Abstract:
A method and system for retrieving a wear bushing from within a subsea wellhead assembly. The system includes a retrieval tool deployable on a wireline that inserts within the bushing. Latches on the tool radially project outwards and mate with a groove on the bushing inner surface. A hydraulically actuated jack is included with the tool and projects downward to the wellhead assembly to pull the bushing from its temporary coupling in the wellhead assembly. A remotely operated vehicle can be used to assist deploying the tool and for supplying hydraulics and/or control for operating the latch and the jack.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application Ser. No. 61/079,636, filed Jul. 10, 2008, the full disclosure of which is hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to production of oil and gas wells, and in particular to a wellhead assembly having a selectively removable wear bushing. 
     DESCRIPTION OF RELATED ART 
     Systems for producing oil and gas from subsea wellbores typically include a subsea wellhead assembly that includes a wellhead housing attached at a wellbore opening, where the wellbore extends through one or more hydrocarbon producing formations. Casing and tubing hangers are landed within the housing for supporting casing and production tubing inserted into the wellbore. The casing lines the wellbore, thereby isolating the wellbore from the surrounding formation. Tubing typically lies concentric within the casing and provides a conduit for producing the hydrocarbons entrained within the formation. 
     Wellhead assemblies also typically include a production tree connecting to the upper end of the wellhead housing. The production tree controls and distributes the fluids produced from the wellbore. Valve assemblies are typically provided within wellhead production trees for controlling the flow of oil or gas from a wellhead and/or for controlling circulating fluid flow in and out of a wellhead. Gate valves and other sliding stem-type valves have a valve member or disc and operate by selectively moving the stem to insert/remove the valve member into/from the flow of fluid to stop/allow the flow when desired. 
     In some techniques, the operator runs drill pipe through portions of a production tree and drills the well deeper before the well is completed. The production tree has internal sealing surfaces that could be damaged by the rotating drill pipe. To avoid damage, the operator will install a drilling protector, also called “wear bushing”, which is a sleeve that fits within the inner diameter of the production tree. After reaching total depth, the operator retrieves the wear bushing, typically by using the string of drill pipe. The operator may then run a string of tubing and land the tubing hanger in the production tree or a wellhead housing that supports the production tree. Retrievable wear bushings are also employed when drilling through other subsea wellhead members, such, as a wellhead housing. Normally, a riser will connect to the wellhead member, such as the tree or wellhead housing, and the operator runs and retrieves the drill pipe and wear bushing through the riser. 
     SUMMARY OF INVENTION 
     A method and system for retrieving a wear bushing from within a subsea wellhead assembly. The method includes providing a retrieval tool having a selectively extendable jack member and a selectively activatable bushing latch, with the bushing latch, coupling the retrieval tool with the bushing, and extending the jack member from the tool and pushing it against the wellhead assembly, so that the retrieval tool and the bushing are urged away from the wellhead assembly together. In one example, engaging the bushing latch is accomplished with the bushing. The bushing can include a recess on its inner surface and the bushing latch can be on a portion of the retrieval tool insertable into the bushing and configured to selectively extend radially outward from the retrieval tool and register with the recess, thereby coupling the retrieval tool and bushing. In one example, the jack member can be substantially parallel with the bushing axis so it contacts the wellhead assembly lateral to the bushing outer periphery. The jack member can be disposed on a portion of the retrieval tool having an outer periphery that is greater than the bushing outer periphery. After latching the retrieval tool to the bushing, the method can further include raising the retrieval tool and bushing from subsea. A remotely operated vehicle (ROV) can optionally be deployed subsea and operatively coupled to the retrieval tool and used to operate the retrieval tool. The bushing can be a wear bushing and the bore can be a main bore of the wellhead assembly. In one example of use, the bushing can be temporarily retained within the bore by a ring set in grooves respectively formed on the bushing outer surface and bore inner surface and wherein the grooves are at least partially registered with one another. 
     Also disclosed herein is a method of completing a well subsea. In this example the method includes providing on the seafloor a wellhead member having a main bore and a wear bushing coupled within the main bore, landing a retrieval tool onto the wellhead member having a portion on the wellhead member and outside of the main bore periphery and latching the retrieval tool to the wear bushing, decoupling the wear bushing from the main bore by applying a separating force on both the wellhead member and retrieval tool, removing the wear bushing from within the main bore, landing tubulars within the main bore, and landing a production tree onto the wellhead member. A drill string can be inserted through the main bore and wear bushing and used for drilling a well into the seafloor. In one example, the retrieval tool can have an upper portion whose outer periphery contacts an upper surface of the wellhead member that circumscribes the main bore; the tool may include an attached lower portion insertable within the wear bushing. A groove may be included in the wear bushing that circumscribes its inner surface. A latch can be included on the tool lower portion that selectively projects radially outward; thus in one example the latching the retrieval tool to the wear bushing is accomplished by projecting the latch into registration with the groove. A jack member can be provided on the retrieval tool that is selectively extendable from its upper portion. Separating the bushing from the main bore may involve extending the jack member from the upper member to push it against the wellhead member apply the separating force. A remotely operated vehicle (ROV) can be coupled with the retrieval tool for operating the retrieval tool. 
     Further described herein is a retrieval tool useful for retrieving a wear bushing from within a subsea wellhead member. The tool can include an upper portion for engagement by a lift line for landing on an upper end of the wellhead member, a lower portion depending from the upper portion and having an smaller outer periphery than the upper portion for insertion into the wellhead member, an elongated jack member selectively projectable from the upper portion and into an orientation substantially parallel with the lower portion axis, and a latch selectively extendable from the lower portion, so that when the retrieval tool is in a retrieval configuration with the lower portion inserted within the wear bushing, the latch engaged with the wear bushing, and the jack member is selectively projected from the upper portion, the jack member pushes against the wellhead member to move the retrieval tool away from the wellhead member and slide the wear bushing from within the wellhead member. The tool can include on it a remotely operated vehicle connection in communication with the latch and jack member. In one example of use, the latch is configured to engage a groove formed on the wear bushing inner surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some of the features and benefits of the present disclosure having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is schematic sectional view of a subsea wellhead assembly constructed in accordance with the present disclosure. 
         FIG. 2  is a schematic sectional view of a tubing hanger being installed in the subsea wellhead housing of  FIG. 1 . 
         FIG. 3  is a schematic sectional view of a spool and tree cap being installed on the wellhead housing of  FIG. 1 . 
         FIG. 4  is a schematic sectional view of the tubing hanger being lowered through the previously installed spool. 
         FIG. 5  is a schematic sectional view of a subsea well having a wear bushing. 
         FIG. 6  is a view of the subsea well of  FIG. 5  with a recovery tool engaging the wear bushing. 
         FIGS. 6A and 6B  provide in an enlarged view embodiments of the latch member of  FIG. 6 . 
         FIG. 7  illustrates a schematic view of the recovery tool of  FIG. 6  pulling the wear bushing from the subsea well. 
         FIG. 8  is a schematic sectional view of the recovery tool engaged with the wear bushing. 
     
    
    
     While the subject device and method will be described in connection with the preferred embodiments but not limited thereto. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the present disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows in a side sectional view a wellhead housing  13  with a conductor casing  15  depending to a predetermined depth within a subsea well  11 . A casing hanger  17  is landed within wellhead housing  13  with a string of casing  19  extending therefrom to another predetermined depth within subsea well  11 . Also landed within wellhead housing  13  is a tubing hanger  21 ; a tubing string  23  is shown within the casing string  19  and supported on its upper end by the tubing hanger  21 . In one example, the tubing string  23  extends to a production depth for receiving well fluid from within subsea well  11 . Tubing hanger  21  has an axially extending production flow passage  22 . A tubing annulus  25  is defined between the interior surface of string of casing  19  and the exterior surface of string of tubing  23 . Tubing hanger  21  optionally may have a tubing annulus passage  24  extending axially through it offset from and parallel to production flow passage  22 . In addition, a tubing annulus valve  26  may be located within tubing annulus passage  24  for opening and closing passage  24 . In one embodiment, tubing annulus valve  26  is biased by a spring to a closed position. Tubing hanger  21  is rotated or oriented to a desired orientation relative to wellhead housing  13 . Orientation may be accomplished in a variety of known ways. 
     A production tree or spool  27  lands on and connects to an upper end portion of wellhead housing  13 . A schematically illustrated external connector  28  connects the spool  27  and wellhead housing  13 . Spool  27  and wellhead housing have a bore  29  extending axially therethrough that has a diameter at least equal to the outer diameter of tubing hanger  21 . This allows the tubing hanger  21  to be retrieved through spool  27 . Optionally, bore  29  may be as at least as large as the portion of the bore of wellhead housing  13  above casing hanger  17  to allow casing hanger  17  to be installed through spool  27 . An outlet port  31  is shown extending through a side wall of spool  27  The outlet port  31  can be used for the flow of production fluids from tubing  23 . At least one outlet valve  30  is mounted to the exterior of spool  27  to control the flow of well fluids exiting spool  27  through outlet port  31 . Well fluids flowing through outlet valve  30  may be delivered by methods known to those skilled in the art to a subsea collection manifold or to a platform located at the surface. 
     A tree cap  33  is illustrated having a lower cylindrical portion that is closely received within bore  29  of spool  27 . Tree cap  33  may either connect to spool  27  internally or externally as shown. In this embodiment, tree cap  33  has an external flange  32  that lands on the rim or upper end of spool  27 . An external connector  34  connects tree cap  33  to a profile formed on the upper portion of spool  27 . 
     Tree cap  33  has an axially extending production passage  36 . An isolation tube  35  is secured to the lower end of tree cap  33 . Isolation tube  35  extends downward and stabs into sealing engagement with production passage  22  in tubing hanger  21 . An outlet opening  37  extends laterally from production passage  36  through a sidewall of tree cap  33  to allow fluid flow to spool outlet port  31 . Upper and lower seals  38 A,  38 B extend around tree cap  33  and sealingly engage spool bore  29  above and below outlet port  31 . In this embodiment, upper seal  38 A is the uppermost pressure barrier that seals to bore  29 . 
     A tubing annulus access port  39  extends through a sidewall of spool  27  below lower seal  38 B for registering with and monitoring annulus  25 . Tubing annulus access port  39  is in communication with spool bore  29  below lower seal  38 B. A valve  41  is mounted to the exterior of tubing annulus access port  39  for opening and closing port  39 . 
     Tree cap  33  has a valve  43  above lateral flow outlet  37  for opening and closing access to its production passage  36 . If desired, a wire line plug profile could be formed in production passage  36  above flow outlet  37  for installing a wire line (or ROV tool installable) plug as a second pressure barrier within production passage  37 . Tree cap  33  optionally has a cylindrical mandrel portion above its flange  32  that has a grooved profile  45  for coupling to pressure control equipment, such as a riser or blowout preventer, during wire line or similar workover operations. Tree cap  33  may have an actuator  47  extending downward from its lower end for engaging and opening tubing annulus valve  26 . Actuator  47  could be a fixed probe that compresses the spring within tubing annulus valve  26  to cause it to open. Alternately, actuator  47  could be hydraulically extended and retracted. 
     In this embodiment, tubing hanger  21  has a number of auxiliary passages  49  (only one shown) extending from its lower end to its upper end. Auxiliary passages  49  are used to control downhole safety valves (not shown), to communicate with downhole sensors, and for other functions, such as supplying power to a downhole electrical submersible pump. Auxiliary passage  49  is shown schematically connected to a downhole auxiliary line  50  that extends alongside tubing  23  for supplying hydraulic fluid pressure or electrical or optical signals. Each auxiliary passage  49  has a coupling receptacle on the upper end of tubing hanger  21 . 
     In one embodiment, the tree cap  33  includes mating auxiliary passages  51 . A coupling  52  associated with each auxiliary passage  51  depends downward from tree cap  33  and stabs into sealing engagement with one of the auxiliary passages  49  in tubing hanger  21 . In this embodiment, the upper ends of at least some of the tree cap auxiliary passages  51  extend to a side of tree cap  33  above spool  27 . A controls module  53  having electrical and hydraulic control circuitry mounts to tree cap  33  for supplying hydraulic fluid pressure and electrical power to downhole safety valves and sensors. Controls module  53  may optionally be retrievable from tree cap  33  as well as retrievable along with tree cap  33 . Controls module  53  may also control tree cap valve  43 , if one is utilized. A separate controls module  55  may be mounted to a side of spool  27  for controlling valves  30 . If so, preferably controls module  55  is retrievable from spool  27 . 
     In an example of operation, subsea wellhead housing  13  and conductor casing  15  are landed within subsea well  11 . As shown in  FIG. 2 , a blowout preventer assembly (“BOP”)  57  is attached to an upper end portion of wellhead housing  13 . BOP  57  is a lower part of a string of drilling riser  59  that extends to a drilling vessel. Drilling operations are conventionally conducted through BOP  57  and wellhead housing  13 . When at total depth, casing hanger  17  and string of casing  19  are lowered through drilling riser  59  and BOP  57 , landed within wellhead housing  13  and cemented into place within the well in a manner known in the art. More than one string of casing may be installed. 
     Tubing hanger  21  and a string of tubing  23  are then lowered on a running tool  61  and drill string through drilling riser  59  and BOP  57 . Tubing hanger  21  is oriented, landed, sealed, and latched conventionally in the bore of wellhead housing  13 . For example, the orientation may be with a pin and slot arrangement associated with BOP  57 , or a separate orientation spool might be employed. When tubing hanger  21  lands, tubing  23  will extend into the subsea well to a production depth. Normally, the operator will circulate the drilling mud from casing  19  by pumping down tubing annulus  25  and returning fluid up tubing  23 , or vice-versa. Running tool  61  can be used to open tubing annulus valve  26  and a downhole safety valve (not shown) to allow circulation to occur. The operator may also perforate and test the well in a conventional manner at this point. 
     After perforating and testing the well, the operator lowers a temporary plug  63  ( FIG. 3 ) on a wire line through the drill string and running tool  61  and latches it within production passage  22  of tubing hanger  21  to seal subsea well  11 . The drilling riser and blowout preventer assembly  57 ,  59  are then removed from connection with wellhead housing  13 . The drilling vessel may also leave the vicinity to drill another well. At this point, the operator can install additional equipment, such as piping on flow lines to a subsea manifold or the surface without BOP  57  and drilling riser  59  being in the way. 
     At the surface, the operator assembles tree cap  33  to spool  27  with the desired orientation. The operator subsequently lowers the pre-unitized assembly of tree cap  33  and spool  27 , as illustrated in  FIG. 3 , preferably on a lift line. It is not necessary for the vessel used to lower the assembly to have a derrick or the capability of running drill pipe. The operator orients and lands flow spool  27  complete and pre-unitized with tree cap  33  on an upper end portion of wellhead housing  13 . The orientation of spool  27  to wellhead housing  13  may be handled conventionally, such as with the assistance of an ROV (remote operated vehicle) and video cameras. Upon landing, isolation spool  35  stabs into engagement with production passage  22  of tubing hanger  21 , thereby defining an axial passage extending from a production depth of subsea well  11  to outlet opening  37  of tree cap  33 . Outlet opening  37  aligns with outlet port  31  so that well fluids can flow directly from outlet opening  37  through outlet port  31 . 
     Also, upon landing of spool  27 , auxiliary couplings  52  connect auxiliary lines  50  to control module  53  via line  51 . In addition, tubing annulus valve actuator  47  stabs into tubing annulus valve  26  and opens it, which places annulus access port  39  in fluid communication with tubing annulus  25 . The operator plugs control modules  53 ,  55  into a subsea umbilical that delivers electrical and hydraulic power and control signals. The operator can then remove plug  63  to initiate well fluid production from subsea well assembly  11 . This may be handled with a subsea plug removal tool (such as shown in U.S. Pat. No. 6,719,059) that is lowered on a lift line and attached to tree cap profile  45  with the assistance of an ROV. Upon removing plug  63 , the operator opens valve  30  to communicate well fluids from string of tubing  23  to a subsea manifold or to a collection facility located on a surface. 
     For workover operations through tubing  23 , the operator may attach a riser to tree cap  33  and perform operations through tubing  23 , such as wire line operations. For a workover operation requiring the retrieval of tubing  23 , the operator can install wire line plug  63  back in tubing hanger  21  using a subsea plug retrieval tool, then retrieve tree cap  33  on a lift line. The operator would then attach a workover or drilling riser to spool  27  and pull tubing hanger  21  and tubing  23  in a conventional manner through the workover riser. Prior to pulling tubing hanger  21 , the operator would typically render the well safe by “killing” in a routine manner. Well circulation would be in the same manner as during completion, which is via running tool  61 , tubing annulus passage  24  in tubing hanger  21  and tubing  23 . 
     If desired, the workover operation may include further drilling, such as drilling a sidetracked portion of the well to a more productive zone. In one method, the operator pulls tubing hanger  21  and production tubing  23  through spool  27  and the workover or drilling riser. The operator would then lower a drill string through the riser and spool  27  and drill a sidetracked portion of the well. The operator would run casing or a liner through the riser and spool  27  into the sidetracked portion and install a string of tubing in the sidetracked portion. The operator would complete the sidetracked portion of the well in the same manner as described above. 
       FIG. 4  illustrates an alternative embodiment, which involves drilling the well through spool  27 . Wellhead housing  13  and conductor casing  15  are installed in a conventional manner as in the first method. After installing wellhead housing  13  and outer casing  15 , the operator then orients, lands and connects spool  27  to an upper end portion of wellhead housing  13 . Typically spool  27  is installed via a lift line, but it could also be run on a drill string. The operator then lowers the drilling riser  59  and connects BOP  57  with the profile on an upper end portion of spool  27 . The operator then continues drilling through BOP  57  and spool  27 . Such an operation is also known as “drill through” operations. 
     Upon drilling subsea well  11  to a desired depth, operator then lowers casing hanger  17  with string of casing  19  attached thereto through drilling riser  59  and BOP  57  and lands, sets and seals casing hanger  17  within wellhead housing  13 . The operator then lowers tubing  23  to the production depth of subsea well  11  and lands tubing hanger  21  in wellhead housing  13 . The operator completes and tests the well in a conventional manner through the drilling riser and BOP  57 . Using a wire line, the operator then lowers plug  63  ( FIG. 2 ) through BOP  57  to sealingly close subsea well  11 . The operator then removes drilling riser  59  and BOP  57 . 
     The operator then lowers tree cap  33  ( FIG. 1 ) via a lift line to land within spool  27 . As before, isolation tube  35  is attached to tree cap  33  and stabs into sealing engagement with production passage  22  in tubing hanger  21 . Tree cap auxiliary passages  51  mate with auxiliary passages  49  in tubing hanger  21 . Upon landing tree cap  33  within spool  27 , the operator can remove plug  63  from tubing hanger  21  to allow well fluids to flow from a lower end portion of string of tubing  23  to outlet opening  37 . The operator then opens valve  30  to allow flow of well fluids from subsea well  11  to a subsea manifold collection manifold or to the surface. 
     Significant advantages are presented herein. In addition to serving as a pressure barrier, the tree cap  33  provides a communication flow path for the production fluid from the tubing hanger  21  to the production flow outlet in the spool. Completing the well before running the spool, as in another embodiment, allows the drilling rig to moved, if desired, before installing the spool. The spool and tree cap can be assembled as a unit and lowered on a lift line on a vessel that may lack a derrick. In the second embodiment, the well may be drilled to total depth and casing installed through the spool. In both embodiments, for workover operations requiring retrieval of tubing, the tree cap can be pulled without disturbing the spool. Auxiliary lines, such as for downhole sensors and safety valves, may be lead through the tree cap to the exterior of the tree cap above the spool. The control module associated with these functions may be mounted to the tree cap and retrievable along with the tree cap. The controls for the valves of the spool may be in a separate module, if desired, and attached to the spool. Landing the tree cap on the rim of the spool avoids the need for a landing shoulder within the bore of the spool. 
     Alternate methods of subsea operations are illustrated in  FIGS. 5 through 8 . A wellhead assembly  10  is shown in a side sectional view in  FIG. 5  having spool  27  mounted on top of wellhead housing  13 . External connector  28  schematically couples the spool  27  and wellhead housing  13 . The wellhead assembly  10  of  FIG. 5  includes a drilling protector or wear bushing  70 . The wear bushing  70  as shown is an annular member or sleeve coaxially inserted within the bore  29 . The wear bushing  70  includes a lower end  71  shown positioned adjacent a radially inwardly directed profile  14  circumscribing the well head housing  13  inner diameter. The profile  14  defines a bore  29  diameter transition and lies in a plane generally orthogonal to the bore  29  axis. The lower end  71  of wear bushing  70  is correspondingly shaped to match the profile  14 . As shown, the respective inner diameters of the wear bushing  70  and bore  29  below the profile  14  are substantially the same to minimize an edge from protruding radially inward along the profile  14 . Without an edge at the profile  14 , a seamless path is provided for tool insertion through the wellhead assembly  10 . Moreover, the wear bushing  70  protects the spool  27  and well head housing  13  inner diameter along the bore  29  from potential damage from tools, such as a drill bit and string  75 , inserted through the bore  29 . 
     A split ring  18  is shown residing in corresponding channels  12 ,  72  respectively formed along the inner and outer diameters of the well head housing  13  and wear bushing  70 . The split ring  18  axially secures the wear bushing  70  in the bore  29 . Optionally, coupling the wear bushing  70  within the bore  29  may be accomplished using an interference  20  comprising corresponding protrusions and indentations. As will be discussed in more detail below, a retrieval channel  73  for removing the wear bushing  70  is shown formed radially along the wear bushing  70  inner diameter near the upper end of wear bushing  70 . Other means for coupling the wear bushing  70  within the bore  29  and retrieving the bushing  70  are available and the scope of the present application is not limited to the embodiments illustrated in the figures. 
     Included with the embodiment of  FIG. 5  is a drilling riser  40 , where its lower end is attached to the spool  27  upper terminal end. Drilling riser  40  would normally include a blow out preventer (BOP). The wear bushing  70  may be preinstalled within the bore  29  on the spool  27 . If a drill system is used, the wear bushing  70  may be optionally recovered through the drilling riser  40  in a conventional manner, such as with a retrieval fitting attached to a drill string. The wear bushing  70  is recoverable with an ROV after riser  40  is disconnected; the recovery can take place in parallel with retrieving the BOP stack and riser  40 . 
       FIGS. 6 through 8  depict a method of retrieval of wear bushing  70  from the subsea well  11  after riser  40  has been disconnected. Referring to  FIG. 6 , a side schematic view is illustrated of a retrieval tool  42  engaging the wear bushing  70 . A lift line  48  shown attached to the retrieval tool  42  can be used for raising and lowering the tool  42 . The retrieval tool  42  includes an ROV panel or port  80  coupled to a schematically depicted ROV  78  through a line  79 . The ROV  78  can be used to assist with deploying the retrieval tool  42 . A cylindrical extension  54  downwardly depends from the retrieval tool  42  lower end where it is coaxially inserted within the wear bushing  70  annulus. A latch member  44  is included with the retrieval tool  42  that is selectively extendable radially outward from the extension  54  shown registering with the retrieval channel  73 . Latch member  44  extension may be initiated by a hydraulic pressure signal sent from the ROV  78  through the line  79 . 
       FIG. 6A , which is an enlarged view of a portion of  FIG. 6 , schematically depicts an embodiment of latch member  44  operation having a hydraulic circuit  82  communicating between the ROV panel  80  and the latch member  44 . Inserting the latch member  44  into the retrieval channel  73 , couples together the retrieval tool  42  and wear bushing  70 . Latch member  44  extension may be initiated by a hydraulic pressure signal sent from the ROV  78  through the line  79 . Optionally, as shown in  FIG. 6B , the latch member  44 A may be a cam ring. An example of a cam ring is provided in Radi, et al., U.S. Pat. No. 6,070,669, issued Jun. 6, 2000 to the assignee of the present application, the contents of which is incorporated by reference herein. A tapered sleeve  84  is pushed downward in response to applied pressurized hydraulic fluid that in turn urges the latch member  44 A into the groove  73  for coupling the retrieval tool  42  and wear bushing  70 . 
     As depicted in  FIG. 7 , a push off jack  56  is urged downward from the tool  42  against the spool  27  upper surface, thereby separating the tool  42  and wear bushing  70  from within the spool  27 . Although a single push off jack  56  is shown, two or more push jacks  56  may be included. The force applied by the push off jack  56  against the spool  27  exceeds the retaining force provided from the split ring  18  in the channels  12 ,  72  as well as that of the interference  20 . The push off jack  56  can be hydraulically activated via the ROV  78  and ROV panel  80 , such as by directing pressurized hydraulic fluid to the panel  80  from the ROV  78  through the line  79 . Optionally, the panel  80  may include a supply or source of pressurized fluid for extending the push off jack  56 , and the line  79  carries a signal from the ROV  78  to deploy the push off jack  56 . Alternatively, an expander (not shown) can be employed to expand the split ring  18  into the channel  12  formed in the well head housing  13  thereby removing it from the bushing channel  72  and releasing the wear bushing  70  from the wellhead assembly  10 . In another alternative, if the interference  20  couples the wear bushing  70  to the bore  29 , an overpull from the lift line  48  can unseat the wear bushing  70  from the interference  20  for retrieval. 
       FIG. 8  is a side schematic sectional view of the wear bushing  70  attached to the retrieval tool  42 , where the retrieval tool  42  is suspended on the lift line  48 . In this embodiment, the retrieval tool  42  and wear bushing  70  can be in the process of being retrieved from a subsea well, or deployed to a subsea well. The ROV  78  is illustrated proximate the wellhead assembly  11 , but could instead be accompanying the retrieval tool  42 . In one embodiment, the wear bushing lower end  74  could be made from or coated with a material softer than the material of most or all components of the wellhead assembly  11 . Thus inadvertent impacts between the wear bushing  70  and wellhead assembly  11  would likely first deform the softer material, thereby preventing damage to the wellhead assembly  11  and its components. Wellhead components susceptible to damage include gaskets that may be struck by the bushing lower end  74  during retrieval. Examples of softer materials include elastomers, soft metals, and other pliable or otherwise malleable materials. 
     It should be apparent to those skilled in the art that the present disclosure is not limited to the embodiments described, but is susceptible to various changes without departing from its scope.