Patent Publication Number: US-7914266-B2

Title: Submersible pumping system and method for boosting subsea production flow

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 60/521,319, entitled, “ELECTRIC SUBMERSIBLE PUMPING SYSTEM AND METHOD FOR BOOSTING SUBSEA PRODUCTION FLOW,” filed on Mar. 31, 2004. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to a system for the boosting of hydrocarbons from a subsea production well, and more particularly to a system for producing hydrocarbons from a subsea production well with a submersible pump connected to the production well and deployed in a dummy well. 
     BACKGROUND 
     Subsea flow boosting pumps are generally used to deliver production fluid from subsea wells to remote storage or processing facilities. Such pumps may be submersible pumps installed in the production well (e.g., electrical submersible pumps or ESPs) or pumps located external the production well (e.g., seabed booster pumps). U.S. Pat. No. 6,688,392 to Shaw, which is incorporated herein by reference, describes a system for flow pressure boosting of hydrocarbon fluids in a subsea environment. Shaw describes a hydrocarbon flow boosting system including: a producing well for producing hydrocarbon fluids, a cased dummy well hydraulically connected to the producing well for receiving hydrocarbon fluids, and a pump and motor disposed in a liner in the dummy well for taking suction flow from the dummy well and boosting the flow energy of the discharge flow of hydrocarbon fluids. Particularly, the flow boosting system of Shaw may be operated by flooding the annulus of the cased dummy well with hydrocarbon fluids and pumping the fluids upward out of the annulus via the liner to a subsea processing station (as shown in  FIG. 1  of Shaw). The motor of the pump in Shaw is thus surrounded by hydrocarbon fluids and may not be accessible for cooling facilities. 
     Accordingly, there exists a need for a flow boosting pump system whereby the pump motor is isolated from the production fluid such that motor cooling facilities may be employed. 
     SUMMARY 
     In general, according to one embodiment, the present invention provides a system for boosting subsea production fluid flow via one or more submersible pumping systems deployed in a dummy well and a conduit for containing the production fluid and isolating the production fluid from the wellbore of the dummy well. According to some embodiments, each submersible pumping system includes a pump and a motor deployed in a dummy well, where seawater (or other cooling agent) is circulated through the dummy well to cool the motor. According to other embodiments, an underwater vehicle (e.g., a remote operating vehicle or autonomous underwater vehicle) is provided for accessing and controlling pump operations. 
     Other or alternative embodiments of the present invention will be apparent from the following description, from the drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The manner in which these objectives and other desirable characteristics can be obtained is explained in the following description and attached drawings in which: 
         FIG. 1  illustrates a profile view of an embodiment of a booster pumping system deployed in a dummy well in accordance with the present invention for use with boosting flow in a production well. 
         FIG. 2  illustrates a profile view of an embodiment of a production well, a dummy well, and a booster pumping system of the present invention having pump, motor, and protector components deployed in the dummy well. 
         FIG. 3  illustrates an enlarged cross-sectional view of an embodiment of a booster pumping system of the present invention having pump, motor, and protector components deployed in a dummy well and operated by a remote operated vehicle. 
     
    
    
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled 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. 
     In the specification and appended claims: the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; and the term “set” is used to mean “one element” or “more than one element”. As used herein, the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly described some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate. 
     In general, an embodiment of the present invention includes a system for producing hydrocarbons from a subsea production well with at least one submersible pumping system hydraulically connected to the production well and deployed in a dummy well. The pumps used in the present invention generally refer to electric submersible pumps or ESPs, however, other types of pumps may be used including, but not limited to piston pumps and positive displacement pumps. 
     With respect to  FIG. 1 , more particularly, one embodiment of the present invention includes a production well  10  having one or more hydrocarbon bearing formations  12  and a casing  30  intersecting the formation and establishing hydraulic communication between the formation and the seabed  20 . The production well  10  further includes a wellhead  14  for sealing the well  10 . A non-producing hole or “dummy well”  40  is provided proximate the production well  10 . The proximity of the dummy well  40  to the production well  10  is relative to the scale of a vast sea, ocean, or other body of water and is determined based on operating conditions (e.g., the pump should be able to overcome pressure losses due to friction and well depth). A pumping system  50  is deployed in the dummy well  40  and is hydraulically connected to the production well  10  by an inlet pipe  60  and an outlet pipe  70 . The pumping system  50  includes a submersible pump  52  having an intake  54 , and a motor  56  coupled to the pump (mechanically, magnetically, or otherwise) to drive the pump. The inlet pipe  60  is connected to the intake  54  and isolates incoming production fluid from the wellbore of the dummy well  40 . A production pipe  80  is connected to the wellhead  14  of the production well  10  to transport the boosted production fluid from the well. The production pipe  80  may include a riser conduit to deliver the boosted production fluid to the surface or else an intermediate conduit to transport the production fluid to a subsea facility (e.g., for storage, separation, or other). Alternatively, the outlet pipe  70  may be a production pipe for delivering the production fluid to other destinations besides back to the wellhead  14  of the production well. 
       FIG. 2  illustrates another embodiment of the booster pumping system of the present invention. This embodiment of the booster pumping system  50  includes a protector  57  connected between the motor  56  and the pump  52 . The protector  57 , for example, may be any motor protector that is well known to those skilled in the art including, but not limited to, a labyrinth-type protector, elastomer bag, piston protector, bellows, and/or gas chamber or positive-pressure protector. The protector may provide the capability of compensating volume changes due to thermal expansion of the oil in the motor  56 , isolating of the oil from the production fluid or other wellbore fluids or seawater in the dummy well  40 , sealing the motor  56  from the production fluid in the pump  52 , carrying the axial load of the pump  52  such as via thrust bearings in connection with the motor  56 , and/or transmitting torque from the motor  56  to the pump  52 . Moreover, the protector  57  may also house the thrust bearings. 
     With respect to both  FIGS. 1 and 2 , in operation, to boost the flow of the production well  10 , a dummy well  40  may be drilled to house a booster pumping system  50 . The booster pumping system  50  is installed in the dummy well  40  and suspended from a dummy wellhead  45 . The motor  56  of the booster pumping system  50  is used to drive the pump  52  to draw production fluid from the production well  10  into the intake  54  of the pump via the inlet pipe  60 . In the embodiment illustrated in  FIG. 1 , the motor  56  transmits the torque directly to the pump  52 . In the embodiment illustrated in  FIG. 2 , the motor  56  transmits the torque to drive the pump  52  via the protector  57 , which also may seal the motor from contact with the production fluid. The production fluid supplied to the pumping system  50  is isolated from the open dummy well  40  by the inlet pipe  60 . The production fluid is then energized by the pump  52  to boost the flow back to the production wellhead  14  (or other destination) via the outlet pipe  70 . The energized or boosted flow of the production fluid is then delivered from the production well  10  to another destination via the production pipe  80 . In some embodiments, seawater may be circulated or otherwise delivered into or free to move into the dummy well  40  to engage the motor  56  for cooling effect. 
       FIG. 3  illustrates yet another embodiment of the pumping system  50  of the present invention for use in boosting the production fluid flow of a production well. This embodiment of the pumping system  50  includes a plurality of pumps  52 . In alternative embodiments, the pumps  52  may be run simultaneous (in series or parallel) to increase the energy imparted to the production flow or as primary and secondary pumps to provide a redundant or back-up pump in the event that one of the pumps is shut down or otherwise becomes inoperable. Each pump  52  is driven by a motor  56 . The pumps  52  may share an intake  54  or otherwise each pump may have a dedicated intake. In this embodiment, the intake  54  is an intake manifold for receiving an inlet flow and delivering a plurality of outlet flows (in this case two). While only two pumps are shown in  FIG. 3 , it is intended that other embodiments of the present invention include a booster pumping system comprising any number of pumps arranged either in series or parallel. The pumps  52  may be suspended from a dummy wellhead  45 . An inlet conduit  60  takes incoming production fluid and directs such fluid to the intake  54  of the pumps  52 . Once energy is imparted into the incoming production fluid to boost the flow by the pumps  52 , the production fluid is directed away from the pumping system  50  to another destination via an outlet conduit  70  (e.g., back to the production well, to a subsea production facility, or to the surface via a riser). Moreover, the pumping system  50  may include an inline valve  90  installed between each pump  52  and the outlet conduit  70  to regulate the boosted production flow. In some embodiments having multiple pumps run in parallel  52 , an outake manifold  72  is provided for combining the energized production flows for delivery to a destination via the outlet conduit  70 . 
     With respect to  FIG. 3 , in some embodiments, the pumping system  50  may further include a gas handling device  53  connected between the pump  52  and the motor  56  to prevent production flow having a high gas-to-liquid ratio from causing the pump to lock or become otherwise inoperable. The gas handling device  53  may include impellers for mixing the gas and liquid content to reduce the formation of gas bubbles, which are known to cause “pump lock.” One such gas handling device is described in U.S. Pat. No. 5,628,616, which is incorporate herein by reference. 
     Still with respect to  FIG. 3 , in some embodiments, the pumping system  50  may further include a monitoring tool  59  connected to each motor  56  for detecting the conditions of the pumping system  50  and/or the dummy wellbore environment. For example, the monitoring tool  59  may include a pressure sensor for detecting dummy wellbore pressure, a temperature gauge for detecting dummy wellbore temperature (e.g., the temperature of the seawater surrounding the motor), a flowmeter for monitoring flow of seawater circulation through the dummy well, a vibration monitor and so forth. 
     Yet still with respect to  FIG. 3 , in some embodiments, seawater may be circulated or otherwise delivered into or may be free to move into the dummy well  40  to engage the motor  56  for cooling effect. For example, the dummy well  40  may be flooded with seawater for cooling the motor  56  of the pumping system  50  deployed therein. Alternatively, the seawater may be circulated via a dedicated circulation pump  100  or circulated naturally due to temperature gradients via an opening in the dummy wellhead  45 . In other embodiments, pipes or other conduits may be installed around the motor  56  for pumping cool fluids in and/or hot fluids out to aid in natural convection cooling of the motor. Furthermore, one or more circulation pumps  100   a  (e.g., jet pumps) may alternatively be arranged within the dummy well or otherwise attached to the bottom of the production fluid booster pumps to circulate seawater. 
     In some embodiments of the present invention, the pumping system  50  may be operated subsea by divers accessing a control station located proximate the dummy well on or near the seabed  20 . At subsea depths not accessible by divers, as shown in  FIG. 3 , the pumping system  50  may include a control station  200  accessible by an underwater vehicle  210  such as a tethered remote operated vehicle (ROV) or an autonomous underwater vehicle (AUV). The underwater vehicle  210  includes devices for: (1) maneuvering in a subsea environment in order to approach the subsea control station  200 , (2) manipulating the controls to operate the pumping system  50 , and (3) communicating with the surface to transmit and receive data necessary to perform tasks and make reports. In some embodiments, the underwater vehicle  210  is an ROV tethered to a surface vessel or rig. In other embodiments, the underwater vehicle  210  is an AUV guided by a remote guidance signaling system sent by an operator at the surface or by automated programming. Moreover, an embodiment of the present invention may include a home station (not shown) for housing the underwater vehicle  210  in a subsea environment near or on the seabed  20 . The home station may provide power to and communicate with the associated underwater vehicle that resides at the home station until control of the pumping system  50  is needed. Therefore, when such control is needed, the underwater vehicle  210  deploys from the home station to the control station  200  that is associated with the pumping system  50  of the dummy well  40  to be operated. The underwater vehicle  210  performs the commands at the control station  200  and subsequently returns to the home station. In some embodiments of the invention, the underwater vehicle  210  is self-guided and self-powered when traveling between the home station and the control station  200 . Therefore, the underwater vehicle  210  does not have a tethered cable or wire connection to the home station or any other point when traveling along the seabed  20 . In other embodiments, the underwater vehicle  210  may have a tethered connection to the home station. In some embodiments, the underwater vehicle  210  may receive power to recharge and maintain the charge on a battery when the underwater vehicle is docked to the home station. Furthermore, when docked to the home station, the underwater vehicle  210  also may communicate to an operator at the surface of the sea via a tethered cable between home station and equipment at the surface. The underwater vehicle  210  may also dock to a particular control station  200  to allow the underwater vehicle to communicate with the surface and receive power from the surface, as each dummy wellhead  45  may also be connected to receive power from and communicate with equipment at the surface. Such power may be used, among other things, to power to pumping system  50  in including the motors  56 , the control valves  90 , the monitors  59 , and the circulation pump  100 . 
     While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.