comprising providing the port in a port collar.

7. The method of claim 1, further comprising providing a shoe at the distal end of the liner and a running tool at a proximal end of the liner, with the inner string extending between the shoe and the running tool.

8. The method of claim 1, further comprising retrieving the inner string from the bore.

9. The method of claim 1, further comprising running the liner into the bore on a work string in fluid communication with the inner string.

10. The method of claim 1, further comprising running the liner into the bore with the inner annulus in fluid communication with the outer annulus, wherein the inner annulus is further in communication with a volume of the bore above the liner.

11. The method of claim 1, further comprising running the liner into the bore with the port in a closed configuration.

12. The method of claim 1, further comprising providing a hanger on the liner and activating the hanger to at least one of secure and seal the liner to a surrounding bore-lining tubing.

13. The method of claim 1, further comprising circulating fluid through the inner annulus to heat or cool the settable material in the outer annulus.

14. A well construction apparatus for use in lining a drilled bore, the well construction apparatus comprising: a liner having a wall and a fluid port in an upper portion of the wall; and an inner string for extending to a distal end of the liner; whereby fluid may be pumped through the inner string, through a distal end of the liner to at least partially fill an outer annulus surrounding the liner, and from the outer annulus through the port in the liner and into an inner annulus between the inner string and the liner.

15. The apparatus of claim 14, wherein the fluid port is configurable in an open configuration and in a closed configuration.

16. The apparatus of claim 14, wherein the port is provided in a port collar.

17. The apparatus of claim 14, wherein a port-operating tool is mounted on the inner string and translatable relative to the port to open or close the port.

18. The apparatus of claim 14, wherein the inner string includes at least one telescopic section to permit selected parts of the inner string to be translated relative to the liner.

19. The apparatus of claim 14, further comprising a shoe at the distal end of the liner and a running tool at a proximal end of the liner, and wherein the inner string extends between the shoe and the running tool, wherein inner string includes a coupling for releasably connecting a distal end of the inner string to the shoe.

20. The apparatus of claim 16, wherein the inner string comprises a valved port openable to permit fluid transit between the inner string and the inner annulus.

21. A well construction method comprising: providing a tubing assembly comprising bore-lining tubing and an inner string extending to a distal end of the tubing; advancing the tubing assembly into a drilled bore; and permitting fluid displaced from a distal portion of the bore by the advancing tubing assembly to flow from an outer annulus surrounding the bore-lining tubing through a port in the tubing and into an inner annulus between the inner string and the tubing.

22. A well construction apparatus comprising: a tubing assembly including: bore-lining tubing having a wall and a fluid port in the wall, and an inner string extending to a distal end of the bore-lining tubing, whereby fluid displaced by advancing the tubing assembly into a drilled bore flows from an outer annulus surrounding the bore-lining tubing through the port in the tubing wall and into an inner annulus between the inner string and the tubing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] These and other aspects of the disclosure will now be described, by way of example, with reference to the drawings, in which:

[0042] FIGS. 1 and 2 are schematics of an oil and gas well illustrating an example of a well construction method and apparatus in accordance with an aspect of the present disclosure, and

[0043] FIG. 3 is a schematic of an oil and gas well illustrating an example of a well construction method and apparatus in accordance with another aspect of the present disclosure.

DETAILED DESCRIPTION

[0044] Referring first to FIG. 1 of the drawings, a deep-water oil and gas well 100 is illustrated. Well construction operations are conducted primarily from a mobile offshore drilling unit 102 on the sea surface 104. The well 100 includes a bore 106 which has been drilled in sections and lined with successively smaller bore-lining tubing sections 108, 110, 112, 120.

[0045] The illustrated well 100 includes three casing sections 108, 110 and 112 which extend back to a wellhead housing assembly (WHHA) located at the seabed 113 and serve to support the surrounding bore wall, which may include weak zones which would otherwise be liable to collapse. The casings 108, 110, 112 also isolate any water, gas or oil-bearing zones and provide support for the next casing. An annulus 114 surrounds the two innermost casings 110, 112 and is at least partially filled with settable material in the form of cement 116.

[0046] The well 100 also includes a liner 120 which extends to the end of the bore 106. The liner 120 may have a generally similar form to the casings 108, 110, 112 but does not extend back to the seabed 113. In this example the liner 120 is sealed and secured to a distal portion of the innermost or last casing 112 with a liner hanger 122. An outer annulus 124 between the liner 120 and the surrounding bore wall will also be sealed with cement 126.

[0047] In the illustrated well 100 the first casing 108, sometimes referred to as a conductor, has been placed by jetting, that is by providing a shoe on the lower or distal end of the casing 108 and pumping water through jetting nozzles in the shoe to displace sediment and allow the casing 108 to be lowered into the seabed 113. In other situations, the casing 108 may have been run into a drilled bore and then sealed and secured in the bore within a cement sheath.

[0048] The second casing 110 is next located in the bore 106, followed by the third casing 112. A shoe 128 in the lower end of the casing 112 is then drilled out and a continuation of the bore 106 is then drilled and under reamed beyond the end of the casing 112. The liner 120 is then run into and cemented in the bore 106, as described in detail below and as illustrated in FIG. 2.

[0049] The liner 120 is made up from liner sections stored on the deck of the drilling unit 102. The leading or distal end of the liner 120 is provided with a liner shoe 134. The shoe 134 is a float shoe and allows an end adaptor/connector 142 on the end of an inner string 140 to form a sealing engagement with the shoe 134, as will be described. The inner string 140 will typically be of significantly smaller diameter than the liner 120.

[0050] The liner sections are coupled together using collars which typically feature female threaded ends for engaging male threads on the ends of the liner sections. One of the collars 130 includes ports 132 which may be opened to permit fluid to flow between the outside and the inside of the liner 120. The port collar 130 is located on the liner 120 such that, when the liner 120 has been run into the bore 106 to target depth, as illustrated in FIG. 1., the collar 130 is located just below the previous casing shoe 128.

[0051] In one example the collar 130 is provided with circumferential rows of twelve ports of ? (1.9 cm) diameter. The collar 130 may feature an internal sleeve that is axially translated to open and close the collar 130 and uncover/cover the ports 132. The collar 130 may be similar in form to a stage cementing collar, examples of which are supplied by TAM International, Inc., Archer Limited and Forum Energy Technologies, Inc.

[0052] Once the liner 120 has been made up and is suspended from the slips on the deck of the drilling unit 102, the inner string 140 is made up and run into the liner 120. The inner string 140 includes an end connector 142 which may be latched into a flow passage 144 in the liner shoe 134. The flow passage 144 features a float or check valve which prevents flow of fluid from below the shoe 134 and into the inner string 140 while permitting flow from the inner string 140 through the flow passage 144 and out of the shoe 134 and into the outer annulus 124. The end connector 142 may be disengaged from the shoe 134 by rotating the connector 142 relative to the shoe 134, or by a straight pull.

[0053] The lower or distal end of the inner string 140 includes a valved port 146 including a burst disc or the like. The valve in the port 146 is initially closed.

[0054] The inner string 140 also includes upper and lower telescopic sections or slip joints 148, 149. When the telescopic sections 148, 149 are extended, complementary splined portions engage and permit the transfer of torque through the sections 148, 149. However, when a section 148, 149 is retracted or compressed a portion of the string 140 above the section 148, 149 is rotatable relative to a portion below the portion 148, 149. The telescopic sections 148, 149 may include features such as described in GB2525148A and GB2545495A, the disclosures of which are incorporated herein in their entirety.

[0055] Further, the inner string 140 is provided with a port collar shifting tool 136. As will be described, the shifting tool 136 may be translated relative to the port collar 130 to open and close the ports 132.

[0056] Once the inner string 140 has been made up to the appropriate length within the liner 120 the end connector 142 may engage and connect with the liner shoe 134. Pulling back on the string 140 will confirm that the connector 142 and shoe 134 are properly engaged.

[0057] The upper or proximal end of the inner string 140 is then coupled to a liner running tool 150 which includes external left-handed threads configured to cooperate with matching internal threads on the upper or proximal end of the liner 120. In other examples an alternative or supplementary coupling arrangement may be employed between the running tool 150 and the liner 120, for example cam-actuated load shoulders.

[0058] The inner string 140 is then lowered to compress the telescopic sections 148, 149 such that the splined portions disengage. The upper end of the string 140 may then be rotated to engage the running tool 150 with the upper end of the liner 120, without transfer of rotation to the string 140 below the section 148.

[0059] An inner annulus 152 between the liner 120 and the inner string 140 may be top filled with drilling fluid before engaging the running tool 150 with the liner 120. Also, the inner string 140 may be top filled, as may a liner running string 154 which is subsequently connected to the liner assembly. The top filling may be achieved simply be locating a hose outlet in the upper end of the annulus 152 or string 140, 154 and pumping drilling fluid into the annulus 152 or string 140, 154, or by use of apparatus such as the Top Jet (trademark) tool supplied by Coretrax Global Limited.

[0060] The resulting liner assembly is lowered into the well supported by the liner running string 154 until the liner 120 reaches target depth. The liner hanger 122 provided at the upper end of the liner 120 may be activated and slips and seals in the hanger 122 engage the surrounding casing 112. This stage of the well construction process is illustrated in FIG. 1. Alternatively, the hanger seals may be initially inactive and be activated subsequently.

[0061] The upper end of the string 140 may then be rotated to disengage the running tool 150 from the upper end of the liner 120, opening the upper end of the inner annulus 152. The inner string 140 may then be lifted to bring the port collar shifting tool 136 into engagement with the port collar 130. By appropriate manipulation of the tool 136 the port collar 130 may be reconfigured, and the port 132 opened. In other examples the port 132 may be initially open and not require reconfiguration.

[0062] The liner 120 is surrounded by the outer annulus 124 which comprises a lower portion 124a in which the walls of the annulus are defined by an outer surface of the liner 120 and the wall of the drilled bore 106. An upper portion 124b of the annulus is defined by the outer surface of the upper or proximal end portion of the liner 120 and an inner surface of a distal end of the last casing section 112. Thus, the upper portion 124b of the annulus is formed at a section of overlap between the lower or distal end of the last casing 112 and the proximal end of the liner 120. The annular flow area provided at this section of overlap is restricted and will thus impede any attempt to circulate fluid through the annulus 124 and will generate elevated fluid friction pressures and an increase in equivalent circulation density (ECD); the pressure of the circulating fluid would thus be increased. If the lower portion 124a of the outer annulus includes drilled bore wall formed by weak or problematic formations the high pressure circulating fluid or higher density settable material may migrate into those formations, resulting in lost circulation or inefficient cement fill-up of the annulus. As described below, the apparatus and method of this example may be utilized to provide at least partial fluid bypass of the restricted area 124b.

[0063] After the liner 120 is located in the bore 106 and secured to the casing using the liner hanger 122, the operator may then circulate a cementing fluid train, which involves pumping various fluids down through the liner running string 154, the liner running tool 150, the inner string 140, and through the flow port 144 in the shoe 134. The fluids will flow into and up through the outer annulus 124. The port collar 130 is located between the lower and upper annulus portions 124a, 124b and as the fluid reaches the level of the port collar 130 the fluid will divert from the outer annulus 124 and flow through the ports 132 and into the inner annulus 152. If the seals on the liner hanger 122 have been set all of the circulating fluid will pass through the ports 132. However, if the seals have not been set some fluid may continue to flow up through the annulus upper portion 124b.

[0064] The fluid train may comprise, for example, wash fluid, spacer fluid, lead cement slurry, tail cement slurry, and displacement fluid. From the inner annulus 152 the fluids will flow up and around the disconnected running tool 150, or through a fluid bypass system provided at the upper end of the liner 120.

[0065] The circulating fluid does not have to negotiate the extended length of the restricted area flow path between the overlapping upper or proximal end of the liner 120 and lower or distal end of the casing 112, or flow through or around the liner hanger 122. The less restrictive flow path available through the ports 132 minimizes fluid friction pressure, encourages preferential flow, and provides a corresponding reduction in ECD. It should be noted that even if the ports 132 provide a smaller flow area than the upper annular portion 124b, the passage of fluid through the ports 132 will generate significantly lower friction pressure than passage of fluid through the annular portion 124b given that the length of the flow passage through the ports 132 is very short, and likely less than 1 (2.54 cm).

[0066] Reverse flow of the relatively dense cement slurry 126a from the annulus 124 back into the inner string 140 is prevented by the check valve provided in the port 144.

[0067] The cement slurry 126a may be separated from the following displacement fluid by an inner string top wiper plug or ball. The cement 126a is thus pumped through the liner running string 154, the liner running tool 150, the inner string 140, and the flow port 144 in the shoe 134, until the ball lands in and blocks the flow port 144. The ball is locked in the port 144 and acts in combination with the flow port check valve to prevent any possibility of U-tubing, that is the dense cement slurry 126a flowing out of the annulus 124, and back through the port 144, and into the inner string 140.

[0068] A valved port 146 closed with a shear or burst disc is provided in the lower end of the inner string 140 and by continuing to pump into the now closed-off inner string 140 the port 146 may be opened.

[0069] By manipulation of the inner string 140 the operator may also translate the shifting tool 136 to close the ports 132 and isolate the outer annulus 124.

[0070] If desired, fluid may be conventionally or reverse circulated through the inner annulus 152 and any residual cement 126a in the string 140 or liner 120 is flushed out of the well; fluid may be pumped into the inner annulus 152 from the bore volume above the running tool 150, and then through the port 146 and up through the inner string 140 to surface, or fluid may be pumped into inner string 140 and then through the port 146 and up through the inner annulus 152 to surface.

[0071] The operator may also circulate fluid through the inner annulus 152 to affect the setting of the cement 126a, as discussed in detail in GB2565098A and U.S. Ser. No. 11/448,037B. For example, the circulation of heated fluid may accelerate the setting of the cement 126a, whereas circulation of cooled fluid may retard cement setting.

[0072] When the operator is ready to retrieve the liner running assembly, the liner running string 154 is raised to extend the telescopic sections 148, 149 in the inner string 140, allowing torque to be transferred through the inner string 140 to disengage the bottom end of the inner string 140 from the liner shoe 134.

[0073] Once the cement 126 has set, any further operations, for example perforating the liner 120, may be carried out immediately. There is no requirement to drill out a plug of cement, or the associated plugs and float collar, from the distal end of the liner 120, as would be the case with a conventional liner cementing operation. This provides for a considerable saving in time, reduces the equipment required to be provided on the drilling unit 102, avoids the potential for drilling-related damage to the liner 120 and the cement 126.

[0074] In another example a liner assembly, such as illustrated in FIG. 3 of the drawings, may be run into the bore 106 with the ports 132 open so that fluid in the bore may pass from the bore 106 and the outer annulus 124 into the inner annulus 152. If the inner string 140 and the running string 154 are configured in a similar manner to the strings as described in applicant's WO2021028689, and the check valve in the flow passage 144 is initially held open, bore fluid displaced from the volume below the shoe 134 may pass from the volume into the inner string 140 through the open flow passage 144, and fluid may also pass from the outer annulus 124 into the inner annulus 152 through the ports 132. Also, open diverter ports 160, 162, 164 provided in flow subs 166, 168, 170 in the inner string 140 and the running string 154 allow fluid to pass between the inner string 140 and the inner annulus 152 and between the running string 154 and the bore volume above the running tool 150. The creation of such additional potential flow paths minimizes the resistance to upwards flow of fluid once the fluid has entered the inner string 140 through the flow passage 144 and facilitates flow from the inner annulus 152 and into the bore volume above the running tool 150.

[0075] Once the liner 120 is at target depth the diverter ports 160, 162, 164 may be closed and the check valve in the passage 144 activated.

[0076] Such an arrangement may facilitate running the liner assembly into the bore more quickly while avoiding pressure surging which may, for example, damage the formation surrounding the open hole by forcing well fluid into the formation or inducing the loss of circulating fluid into the formation.

[0077] It will be apparent to the skilled person that many of the elements of the various well constructions described above may be modified or omitted. For example, the skilled person would recognize that the number and dimensions of the various casing and liner sections may differ in other wells.

[0078] In the examples described above the inner string extends to a shoe provided at the lower or distal end of the liner. However, in other examples the inner string may extend to a packer which locates the inner string in the liner and provides a seal between the inner string and the liner. The inner string may terminate at the packer or may extend beyond the packer to a location just short of the liner shoe. Thus, in such an arrangement a section of the liner may provide fluid communication between the end of the inner string and the shoe and the outer annulus. Further, the drawings illustrate methods being utilized in deep-water applications. The skilled person will recognize that the methods and apparatus described may also be utilized in shallower water, and indeed in land wells.