Abstract:
A submersible pumping system for use downhole, wherein the system includes a pump, an inlet section for receiving fluid, a pump motor, and an actively controlled flow restriction device for controlling flow to the submersible pump from an upper fluid producing zone. Active flow control proximate to the submersible pump motor protects the pump motor from overheating.

Description:
BACKGROUND 
     1. Field of Invention 
     The present disclosure relates to downhole pumping systems submersible in well bore fluids. More specifically, the present disclosure concerns actively controlling flow to the intake of a submersible pump. Yet more specifically, the present disclosure relates to a method and apparatus for actively restricting gas flow and/or flow from a higher zone to an electrical submersible pump. 
     2. Description of Prior Art 
     Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs a electrical submersible pump (ESP). ESPs are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power may be supplied to the pump motor via wireline. Typically, the pumping unit is disposed within the well bore just above where perforations are made into a hydrocarbon producing zone. This placement thereby allows the produced fluids to flow past the outer surface of the pumping motor and provide a cooling effect. 
     With reference now to  FIG. 1 , an example of a submersible ESP disposed in a well bore is provided in a partial cross sectional view. In this embodiment, a downhole pumping system  12  is shown within a cased well bore  10  suspended within the well bore  10  on production tubing  34 . The downhole pumping system  12  comprises a pump section  14 , a seal section  18 , and a motor  24 . The seal section  18  forms an upper portion of the motor  24  and is used for equalizing lubricant pressure in the motor  24  with the wellbore hydrostatic pressure. Energizing the motor  24  then drives a shaft (not shown) coupled between the motor  24  and the pump section  14 . Impellers are coaxially disposed on the shaft and rotate with the shaft within respective diffusers formed into the pump body  16 . As is known, the centrifugal action of the impellers produces a localized reduction in pressure in the diffuser thereby inducing fluid flow into the diffuser. In this embodiment, a series of inlets  30  are provided on the pump housing wherein formation fluid can be drawn into the inlets and into the pump section  14 . The source of the formation fluid, which is shown by the arrows, are perforations  26  formed through the casing  10  of the well bore and into a surrounding hydrocarbon producing formation  28 . Thus the fluid flows from the formation  28 , past the motor  24  on its way to the inlets  30 . The flowing fluid contacts the housing of the motor  24  and draws heat from the motor  24 . 
     In some situations submersible pumping systems are disposed in a section of a wellbore between two producing formations or zones. For example in a dewatering situation the upper zone primarily produces gas whereas the low zone produces water. Thus with reference now to  FIG. 1 , the upper formation  29  is shown producing a mixture of water and gas flowing through the perforations  27 . The upwardly directed arrow A G  represents gas flowing up the borehole  8  and the downwardly directed arrow A w  represents water (or other liquids) flowing down the borehole  8 . In some situations the upper formation can cause problems for the pumping system  12 . For example, too much water flow from the upper formation  29  can restrict water production from the lower formation  28  thereby limiting liquid flow across the pump motor  24  and its corresponding cooling effect. Additionally, excessive gas from the upper formation can become entrained with the downflowing water and potentially cause pump cavitation. Gas from the lower formation can also make its way to the pump inlet. 
     SUMMARY OF INVENTION 
     The present disclosure includes a downhole submersible pumping system for use in a cased wellbore comprising, a pump, a motor coupled to the pump; and a variable flow regulator disposed in the annulus between the wellbore casing and the pumping system. The variable flow regulator is responsive to motor temperature, motor energy consumption, motor performance, gas flow to the pump, and combinations thereof. A control system may be included with the pumping system. A controller may be included with the control system. The controller may be connected to an indicating monitor. The indicating monitor may include a pump motor temperature indicator, a pump motor energy consumption indicator, and a gas flow meter. Optionally, the controller is configurable for controlling the variable flow regulator. The flow regulator may be a packer as well as a controllable valve. In one mode of operation, the system is disposable in a well used for dewatering operations. 
     The present disclosure also includes a method of operating an electrical submersible pumping system within a cased wellbore, wherein the pumping system comprises a pump, a pump motor, and a variable flow control device between the pump motor and the pump. The method comprises monitoring pumping system conditions and regulating fluid flow with the variable flow control device based on the pumping system conditions. The flow being regulated is fluid flow passing between the pumping system and the wellbore casing. The pumping system conditions include pump motor rpm, pump motor temperature, gas flow to the pump, pump motor power consumption, and combinations thereof. The steps of monitoring and regulating may be performed with a control system. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows a prior art downhole submersible system shown in a partial cross sectional view. 
         FIG. 2  shows a side view of an embodiment of a pumping system in accordance with the present disclosure disposed within a cased well bore. 
         FIG. 3  shows a side view of another embodiment of a pumping system in accordance with the present disclosure disposed within a cased well bore. 
         FIG. 4  illustrates a side view of variable flow device embodiments. 
         FIG. 5  illustrates a side view of variable flow device embodiments. 
         FIG. 6  illustrates a side view of variable flow device embodiments. 
     
    
    
     While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     The present disclosure provides embodiments of a downhole submersible pumping system for producing fluids from within a wellbore up to the surface. More specifically, the downhole submersible pumping system described herein includes a variable flow control device for regulating flow to the pump inlet. The variable flow control device may comprise a deformable elastomeric material, such as a packer. Optionally, a responsive control valve may be used for regulating this flow. The variable flow control device may be used in combination with a control system, wherein the control system is in communication with various operating parameters of the submersible pumping system. Those operating parameters include motor temperature, gas flow to the pump, pump energy consumption, as well as pump revolutions per minute (RPM), and pump flow rate. 
       FIG. 2  provides a side view of a pumping system disposed within a cased wellbore. The pumping system  36 , also referred to herein as an electrical submersible pumping system, is within a cased wellbore  38  between an upper formation  52  and a lower formation  54 . As will be discussed later, the upper formation  52  produces a two-phase gas/liquid combination, whereas the lower formation  54  produces primarily liquid. 
     The pumping system  36  comprises a motor  40 , a seal section  42 , an optional separator  44 , and pump  46 . In the embodiment of  FIG. 2 , inlets  47  are provided on the separator for allowing fluid to the pump  46 . The inlets  47  are to be below the perforations  53  of the upper formation  52  and above the perforations  55  of the lower formation  54 . The pump motor  40  as shown is an electrically powered pump mechanically coupled to the pump  46  via a shaft (not shown). The pump  40  size and capacity is dependent upon the particular application it will be used in. The seal section  42  may be included with the pumping system  36  disposed on the upper portion of the motor  40  in a coaxial fashion. The seal section  42  may be included for equalizing hydrostatic pressure of the well fluid with internal fluids within the system  36 , such as the lubricant used within the motor  40 . 
     The separator  44  is optionally included with the system  36  for removing any gas that may be entrained in the fluid flowing to the pump  46 . Allowing gas to a pump inlet can lock the pump and prevent fluid flow or can damage a pump&#39;s internal components, such as its impellers. The gas separator  44  discharges into the wellbore surrounding the pump  46 . The pump  46 , which is coaxially disposed on the upper portion of the separator  44  can be any type of pump used for pumping wellbore fluids up an associated tubing  50  and to the wellbore surface. 
     Included in a recess formed on the pump outer surface is a variable flow device  48 , also referred to herein as a variable flow regulator. The variable flow device  48  is configured to regulate fluid flow between the outer circumference of the pumping system and the inner circumference of the wellbore casing. The flow controller  48  is located upstream of the inlets  47 , considering the direction of the fluid flow. In this embodiment, the flow controller  48  is below the inlets  47 . In the embodiment of  FIG. 2 , the variable flow device  48  is shown in a retracted condition. However it is expandable to fully encompass the annulus existing between the pumping device  36  and the wellbore casing. By fully encompassing the annulus, any fluid flowing down adjacent the pumping system will be blocked from making its way to the lower sections of the pumping system. Optionally, the variable flow regulator&#39;s expansion can be limited to correspondingly limit fluid flow. Thus, the variable flow regular  48  can limit flow rates to a particular value or simply block the flow rate entirely. 
     A control system  58  shown in schematic view is provided along with the electrically submersible pumping system  36  of  FIG. 2 . The control system includes a monitor  60 , a controller  62 , and an actuator  64 . The controller  62 , which may comprise an information handling system (IHS) or a microprocessor, is shown in electrical communication with the monitor  60 . Based upon data signals from the monitor, the controller  62  may be configured to correspondingly provide a signal to the actuator  64 . 
     The IHS may be employed for controlling the initiating monitoring commands herein described as well as receiving the controlling the subsequent recording of the data. Moreover, the IHS may also be used to store recorded data as well as processing the data into a readable format. The IHS may be disposed at the surface, in the wellbore, or partially above and below the surface. The IHS may include a processor, memory accessible by the processor, nonvolatile storage area accessible by the processor, and logics for performing each of the steps above described. 
     The actuator  64  is coupled with the flow controller  48  for activating the flow controller  48  into different modes for regulating flow, i.e. fully open, fully closed, or partially closed to allow a desired flow rate between the pumping system and wellbore wall. The configuration of the actuator  64  is dependent upon embodiments of the variable flow regulator  48 . For example, when the variable flow regulator  48  is an inflatable packer, the actuator can comprise a line for providing pressurized fluid to the packer to inflate the packer to an appropriate size. The pressurized fluid may comprise hydraulic as well as pneumatic fluids. In the embodiments where the packer is a compressible packer, the actuator may comprise a means for providing compression for outwardly expanding the packer. These means may be electrical as well as hydraulic or pneumatic. In the event the variable flow regulator  48  is a control valve or choke, the actuator can be a linkage system for opening and closing the valve to a certain percentage opening. In such a case, the actuator can be hydraulically as well as electrically powered. 
     Also optionally included is a fluid flow meter (or flow indicator)  66  for detecting fluid flow in the annulus adjacent the pump motor  40 . Insufficient fluid flow across the pump motor  40  may lead to overheating. Also, as previously noted, the presence of gas within the pumping system can cause pump motor overheating. Therefore, when an excessive amount of gas is flowing towards the pump intake, it may be desirable to regulate that flow. 
     In one mode of operation, as previously discussed, the upper formation  52  produces a two phase flow exiting from the perforations  53  into the cased wellbore  38 . As shown by the arrows, the gas typically will flow upward toward the surface, whereas the liquid, such as water, would flow downward towards the pumping system  36 . In situations when too much water is flowing downward, the downward flowing water, either because of its flow rate or its hydrostatic pressure, may prevent water exiting the lower formation  54  from perforations  55  from flowing past and cooling the motor  40 . This flow of water from the lower formation is also shown by the corresponding arrows. Thus it may be necessary to restrict or hinder water flow from the upper formation  52  via the variable flow device  48 . One mode of detecting excessive water flow from the upper formation  52  includes monitoring pump motor  40  temperature. 
     In instances where an excessive amount of gas makes its way to the pump intake, the pump might experience vapor lock resulting in lowered amperage consumed by the motor  40 . Pump motor  40  overheating can also occur also by an excessive amount of gas to the pump  46 . The monitor  60  therefore can be a temperature indicator. Optionally the monitor can also measure the amount of energy consumption of the pump motor  40 . For the purposes of discussion herein, energy consumption includes current as well as voltage. Moreover, the monitor  60  in addition to measuring temperature and energy consumption of the motor  40  can also measure operating parameters of the pump motor  40  such as revolutions per minute (RPM). 
     In one mode of operation, the data recorded by either the monitor  60  or the flow meter  66  is transmittable to the controller  62 . The controller  62 , which can be either programmable by software or hardware, can quantify these values and determine if it is necessary to restrict flow along the length of the pumping system using the variable flow regulator  48 . The controller  62  is programmable to read these values from the monitor  60  and/or flow meter  66  then appropriate provide controlling commands to the actuator  64  for actuating the variable flow control device  48 . When the amount of gas flowing into the pump  46  is not excessive, the flow controller  48  may be opened fully to allow full liquid flow down the casing. 
     The controller  62  can be included with the electrical pumping system  36  and disposed totally downhole. Optionally, the controller  62  can be situated at surface wherein commands to and from the electrically submersible pumping system  36  can be via a hardwire line downhole or telemetry. Also optionally, commands to the controller  62  can either be made solely from a surface operator, or in conjunction with stored software commands stored within the controller  62  for another type of system control device. 
     With reference now to  FIG. 3 , which is another embodiment of a downhole submersible electrical pumping system  70  (ESP), is shown in a side view, where this pumping system  70  is disposed within a cased wellbore  71 . In this embodiment, the ESP  70  comprises a motor  72  having a coaxially formed seal section  74  disposed on the upper portion of the motor  72 . Also included in this embodiment is a charge pump  76 , a gas separator  78  and a corresponding pump  80 . The charge pump can handle gas better than the primary lift pump and increases pressure such that a gas separator would displace higher pressure gas out the discharge tubes. 
     Stand pipes  82  are included with this embodiment of  FIG. 3  and are shown exiting the separator  78  and extending upward into the wellbore. In this embodiment, the gas received by the pumping system is separated from the total fluid intake and inserted in the stand pipes for delivery uphole in the casing annulus surrounding the tubing. Due to the presence of the standpipes  82 , a modified variable flow device  84  is provided. This embodiment of  FIG. 3  therefore uses a dual variable flow controller  84  having an inner portion  85  and an outer portion  86 . As shown the pump intake  81  is disposed below the flow controller  84 . 
     Similar to the embodiment of  FIG. 2 , the downhole pumping system  70  of  FIG. 3  includes a control system  92  for monitoring downhole conditions and providing flow control commands to the flow controller  84 . The control system  92  comprises a monitor  94  in communication with the motor  72  and configured for monitoring motor temperature, motor RPM, and motor energy consumption. The monitor  94  is in communication with the controller  96 . Although communication is shown with an electrical connection, the communication can be via software, telemetry, pneumatic, or any other known way of transmitting data from one device to another. 
     Also included is a flow meter  100  in communication with the controller  96 . As with the monitor, the communication between the flow meter and the controller can be of any known manner. The embodiment of  FIG. 3  further includes the actuator  98  that operates based upon dependent commands from the controller  96 . In this embodiment, the actuator  98  can actuate one of the inner portion  85  or the outer portion  86  independent of one another. Thus, flow control could be by actuating one of these portions as well as both of the portions simultaneously. As shown, the standpipes extend through the flow controller  84  thus flow controller  84  may expand into the region azimuthially disposed between adjacent standpipes  82 . 
     In the ESP  70  of  FIG. 3 , it is disposed also between a upper formation  88  and a lower formation  90 , wherein the upper formation produces a two phase flow from corresponding perforations  89 . The two phase flow, being a gas and a liquid, is illustrated by the arrows extending from the perforations into the wellbore  71 . Similarly, the lower formation  90  produces primarily water from its perforations  91  extending from the formation into the cased wellbore. Arrows within the wellbore illustrate water flow from the lower formation  90  up towards the electrically submersible pumping system  70 . 
       FIGS. 4 through 6  provide a side and cross sectional view of alternative embodiments of a variable flow regulator.  FIG. 4  shows in side view an embodiment of a portion of an electrical submersible pumping system  36  disposed within a cased wellbore  38 . In this embodiment, the variable flow regulator  48  is an expandable packer disposed along the outer portion of the pump section  46  of the pumping system  36 . As shown in  FIG. 4 , the variable flow regulator  48  has been expanded for restricting flow through the wellbore  38 . Fluid flow, shown as arrows, can be seen blocked in one portion of the wellbore. In another portion, the flow is restricted to a small annular portion between the pumping system and the cased wellbore. In this example therefore, it is illustrated how the variable control device can either totally block the flow along the pumping system or may restrict it to some portion of the possible total flow by blocking only a portion of the annular region between the pumping system and the cased wellbore. 
     Another embodiment of the variable flow regulator  69  is shown in side view in  FIG. 5 . In this embodiment, the variable flow regulator  69  comprises a compressible packer  67  and is in the compressed state thereby expanding outward to restrict the annular region and impede fluid flow between the pumping system and the cased wellbore. A sleeve  49  is provided in this embodiment shown urged downward against the packer for pressing the packer and causing it to expand outward. The sleeve  49  may be powered either from an electrical motor as well as hydraulically actuated. 
       FIG. 6  provides yet another embodiment of the variable flow regulator. In this embodiment, the variable flow regulator comprises an annular barrier  56  that fully blocks the annular region between the pumping system  36  and the wellbore  38 . The annular plug  56  circumscribes the pumping system  36  proximate to the outer housing of the pump. A control valve  57  is provided in an opening axially formed through the annular barrier  56 . While the embodiment of  FIG. 6  illustrates two control valves  57 , a single control valve can be used in this embodiment as well as more than two. The control valve  57  may be actuatable by the actuator such as the one shown in  FIG. 2  and be put in either a fully open position, a fully closed position, or an intermediate position for regulating the amount of flow passing within this annular region. 
     It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.