Abstract:
A technique is provided for pumping fluid in subsea applications, such as booster pumping applications. A self-contained pumping module has a pump and a motor mounted on a skid. The self-contained pumping module also includes electrical connections by which electrical power can be provided to the motor and hydraulic connections for connecting suitable hydraulic lines with a pump intake and a pump discharge. The self-contained nature of the pumping module enables easy deployment to a sea floor in a variety of applications.

Description:
BACKGROUND 
       [0001]    In a variety of subsea applications, fluids are pumped from one region to another. For example, fluid can be produced upwardly from a subsea well, or fluid can be directed through subsea flowlines or injected into subsea wells. Sometimes existing pumping equipment is not adequate for a given task, and boosting pumps and equipment are added to the subsea equipment to facilitate the pumping applications. However, existing subsea pumping equipment used for boosting pumping capacity can be difficult and expensive to construct and/or use in the subsea environment. 
       SUMMARY 
       [0002]    In general, the present application provides a system and methodology for pumping fluid in subsea applications, such as booster pumping applications. A self-contained pumping module is created by combining a pump and a motor on a skid. The self contained pumping module also comprises the electrical connections by which electric power can be provided to the motor. The pumping module further comprises a plurality of hydraulic connections for connecting suitable hydraulic lines with a pump intake and a pump discharge. The self-contained nature of the pumping module enables easy deployment to a sea floor/retrieval from the sea floor, which allows the pumping module to be deployed in a variety of applications with reduced complexity and cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    Certain embodiments will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
           [0004]      FIG. 1  is a front elevation view of one example of a self-contained pumping module, according to an embodiment; 
           [0005]      FIG. 2  is a top view of the pumping module illustrated in  FIG. 1 , according to an embodiment; 
           [0006]      FIG. 3  is another example of the self-contained pumping module, according to an alternate embodiment; 
           [0007]      FIG. 4  is another example of the self-contained pumping module, according to an alternate embodiment; 
           [0008]      FIG. 5  is another example of the self-contained pumping module, according to an alternate embodiment; and 
           [0009]      FIG. 6  is another example of the self-contained pumping module, according to an alternate embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In the following description, numerous details are set forth to provide an understanding of the present application. However, it will be understood by those of ordinary skill in the art that many embodiments may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
         [0011]    The present application generally relates to a system and methodology for facilitating pumping of a fluid at a subsea location, e.g. a location proximate a subsea wellhead. The technique utilizes a self-contained pumping module that can be lowered to the sea floor and retrieved from the sea floor as a single module to provide additional pumping capacity without undue increases in time and costs. Additionally, the self-contained pumping module may have modular features that allow the pumping system to be tailored to specific application requirements. 
         [0012]    In many applications, the self-contained pumping module is used to supplement or boost the pumping of fluids in a subsea environment. The pumping module is lowered to the sea floor where hydraulic and electrical connections are easily made by, for example, use of a remotely operated vehicle. In many applications, the pumping module is positioned directly onto the sea floor. Because of the self-contained design, positioning of the pumping module on the sea floor can be accomplished via a crane mounted on a work boat instead of requiring a work-over rig, semi-submersible platform, or drilling rig. 
         [0013]    By way of example, the self-contained pumping module can be used in boosting fluids from subsea wells when it is not practical, feasible or desirable to install large horsepower electric submersible pumping systems or other artificial lift systems into a subsea wellbore to produce a fluid to a surface location. The self-contained pumping module can be lowered to the sea floor near a wellhead, for example, to provide boosting to a surface platform, subsea processing facility, floating production, storage and offloading vessel, or other surface locations. In some applications, the pumping module can be placed downstream of subsea processing facilities to provide lift required to produce the fluid to the surface. 
         [0014]    Apart from production applications, the self-contained pumping module also can be positioned at the sea floor and used to inject fluid into subsea wells. For example, the pumping module can be used to inject water to facilitate pressure maintenance of a reservoir. In this type of application, the pumping module can be connected to a suitable source of water, such as drilled water source wells, subsea processing facilities, surface processing facilities, or the surrounding ocean. In other applications, the self-contained pumping module can be used in the commissioning of subsea pipelines by removing the water used to sink and hydrostatically test the subsea pipelines. In many of these types of applications, the pumping module can be used to discharge the water directly into the ocean or to deliver the water to appropriate surface or subsea facilities. 
         [0015]    Referring generally to  FIG. 1 , a pumping system  20  is illustrated according to one embodiment. In this embodiment, pumping system  20  comprises self-contained pumping module  22  that can be lowered to and retrieved from a sea floor  24 . The self-contained pumping module  22  may be constructed in a variety of configurations with a variety of components, and several examples are described below. 
         [0016]    In the embodiment illustrated in  FIGS. 1 and 2 , the self-contained pumping module  22  comprises a skid  26  on which a pump  28  and a motor  30  are mounted. As illustrated, the pump  28  and the motor  30  are constructed and oriented as a horizontal pumping system. Although pump  28  and motor  30  may be mounted on skid  26  in a variety of orientations and with a variety of mechanisms, the embodiment illustrated uses a substructure or platform  32  by which the components are mounted to a base portion  34  of skid  26 . By way of example, motor  30  may be mounted to substructure  32  via appropriate brackets  36 , and pump  28  may be mounted to substructure  32  via appropriate clamp mechanisms  38 . 
         [0017]    The various components are designed to work in a subsea environment. For example, skid  26  may be constructed from structural steel welded or otherwise fastened together to provide a rigid base. The structural steel or other suitable component also can be painted or otherwise coated to prevent corrosion during operation in the subsea environment. Additionally, skid  26  may comprise a lower support structure  40  to secure the self-contained pumping module  22  on the sea floor. For example, support structure  40  may comprise a material or structure designed to secure the self-contained pumping module  22  in a typical seafloor constituent, such as mud or sand. In one embodiment, support structure  40  comprises a mesh material  42  constructed as a “mud mat” that securely positions pumping module  22  at a desired location in the mud/sand of the sea floor. 
         [0018]    A variety of pumps  28  and motors  30  can be used according to the specific application requirements. Additionally, new or different types of pumps and motors can be substituted as needed based on wear or changes in the application requirements. Individual motors and pumps may be used in some applications, as illustrated in  FIG. 2 , however additional motors and pumps also may be incorporated into the design, as described in greater detail below. 
         [0019]    In one embodiment, pump  28  comprises a centrifugal pump, such as a centrifugal pump used in a standard electric submersible pumping system application. Fluid enters pump  28  through an intake section  44  and passes through multiple centrifugal pumping stages that incrementally increase the fluid pressure until the fluid is discharged through a discharge head  46 . By using clamp mechanisms  38 , the alignment of pump  28  can be adjusted relative to intake  44  and motor  30 . It should be noted that other types of pumps can be used in some applications, including helicoaxial pumps. 
         [0020]    Motor  30  also may have a variety of forms and configurations. In the embodiment illustrated, for example, motor  30  is a three-phase induction motor. The motor is hermetically sealed to prevent contamination from the surrounding environment. Additionally, motor  30  may be pressure balanced with the surrounding environment to reduce the need for managing high differential pressures when operated in deep water. The motor  30  may be mounted horizontally such that its shaft extends through intake section  44  for direct coupling to a corresponding shaft of pump  28 . 
         [0021]    The self-contained pumping module  22  can also comprise a plurality of connectors, including electrical connectors  48  and hydraulic connectors  50  and  52 . In many applications, electrical connectors  48  are wet mate connectors that enable easy connection with corresponding electric cable via, for example, a remotely operated vehicle. In the specific example illustrated, electric lines  54  are used to connect motor  30  with female receptacles of electrical wet mate connectors  48 . The electrical connectors  48 , in turn, are mounted in a structure  56 , such as a stab plate secured to skid  26 . The stab plate may be mounted at various locations along the edge of the skid  26  or at other suitable locations that enable easy connection with a subsea power grid or other source of power. 
         [0022]    Similarly, hydraulic connectors  50 ,  52  may be formed as hydraulic wet mate connectors that enable easy connection of hydraulic lines via, for example, a remotely operated vehicle. In the embodiment illustrated, hydraulic connector  50  is coupled with pump intake section  44  via flow tubing  58 , and hydraulic connector  52  is coupled with pump discharge head  46  via flow tubing  60 . The hydraulic connectors  50 ,  52  can be located at the same end of skid  26  or at other suitable locations along the pumping module  22 . For example, an optional discharge hydraulic connector  62  is illustrated by dashed lines in  FIG. 2 . The hydraulic inlet connector  50  may be connected to piping that extends directly from a subsea wellhead, a subsea processing facility, a subsea pipeline, or another subsea structure carrying fluid for which boosted fluid flow is desired. 
         [0023]    In a variety of applications, various instrumentation  64  also can be added to self-contained pumping module  22  to monitor parameters related to the pumping operation. For example, the instrumentation  64  may comprise sensors, such as temperature sensors, pressure sensors, flow rate sensors and other sensors. The instrumentation  64  also may include other components, such as control modules used to provide feedback and/or to control specific functions, such as the opening and closing valves. 
         [0024]    Referring generally to  FIG. 3 , another embodiment of self-contained pumping module  22  is illustrated. In this embodiment, the pumping module  22  comprises a plurality of pumps  28  and a plurality of motors  30 . By way of example, individual motors  30  can be connected with individual corresponding pumps  28  to create a series of combined motors and pumps arranged as individual pumping units  65 . The groupings of motors and pumps are combined on a single skid  26  to enable increased system flexibility and to allow for redundant pumping systems. In the embodiment of  FIG. 3 , for example, the series of motors  30  and corresponding pumps  28  comprise four individual pump/motor units  65  mounted in parallel. During operation of pumps  28 , fluid is drawn in through a supply tubing  66  that is coupled with hydraulic connector  50 . The supplied fluid flows through hydraulic connector  50  and into an intake manifold  68  that supplies the individual intake tubes  58  for the plurality of pumps  28 . Once the fluid is discharged by the pumps  28 , the fluid flows into a discharge manifold  70 , out through hydraulic connector  52 , and subsequently through an outflow tubing  72 . 
         [0025]    The plurality of motors  30  can be supplied with electrical power via electric lines  54  which may be in the form of electric cables or an electric bus connected to structure  56 . Electrical power is supplied to wet mate electrical connectors  48  in structure  56  via corresponding wet mate connectors  74  carried on electric supply cables  76 . The electric power supplied is controlled by a control system  78  which can be located top side, on a floating production, storage and offloading vessel, on a production platform, or at a subsea location. The control system  78  can be designed to control any of the various embodiments of self-contained pumping module  22 . Additionally, the control system  78  can be used for receiving and/or outputting data with respect to instrumentation  64 . 
         [0026]    Another embodiment of self-contained pumping module  22  is illustrated in  FIG. 4 . In this embodiment, a plurality of motors  30  and pumps  28  are again arranged in individual pumping units  65 . In the particular example illustrated, four pumping units  65  are mounted on skid  26  with pairs of the pumping units  65  connected in series to provide twice the boost pressure of a single pumping unit. The two pairs of pumping units  65  are then operated in parallel, via connections to intake manifold  68  and discharge manifold  70 , to provide twice the flow rate relative to a single pair of the pumping units  65  connected in series. 
         [0027]    Referring generally to  FIG. 5 , another embodiment of self-contained pumping module  22  is illustrated. The illustrated embodiment is similar to the embodiment of  FIG. 4 , however a plurality of isolation valves  80  have been added. The isolation valves  80  allow one pair of pumping units  65  to operate, while the other is available as a back-up in case the first pair fails to function as desired. In the embodiment illustrated in  FIG. 5 , the isolation valves  80  are positioned in the pair of intake tubings  58  coupled with intake manifold  68 , and in the pair of outflow tubings  60  coupled with discharge manifold  70 . However, the isolation valves  80  can be used in a variety of other self-contained pumping module embodiments. For example, isolation valves can be used in the embodiment illustrated in  FIG. 3  to make all four pumping units  65  capable of independent operation. 
         [0028]    Referring generally to  FIG. 6 , another embodiment of self-contained pumping module  22  is illustrated. In this embodiment, a plurality of motors  30  and a plurality of pumps  28  are mounted on skid  26  and arranged in pumping units  65  that are connected in series. In the specific example illustrated, four pumping units  65  are connected in series, although the number of pumping units can be varied according to the requirements of a given application. The four pumping units connected in series provide four times the discharge pressure at a given flow rate. 
         [0029]    The size, configuration, and component types used to construct self-contained pumping module  22  can be varied to accommodate many types of subsea pumping applications, including boosting production and injection applications. An individual motor and pump can be mounted on the skid, or a plurality of motors and pumps can be mounted on the skid in many configurations, including parallel configurations, serial configurations, and numerous combinations of parallel and serial configurations. Additionally, the materials and structure of skid  26  and support structure  40  can be selected to accommodate easy positioning of the self-contained pumping module  22  directly onto seafloor  24 . The skid  26  can be deployed to many locations for use in a variety of subsea pumping applications, including the boosting of fluid flow from subsea wells. Similarly, the position and configuration of the wet mate connectors, both hydraulic and electrical, can vary from one application to another to accommodate easy connection of electric lines and hydraulic lines. 
         [0030]    Although only a few embodiments have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible. Such modifications are intended to be included within the scope of the claims.