WELL COLLAPSE RECONNECT SYSTEM

Abstract

The invention relates to a method and apparatus for remediating damaged casing or liner in a hydrocarbon well, e.g. caused by collapsed formation. Damaged liner is milled away and a straddle joint (20) located in the exposed ends of liner (8,9), bridging the gap between them and restoring most of the inner diameter. The straddle joint (20) includes cement ports (25) through which cement may be injected into any cavity (4) in the rock surrounding the straddle joint (20), thereby supporting the rock and helping to prevent further collapse.

Claims

1. A process for remediating a well having a restriction caused by inward deformation of a well casing or liner, the process comprising: a) passing down the well a milling tool and milling away casing or liner in the region of the restriction such that rock surrounding the casing or liner is exposed and such that the casing or liner is divided into an upper and a lower portion each having an open end; b) passing down the well a straddle joint; c) locating upper and lower ends of the straddle joint in the upper and lower portions of casing or liner.

2. The process according to claim 1, wherein, between steps (a) and (b), an under-reaming operation is performed to ream away rock and/or cement in a region between the upper and lower portions of liner or casing.

3. The process according to claim 1, wherein, between steps (a) and (b), a wash operation is performed to remove loose rock, cement and/or metal swarf.

4. The process according to claim 1, including forming a seal between the straddle joint and the upper and lower casing portions.

5. The process according to claim 1, wherein the straddle joint grips the interior surface of the upper and lower portions of casing or liner.

6. The process according to claim 5, wherein the straddle joint is placed in axial compression.

7. The process according to claim 1, wherein, after placement of the straddle joint, cement or other settable medium is injected outwardly through a port in the straddle joint.

8. The process according to claim 7, wherein the cement or other settable medium enters and substantially fills a cavity adjacent the exterior of the straddle joint, thereby providing a degree of support against collapse of the rock.

9. The process according to claim 7, wherein, prior to injection of cement or other settable medium, wash fluid is circulated through a port in the straddle joint.

10. The process according to claim 7 wherein, following injection of cement, the port is closed.

11. A straddle joint for use in a process according to claim 1, the straddle joint comprising: (a) A generally tubular body; (b) Upper and lower seals, such as packers, axially spaced along the body; (c) A closable cement port in the body, located between the seals.

12. A straddle joint for bridging an open hole region between two portions of casing or liner in a well, the straddle joint comprising: (a) A generally tubular body; (b) Upper and lower seals, such as packers, axially spaced along the body; (c) A closable cement port in the body, located between the seals.

13. The straddle joint according to claim 12, further comprising a closure member, such as an axially slidable sleeve, which is movable to close the port.

14. The straddle joint according to claim 12, having upper and lower gripping means, such as slips, axially spaced along the body, for gripping an interior surface of liner or casing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings in which:

[0027] FIG. 1 is a schematic cross section though a liner in a reservoir rock formation, showing a collapsed section of the formation and buckled portion of liner;

[0028] FIG. 2 is a view similar to FIG. 1, showing a wash tool cleaning out a rock cavity; and

[0029] FIG. 3 is a view similar to FIGS. 1 and 2, showing a straddle joint according to the invention in the process of being delivered by a running tool.

DETAILED DESCRIPTION

[0030] Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow.

[0031] Referring firstly to FIG. 1, a liner 1 passing through a reservoir formation 2 has a buckled region 3 where the internal diameter of the liner is severely restricted. The formation 2 has partially collapsed, leading to a void 4 in the region of the buckled casing. The void 4 is partially filled with broken rock or rubble 5.

[0032] When formation collapses, a void is not necessarily formed and the exact state of the formation in the region of the buckled liner may not be known and could be solid, cracked or broken rock, void spaces or a mixture of any of these.

[0033] The collapse need not necessarily be in the reservoir but could be in the overburden, in which case the situation is the same as that described above and shown in FIG. 1, except that reference numeral 1 would in that event refer to casing rather than liner. However, the inventors believe that formation collapse is more prevalent in reservoir rock where draining of hydrocarbons and stimulation, e.g. with acid, may affect the formation pressure, the strength of the formation and/or create cracks or voids in the rock.

[0034] The region of FIG. 1 described as formation, may in some cases include cement, for example if the liner or casing was cemented in place when the well was first established.

[0035] Deformation of casing or liner can severely limit the downhole procedures which may be performed on the well. The size of tool which it is possible to pass down the casing or liner may be restricted, thereby restricting the types of procedure to those which may be carried out using downhole tools with a relatively small outer diameter.

[0036] In some cases the deformation may be so severe that it is not possible to get any tool past the restriction, in which case procedures are limited to bullheading fluids into the casing or liner beyond the restriction (i.e. simply passing fluids down the well under pressure).

[0037] The inventors have conceived a way of addressing this problem. They have devised a reconnect system and method which includes milling out the liner/casing and then reconnecting the milled ends with modified a straddle packer assembly. To the inventors' knowledge a straddle assembly has never been run in this way to connect two liner/casing stumps with open hole between the two liner/casing stumps.

[0038] FIG. 1 shows a milling tool 6 (e.g. a bullnose mill) being run down the liner 1 on drillpipe 7. The milling tool 6 is of a well-known type, capable of milling out a bore with substantially the inner diameter of the liner.

[0039] FIG. 2 shows the liner after the milling operation; the buckled part of the liner has been milled away, leaving an upper liner portion 8 and a lower liner portion 9, and the milling tool (not shown in FIG. 2) has advanced beyond the milled section. The interior of the liner is now exposed to the rock formation 2.

[0040] If there had been no void 4 in the rock and instead the rock had come right up to the exterior of the deformed region 3 of liner, then the milling tool 6 would have milled away rock as well as steel. In any event, there will normally be metal swarf 11 in the milled away region as well as rock debris 12 either due to formation collapse, milling or both. It may be desirable, e.g. if there is rock adjacent the milled away section, to under-ream, that is to say to use an under-reaming milling tool which is capable of milling away rock and/or cement to a larger internal diameter than the liner. The underreamer tool is not shown, but its design and operation will be familiar to those skilled in this field. If an under-reaming step is performed, this will obviously also create rock and/or cement debris 12.

[0041] On the same drill string assembly as the milling tool 6 (and underreamer if present) is a wash tool 10 which, in FIG. 2, has been advanced into position adjacent the milled section. Wash fluid (e.g. drilling mud) is circulated through the wash tool as shown by the arrows in FIG. 2, in a conventional manner. The wash tool 10 would normally be moved axially within the liner to wash fully the milled area and the exposed ends of liner and clear away far as possible all metal, rock and cement debris.

[0042] Once the washing operation is complete, the milling and washing assembly is withdrawn and then a straddle joint run into the well on a running tool. FIG. 3 shows, in highly schematic form, a straddle joint 20 and associated running tool 21. The straddle joint 20 can be seen to have entered the lower portion 9 of liner and be bridging the gap between the lower portion 9 and upper portion 8 of the liner.

[0043] At the lower end of the straddle joint 20 is a packer 22 and slips 23, both of which have been set by means of an actuating mechanism 24 of the running tool. The details of such mechanisms would be well known to those with knowledge of this field. As an alternative, a hydraulic system could be used to set the packer seal and slips. The function of the packer 22 is, when set, to seal against the interior of the liner, while the function of the slips 23 is, when set, to grip the interior of the liner so that the straddle may withstand downward axial loading and not move with respect to the liner.

[0044] Towards the upper end of the straddle joint 20, but not in the part of the straddle joint which is received in the upper portion 8 of the liner, are a number of wash/cement ports 25. The running tool also includes ports 26 for delivering wash fluid or cement.

[0045] Wash fluid (drilling mud) is again circulated though the ports 25, 26 and up through the annulus 27 between the straddle joint and liner (see arrows in FIG. 3 indicating flow). Cement is then delivered through the same ports into the annulus or void 4 surrounding the straddle joint 20, displacing the wash fluid and filling the annulus or void 4.

[0046] An upper packer and slips (not shown) may be set by an upper actuating mechanism (not shown) and engaged with the interior of the upper portion 8 of liner in exactly the same way as described for the lower packer and slips 22, 23. Prior to setting the upper slips, the straddle joint may be placed in compression, e.g. by setting string weight down while applying pressure. Alternatively, this could be accomplished in a secondary run or mechanically actuated through rotation while setting string weight down on top of straddle assembly.

[0047] The running tool is then released from the straddle joint by means which would be well known to those knowledgeable in this field and pulled out of the well. The action of pulling the running tool moves a closure sleeve 28 across the cement ports 25 of the straddle joint 20.

[0048] As the running tool is pulled out of the well, there may be further circulation of wash fluid to clean away any residual cement on the interior of the straddle joint and upper liner portion 8. After full withdrawal of the running tool, a clean out string (well-known to those knowledgeable in this field) may be run the full length of the well. Pressure tests may be performed to test the packer seals.

[0049] With access through the full wellbore restored, standard downhole operations, e.g. stimulation, may be performed. In one example, a 127 mm (5.0″) casing or liner with a nominal inner diameter of 102.7 mm (4.044″) could be restored to a 70 mm (2.75″) nominal ID using a 89 mm (3.5″) straddle. in another example, a 273 mm (10.75″) casing or liner with a nominal ID of 243 mm (9.56″) could be restored to 141 mm (6.56″) nominal ID using a 197 mm (7-¾″) straddle.

[0050] Increase in production and access to lower reservoir sections would vary by well, but for example wells with uplift values of 80 m.sup.3 per day or more (500 barrels per day) would likely be identified as candidates. The ability to re-access lower reservoir sections and re-stimulate, descale, and allow production are all benefits.

[0051] It is envisaged that long sections of damaged liner or casing may be remediated using this method and tooling. For example a length of anything from 0.3 to 152 metres (1 to 500 feet), 3 to 91 metres (10 to 300 feet), or 6 to 61 metres (20 to 200 feet) may be milled away and replaced. The straddle tool may be modular and may be assembled to fit the job. The diameter of the straddle joint will of course be selected according to the diameter of casing or liner which is damaged. Upper and lower parts of the straddle, which have the packers and slips and (normally in the case of the upper part) the cement ports, are assembled with an appropriate length of steel tubing (e.g. washpipe) between them.

[0052] In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as a additional embodiments of the present invention.

[0053] Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims while the description, abstract and drawings are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents.

REFERENCES

[0054] All of the references cited herein are expressly incorporated by reference. The discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication data after the priority date of this application. Incorporated references are listed again here for convenience: [0055] 1. EP3255240A1 (Welltech) Downhole Straddle System (2017). [0056] 2. EA201500410A1, Method of Repair in a Well with a Defective Section and Internal Restriction of a Casing String, and Device for Its Implementation (2016).