Patent Publication Number: US-2010108323-A1

Title: Reliable Sleeve Activation for Multi-Zone Frac Operations Using Continuous Rod and Shifting Tools

Description:
BACKGROUND 
     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&#39;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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a system using continuous rod and a tool actuating device. 
         FIG. 2A  shows a cross-section of a sliding sleeve in a closed condition. 
         FIG. 2B  shows a cross-section of the sliding sleeve in an opened condition. 
         FIG. 3  shows a tool actuating device on an end of a continuous rod. 
         FIG. 4A  shows an isolated cross-section of an upper (opening) shifting tool for the tool actuating device. 
         FIG. 4B  shows a cross-section of the upper (opening) shifting tool having the continuous rod and an intermediate sucker rod coupled at its ends. 
         FIG. 5  shows a cross-section of a lower (closing) shifting tool for the tool actuating device. 
         FIG. 6A  shows the upper (opening) shifting tool opening a sliding sleeve initially in the closed (up) condition. 
         FIG. 6B  shows the lower (closing) shifting tool closing a sliding sleeve initially in the opened (down) condition. 
         FIGS. 7A-7E  shows stages of actuating sliding sleeves with the tool actuating device. 
         FIGS. 8A  shows another tool actuating device. 
         FIG. 8B  shows a cross-section of the tool actuating device of  FIG. 8A . 
     
    
    
     DETAILED DESCRIPTION 
     A system  10  schematically shown in  FIG. 1  uses a continuous rod  40  and a tool actuating device  60  to actuate downhole tools during well operations. In the current example, the system  10  is used in conjunction with frac operations, and the continuous rod  40  and tool actuating device  60  allow operators to selectively open and close sliding sleeves  50  downhole. In the typical implementation as shown, a cased borehole  12  passes through a formation, and a tool string  14  installed in the borehole  12  has several sliding sleeves  50  positioned adjacent perforations  13  at various intervals in the cased borehole  12 . Packers  20  isolate portions of the annulus  15  of the borehole  12  and string  14  between each section of perorated borehole  12 . In this way, frac fluid pumped down the tool string  14  can be diverted by an open sliding sleeve  50  through the isolated perforations  13  to treat the isolated zone of the formation. 
     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  FIG. 2A  has a housing  52  with an insert  54  movably disposed therein. When closed as shown in  FIG. 2A , the insert  54  is positioned toward the lower end of the housing  52 . In this position, slots  55  in the insert  54  do not align with ports  53  in the side of the housing  52  so that fluid passing in the sleeve  50  is not diverted outside the sleeve  50  and the tubing to which it is coupled at both ends. When opened as shown in  FIG. 2B , the insert  54  is positioned toward the upper end of the housing  52 . In this position, the slots  55  in the insert  54  align with the ports  53  in the side of the housing  52  so that fluid passing in the sleeve  50  can be diverted outside the sleeve  50 . 
     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  FIG. 3 , the tool actuating device  60  couples to a threaded pin  42  on the continuous rod  40 . At top, the device  60  has an upper (opening) shifting tool  100  that couples to the rod&#39;s threaded pin  42  using a rod coupling  70 . At bottom, the device  60  has a lower (closing) shifting tool  200  that couples below the upper tool  100  using rod couplings  70  and an intermediate length of sucker rod  80 . When the continuous rod  40  is moved upper or down in a tubing string, the upper and lower tools  100 / 200  move together. 
     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  FIGS. 2A-2B ). Likewise in this example, the lower tool  200  is designed to be the closing tool for closing the sliding sleeves  50  by engaging the lower profile ( 56 ) and shifting the insert ( 54 ) downward in the housing ( 50 ). (See  FIGS. 2A-2B ). Thus, the upper shifting tool  100  opens the sleeve  50  by jarring up, and the lower shifting tool  200  closes the sleeve  50  by jarring down. However, a reverse arrangement could also be used. For example, the arrangement of tools  100  and  200  on the device  60  could be switched so that the (closing) shifting tool  200  can be the upper tool and the (opening) shifting tool  100  can be the lower tool. Congruent with this, the sliding sleeves  50  could also be open and closed by respectively shifting down and up—opposite to that shown in  FIGS. 2A-2B . 
     The upper (opening) shifting tool  100  shown in  FIG. 4A  has a core mandrel  110  with fishneck couplings  102  and  104  threaded at both ends. A biased collet  120  fits around the mandrel&#39;s recessed intermediate portion  116  and connects at both ends to stops  112  and  114  fixed to the core mandrel  110 . The collet  120  has B-profiles  122  that include an upward facing shoulder  124 , an upper (shortened) cam  126 , and a lower (extended) cam  128 . As discussed in more detail later, the B-profiles  122  enable the collet  120  to engage recessed profiles in the sliding sleeve in one direction and bypass the recessed profiles in the sliding sleeve in the opposite direction. This type of shifting tool is typically referred to as a B shifting tool with a B-profile. 
     As shown in  FIG. 4B , the upper (opening) shifting tool  100  couples to the distal end  42  of the continuous rod  40  using a sucker rod coupling  70 . As shown, this coupling  70  has a cylindrical body  72  with internal thread  74  that connects to the rod&#39;s threaded pin  42  and to the pin  103  on the tool&#39;s upper fishneck coupling  102 . The sucker rod coupling  70  can use thread  74  that is preferably cold form-rolled as opposed to cut and can use the PRO/KC design available from Weatherford/Lamb, Inc. As shown, the coupling  70  can also use a center torque button  76  positioned between the threaded pins  42 / 103  of the rod  40  and fishneck  102  for equal contact pressure of both pin noses. In a similar fashion, another sucker rod coupling  70  couples the tool&#39;s lower fishneck  104  to the upper pin on the device&#39;s intermediate sucker rod  80 . 
     As with upper tool  100 , the lower (closing) shifting tool  200  shown in  FIG. 5  includes similar components, including a core mandrel  210  with a fishneck coupling  202  threaded at its top and including a collet  220  fitting around the mandrel&#39;s recessed intermediate portion  216  and connected at both ends to stops  212  and  214  fixed to the core mandrel  110 . The tool  200  has a nose  204  at its distal end. The collet  220  has B-profiles  222  that include a shoulder  224 , an upper cam  226 , and a lower cam  228 . For this closing tool  200 , however, the B-profile  222  is reversed so that the shoulder  224  is downward facing and the upper cam  228  is extended. 
     Operation of the upper tool&#39;s B-profile  122  in opening a sliding sleeve  50  is shown in  FIG. 6A . Operators manipulate the upper tool  100  upward in the sleeve&#39;s housing  52  using the continuous rod  40  and rig equipment at the surface. The B-profile&#39;s (upward-facing) shoulder  124  engages a downward-facing shoulder in the insert&#39;s upper recess profile  58 . When engaged, further upward movement of the tool  100  moves the insert  54  upward within housing  52  toward an opened condition in which the insert&#39;s slots align with the housing&#39;s ports so fluid can be diverted. Eventually, full upward movement on the tool  100  causes the upper cam ( 126 ) to engage an upper release  59  defined in the housing  52 , biasing the collet  120  inward and releasing the shoulder  124  from the insert&#39;s profile  58 . At this point, the tool  100  can move out of the housing  52  while the insert  54  remains in the opened (upward) condition. 
     Operation of the lower tool&#39;s B-profile  222  in closing the sliding sleeve  50  is shown in  FIG. 6B  and follows a reversed configuration. Here, the B-profile&#39;s (downward-facing) shoulder  224  engages an upward-facing shoulder in the insert&#39;s lower recess profile  56 . When engaged, further downward movement of the tool  200  moves the insert  54  downward within housing  52  toward a closed condition. Eventually, the lower cam ( 228 ) engages a lower release  57  so the shoulder  224  is released and the tool  200  can move out of the housing  52  while the insert remains in the closed (downward) condition. 
     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  FIG. 7A-7E , the tool actuating device  60  selectively actuates the various sliding sleeves  50  downhole by successively opening and closing the sleeves  50  to treat isolated zones. Using the continuous rod  40  to manipulate the device  60  is more reliable than using coiled tubing, which would tend to produce more friction and would require more time to actuate the sleeves  50 . 
     As initially shown in  FIG. 7A , the sliding sleeves  50  are deployed on the string  14  downhole before the frac operation. Operators couple the upper shifting tool  100  to the distal end of the continuous rod  40 , couple the intermediate rod  80  to the bottom of the upper tool  100 , and coupled the lower shifting tool  200  to the free end of the intermediate rod  80 . Operators then install the device  60  in a lubricator fitted atop the wellhead at the surface and deploy the continuous rod  40  and selective shifting tools  100 / 200  downhole using the drive and other components of the rig ( 30 ; See  FIG. 1 ). 
     When lowered, the tools  100 / 200  are passed through each of the sliding sleeves  50 A-C, which are initially installed closed on the string  14 . The sleeves  50 A-C may be deployed with grease or other material packed inside to maintain the sliding inserts ( 54 ) in the closed condition in the sleeves  50 A-C during deployment. As the tools  100 / 200  are deployed downhole, they cam past each of the sleeves&#39; inserts ( 54 ) without engaging the profiles ( 56 ,  58 ). Eventually, the upper (opening) tool  100  passes into the lowermost sliding sleeve  50 A. Using a upward jarring movement, the upper (opening) tool  100  opens the lowermost sliding sleeve  50 A by engaging the collet&#39;s B-profiles ( 122 ) into the insert&#39;s upper recess ( 58 ) (See  FIG. 6A ). A jar (not shown) installed on the continuous rod  40  or the rig ( 30 ) at the surface can impart this jarring movement. Once the sleeve  50 A opens and the B-profiles ( 122 ) cams free, the continuous rod  40  and tools  100 / 200  are moved below the open lowermost sleeve  50 A, as shown in  FIG. 7B . 
     As then shown in  FIG. 7B , operators perform a frac treatment by pumping frac fluid down the tool string  14  while the continuous rod  40  remains in the tubing sting  14 . Leaving the continuous rod  40  and shifting tools  100 / 200  in the string  14  during the frac treatment below the open sleeve  50 A eliminates the rig time that would be required to trip the tools  100 / 200  and rod  40  out of the sting  14  between frac treatments, as would conventionally be done to protect coiled tubing if used to actuate the sleeves. 
     During treatment, the frac fluid diverts through the open sleeve  50 A 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  FIG. 7C , the upper tool  100  freely passes through the lowermost sliding sleeve  50 A that remains open. With further lifting, the lower (closing) tool  200  is positioned to engage this open sliding sleeve  50 A. Using a downward jarring movement, the lower tool  200  closes this lowermost sleeve  50 A. 
     As shown in  FIG. 7D , the device  60  and rod  40  are then lifted in the tubing string  14 , and the upper (opening) tool  100  engages the next uppermost sliding sleeve  50 B (which is closed). Using an upward jarring movement, the tool  100  is used to open this sleeve  50 B. As shown in  FIG. 7E , once the upper tool  100  cams free, operators position the two tools  100 / 200  in between the sliding sleeves  50 A- 50 B, pump frac fluid in the string  14 , and treat the next isolated zone adjacent the open sleeve  50 B. Once fracing is complete for this zone, operators lift the tools  100 / 200  and again close the open sliding sleeve  50 B, open the next upper most sliding sleeve  50 C, and frac the next zone. Operations then continue in this same manner up the string  14  as each successively higher isolated zone is treated. 
     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  50 A 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  50 A. 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  FIG. 3  uses upper and lower shifting tools  100  and  200  separated by an intermediate sucker rod  80 . Another arrangement of the device  60  can uses a two-way shifting tool  300  as shown in  FIGS. 8A-8B . Here, the two-way shifting tool  300  couples to the threaded pin  42  of the continuous rod  40  using a sucker rod coupling  70 . The two-way tool  300  includes many of the same components as the upper and lower tools discussed previously so that the tool  300  includes a core mandrel  310 , a fishneck coupling  302 , stops  312 / 314 , a biased collet  320 , and a nose  304 . On this tool  300 , the collet  320  has dual B-profiles  322  having a downward-facing shoulder  324 , an upper cam  326 , an upward-facing shoulder  325 , and a lower cam  328 . Depending on the sleeve&#39;s configuration, the shifting tool  300  can open/close the sleeve by jarring down and can close/open the sleeve by jarring up. This tool  300  can be used for selective frac treatments of isolated zones in a similar fashion to that discussed above with reference to  FIGS. 7A-7E . 
     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  FIGS. 2A-2B  and  6 A- 6 B, the system  10  when used for frac operations can be used with a mono-bore type of sliding sleeve, but other types of sliding sleeves could also be used. Examples of suitable sliding sleeves include the Otimax™ Sliding Sleeve, the Optislim™ Sliding Sleeve, and WXO and WXA Standard Sliding Sleeves, each of which are products of Weatherford/Lamb, Inc.—assignee of the present application. 
     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.