Abstract:
A method for sealing a conduit in a spoolable wellbore intervention rod includes exposing an interior of the conduit at a location proximate the earth&#39;s surface while the spoolable rod is deployed in a wellbore. A curable sealing compound is introduced into the exposed interior of the conduit and the compound is allowed to cure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States National Phase of PCT Patent Application No. NO2009/000402 filed on 24 Nov. 2009, which was published in English on 10 Jun. 2010 under Publication No. WO 2010/064920 A1, which claims priority to U.S. Provisional Patent Application No. 61/119,389 filed 3 Dec. 2008, both of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to the field of wellbore intervention using spoolable rods or tubes. More specifically, the invention relates to methods for sealing leaks in such rods or tubes while the rod or tube is disposed in a wellbore. 
     2. Background Art 
     In the extraction of oil and gas from underground reservoirs, it is frequently necessary to insert tool strings into a wellbore drilled through the reservoir to perform various completion and recompletion tasks. 
     There is known in the art a semi-stiff (stiff being defined in terms of bending moment), spoolable intervention rod having one or more internal fluid conduits and/or electrical and optical conductors. Such rod is used to provide wellbore intervention services under the name ZIPLOG, with is a mark of Ziebel, AS, the assignee of the present invention. A breakage or leak in the conduit in the spoolable rod below the surface (wellhead) can cause wellbore fluids and/or gas to migrate to the Earth&#39;s surface where the fluids can cause a safety hazard. The same gas and/or fluid migration may occur through the rod if seals on a guide nose coupled to the lower end of the rod fail to seal, or this guidenose is broken off the rod downhole. 
     Systems are being currently being developed and introduced for wellbore intervention for deployment of sensors, where the sensors can be incorporated into one of the foregoing semi-stiff, spoolable rod. The rod can be pushed into wellbores that are in operation (i.e. producing or injecting fluid), where the stiffness of the “rod” enables long lateral displacement to be achieved. Henning Hansen et al. describe a methodology for such a spoolable rod system in International Patent Application Publication No. WO 2006/003477 entitled “Intervention rod”. The foregoing described rod is the same as that used to provide the previously stated ZIPLOG services. 
     Also there are systems known in the art that are based on pushing a spoolable, small diameter tubing associated with the rod into wellbores for purposes such as chemical injection, as for example, for gas well dewatering. See, e.g., U.S. Patent Application Publication No. 2009/0266537 filed by Hansen et al., and which is commonly owned with the present invention. 
     In case of breakage or leakage downhole (below the Earth&#39;s surface) of such a rod or a small diameter tube, gas or wellbore fluids can migrate to surface where they can become a safety hazard. Spoolable rod and small diameter tube systems normally have one or several pressure barriers implemented in the lower end of the rod or tube being inserted into the wellbore, but the challenge is if there is a leakage within these barriers or leakage or breakage in the rod or tube above these barriers. 
     Typically a pressure seal, as for example in the form of a valve, can be coupled to the upper end of the “rod” or tube, located outside the wellhead as for example on a surface winch unit, but this is in many instances not sufficient barrier to obtain sufficiently safe wellbore operations with contingency built in. 
     SUMMARY OF THE INVENTION 
     A method for sealing a conduit in a spoolable wellbore intervention rod includes exposing an interior of the conduit at a location proximate the Earth&#39;s surface while the spoolable rod is deployed in a wellbore. A curable sealing compound is introduced into the exposed interior of the conduit. The compound is allowed to cure. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cut away view of a spoolable, fiber rod including a conduit and optical fibers therein. 
         FIG. 1A  shows using the spoolable rod in a wellbore. 
         FIG. 2  shows a valve that may be used to hydraulically shut off the interior of a rod according to  FIG. 1 . 
         FIG. 3  shows a side valve used in connection with the shut off valve of  FIG. 2 , where the side valve can be used to inject sealant material into the inner tube of the rod. 
         FIG. 4  shows using a blow-out preventer (also referred to as a BOP) and lubricator stack with a rod according to  FIG. 1 . 
         FIG. 5  shows the first part of a second method to seal the interior of a leaking rod or tube, where the rod is cut by the BOP shear ram. 
         FIG. 6  shows the second part of the second method procedure shown in  FIG. 5 , where plugging compound is injected into a rod cut according to  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a semi-stiff, spoolable wellbore intervention “rod”  10  that has been developed (e.g., as used with the ZIPLOG service explained in the Background section herein) to be pushed into producing wellbores for well logging purposes and other wellbore operations. The rod  10  generally consists of an exterior of fiber reinforced plastic  11 , and may be generally cylindrically shaped as shown in  FIG. 1 . As can also be observed in  FIG. 1 , there is typically a small steel tube or conduit  12  disposed generally in the center of the rod  10 . The tube  12  or other portion of the interior of the rod  10  may contain fiber optic and/or electrical cable(s). See  10 A through  1 D in  FIG. 2 . The issue addressed by the present invention is wellbore fluid or leakage through, for example, the conduit  12  to the Earth&#39;s surface if part of the spoolable rod becomes damaged or broken in the wellbore. In such cases, the wellbore fluid can enter the interior of the spoolable rod&#39;s tube  12  and migrate to the Earth&#39;s surface. As will be explained with reference to  FIGS. 4 and 5 , if the spoolable rod  10  passes through the sealing devices in a wellhead system, the conduit  12  may provide in a fluid conduit through the wellhead in the event of such breakage or damage. Such situation can present safety hazards. 
     A typical wellbore intervention operation using the spoolable rod  10  of  FIG. 1  is shown in  FIG. 1A . The rod  10  may be unspooled from a winch  13  or similar device into a wellbore  21  drilled through the subsurface. The tube  12 , electrical cables, and optical fibers (see  FIG. 1 ) in the rod  10  may terminate in a slip ring  15  or similar device to enable rotation of the winch  13  to extend and retract the rod  10  from a wellbore  21  drilled through the subsurface. Electrical and/or optical connections may be made from the slip ring  15  to a control unit  19  which may include devices for decoding and recording signals from the rod, and may include controls to operate the winch  15 . The tube ( 12  in  FIG. 1 ) may be hydraulically coupled to a pump  17  for moving fluid through the conduit ( 12  in  FIG. 1 ) or similar device. Thus, while the rod  10  is in the wellbore, a sealing fluid may be pumped into the rod toward a guide nose or tool  29  coupled to the bottom end of the rod. 
     The intervention rod  10  shown in cut away view  FIG. 1  is only one example of a wellbore intervention rod that may be used in accordance with the invention. Other examples include steel or composite tubes, which may include electrical conductors, hydraulic lines and/or optical fibers in the interior thereof. The principle of the invention is applicable to any type of wellbore intervention rod or conduit that would introduce a fluid path to the surface if the rod or conduit was exposed on its interior to fluid pressure in the wellbore below the Earth&#39;s surface or wellhead. 
       FIG. 2  illustrates how a valve such as a ball valve  22  can be mounted at the Earth&#39;s surface between the spoolable rod  10  and a junction box, slip-ring or similar device, shown generally at  20 . The valve  22  is sealingly engaged to the end of the rod  10  nearest a slip ring junction box  20  and can be used stop any wellbore fluids (e.g., gas, oil and/or water) from flowing through the tube to the surface environment. The junction box provides suitable terminations for the ends of optical fibers  10 A,  10 B,  10 C,  10 D and may use optical connectors  16  before the conductors or fibers are communicated to the slip ring ( 15  in  FIG. 1A ). The seal can consist of a sleeve  24  having internal diameter to enable movement of the rod  10  therethrough. One end of the tube  24  may be threadedly engaged to a mating, sealing threaded connection  30  on the valve  20 . The other end of the tube  24  may be sealed to the rod by a compression union  28  or similar device. A hydraulic fitting  26  enables pumping sealant into the interior of the tube  24 . In the event any wellbore fluid leakage occurs into the interior of the rod  10 , the valve  22  may be closed to prevent further upstream movement of the fluid. Preferably the valve  22  is suitably configured be able to cut the tube, cables, lines or optical fibers within such tube. When the valve is closed, fluid discharge from the well will be stopped. 
       FIG. 3  is similar to  FIG. 2 , but includes an inlet port (T-fitting  34 ) downstream (in the direction of the wellbore) of the valve  22  (also shown in  FIG. 2 ) and used to inject a plugging or sealing compound (which can be resin material, epoxy, fluidized elastomer and similar curable sealing materials) into the tube in the spoolable rod. The sealing material may be pumped through a valve  32  and the injection pressure measured by a gauge  36  to determine when sealant injection should be stopped, as for example, by measuring a substantial increase in pressure while sealant flow remains constant. Also this gauge  36 , will, prior to injecting sealant provide information about fluid and/or gas leakage to surface and the pressure response of such. As explained above, the fiber optic and/or electrical cable(s) in the tube  24  can be cut by the valve  22  coupled between the inlet port system and a slip-ring or junction box. 
     When the above operation has been performed, the winch and control unit may be removed from the area of the wellbore ( 21  in  FIG. 1 ), and the rod ( 10  in  FIG. 1 ) can be left for extended periods of time in the wellbore without any wellbore fluid or gas leakage to surface. Alternatively, the rod  10  can be pulled out of the wellbore ( 21  in  FIG. 1 ) in a controlled fashion. 
       FIG. 4  illustrates a typical surface rig-up for wellbore interventions, where a pressure control device called a “blow out preventer” (BOP)  50  is mounted on top of a wellhead. The wellhead (not shown in  FIG. 4  for clarity) may include a “christmas tree” or similar surface valve arrangement known in the art. The uppermost section of the BOP typically includes a′“pack-off” or “lubricator”  52  system to provide an external seal to the rod  10  or tube deployed into the wellbore. The BOP  50  typically includes two hydraulically actuated rams  54  that when closed for a seal against the exterior of the rod  10 . The BOP may also include one or more “shear rams”  56  that when closed completely cut through and sever the rod  10  or tube within. The BOP stack  50  is generally coupled to the wellhead (not shown) by a flange type coupling  58 .  FIG. 4  also shows the pressure barrier challenge created by a broken or leaking “rod” or tube (at  10 B) where the leak is below the BOP. 
     Protruding out of the pack-off or lubricator  52  at the upper end of the wellhead is the “rod” or tube, which is typically deployed by a winch system or similar device (See, e.g.,  FIG. 1 ) where the above described (with reference to  FIGS. 2 and 3 ) system can be mounted. If no spooler system is in place, the “rod” or tube may be routed to a connection point away from the wellhead system. 
       FIG. 5  illustrates how an internally leaking “rod”  10  or tube can be sealed off externally in a BOP system  50 . First, the seal rams  54  will be closed against the rod, followed by closure of the shear rams. This will expose the interior of the rod  10  to fluid pressure in the space between the two seal rams  54 .  FIG. 6  illustrates how sealing compound, examples of which are stated above, can be injected at high pressure through an inlet  60  between the lower seal ram and the shear ram of the BOP system  50 . The wellbore fluids in the area between these two rams can be evacuated prior to performing such injection by a second port. Also such fluids can be displaced by the plugging compound, by controlled evacuation of such through a second port (not shown) by pumping in sealing compound into port  60 . When the sealing compound reaches the exposed and cut end of the “rod” or tube  10 , continued pumping of compound into the BOP port  60  will force such compound into the “rod” or tube  10 , whereafter the compound will cure and seal off the internal of this “rod” or tube. At such time, the upper seal ram may be opened and the cut end of the tube may be removed from the BOP  50  and lubricator  52 . The remaining portion of the rod  10  may remain sealed in the lower seal ram as long as is necessary to prepare the well for ultimately removing the rod therefrom. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.