REMEDIAL TECHNIQUE FOR MAINTAINING WELL CASING
A method for repairing a leak in a wellbore includes determining a location of the leak in the wellbore, lowering a casing drilling tool to approximately the location of the leak, drilling a hole in a casing lining the wellbore, pumping a sealing fluid into the hole drilled in the casing, and installing a plug in the hold in the casing.
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This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/678,289, filed on Aug. 1, 2012, and entitled “Remedial Technique for Maintaining Well Casing Integrity and Inner Diameter,” which is incorporated by reference.
BACKGROUNDFor wells produced using a thermal heavy oil production method, in particular Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS), there is sometimes a need to perform remedial work if the steam has broken through the cement barrier and is seeping to the surface.
Prior art remedial methodologies typically use of a combination of the ultrasonic imaging tool (USIT), Isolation Scanner cement evaluation service (both available from Schlumberger Technology Corporation of Sugar Land, Tex., USA), and cement bond logs to identify the source of the leak. Once the source of the leak is identified, the next step is typically to perforate the well where the leak has been identified, and squeeze cement into the perforations followed by the insertion of a liner. On rare occasions a casing patch will be used. In both cases, the remedial methods result in a reduction of effective casing inner diameter (ID).
SUMMARYIn one aspect, this disclosure relates to a method for repairing a leak in a wellbore that includes determining a location of the leak in the wellbore, lowering a casing drilling tool to approximately the location of the leak, drilling a hole in a casing lining the wellbore, pumping a sealing fluid into the hole drilled in the casing, and installing a plug in the hold in the casing.
In another aspect, this disclosure relates to a tool for repairing leaks in casing that includes a drill for boring through the casing, a seal for sealing around a hole in the casing, and a supply of sealing fluid.
A method for performing remedial work may include using a cased hole drilling type tool, such as the Cased Hole Dynamics Tester (CHDT™) available from Schlumberger Technology Corporation, to drill a hole in the casing in the area identified as the source of the leak, inject sealing fluid, and plug the hole, leaving a full diameter casing intact with full metallic pipe integrity. A cased hole drilling tool is described in U.S. Pat. Nos. 7,999,542; 5,779,085; 5,746,279; and 5,687,806, each of which is incorporated by reference.
A cased hole drilling type tool may be used to drill a hole in the casing in the area identified as the source of the leak. The tool may then inject a sealing fluid (e.g., cement) and plug the hole in the casing leaving the casing ID substantially intact.
To place the tool in the exact area that has been identified as the source of the steam leak, a gyroscope may be run downhole both during the leak identification phase and before the drilling phase.
In one example, the tool may include a packer that seals against the casing. Once a seal has been established the tool's drill bit drills a hole through the casing, cement, and formation.
The sealant injection phase may be performed using a pump module within the tool. The pump module is used to pump the fluid from a storage tank within the tool to the area behind the casing. The storage can be either sample chambers stacked to carry sufficient sealant volume. In another example, coiled tubing may be used to continuously delivering the sealant from the surface to the tool's flowline. This second method has the benefit of removing the sealant volume limitation that exists if the sealant is carried downhole using sample chambers.
Next, a plug may be installed in the hole drilled by the casing drilling tool. A mechanical expansion plug able to sustain bi-directional pressure differentials may be used. In one example, the mechanical plug material is selected such that the expansion rate of that material is the same or greater than the casing so that the severe temperature cycles characteristic of thermal production methods do not cause the plug/casing seal to be broken.
The packer 22 may be urged against the casing to create a seal inside of which a hole may be drilled and through which sealing fluid may be pumped. This is just one example of how to make an effective seal. Other methods are known in the art, such as using double annular packers to create an isolated annular volume within the borehole. The tool 20 in the example of
It is noted that
In one example, the sealing fluid is cement. Cement can be used to reinforce the cement 12 that is already in place behind the casing 14. Other sealing fluids may be used.
In the example in
The method shown in
The method shown in
The method shown in
The method may include installing a plug in the hole, at step 65. The plug is inserted so that the sealing fluid stays behind the casing and to prevent wellbore fluid from leaking behind the casing during further operations.
Although only a few example examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example examples without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. Moreover, examples disclosed herein may be practiced in the absence of any element which is not specifically disclosed.
Claims
1. A method for reparing a leak in a wellbore, comprising:
- determining a location of the leak in the wellbore;
- lowering a casing drilling tool to approximately the location of the leak;
- drilling a hole in a casing lining the wellbore;
- pumping a sealing fluid into the hole drilled in the casing; and
- installing a plug in the hold in the casing.
2. The method of claim 1, wherein the sealing fluid comprises cement.
3. The method of claim 1, wherein the plug is a mechanical expansion plug able to sustain bi-directional pressure differentials.
4. The method of claim 1, further comprising:
- setting a packer in the casing drilling tool before drilling the hole; and
- wherein pumping the sealing fluid into the hole drilled in the casing comprises pumping cement from a chamber within the casing drilling tool.
5. The method of claim 1, wherein pumping the sealing fluid into the hole drilled in the casing comprises pumping a cement from the surface through coiled tubing coupled to the cased hole drilling tool.
6. The method of claim 1, wherein the plug is made of a material selected such that an expansion rate of the material is the same or greater than an expansion rate of the casing.
7. A tool for repairing leaks in casing, comprising:
- a drill for boring through the casing;
- a seal for sealing around a hole in the casing; and
- a supply of sealing fluid.
8. The tool of claim 7, wherein the supply of sealing fluid comprises cement stored in a chamber within the tool.
9. The tool of claim 7, wherein the supply of sealing fluid comprises a reservoir of sealing fluid at a surface location connected to the tool by coiled tubing.
10. The tool of claim 7, wherein the seal is a set of packers capable of setting above and below the hole in the casing.
Type: Application
Filed: Jul 31, 2013
Publication Date: Jul 16, 2015
Applicant: SCHULUMBERGER TECHNOLOGY CORPORATION (Sugar Land, TX)
Inventors: David Bexte (Arrowwood), Michele Tesciuba (Rosharon, TX), Douglas Pipchuk (Calgary)
Application Number: 14/419,221