Abstract:
A technique for subsea operations utilizes a surface vessel to perform the installation and retrieval of submersible pumps or other tools with respect to a subsea well. A submersible pump is conveyed from a surface vessel to a subsea installation which is used to temporarily secure the submersible pump. Subsequently, the surface vessel is again used in cooperation with a conveyance to deliver the submersible pump to a desired location in a wellbore beneath the subsea installation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present document is based on and claims priority to U.S. Provisional Application Ser. No. 61/112,629, filed Nov. 7, 2008. 
    
    
     BACKGROUND 
     In a variety of subsea well related operations, the use of a submersible pump can be beneficial for producing fluid or for performing well servicing procedures. However, the installation and retrieval of submersible pumps to/from subsea wells are difficult procedures. Semi-submersible drilling rigs can be used to deploy, install and retrieve submersible pumps, but the use of such drilling rigs creates undesirable complexities, costs, and other difficulties that detract from the desirability of employing the submersible pump. 
     SUMMARY 
     In general, the present invention provides a methodology and system for utilizing a surface vessel to perform the installation and retrieval of submersible pumps with respect to a subsea well. A submersible pump is conveyed from a surface vessel to a subsea installation which is used to temporarily secure the submersible pump. Subsequently, the surface vessel is again used in cooperation with a conveyance to deliver the submersible pump to a desired location in a wellbore beneath the subsea installation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
         FIG. 1  is a schematic view of a surface vessel used to deploy a submersible pump to a subsea installation, according to an embodiment of the present invention; 
         FIG. 2  is a view similar to that of  FIG. 1  but showing the submersible pump deployed to the subsea installation, according to an embodiment of the present invention; 
         FIG. 3  is a view similar to that of  FIG. 2  but showing the submersible pump positioned in the subsea installation, according to an embodiment of the present invention; 
         FIG. 4  is a view similar to that of  FIG. 3  but showing the submersible pump secured in the subsea installation while a conveyance is retrieved to the surface vessel, according to an embodiment of the present invention; 
         FIG. 5  is a view similar to that of  FIG. 4  but showing a compliant guide engaged with the subsea installation, according to an embodiment of the present invention; 
         FIG. 6  is a view similar to that of  FIG. 5  but showing an internal conveyance coupled to the submersible pump and moved through the compliant guide to deliver the submersible pump to a desired wellbore location, according to an embodiment of the present invention; 
         FIG. 7  is a schematic illustration of an alternate embodiment of a surface vessel and a submersible pump deployment system incorporating a hanger adapter, according to an embodiment of the present invention; 
         FIG. 8  is a schematic illustration of the alternate embodiment delivered to a subsea installation, according to an embodiment of the present invention; 
         FIG. 9  is a schematic illustration of the alternate embodiment supported in the subsea installation while a compliant guide is connected to the subsea installation, according to an embodiment of the present invention; 
         FIG. 10  is a schematic illustration of the alternate embodiment in which a submersible pump is delivered into the wellbore via a power cable having a power cable termination designed for engagement with the hanger adapter, according to an embodiment of the present invention; 
         FIG. 11  is a schematic illustration of the alternate embodiment in which the power cable termination is supported in the hanger adapter, according to an embodiment of the present invention; and 
         FIG. 12  is a schematic illustration of the alternate embodiment in which a separate power cable has been engaged with the power cable termination to provide electrical power to the submersible pump, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The present invention generally relates to a technique for deployment of a tool, such as a submersible pump, downhole in a subsea well. A methodology and system are provided for using a surface vessel, e.g. a mono hull vessel, to install and/or retrieve the tool from a subsea well. 
     According to one embodiment, a submersible pump is deployed to a desired location in a subsea wellbore by lowering the submersible pump from the surface vessel. The submersible pump is conveyed from the surface vessel to a subsea installation by a conveyance, such as a cable, and then the submersible pump is temporarily secured in the subsea installation. By way of example, the subsea installation may be positioned on the seabed and comprise an intervention package used to hang or otherwise secure the submersible pump. Subsequently, the submersible pump is lowered into the wellbore by a suitable conveyance, such as coiled tubing, until positioned at a desired location within the wellbore. 
     According to one methodology, the submersible pump is landed in preinstalled landing hardware and automatically connected to a preinstalled electrical cable that may be routed outside of production tubing. In an alternate methodology, an electrical cable may be deployed while attached to the submersible pump and terminated with an electrical cable termination positioned proximate the seabed. With these and other methodologies, the submersible pump can be retrieved by reversing the installation sequences, embodiments of which are described below. 
     Referring generally to  FIG. 1 , an example of a system  20  for deploying a tool  22  in a subsea well  24  is illustrated. In this specific embodiment, tool  22  comprises a submersible pump that may be part of an overall electric submersible pumping system  26 . The electric submersible pumping system  26  is deployed from a surface vessel  28 , e.g. a mono hull surface vessel, located at a surface  30  of the sea. The surface vessel  28  is generally positioned above a subsea installation  32 . By way of example, subsea installation  32  may be mounted at a seabed  34 . 
     In the example illustrated, electric submersible pumping system  26  is positioned in a lubricator  36  while on surface vessel  28 . The pumping system  26  and lubricator  36  are then lowered from surface vessel  28  via a conveyance  38 . A dynamic seal  40  may be mounted on top of the lubricator  36  to seal against conveyance  38  when the pumping system  26  is deployed into the subsea installation  32 . By way of example, conveyance  38  comprises a flexible conveyance that may be in the form of a cable  42 , such as a crane wire, a wireline high strength cable, or another suitable flexible conveyance. 
     The subsea installation  32  may be constructed in a variety of configurations and with a variety of components. For example, subsea installation  32  may comprise a Christmas tree  44  positioned at seabed  34  and an intervention package  46  positioned above Christmas tree  44 . While submersible pump  22  is being conveyed to subsea installation  32  from surface vessel  28 , the subsea well  24  may be secured with barriers  48  of intervention package  46 . Depending on the well operation to be performed, intervention package  46  is constructed with components selected to facilitate the desired operation. By way of example, intervention package  46  may comprise valves  50 , used to selectively control barriers  48 , combined with a securing mechanism  52  that may be in the form of pipe rams or other suitable devices used to secure, e.g. support, tool  22  in subsea installation  32 , as described in greater detail below. 
     In the embodiment illustrated in  FIG. 1 , preinstalled hardware  54 , e.g. a preinstalled completion, is positioned in a wellbore  56  of subsea well  24 . The preinstalled hardware  54  is designed to receive and engage the tool/submersible pump  22  when landed in the preinstalled hardware. A preinstalled electrical connector  58  also is positioned in or proximate to the preinstalled hardware  54  and is connected to a preinstalled power cable  60 . Power cable  60  is routed up to subsea installation  32  or to another desired location for connection to a power cable umbilical or to another source of electrical power. The preinstalled power cable  60  may be routed along the outside of a tubing  62 , e.g. a production tubing, a casing, or another type of well tubing, in which the pumping system  26  is deployed and/or to which the pumping system is connected once delivered downhole into wellbore  56 . 
     When electric submersible pumping system  26  is landed in preinstalled hardware  54 , electrical connection with the pumping system is automatically formed via engagement with preinstalled electrical connector  58 . By way of example, preinstalled electrical connector  58  may be part of an electrical wet connect that engages its corresponding component mounted on electric submersible pumping system  26 . 
     In  FIG. 2 , the submersible pump  22  and lubricator  36  have been lowered from surface vessel  28  via conveyance  38  to subsea installation  32 . In this example, the lubricator  36  is connected to intervention package  46  and dynamic seal  40  is used to ensure a seal against conveyance  38 . Once the seal is established against the conveyance, e.g. cable  42 , the well barriers  48  may be opened to enable lowering of the submersible pump  22  into subsea installation  32 . In this example, the entire electric submersible pumping system  26  is lowered into intervention package  46  of subsea installation  32 . 
     To facilitate formation of the seal against conveyance  38  via dynamic seal  40 , the lower part of conveyance  38  may be formed as a cable with a flush, slick exterior surface  63  or as a rigid bar with the flush, slick exterior surface  63  to ensure maintenance of a seal as the electric submersible pumping system  26  is lowered into the subsea installation, as illustrated in  FIG. 3 . The smooth exterior surface  63  only needs to extend along a relatively short length of the conveyance  38 , e.g. cable  42 , because the length of conveyance lowered through the dynamic seal  40  is limited. If lubricator  36  is not long enough to cover the full length of the electric submersible pumping system  26 , a valve can be employed in the well to provide a barrier to well pressure at a position that allows deployment of a toolstring longer than the lubricator. 
     In  FIG. 3 , the electric submersible pumping system  26  has been delivered into subsea installation  32 . Once an upper portion of pumping system  26  is within securing mechanism  52 , the securing mechanism, e.g. pipe rams, are actuated to grab and secure the electric submersible pumping system in subsea installation  32 . Subsequently, the conveyance  38  is disconnected from pumping system  26  and an upper barrier  48  of the intervention package  46  is closed, as illustrated in  FIG. 4 . The lubricator  36  may be disconnected from the intervention package  46  and retrieved to the surface vessel  28  via conveyance  38 . 
     At this stage, a guide system  64  may be deployed from surface vessel  28  to subsea installation  32 , as illustrated in  FIG. 5 . The guide system  64  provides an enclosed pathway between the surface vessel  28  and the subsea installation. By way of example, guide system  64  may comprise a spoolable compliant guide system, e.g. a spoolable compliant guide system available from Schlumberger Corporation, connected between surface vessel  28  and intervention package  46 . Additionally, a second conveyance  66  is delivered from surface vessel  28  down through guide system  64  to the intervention package  46 . By way of example, the conveyance  66  may comprise coiled tubing  68  and guide system  64  may comprise a dynamic seal  70 . Guide system  64  also may comprise a lubricator  71  positioned below dynamic seal  70 . 
     The dynamic seal  70  is activated against the coiled tubing  68  (or other suitable conveyance) to establish a pressure barrier as the lower end of coiled tubing  68  is moved into proximity with the intervention package  46 . The upper barrier  48  of the intervention package may then be opened to enable connection of coiled tubing  68  with the upper end of electric submersible pumping system  26 , as illustrated in  FIG. 6 . Once the connection has been made, securing mechanism  52  may be released by, for example, retracting the pipe rams to release the electric submersible pumping system. The coiled tubing  68  is then be used to lower submersible pump  22 /pumping system  26  down into wellbore  56  until a desired wellbore location is reached. 
     For example, electric submersible pumping system  26  may be lowered into engagement with preinstalled hardware  54  as indicated by the dashed line silhouette of electric submersible pumping system  26  in  FIG. 6 . As pumping system  26  is landed in preinstalled hardware  54 , the pumping system is automatically electrically engaged with preinstalled electrical connector  58  which can be powered via preinstalled power cable  60 . 
     After delivering the submersible pump/tool  22  to the desired wellbore location, the coiled tubing  68  or other suitable conveyance may be released and retrieved to surface vessel  28 . Following retrieval of the coiled tubing  68 , pressure barriers are reestablished in Christmas tree  44  to enable activation of submersible pump  22 . Reestablishing pressure barriers in Christmas tree  44  also allows the guide system  64  and intervention package  46  to be retrieved to surface vessel  28 . 
     In an alternate embodiment, electrical power is provided to submersible pumping system  26  without installing power cable  60  or electrical connector  58  with a preinstalled completion, e.g. preinstalled hardware  54 . In this alternate embodiment, the power cable is deployed when the submersible pump  22  is installed which enables a variety of additional well related applications, such as retrofit applications in which a submersible pump is retrofitted in an existing well. 
     In one embodiment, the alternate approach may be designed to deploy a power cable in the form of power lines installed inside coiled tubing, such as RedaCoil available from Schlumberger Corporation. The coiled tubing serves as a strength member to support the weight of the electric submersible pumping system during deployment into the subsea well  24  and it also protects the power lines during deployment. This approach provides a slick surface against which the dynamic seals can seal while the electric submersible pumping system is lowered through wellbore  56 . In another embodiment of the alternate approach, the power cable comprises an umbilical type cable which may be deployed in a self-supporting manner inside the well. The umbilical type cable is designed with sufficient strength to support the weight of the pump. The cable also has a sufficiently slick exterior surface to enable proper operation of the dynamic seals while the electric submersible pumping system is lowered through wellbore  56 . 
     Referring generally to  FIG. 7 , one methodology for employing this alternate approach is illustrated. In the illustrated embodiment, the tool  22  (in this case the entire electric submersible pumping system  26 ) is rigged up at the surface vessel  28  inside lubricator  36  as discussed above with respect to the previous embodiment. However, an adaptor  72  is positioned at the top of the tool, which in the illustrated example is at the top of electric submersible pumping system  26 . The adapter  72  may be constructed as a tubing hanger adapter designed to land in a tubing hanger at the subsea installation  32  when the electric submersible pumping system  26  is lowered into the well. 
     After the pumping system  26  and adapter  72  are placed within lubricator  36 , the assembly is lowered to subsea installation  32 , as illustrated in  FIG. 8 . The lubricator  36  is engaged with intervention package  46 , and barriers  48  are removed to enable movement of electric submersible pumping system  26  and adapter  72  into the subsea installation  32 . The assembly is secured, e.g. hung, via securing mechanism  52  which may be in the form of pipe rams designed to grab the assembly. 
     Once the electric submersible pumping system  26  is supported by securing mechanism  52 , the upper barrier  48  is closed and the lubricator  36  may be retrieved to allow deployment of guide system  64 , e.g. a spoolable compliant guide system, as illustrated in  FIG. 9 . Instead of delivering coiled tubing through the guide system  64 , a pump power cable  74  is connected to the lower end of conveyance  66 , e.g. coiled tubing  68 , and delivered to the electric submersible pumping system  26  for connection, as illustrated. By way of example, pump power cable  74  may comprise an umbilical type of power cable or an instrumented tubing, such as RedaCoil which is available from Schlumberger Corporation. The upper end of the pump power cable  74  comprises a power cable termination  76  that may be landed in the hanger adapter  72 . 
     The length of the pump power cable  74  is selected to match the distance between the upper end of the electric submersible pumping system  26  and the installed position of power cable termination  76  when landed in hanger adapter  72 . As discussed below, the adapter  72  may be landed in Christmas tree  44 . 
     After engaging the lower end of pump power cable  74  with electric submersible pumping system  26 , the pumping system is lowered into wellbore  56  and tubing hanger adapter  72  is landed in Christmas tree  44 , as illustrated in  FIG. 10 . The pump power cable  74  moves freely through adapter  72  until termination  76  is landed in the adapter. It should be noted that the subsea dynamic seals, e.g. dynamic seal  70 , are temporarily opened to enable passage of the pump cable termination  76  and then closed against coiled tubing  68 . In this example, the diameter of pump power cable  74  is the same as the diameter of coiled tubing  68  to facilitate formation of sufficient sealing via the dynamic seal or seals. 
     As illustrated in  FIG. 11 , once the power cable termination  76  is moved past the dynamic seal or seals, the pumping system  26  is landed in downhole landing hardware  54 . The coiled tubing  68  is then lowered a small, additional amount until the power cable termination  76  lands in the tubing hangar adapter  72 , as illustrated. Both the tubing hanger adapter  72  and the power cable termination  76  are designed to provide suitable pressure barriers to secure the subsea well. Additionally, the power cable termination  76  may be locked into tubing hanger adapter  72  to prevent unwanted separation. 
     At this stage, the coiled tubing  68  may be disconnected and retrieved to the surface vessel  28 . Additionally, the guide system  64 , dynamic seal  70 , any lubricator positioned below the dynamic seal  70 , and intervention package  46  also may be retrieved to surface vessel  28 . The power cable termination  76  is designed to receive an electrical wet connector  78 , as illustrated in  FIG. 12 . By way of example, the electrical wet connector  78  may be stabbed into power cable termination  76  by a remotely operated vehicle (ROV). Engagement of the wet connector  78  and a corresponding power cable  80  enable operation of the submersible pump  22 . 
     With the embodiments described above, the electric submersible pumping system  26  or other type of tool  22  is readily retrieved to the surface vessel  28 . The sequence of events for installing the pumping system  26 /tool  22 , as described above, is simply reversed to enable retrieval of the equipment upon completion of the desired well related operation. 
     System  20  may be constructed in a variety of configurations for use in many types of subsea wells. For example, the submersible pump may be constructed in several configurations and sizes. Additionally, the submersible pump may be combined with many types of other components to provide electric submersible pumping systems suitable for desired applications. The subsea installation also may incorporate various components to facilitate installation and/or retrieval of tools or to enable other well related functions. Consequently, the Christmas tree and intervention package may be constructed in suitable corresponding configurations. Similarly, the first and second conveyances used in the installation and/or retrieval procedures may be selected according to the various goals or constraints of a given application. 
     Although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.