Selectively fracing multiple zones of a formation improves the production capabilities of a well. The equipment string for such a frac operation uses a series of packers to sequentially isolate different zones of a downhole formation. Sliding sleeves on the tubing string position between each of the packers and provide exit ports for frac fluid to interact with the adjacent zones of the formation. Performing successive frac treatments on the isolated zones requires the sliding sleeves to be opened and closed in a desired sequence so that zones of interest can be fraced independently of the other zones. To do this, the frac operation uses several steps. First, one sliding sleeve is opened, while the others remain closed. Frac fluid is pumped downhole and through the open sleeve to interact with the adjacent zone of the formation. When facing is done for this zone, the sliding sleeve is then closed, and another sliding sleeve is opened so the next zone can be treated.
Sliding sleeves can be activated using many types of devices, including balls, darts, and pulling tools. Currently, operators experience problems when performing frac operations For example, the number of zones that can be treated may be limited by the method used to actuate the sleeves. Also, operators can have difficulties ensuring that the proper sleeve is open for the frac treatment and then that the proper sleeve is closed and sealed after that treatment. This difficulty can be even more problematic when fracing a horizontal well.
When balls are used to actuate the sliding sleeves, for example, the frac treatment is applied successively to each isolated zones by selectively opening the sliding sleeves and allowing the treatment fluid to interact with the adjacent zones of the formation. To open each sliding sleeve, operators drop a specifically sized ball into the tubing string and land the ball on a corresponding ball seat on a designated sliding sleeve. Once seated, the ball closes off the lower zone just treated, and built up pressure on the seated ball forces the sliding sleeve open so frac fluid can interact with the adjacent zone of the formation. Operators repeat this process up the tubing string by successively dropping larger balls against larger ball seats in the sliding sleeves.
The required diameters of the ball seats and the required increments between ball sizes limits how many zones can be treated using balls to open the sliding sleeves. For example, the lowermost ball seat must be the smallest, and each shallower seat must be sized slightly larger. In general, the balls can range in size from 1-in. to 3¾-in. Therefore, only a finite number of frac zones can be successfully used when opening the sleeves with balls due to the needed increments between ball sizes to differentiate them from one another. Therefore, actuating sliding sleeves with balls is not practical for frac operations involving several (e.g., more than about eleven) frac zones. In addition to the limit on the number of frac zones that can be handled, using balls and darts to open sliding sleeves only allows for one shot operations. In other words, the balls and darts are only capable of opening the sleeves, which cannot be closed unless another device is used. Finally, any balls and darts used to operate sleeves must be removed either by floating or milling them, which involves time and expense to perform.
Other than balls and darts, a pulling tool connected to wireline can be used to actuate sliding sleeves during a frac operation. However, actuating sliding sleeves using wireline can be limited in horizontal sections downhole. In many cases, wireline has no real pushing capabilities, which limits its use in operating sliding sleeves or other flow control systems within a wellbore.
Using coiled tubing can overcome the limitations of wireline. Unfortunately, a pulling tool on coiled tubing can still have limited access in extended horizontal wellbores, making it difficult for the pulling tool to reach sliding sleeves in horizontal sections. This difficulty is due at least in part to the fact that coiled tubing has some memory inherent in its material. Therefore, the coiled tubing as it is run downhole with the pulling tool is more likely to produce friction within the tubing string in which it is run, making moving the coiled tubing and the pulling tool more difficult. When used under these circumstances, the coiled tubing requires operators to spend an excessive amount of time to locate and subsequently open or close a sliding sleeve—sometime without success altogether. Furthermore, coil tubing is expensive and is preferably removed from the tubing string with each frac treatment to avoid damage to the coil tubing. Finally, the physical nature of coiled tubing inherently limits the coil tubing's ability to operate sliding sleeves by pushing. All of these issues greatly increase the time and cost of performing a frac operation with coiled tubing and make coiled tubing less desirable for operating sliding sleeves.
What is needed is a solution for cycling sliding sleeves open and closed in extended horizontal applications that can be better manipulated from the surface and that is more reliable in opening and closing the sleeves downhole.
A system 10 schematically shown in
As shown, the cased borehole 12 can have an extended horizontal section that makes actuating the sliding sleeves 50 difficult with conventional coiled tubing or wireline techniques. To overcome these difficulties, the tool actuating device 60 is disposed on the distal end of the continuous rod 40, and the rod 40 and device 60 are used together to effectively and reliably open and close the sliding sleeves 50 in such an extended horizontal section. (The system 10 can be used equally as well in vertical applications). In general, the tool actuating device 60 can be moved up or down in the string 14 to selectively actuate a given sleeve 50 between opened and closed conditions by engaging specific profiles on the device 60 with profiles in the sleeve 50. The rigid continuous rod 40 stiffly conveys the desired movement of the device 60 relative to the sleeves 50, making the opening and closing of the sleeves 50 more predictable and ensuring that more complete travel of the sleeves 50 is achieved.
As noted previously, coiled tubing has some memory inherent in its material and produces undesirable friction when conveyed in a horizontal borehole. As a result, operators must spend an unwarranted amount of time attempting to locate and actuate the sliding sleeves downhole—sometimes with no success. However, the continuous rod 40 attempts to straighten out in the tubing string 14 and produces a lower friction component. The reduced friction allows operators to move the tool actuating device 60 as needed with better control from the surface. In this way, the rod 40 and device 60 facilitate frac operations in the horizontal length of the borehole.
As shown, the continuous rod 40 deploys in the tool string 14 to convey the device 60 downhole to the sliding sleeves 50. At the surface, a rig 30 for extended continuous rod is used to manipulate (raise and lower) the continuous rod 40 in the string 14 and thereby move the actuating device 60 relative to the sliding sleeves 50. This rig 30 can be similar to that used with extended continuous rod. For example, the rig 30 can include a reel for the continuous rod 40 and a variable-speed, hydraulically driven gripper mechanism (not shown), and the rig 30 can be adapted to operate like a heavy duty slickline unit at the surface to deploy the continuous rod 40 and device 60 downhole. In addition to the rig 30, other components (not shown), such as wellhead, lubricator, etc., are also used at the surface.
The sliding sleeves 50 can be selectively opened and closed to divert frac fluid in the tubing string 14 to the isolated zone of the annulus 15 between packers 20. An example sliding sleeve 50 shown in
To move the insert 54 between the opened and closed conditions, the insert 54 has a lower profile 56 and an upper profile 58 that allow the insert 54 to be engaged and moved within the housing 52. For the present sleeve 50, the lower profile 56 is used to move the insert 54 downward in the housing 52, thereby closing the sleeve 50. By contrast, the upper profile 58 is used to move the insert 54 upward in the housing 52, thereby opening the sleeve 50. A reverse arrangement is also possible in which upward movement of the insert 54 by the upper profile 58 can close the sleeve 50 and downward movement by the lower profile 56 can open the sleeve 50.
With an understanding of the system 10, continuous rod 40, sliding sleeves 50, and tool actuating device 60 provided above, discussion now turns to a more detailed description of the tool actuating device 60. As shown in
In the present example, the upper tool 100 is designed to be the opening tool for opening the sliding sleeves 50 by engaging the upper profile (58) and shifting the insert (54) upward in the housing (50). (See
The upper (opening) shifting tool 100 shown in
As shown in
As with upper tool 100, the lower (closing) shifting tool 200 shown in
Operation of the upper tool's B-profile 122 in opening a sliding sleeve 50 is shown in
Operation of the lower tool's B-profile 222 in closing the sliding sleeve 50 is shown in
As discussed above, the continuous rod 40 and tool actuating device 60 can be deployed by a surface rig 30 to open and close sliding sleeves during a frac operation. In stages of a frac operation shown in
As initially shown in
When lowered, the tools 100/200 are passed through each of the sliding sleeves 50A-C, which are initially installed closed on the string 14. The sleeves 50A-C may be deployed with grease or other material packed inside to maintain the sliding inserts (54) in the closed condition in the sleeves 50A-C during deployment. As the tools 100/200 are deployed downhole, they cam past each of the sleeves' inserts (54) without engaging the profiles (56, 58). Eventually, the upper (opening) tool 100 passes into the lowermost sliding sleeve 50A. Using a upward jarring movement, the upper (opening) tool 100 opens the lowermost sliding sleeve 50A by engaging the collet's B-profiles (122) into the insert's upper recess (58) (See
As then shown in
During treatment, the frac fluid diverts through the open sleeve 50A and treats the adjacent isolated zone though the perforations 13. Once this zone has been treated, operators use the rig to lift the continuous rod 40 in the string 14. As shown in
As shown in
Although the frac operation discussed above involved opening the sleeves 50 in the uphole direction and closing them in the downhole direction, the reverse arrangement could be used. Likewise, treatment of successive zones could proceed successively from the uppermost zone to the lowermost zone or could be performed selectively at any of the various zones. In addition, although the device 60 and continuous rod 40 are initially deployed from the surface downhole to the lowermost sleeve 50A in the above discussion, it is also possible to deploy the device 60 independently in a bottomhole assembly (not shown) coupled in a conventional manner to the tubing string 14 below the lower most sliding sleeve 50A. In this case, the continuous rod 40 can then be deployed downhole with a suitable coupling known in the art to connect to the device 60 and retrieve if from the bottomhole assembly to conduct the successive frac operations up the wellbore.
The tool actuating device 60 of
In general, the continuous rod 40 used with the system 10 can be COROD® and can have similar properties and characteristics. (COROD is a registered trademark of Weatherford/Lamb Inc.—the assignee of the present disclosure). For example, the continuous rod 40 can be composed of carbon steel, chromium-molybdenum alloy steel (e.g., AISI 4142), or other suitable material and can have round or semi-elliptical cross-section with a diameter ranging from 12/16-inch to 18/16-inch, for example.
As shown in
Although the system 10 has been described for opening and closing sliding sleeves on a frac string, the system of continuous rod 40 and tool actuating device 60 can also be used to actuate other downhole tools that can be actuated to a first operative condition in a first direction and to a second operative condition in a second direction. Some other suitable downhole tools include, for example, a gravel pack closing sleeve, a completion isolation valve, or other downhole tool having shiftable operation. With any of these downhole tools, the ability to actuate the tool with the continuous rod 40 and actuating device 60 can be enhanced by the reliable and efficient operation that the rod 40 and device 60 offer in either vertical or horizontal wells.
The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.