DISSOLVABLE SLEEVE FOR HYDROCARBON WELL COMPLETIONS

Abstract

The invention relates to the use of a sleeve (9) installed in a liner or casing (1) prior to a cementing operation. Completion equipment in the liner/casing creates an irregular inner profile which can cause cement to get trapped. A wiper dart (3) passed down the casing/liner (1) may have difficulty removing all residual cement (5). By using a sleeve or insert (8) in the liner/casing (1), a smooth inner profile (9) may be created which can be cleaned relatively easily by a wiper dart. Once cementing and cleaning are complete, the sleeve (9) may be removed by wellbore fluid or acid if it is made from a dissolvable material such as aluminum or magnesium.

Claims

1. A process for cleaning a liner or casing prior to completion, wherein the liner or casing has a region with a non-uniform inner profile, the process comprising: a) installing a protective sleeve in the liner or casing, the sleeve extending over the said region, the protective sleeve having a through bore with a substantially circular section; b) passing a wiper dart or other cleaning device through the said region; c) removing the sleeve; and d) performing the completion.

2. The process according to claim 1, wherein the sleeve has no abrupt changes in diameter or shoulders.

3. The process according to claim 1, wherein the said region comprises completion or other equipment having a non-uniform inner profile.

4. The process according to claim 3, wherein the sleeve has an outer profile complementary to the non-uniform inner profile of the said equipment.

5. The process according to claim 1, wherein the bore of the sleeve has a tapered distal portion, a tapered proximal portion, or both tapered distal and proximal portion.

6. The process according to claim 1, wherein the step of removing the sleeve comprises dissolving the sleeve.

7. The process according to claim 6, wherein the sleeve is dissolved in a fluid selected from well bore fluid, acid, alcohol, surfactant, and combinations thereof.

8. The process according to claim 1, wherein the step of removing the sleeve comprises milling away the sleeve using a milling tool.

9. A sleeve having a through bore with a substantially circular cross section with no abrupt changes in diameter and an outer surface profiled in a complementary manner to a non-uniform inner profile of a region of liner or casing, the sleeve being made from a material which is dissolvable or millable.

10. The sleeve according to claim 9, wherein the bore has a tapered distal portion, a tapered proximal portion, or both tapered distal and proximal portion.

11. The sleeve according to claim 9, being made from aluminium, magnesium, thermoplastic, composite, or a combination thereof.

12. An assembly comprising: a) a liner or casing having a region with a non-uniform inner profile; and b) fitted to the said region, a sleeve having a through bore with a substantially circular cross section with no abrupt changes in diameter and an outer surface profiled in a complementary manner to the non-uniform inner profile of the said region of liner or casing, the sleeve being made from a material which is dissolvable or millable; whereby a bore through the assembly is provided, the bore having a circular cross section with no abrupt changes in diameter or shoulders.

13. The assembly of claim 12, wherein the said region comprises completion or other equipment having a non-uniform inner profile.

14. The sleeve according to claim 11, wherein the bore has a tapered distal portion, a tapered proximal portion, or both tapered distal and proximal portion.

15. The sleeve according to claim 11, being made from aluminium, magnesium, thermoplastic, composite, or a combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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:

[0035] FIG. 1 is a highly schematic section through a portion of liner incorporating completion equipment, showing a known type of wiper dart passing through;

[0036] FIG. 2 is a view similar to FIG. 1 showing a protective sleeve according to the invention in place.

DETAILED DESCRIPTION

[0037] 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.

[0038] FIG. 1 represents the prior art. A schematic section through a portion of a completion liner 1 is shown. The liner 1 is installed in a wellbore (not shown) intended for hydrocarbon production or for water injection to facilitate hydrocarbon production. The liner 1 is fitted with completion equipment, e.g. sliding sleeves, valves, etc., all of which is conventional and would be familiar to one skilled in this field. The liner 1, with completion equipment, has an irregular internal profile 2. Although a liner is shown and described, the embodiment shown in the Figures could alternatively represent a casing.

[0039] The liner 1 has just had cement displaced through it in order to fill the annular space between it and the wellbore, thereby cementing the liner in place prior to completion. This process will have left residual cement in the liner 1, especially in parts of the irregular inner profile 2. Residual cement is shown in FIG. 1 by reference numerals 5.

[0040] A wiper dart comprising a number of elastomeric fins 3 is shown being passed through the liner on drill string 4. The dart is passed down the liner 1 from left to right in FIG. 1, which is from the more proximal end of the liner (with respect to the surface) to the more distal end (i.e. the end nearer the bottom end of the wellbore). Whilst the wiper dart is effective at removing cement from the relatively uniform parts of the liner inner profile, numbered 10 on the left and right of FIG. 1, cement is often not effectively removed by the wiper from the irregular profile, leaving pockets 5 of residual cement. The elastomeric fins 3 are designed to deform to adapt to different inner diameters of the liner but the ability of the fins to conform completely to the inner profile 3 is limited. Where there is a sharp shoulder in the inner profile, e.g. as shown at reference 6, it may be impossible for the wiper dart fins to access it. This is especially true for a shoulder with a distally-directed surface as shown in FIG. 1 at reference 7.

[0041] If pockets 5 of cement remain, the cement may set and can obstruct the functioning of the completion components, e.g. sliding sleeves, installed in the liner 1. The cement can also become loosened over time and contaminate fluids in the well.

[0042] FIG. 2 shows a similar section of liner 1 with completion equipment making an irregular inner profile 2. An insert 8 is fitted to the liner and completion equipment prior to running the liner into the well bore. In fact the insert 8 may be included with the completion equipment at the manufacturing stage. The insert fits snugly to the inner profile 2 of the liner and completion equipment. In this embodiment, the inner surface 9 of the insert 7 is slightly proud of the regular parts 10 of the liner inner surface on each side of the irregular surface 2. The insert 9 has profiled proximal and distal (entry and exit) inner surfaces 11 to create a smooth transition between the uniform inner liner surface 10 on each side of the irregular surface 2.

[0043] In an alternative embodiment, the inner surface 9 of the insert is flush with the uniform portions 10 of inner liner surface.

[0044] When a wiper dart (not shown in FIG. 2) is passed through the liner with the insert/sleeve 8, there are no abrupt shoulders to trap cement and the wiper may efficiently clean the whole surface of the insert.

[0045] After cleaning, the well is then completed. Since this requires access to the completion equipment, the insert/sleeve needs to be removed. The insert is made from aluminium metal in contrast to the remainder of the liner and completion equipment which is of steel. Aluminium is considerably more reactive than steel and can be dissolved away using standard 28% hydrochloric acid such as is commonly used in completions in carbonate reservoirs. Once acid has been passed down the liner, the completion equipment including sliding sleeves, etc. is freed up and a standard completion operation can be carried out.

[0046] 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.

[0047] 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

[0048] 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: [0049] 1. US2019040695, “Sacrificial Protector Sleeve,” (2016).