Patent Publication Number: US-10329887-B2

Title: Dual-walled coiled tubing with downhole flow actuated pump

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the use of strings of coiled tubing to dispose flow actuated pumps into a wellbore and operation of such pumps. 
     2. Description of the Related Art 
     Downhole pumps are used to pump hydrocarbon fluids and/or water from subterranean locations. Electric submersible pumps (“ESPs”) require electrical power to be supplied to them from surface. A typical ESP assembly includes a centrifugal pump that is mounted to an electrical motor. A power cable extends from the surface to the motor of the ESP assembly. 
     Flow actuated pumps are also known which utilize a piston or plunger to flow fluid, as opposed to a centrifugal pumping mechanism. A flow actuated pump is described in U.S. Pat. No. 7,789,131 entitled “Hydraulic Pump System for Deliquifying Low Rate Gas Wells.” The &#39;131 patent is owned by the assignee of the present invention and is hereby incorporated by reference in its entirety. The flow actuated pump described in the &#39;131 patent uses a power fluid supplied from surface to operate the pumping mechanism rather than electrical power. Most flow actuated pumps return exhausted power fluid with the wellbore fluid (water, gas, etc.) being produced. However, some flow actuated pumps may have separate outputs for the exhausted power fluid and the wellbore fluid. 
     Dual-walled piping has been used in subsea applications to raise production fluid from a pump located on a seabed and not directly into a well. Such an arrangement is described in U.S. Patent Publication 2003/0170077 by Herd et al. However, dual-walled coiled tubing has not heretofore been successfully used in subterranean wellbores in conjunction with fluid driven or flow actuated pumps or for dewatering gas wells. The high pressure, high temperature conditions associated with a subterranean wellbore make the use of risers and flexible tubing impractical. 
     SUMMARY OF THE INVENTION 
     The invention provides systems and methods for disposing a flow actuated pump into a wellbore using running arrangements which incorporate a dual-walled coiled tubing running string having inner and outer coiled tubing strings. Fluid pumping arrangements are described in which the dual-walled coiled tubing running string supports the flow actuated pump and provides first and second fluid flow paths for fluid communication between the pump and the surface. An annulus is defined between the outer coiled tubing string and the wall of the wellbore. The annulus serves as a third fluid flow path for the fluid pumping arrangements. 
     According to a first described embodiment, a flow actuated pump is interconnected with the running string so that power fluid is provided to the pump via the first fluid flow path and the production fluid is returned via the second fluid flow path. Exhausted power fluid is returned via the third fluid flow path. 
     According to a second described embodiment, a flow actuated pump is interconnected with the running string so that power fluid is provided to the pump via the first fluid flow path and exhausted power fluid is returned via the second fluid flow path. Production fluid is returned via the third fluid flow path. In instances where the flow actuated pump is of the type which provides only a single output for intermingled water and power fluid, either or both of the second and third flow paths may be used to return the commingled fluid to the surface. 
     An embodiment is described wherein the flow actuated pump is zonally isolated such that fluid below a packer can be produced through the dual-walled coiled tubing running string. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein: 
         FIG. 1  is a side, cross-sectional view of an exemplary wellbore within which is disposed a fluid pumping assembly in accordance with the present invention. 
         FIG. 2  is an enlarged cross-sectional view of the flow actuated pump portion of the fluid pumping assembly of  FIG. 1  and associated components. 
         FIG. 3  is a cross-sectional view taken along lines  3 - 3  in  FIG. 2 . 
         FIG. 4  is a side, cross-sectional view of a wellbore within which is disposed an alternative dual-walled coiled tubing running arrangement with flow actuated pump. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The term “dual-walled,” as used herein, is intended to refer broadly to arrangements wherein an inner tubular string or member is located radially within an outer tubular string or member to provide a dual-walled tubing structure. A structure can be dual-walled without regard to whether the inner and outer tubular strings are coaxial or concentric. 
       FIG. 1  depicts an exemplary wellbore  10  that has been drilled through the earth  12  from the surface  14  down to a hydrocarbon-bearing formation  16 . It is desired to pump fluids from the formation  16  to the surface  14 . It is noted that, while wellbore  10  is illustrated as a substantially vertical wellbore, it might, in practice, have portions that are inclined or horizontally-oriented. The wellbore  10  is lined with metallic casing  18  in a manner known in the art. Perforations  20  pass through the casing  18  and into the formation  16 . In the depicted embodiment, the formation  16  is a gas formation which contains water  22 . It is desired to remove the water  22  from the formation  16 . 
     In the arrangement shown in  FIG. 1 , a fluid pumping arrangement, generally indicated at  24 , is disposed within the wellbore  10 . The fluid pumping arrangement  20  is used to remove fluids from a subterranean location, such as formation  16 . In the depicted embodiment, it is desired to pump the water  22  from the wellbore  10  to surface  14 . A fluid pump  26  is located at the surface  14  and is operable to pump fluid down through the fluid pumping assembly  24 . 
     The fluid pumping arrangement  24  includes a flow actuated pump  28  and a dual-walled coiled tubing running string  30 . The flow actuated pump  28  is a non-electric fluid pump that is hydraulically-powered by a power fluid which is pumped by pump  26  from surface  14 . The flow actuated pump  28  may be a pump of the type described in U.S. Pat. No. 7,789,131 entitled “Hydraulic Pump System for Deliquifying Low Rate Gas Wells.” The &#39;131 patent is owned by the assignee of the present application/patent and is hereby incorporated by reference in its entirety. The pump described in the &#39;131 patent will return exhausted power fluid intermingled with the wellbore fluid being produced. As a result, it only requires a single flow path back to the surface  14 . However, the flow actuated pump  28  might also be a pump which operates by returning the exhausted power fluid and the produced fluid separately. In that case, the pump  28  would require two separate flow paths back to the surface  14 . In operation, water  22  is drawn into fluid inlets  32  of the flow actuated pump  28  and exits proximate the upper axial end of the pump  28  as will be described. 
     Referring now to  FIGS. 2 and 3 , the dual-walled coiled tubing running string  30  includes an inner coiled tubing string  34  and an outer coiled tubing string  36  which radially surrounds the inner coiled tubing string  34 . The inner coiled tubing string  34  defines a central axial fluid flow path along its length. A first fluid flow path  38  is in turn defined along this central axial fluid flow path. The outer coiled tubing string  36  defines an outer coiled tubing fluid flow path along its length, and a second fluid flow path  40  is defined radially between the inner and outer coiled tubing strings  34 ,  36 . Exemplary sizes for the inner and outer coiled tubing strings  34 ,  36  are: 1.25″ O.D.×0.125″ wall thickness for the inner coiled tubing string  34  and 2.375″ O.D.×0.156″ wall thickness for the outer coiled tubing string  36 . However, these dimensions are exemplary only, and other dimensions might be used. The inner and outer coiled tubing strings  34 ,  36  are normally connected together mechanically at surface and downhole ends and both would be hung off from the wellhead. Therefore, both strings  34 ,  36  may aid in supporting the weight of the flow actuated pump  28  as well as the inner and outer coiled tubing strings  34 ,  36 . A third fluid flow path  42  is formed by the annulus between the outer coiled tubing string  36  and the casing  18 . The presence of three separate fluid flow paths  38 ,  40  and  42  allows for a power fluid, used to actuate the flow actuated pump  28 , to be flowed down to the flow actuated pump  28  and returned to surface  14 . 
       FIG. 2  illustrates a first exemplary fluid pumping arrangement wherein a power fluid, used to actuate the flow actuated pump  28 , is flowed down through the first fluid flow path  38 , as indicated by arrow  44 . Exhausted power fluid is flowed back to the surface  14  via the second fluid flow path  40  (arrow  46 ). Water  22  is flowed to surface  14  via the third fluid flow path  42 , as indicated by arrow  48 . In the instance wherein the flow actuated pump  28  is of the type which provides only a single output for intermingled water  22  and power fluid, either or both of the second and third flow paths  40 ,  42  may be used to return the commingled fluid to the surface  14 . 
     According to a second exemplary fluid pumping arrangement, power fluid is flowed down through the first fluid flow path  38 . Water  22  is flowed to surface  14  via the second fluid flow path  40 . Exhausted power fluid is flowed back to the surface  14  via the third fluid flow path  42 . Again, if the flow actuated pump  28  is of the type which provides only a single output for intermingled water  22  and power fluid, either or both of the second and third flow paths  40 ,  42  may be used to return the commingled fluid to the surface  14 . 
     An assembled dual-walled coiled tubing assembly  30  can be wound onto a coiled tubing reel of a type known in the art for retaining spools of coiled tubing and transported to a well site for use. A flow actuated pump assembly, such as pump  28 , is then affixed to the coiled tubing assembly  30  and run into the wellbore  10  in conventional fashion. 
     The dual-walled coiled tubing assembly  30  may be assembled by inserting the inner coiled tubing string  34  into the outer coiled tubing string  36 . An assembled dual-walled coiled tubing assembly  30  can be wound onto a coiled tubing reel of a type known in the art for retaining spools of coiled tubing and transported to a well site for use. A flow actuated pump  28  is then affixed to the coiled tubing assembly  30  and run into the wellbore  10 . 
     The invention provides methods of pumping fluid from a subterranean location in a wellbore. In accordance with these methods, a fluid pumping arrangement  24  is disposed into a wellbore  10  so that the pump  28  is located proximate the formation  16  from which it is desired to remove liquid (water  22 ). Power fluid is then pumped by pump  26  through the first fluid flow path  38  to the pump  28  to actuate the pump  28  to flow water  22  to surface  14  via either the second or third flow paths  40  or  42 . Exhausted power fluid is returned to surface  14  via either the second or third flow paths  40  or  42 . 
       FIG. 4  illustrates an exemplary fluid pumping arrangement  50  which is being used for artificial lift of hydrocarbon production fluid from a wellbore  10 . The fluid pumping arrangement  50  of  FIG. 4  includes a packer  52  which is set against the casing  18  to isolate the flow actuated pump  28  below the packer  52 . The flow actuated pump  28  of the fluid pumping arrangement  28  is carried by dual-walled coiled tubing running string assembly  30 . The dual-walled coiled tubing assembly  30  includes an inner coiled tubing string  34  and an outer coiled tubing string  36 . In this instance, the flow actuated pump  28  is of the type which provides a fluid output which is commingled exhausted power fluid and well fluid to be produced. A first fluid flow path  38  is defined radially within the inner coiled tubing string  34 , and a second fluid flow path  40  is defined radially between the inner coiled tubing string  34  and the outer coiled tubing string  36 . 
     It can be seen that the exemplary pumping arrangement  50  allows for zonal isolation within wellbores and permits fluids to be readily flowed past a packer  52  within a wellbore  10 . The flow actuated pump  28  can be installed at a certain depth and one or more packers  52  are used to isolate well fluids above and below the flow actuated pump  28 . Well fluids below the packer  52  can be lifted by the flow actuated pump  28  past the packer  52  via the second flow path  40 . 
     The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.