Patent Publication Number: US-9850743-B2

Title: Safety device for retrieving component within wellhead

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and benefit of U.S. Non-Provisional application Ser. No. 14/339,439, entitled “Safety Device for Retrieving Component Within Wellhead,” filed Jul. 23, 2014, which is herein incorporated by reference in its entirety, and which claims priority to and benefit of U.S. Non-Provisional application Ser. No. 12/743,818, entitled “Safety Device for Retrieving Component Within Wellhead,” filed May 19, 2010, which is herein incorporated by reference in its entirety, and which claims priority to and benefit of PCT Patent Application No. PCT/US2008/083461, entitled “Safety Device for Retrieving Component Within Wellhead,” filed Nov. 13, 2008, which is herein incorporated by reference in its entirety, and which claims priority to and benefit of U.S. Provisional Patent Application No. 61/013,914, entitled “Safety Device for Retrieving Component Within Wellhead”, filed on Dec. 14, 2007, which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     As will be appreciated, oil and natural gas have a profound effect on modern economies and societies. In order to meet the demand for such natural resources, numerous companies invest significant amounts of time and money in searching for and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired resource is discovered below the surface of the earth, drilling and production systems are employed to access and extract the resource. These systems can be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly that is used to extract the resource. These wellhead assemblies include a wide variety of components and/or conduits, such as various control lines, casings, valves, and the like, that are conducive to drilling and/or extraction operations. In drilling and extraction operations, in addition to wellheads, various components and tools are employed to provide for drilling, completion, and the production of mineral resources. For instance, during drilling and extraction operations seals and valves are often employed to regulate pressures and/or fluid flow. 
     A wellhead system may include a various support structures, such as a casing spool or bowl or a tubing head or bowl, configured to secure and support tubing and casing suspended in the well bore. Additionally, a wellhead system may include pressure control and regulation devices, such as a “Christmas tree” or a blowout preventer (BOP). The blowout preventer can be used a primary or back-up pressure regulation device, and often prevents high-pressure release of oil, gas or other fluids in the well in the case of an overpressure condition. During the course of drilling or operating the well, it may be desirable to switch between different sizes of blowout preventers or pressure regulation devices. In such instances, the well is generally plugged or sealed in some manner so that oil, gas, or other fluids are contained within the well when the system&#39;s pressure regulation device is disengaged. 
     Typically, a plug may be used in the casing spool or bowl (or in the tubing spool or bowl) to plug the well, or a backpressure valve may be used to relieve any pressure building up in the well. The plug may be installed before removal of a pressure regulation device, and then retrieved once another pressure regulation device is in place, using a retrieval tool, for example. In such instances, installation or removal of the plug may result in accidental release of pressure from the well, causing the plug to eject from the casing spool or bowl and exit the wellhead, for example. An accidental release may damage the plug or the wellhead, and may also result in the unintentional release of oil, gas, or other fluids in the well. Another challenge may include an attempt to equalize the pressure across the plug to prevent such a blowout or ejection of the plug. However, it may be difficult to accomplish such an equalization, and any unequal pressure may still allow the plug to potentially eject from the wellhead. Additionally, some wells may not be amendable to use of a back pressure valve, such as those using an annular blowout preventer. As a result, use of a plug may be used to seal these wells despite the various challenges and drawbacks. Further, the use of devices or techniques to allow safe installation and/or removal of the plug may introduce increased complexity and cost, and result in multiple trips into the wellhead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a block diagram that illustrates a mineral extraction system according to an embodiment of the present invention; 
         FIG. 2  is a partial cross-section of the mineral extraction system of  FIG. 1  illustrating a plug in the mineral extraction system according to an embodiment of the present invention. 
         FIG. 3  is a partial cross-section of a sleeve and tubing spool coupled to the casing spool of  FIG. 2  according to an embodiment of the present invention; 
         FIG. 4  is a cross-section of the sleeve of  FIG. 3  according to an embodiment of the present invention; and 
         FIG. 5  is a flowchart illustrating a process for using the sleeve and tubing spool of  FIGS. 2-4  according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
     Certain exemplary embodiments of the present technique include a system and method that addresses one or more of the above-mentioned challenges of conventional plug installation and retrieval systems and methods. As explained in greater detail below, the disclosed embodiments include a safety device, such as a retaining sleeve, that can be installed into a mineral extraction system in a single trip as a part of another tool, such as a tubing spool. In certain embodiments, the sleeve may include an annular body having a tapered edge, a retaining groove, and a selected ratio of inside diameter to outside diameter to accommodate the plug used with the sleeve. In one embodiment, any accidental ejection or release of the plug results in a shoulder of the plug contacting the tapered edge of the sleeve, such that the plug cannot eject from the wellhead. Embodiments of the present invention may also include a tubing spool having a retention mechanism for embodiments of the retaining sleeve. In one embodiment, the sleeve may be coupled to the tubing spool and the entire tubing spool and sleeve assembly may then be coupled to the casing spool of the wellhead. Once the sleeve is in place, the plug may then be retrieved via a retrieval tool. 
       FIG. 1  is a block diagram that illustrates an embodiment of a mineral extraction system  10 . The illustrated mineral extraction system  10  can be configured to extract various minerals and natural resources, including hydrocarbons (e.g., oil and/or natural gas), or configured to inject substances into the earth. In some embodiments, the mineral extraction system  10  is land-based (e.g., a surface system) or subsea (e.g., a subsea system). As illustrated, the system  10  includes a wellhead  12  coupled to a mineral deposit  14  via a well  16 , wherein the well  16  includes a wellhead hub  18  and a well-bore  20 . 
     The wellhead hub  18  generally includes a large diameter hub that is disposed at the termination of the well-bore  20 . The wellhead hub  18  provides for the connection of the wellhead  12  to the well  16 . 
     The wellhead  12  typically includes multiple components that control and regulate activities and conditions associated with the well  16 . For example, the wellhead  12  generally includes bodies, valves and seals that route produced minerals from the mineral deposit  14 , provide for regulating pressure in the well  16 , and provide for the injection of chemicals into the well-bore  20  (down-hole). In the illustrated embodiment, the wellhead  12  includes what is colloquially referred to as a Christmas tree  22  (hereinafter, a tree), a tubing spool  24 , a casing spool  25 , and a hanger  26  (e.g., a tubing hanger or a casing hanger). The system  10  may include other devices that are coupled to the wellhead  12 , and devices that are used to assemble and control various components of the wellhead  12 . For example, in the illustrated embodiment, the system  10  includes a tool  28  suspended from a drill string  30 . In certain embodiments, the tool  28  includes a running tool that is lowered (e.g., run) from an offshore vessel to the well  16  and/or the wellhead  12 . In other embodiments, such as surface systems, the tool  28  may include a device suspended over and/or lowered into the wellhead  12  via a crane or other supporting device. 
     The tree  22  generally includes a variety of flow paths (e.g., bores), valves, fittings, and controls for operating the well  16 . For instance, the tree  22  may include a frame that is disposed about a tree body, a flow-loop, actuators, and valves. Further, the tree  22  may provide fluid communication with the well  16 . For example, the tree  22  includes a tree bore  32 . The tree bore  32  provides for completion and workover procedures, such as the insertion of tools (e.g., the hanger  26 ) into the well  16 , the injection of various chemicals into the well  16  (down-hole), and the like. Further, minerals extracted from the well  16  (e.g., oil and natural gas) may be regulated and routed via the tree  22 . For instance, the tree  12  may be coupled to a jumper or a flowline that is tied back to other components, such as a manifold. Accordingly, produced minerals flow from the well  16  to the manifold via the wellhead  12  and/or the tree  22  before being routed to shipping or storage facilities. A blowout preventer (BOP)  31  may also be included, either as a part of the tree  22  or as a separate device. The BOP may consist of a variety of valves, fittings and controls to prevent oil, gas, or other fluid from exiting the well in the event of an unintentional release of pressure or an overpressure condition. 
     The tubing spool  24  provides a base for the tree  22 . Typically, the tubing spool  24  is one of many components in a modular subsea or surface mineral extraction system  10  that is run from an offshore vessel or surface system. The tubing spool  24  includes a tubing spool bore  34 . The tubing spool bore  34  connects (e.g., enables fluid communication between) the tree bore  32  and the well  16 . Thus, the tubing spool bore  34  may provide access to the well bore  20  for various completion and worker procedures. For example, components can be run down to the wellhead  12  and disposed in the tubing spool bore  34  to seal-off the well bore  20 , to inject chemicals down-hole, to suspend tools down-hole, to retrieve tools down-hole, and the like. 
     As will be appreciated, the well bore  20  may contain elevated pressures. For example, the well bore  20  may include pressures that exceed 10,000 pounds per square inch (PSI), that exceed 15,000 PSI, and/or that even exceed 20,000 PSI. Accordingly, mineral extraction systems  10  employ various mechanisms, such as seals, plugs and valves, to control and regulate the well  16 . For example, plugs and valves are employed to regulate the flow and pressures of fluids in various bores and channels throughout the mineral extraction system  10 . For instance, the illustrated hanger  26  (e.g., tubing hanger or casing hanger) is typically disposed within the wellhead  12  to secure tubing and casing suspended in the well bore  20 , and to provide a path for hydraulic control fluid, chemical injections, and the like. The hanger  26  includes a hanger bore  38  that extends through the center of the hanger  26 , and that is in fluid communication with the tubing spool bore  34  and the well bore  20 . Unfortunately, pressures in the bores  20  and  34  may manifest through the wellhead  12  if not regulated. A back pressure valve, plug, or other sealing device  36  is often seated and locked in the hanger bore  38  to regulate the pressure. Similar sealing devices may be used throughout mineral extraction systems  10  to regulate fluid pressures and flows. 
     During operation of the well, the blowout preventer  31  may be removed and replaced by another blowout preventer. For example, during initial drilling and/or operation of the well  16 , a larger blowout preventer may be used to accommodate larger casing strings and tools. For easier operation and use of the well, and easier installation and retrieval of equipment, a smaller blowout preventer may be used after some period of operation of the well  16 . Thus, while removing the larger blowout preventer and installing a smaller blowout preventer, the well  16  may be sealed by the sealing device  36 , such as a backpressure valve, a plug, or other sealing device. In some instances, the well  16 , wellhead  12 , blowout preventer  31 , or other equipment may only be amenable to use of a plug to seal the well. Further, a backpressure valve may undesirably leak or lose pressure, affecting the performance of the seal of the well  16 . When using a plug to seal the well  16 , the methods used to install and/or remove the plug may allow a possibility of the plug being ejected from the well  16  if the pressure across the plug is not equalized, the plug is not vented, and/or an unexpected pressure levels are encountered. Thus, according to an embodiment of the invention, the mineral extraction system  10  may include a safety device, such as a sleeve, to prevent the plug from ejecting from the wellhead  12 . 
       FIG. 2  depicts a cross section  100  of a plug  102  being inserted into the casing spool  25 . As discussed above, the plug  102  may be inserted to plug the well during the removal of the blowout preventer  31 . The plug  102  may be installed by an installation/retrieval tool  104  that may be coupled to the plug  102 . The plug  102  may be retained in a casing hanger  106 , and the casing hanger  106  may be retained in the casing spool  25  by tie down screws  108 . As can be seen in  FIG. 2 , the plug  102  seals the bore of the wellhead  12  and prevents pressurized oil, gas or other fluids from releasing up the production tubing  111 . The plug  102  may also include a relief groove  110  to relieve pressure in the wellhead. In some embodiments, the plug  102  may be primarily retained by threads on the body of the plug  102  or by lugs, screws, or other mechanical fasteners. In other embodiments, the plug may alternatively or additionally be sealed by an elastomer energized during installation of the plug. As discussed further below, a sleeve may retain the plug in the event the plug ejects up the wellhead if it accidentally unsecured or during removal of the plug. 
     Turning now to  FIG. 3 , a cross-section of the tubing spool  24  having a safety device, e.g., a retaining sleeve  150 , is shown coupled to the casing spool  25  of the wellhead  12 . As discussed below the safety device, e.g., sleeve  150 , may serve as a backup safety feature (or secondary retainer) to block the plug  102  after the primary retainer is released during removal of the plug  102 . The tubing spool  24  may be coupled to the casing spool  25  by bolts  152  through a flange  154 . In one embodiment, as described further below, the sleeve  150  may be first inserted into the tubing spool  24  before coupling to the casing spool  25 . 
     In one embodiment, the sleeve  150  may be retained in the tubing spool  24  by tie down screws  160 , which engage a retaining groove  162  in the sleeve  150 . The sleeve  150  may be retained by any number of tie down screws, such as 2, 6, 8, 12, etc. In other embodiments, the sleeve  150  may be retained in the tubing spool  24  by hangers, snap rings, or any other suitable retention mechanism. Additionally, in some embodiments, the tubing spool  24  may include an annular recess  163  configured to solely or in combination with the above features retain the sleeve  150 . In addition, to aid in installation and/or removal of the sleeve  150 , the top portion  164  of the sleeve  150  may extend from the top of the tubing spool  24 . During installation or removal of the sleeve  150 , an operator or tool may grab or hold the sleeve  150  via the top portion  164 . In other embodiments, the sleeve  150  may not include the top portion  164  extending above the tubing spool  24 . 
     As discussed above, the retaining sleeve  150  is a safety device configured to block the plug  102  from releasing from the wellhead  12 . This safety or backup retention feature of the sleeve  150  may also function to retain the sleeve  150  in the event that the primary retainer of the plug  102  fails. In either case, the sleeve  150  is configured to block axial movement of the plug  102  beyond some point in the wellhead  12 . In the illustrated embodiment, the retaining sleeve  150  may be offset from the plug  102  by a distance, such that the retaining sleeve  150  does not function as a retainer until the plug  102  is released from its primary retainer and travels the distance up the wellhead. 
     In the illustrated embodiment, the bottom  166  of the sleeve  150  may engage the shoulder  168  of the plug if the plug  102  ejects to the top of the tubing spool  24 . Otherwise, without such a safety member, e.g., sleeve  150 , the plug  102  may be allowed to eject axially up through the tubing due to pressure differences in the system  10 . In some embodiments, the bottom  166  of the sleeve  150  may be designed to optimally engage a shoulder  168  of the plug  102 . For example, in the embodiment depicted in  FIG. 3 , the shoulder  168  portion of the plug  102  features a tapered or beveled edge; thus, the bottom  166  of the sleeve  150  may be tapered or beveled at an opposing angle so that the shoulder  168  of the plug  102  is flush against the bottom  166  of the sleeve  150  during engagement with the sleeve  150 . Further, the sleeve  150  may also provide protection to the bore  34  of the wellhead  12  by covering the entire bore  34  in the area of the sleeve  150 . 
       FIG. 4  illustrates a cross-section of an embodiment of the retaining sleeve  150 . As shown in  FIG. 4 , the retaining sleeve may be a generally annular shape having an inside diameter  170  and an outside diameter  172 . The inside diameter  170  of the sleeve may be selected to allow tools, and any other equipment to pass through the sleeve when it is installed in the tubing spool  24 . Additionally, the ratio of the inside diameter  170  to outside diameter  172  (or the thickness of the wall of the sleeve  150 ) may be selected to ensure optimal engagement with a plug or other tool intended to be retained by the sleeve  150 . For example, the sleeve  150  should be thick enough to retain the plug  102  in the event of an accidental ejection of the plug  102  from the wellhead  12 , but should also be thin enough to allow installation or removal of the tool  104  or other tools in the wellhead  12 . Additionally, as mentioned above, the bottom of the sleeve  166  may be configured to engage the plug  102  and block the plug from ejecting. 
     As mentioned above, the sleeve  150  may also include the retaining groove  162  around the circumference of a section of an outer wall  176  of the sleeve  150 . The retaining groove  162  may be deep enough to ensure retention of the sleeve  150  via one or more tie down screws, as illustrated above in  FIG. 3 . In some embodiments, the groove  162  may be formed around some or the entire circumference of the outer wall (e.g., annular groove). The sleeve  150  may be manufactured from steel, such as 4340 steel, 4140 steel, or may be formed from any other suitable material. 
     Turning now to operation of the sleeve,  FIG. 5  is a flowchart illustrating one embodiment of a process  200  for using the sleeve  150  with a mineral extraction system. Initially, a wellhead may already be in operation with a blowout preventer coupled to the “Christmas tree” or top of the wellhead (block  202 ). A plug may inserted into the wellhead (block  204 ), such as via a casing bowl or a plug insertion/retrieval tool, as discussed above. Once the well is plugged, the blowout preventer may be removed in preparation for replacement with a different size blowout preventer (block  206 ). 
     A separate tubing spool may be prepared for coupling to the wellhead (block  208 ). A retaining sleeve, such as illustrated in  FIG. 4 , may be coupled to the tubing spool via tie down screws or another suitable retention mechanism (block  210 ). After the sleeve is coupled to the tubing spool, the tubing spool may then be coupled to the casing spool of the wellhead (block  212 ). Once the tubing spool and sleeve are secured to the wellhead, the plug is ready for removal as the sleeve provides protection against accidental release of the plug during the removal process. 
     Another blowout preventer may be coupled to the Christmas tree and wellhead so that operation of the well may continue after the plug is removed (block  214 ). To remove the plug, a plug retrieval tool may be inserted into the tubing spool, through the bore of the sleeve, and into the plug (block  216 ), and the plug may be removed (block  218 ). In one embodiment, the retrieval tool may be reverse threaded and provide for unscrewing the plug after engagement. In other embodiments, depending on the primary retainer of the plug, other lugs, screws or fasteners may be removed to allow removal of the plug. When removing the plug, the retrieval tool, sleeve, and plug may all be removed at once, thus eliminating another insertion into the well to separately retrieve the sleeve. For example, during removal of the plug, the tie down screws or other mechanism retaining the sleeve may be removed so that when the plug contacts the sleeve, the sleeve may be pulled out with the plug. After the plug is removed, operation of the well may continue normally. 
     Although the embodiment described above illustrates an annular sleeve as a secondary retaining device for a wellhead plug, other shapes or designs may also be used. For example, in other embodiments the secondary retaining device may be tubular, cylindrical, rectangular, and may include various features, such as multiple retaining grooves, a plug receptacle, or a bottom portion of any shape such as flat, beveled, tapered, etc. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.