The present application is a U.S. National Stage Application of International Application No. PCT/US2015/031545 filed May 19, 2015, which is incorporated herein by reference in its entirety for all purposes.
The present disclosure relates generally to downhole cementing applications, and, more particularly, to an improved method and apparatus for bonding casing to a subterranean formation in cyclic load applications.
Hydrocarbons, such as oil and gas, are commonly obtained from subterranean formations that may be located onshore or offshore. The development of subterranean operations and the processes involved in removing hydrocarbons from a subterranean formation typically include a number of different steps such as, for example, drilling a wellbore at a desired well site, treating the wellbore to optimize production of hydrocarbons, and performing the necessary steps to produce and process the hydrocarbons from the subterranean formation.
Certain subterranean reservoirs contain hydrocarbons, which are difficult to produce because they are highly viscous. Tar sand formations are one example of such a reservoir. One common technique for recovering oil and gas from such subterranean reservoirs is to inject them with steam. The steam makes the hydrocarbons less viscous thereby making them easier to produce through conventional production casing or tubing. There are several different methods for injecting steam into the formation. One such manner is simple injection of steam into a wellbore and producing from a nearby or adjacent wellbore. The other is by use of a Huff & Puff well. A Huff & Puff well has the advantage of simply requiring a single well and thereby avoids the cost and expense of drilling multiple wells.
A drawback, however, of Huff & Puff wells, and other steam injection wells is that the wide temperature and pressure variations that are generated through the steam injection process and subsequent cooling of the well to allow production to flow puts stress on the cement bonds that are formed between the casing string and the wellbore. This is because the casing string itself expands and contracts in response to the temperature and pressure variations. Over time, this expansion and contraction of the casing string can result in a failure of the bond formed between the casing string and the wellbore, which can be detrimental to the structural integrity of the well and to the hydraulic seal formed by the cement.
Studies have found that if the casing string is pre-stressed, for example, by being put under tension prior to cementing to the wellbore, it can better withstand the wide temperature and pressure swings that occur with the steam injection process. This is because the pre-stressing of the casing string limits the expansion and contraction that occurs with the temperature and pressure swings.
One technique that has been developed to pre-tension the casing string involves employing two different types of cement slurries, each having different set times. The first step in this process is to pump the slurry having the longer set time, known as the lead slurry, down the casing string after it has been installed in the wellbore and back up the annulus formed between the casing string and the wellbore. The next step is to pump the slurry with the shorter set time, known as the tail slurry, behind the lead slurry. The tail slurry is pumped down the casing string and back up the annulus. It is placed along the bottom portion of the annulus, for example, along the bottom 500 feet in a 2,000-foot well. Once the tail slurry sets, rigidly securing the bottom portion of casing string to the formation, then the rig pulls up on the top of the casing string, the casing string is thereby put into tension. Slips are then set at the surface to hold the casing string in tension as the lead slurry sets. Once both slurries have set, the casing string remains bonded in place under tension.
While this technique puts the casing string in a pre-stressed condition and thereby minimizes the cement bond failures that would otherwise occur without pre-loading, it has the drawback of requiring the rig to remain idle while the tail slurry sets. This results in lost rig time of approximately 5 hours or more for each cement job performed. In fields having hundreds or thousands of wells, this can be quite costly for the well operator.
The present disclosure is directed to a method and apparatus that seeks to pre-stress the casing string while minimizing the costly rig time required with current pre-tensioning techniques.
For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
Illustrative embodiments of the present disclosure are described in detail herein. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation specific decisions must be made to achieve developers' specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure. Furthermore, in no way should the following examples be read to limit, or define, the scope of the disclosure.
Turning to
The casing anchor 16 is formed of a number of different components, including a main body 18, which is a generally tubular-shaped member formed of a steel alloy having the same general size, weight, grade and thread as the casing string. As those or ordinary skill in the art will appreciate, the outer diameter of the main body 18 is smaller than the inner diameter of the casing collar 12 and parent casing 14 to allow the casing anchor 16 to travel down the interior of the surface casing. The casing anchor 16 also includes a lock sleeve 20, which is slidably installed on the main body 18. The casing anchor 16 further includes a lock sleeve wedge 22, which is slidably installed on the main body 18 adjacent to the lock sleeve 20. The wedge 22 supports the lock sleeve 20 as it engages the casing anchor collar 14. The lock sleeve 20 and wedge 22 are also formed of a steel alloy having the same general size, weight, and grade as the production casing.
In one embodiment, the lock sleeve 20 has a generally spider-like shape. It is defined by a generally circular ring 24 having a plurality of arms 26 projecting therefrom. In one exemplary embodiment, there are eight arms 26 projecting from, and equally-spaced around, the generally circular ring 24. The plurality of arms 26 are generally flexible at least in the radial direction, such that they may be placed in compression when the casing anchor 16 is deployed downhole into the surface casing. Each of the arms 26 has an end or tip 28 which has opposing tapered surfaces, as better illustrated in
The wedge 22 is a generally ring-shaped member and functions to wedge the tapered tips 28 of the lock sleeve arms 26 into the recesses 30 formed in the inner surface of the casing collar 12 when the work string pulls up on the casing anchor 16 once it has been set in the casing collar 12, as shown in
The present disclosure is also directed to a method for cementing a production casing string to the surface casing and well bore. The method includes landing the production casing string 40 in the surface casing 14, as shown in
With the casing anchor 16 set, the rig is able to put the casing string in tension. Slips can be set at the surface to maintain the production casing string 40 in tension while the production casing string is being cemented to the surface casing 14 and wellbore. The production casing string 40 above the slips can be detached from the rest of the casing once the slips have been set, thereby enabling the rig to be deployed to another well, which can save valuable rig time and money for the well operator. Once the production casing string has been placed in tension, cement slurry can be pumped down the bore of the production casing string and up into the annulus formed between the production casing string 40 and the surface casing 14 and wellbore below the surface casing 14. The cement slurry then can be allowed to set while the production casing string 40 is under tension. This acts to preload the casing string and thereby minimize its expansion and contraction during large swings in downhole temperature and pressure, which are common in a number of well types, including, for example, Huff & Puff wells.
Once the cement bond has formed between the production casing string 40 and the surface casing 14 and wellbore below the surface casing, further well operations, such as perforation, gravel packing, zonal isolation, etc., may be performed on the well.
Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the following claims.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/US2015/031545 | 5/19/2015 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2016/186655 | 11/24/2016 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
3976139 | Wilder | Aug 1976 | A |
4538442 | Reed | Sep 1985 | A |
9238952 | Rogers et al. | Jan 2016 | B2 |
20050023000 | Warren | Feb 2005 | A1 |
20060032640 | Costa et al. | Feb 2006 | A1 |
20080087418 | Cook et al. | Apr 2008 | A1 |
20120298380 | Rogers et al. | Nov 2012 | A1 |
Number | Date | Country |
---|---|---|
2837250 | Nov 2012 | CA |
59080818 | May 1984 | JP |
Entry |
---|
International Search Report and Written Opinion issued in related PCT Application No. PCT/US2015/031545 dated Feb. 17, 2016, 19 pages. |
International Preliminary Report on Patentability issued in related PCT Application No. PCT/US2015/031545, dated Nov. 30, 2017, 10 pages. |
Office Action issued in related Canadian application No. 2978273 dated Aug. 16, 2018 (6 pages). |
Number | Date | Country | |
---|---|---|---|
20180283115 A1 | Oct 2018 | US |