Abstract:
A downhole device having an oil/water separator having a well fluid inlet, an oil stream outlet conduit, and a water stream outlet conduit; a removable flow-restrictor located in at least one of the water stream outlet conduit or the oil stream outlet conduit.

Description:
This application claims priority to provisional application No. 60/969,066 that was filed on Aug. 30, 2007. 
    
    
     TECHNICAL FIELD 
     The present application relates generally to the field of artificial lifts, and more specifically to artificial lifts in connection with hydrocarbon wells, and more specifically, associated downhole oil/water separation methods and devices. 
     BACKGROUND 
     Oil well production can involve pumping a well fluid that is part oil and part water, i.e., an oil/water mixture. As an oil well becomes depleted of oil, a greater percentage of water is present and subsequently produced to the surface. The “produced” water often accounts for at least 80 to 90 percent of a total produced well fluid volume, thereby creating significant operational issues. For example, the produced water may require treatment and/or re-injection into a subterranean reservoir in order to dispose of the water and to help maintain reservoir pressure. Also, treating and disposing produced water can become quite costly. 
     One way to address those issues is through employment of a downhole device to separate oil/water and re-inject the separated water, thereby minimizing production of unwanted water to surface. Reducing water produced to surface can allow reduction of required pump power, reduction of hydraulic losses, and simplification of surface equipment. Further, many of the costs associated with water treatment are reduced or eliminated. 
     However, successfully separating oil/water downhole and re-injecting the water is a relatively involved and sensitive process with many variables and factors that affect the efficiency and feasibility of such an operation. For example, the oil/water ratio can vary from well to well and can change significantly over the life of the well. Further, over time the required injection pressure for the separated water can tend to increase. 
     Given that, the present application discloses a number of embodiments relating to those issues. 
     SUMMARY 
     An embodiment is directed to a downhole device comprising an electric submersible motor; a pump connected with the electric submersible motor, the pump having an intake and an outlet; the electric submersible motor and the pump extending together in a longitudinal direction; an oil/water separating device having an inlet in fluid communication with the pump outlet and having a first outlet and a second outlet, the first outlet connecting with a first conduit and the second outlet connecting with a second conduit; a redirector integrated with the first conduit and the second conduit, the redirector having a flow-restrictor pocket that extends in the longitudinal direction, a downhole end of the flow-restrictor pocket connecting with a re-injection conduit; the first conduit extending uphole to a level of the flow-restrictor pocket, and the second conduit extending farther uphole than the first conduit; the uphole end of the flow-restrictor pocket connecting with the second conduit; and a passage connecting the first conduit with the flow-restrictor pocket. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a configuration of an embodiment; 
         FIG. 2  shows a portion of a cross section of an embodiment; 
         FIG. 3  shows a portion of a cross section of an embodiment; 
         FIG. 4  shows a portion of a cross section of an embodiment; 
         FIG. 5  shows a configuration of an embodiment; 
         FIG. 6  shows a cross section of a portion of an embodiment; 
         FIG. 7  shows a cross section of portion of an embodiment; 
         FIG. 8  shows a cross section of a portion of an embodiment; and 
         FIG. 9  shows a cross section of a portion of an embodiment in use. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, those skilled in the art will understand that the present invention may be practiced without many of 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. 
     The present application relates to downhole oil/water separation, and more particularly, advantageously managing back-pressure to manipulate the oil/water separation. One way to advantageously control separation of fluids is by regulating back-pressure applied to the oil stream and/or the water stream. One way to regulate back-pressure is by regulating a flow-restriction (i.e., throttling) of the oil stream and/or the water stream exiting the oil/water separator. Embodiments herein relate to equipment that allows a stream to be throttled, i.e., a back-pressure to be manipulated. The magnitude of a throttling can cover a range from completely closed to wide open depending on the oil/water content of the well fluid. 
     The form and function controlling backpressure and related flow is highly dependent upon the injection zone orientation relative to the producing zone (injection zone uphole or downhole of the producing zone). Some key differences between the two orientations relate to injecting uphole where the device can throttle and vent to a tubing annulus in a single operation, and injecting downhole where the device may need to throttle the flow “in-line”, .i.e. receive the injection flow from the tubing, throttle the flow, and then return the flow to another tube headed toward the injection zone. Some or all of these factors can be considered. The diameter of a throttle opening can generally be from 0.125 to 1.0 inches. 
       FIG. 1  shows an overall schematic for an embodiment of a device. Some of the main components of the device are an ESP  100  comprising a motor  110  and a pump  120 . A centrifugal or cyclone oil/water separator  200  is connected adjacent to the pump  120 . The apparatus is placed downhole in a hydrocarbon well, preferably inside a well casing  10 . The motor  110  drives the pump  120 . The motor  110  also drives the oil/water separator  200 . During operation, well fluid is drawn into the pump  120  through a vent  125 . The oil/water mixture is driven out of the pump  120  and into the oil/water separator  200 , a centrifugal type separator in this case. The oil/water separator  200  accelerates and drives the oil/water mixture in a circular path, thereby utilizing centrifugal forces to locate more dense fluids (e.g., water) to a farther out radial position and less dense fluids (e.g., oil) to a position nearer to the center of rotation. An oil stream and a water stream exit the oil/water separator  200  and travel separately along different paths to a redirector  250 , where the water stream is redirected and re-injected into formation while the oil stream is directed uphole to surface. 
       FIG. 2  shows a cut away view of the oil/water separator  200 , which is of the centrifugal type. A well fluid mixture is driven into and rotated in a cyclone chamber  201  of the oil/water separator  200 . The layers of the stream are separated by a divider  202  that defines a beginning of an oil conduit  204  and a beginning of a water conduit  206 . The oil conduit  204  is further inward in a radial direction with respect to the water conduit  206 . Back-pressure of the streams affects the oil/water separation process. For example, for well fluids having a high percentage of oil, higher back-pressure for the water stream  206  can improve separation results. Similarly, for well fluids having a higher percentage of water, a higher back-pressure for the oil stream  204  can improve oil/water separation. Essentially the same back-pressure principal applies to cyclone type oil/water separators. 
       FIG. 3  shows another sectional view of the oil/water separator  200  having the oil conduit  204  and the water conduit  206 . Arrows  350  show a representative path of the oil stream. Arrows  355  show a representative path of the water stream. A flow-restrictor  304 , e.g., a throttle, is in the water conduit  206 . The water stream flows uphole into the flow-restrictor  304 . The flow-restrictor  304  could be located in the oil conduit  204 . One flow-restrictor  304  could be in the water conduit  206  and another flow-restrictor  304  could be in the oil conduit  206  simultaneously. Selection of a flow-restrictor  304  from a number of different flow-restrictors having different variations of orifice size and configuration enables adjustment of the aforementioned backpressure in the water stream  206 . There are many ways to replace the flow-restrictor  304  with another different flow-restrictor  304  having a different throttle, thereby adjusting the backpressure situation. Preferably, a wireline tool can be lowered to place/remove a flow-restrictor  304 . A flow-restrictor  304  can also be inserted and removed using slickline, coiled tubing, or any other applicable conveyance method. Slickline tends to be the most economical choice. In connection with use of a slickline, or coiled tubing for that matter, the oil stream channel is preferably positioned/configured to prevent tools lowered down by wireline, slickline or coiled tubing from inadvertently entering the oil conduit  204 . The oil conduit  204  can be angled to prevent the tool from entering the oil conduit  204 . The oil conduit  204  can further be sized such that the tool will not be accepted into the bore. 
     Alternately, the flow-restrictor  304  can have a variable size throttle orifice so that replacement of the flow-restrictor is not required to vary orifice size. The orifice size can be varied mechanically in many ways, e.g., at surface by hand, by a wireline tool, a slickline tool, a coil tubing tool, a hydraulic line from the surface, by an electric motor controlled by electrical signals from the surface or from wireless signals from the surface, or by an electrical motor receiving signals from a controller downhole. 
     Check valves  302  can be located in the oil conduit  204  and/or the water conduit  206 . The check valves  302  can prevent fluid from moving from the oil conduit  204  and the water conduit  206  down into the oil/water separator  200 , thereby causing damage to the device. 
     Packers can be used to isolate parts of the apparatus within the wellbore. For example,  FIG. 1  shows packers  410  and  420  isolating an area where water is to be re-injected into the formation from an area where well fluid is drawn from the formation. The packer configuration effectively isolates the pump intake from re-injection fluid. Alternately, the packer  420  could be located below the pump  200 , so long as the water is re-injected above the packer  410  or below the packer  420 , thereby adequately isolating the area where the well fluids are produced from the area of the formation where water is re-injected. No specific packer configuration is required, so long as isolation between producing fluid and injecting fluid is adequately achieved. 
     The above noted configurations can also be used to inject stimulation treatments downhole.  FIG. 4  shows the apparatus of  FIG. 3  except with the flow-restrictor  304  removed.  FIG. 4  shows pumping of stimulating treatments down the completion tubing and into both the oil conduit  204  and the water conduit  206 . A flow-restrictor can be replaced with a flow device that prevents treatment fluid from following along the path of re-injection water. The arrows  360  illustrate a representative path of the stimulating treatment. The check valves  302  can prevent the stimulation fluid from traveling into the oil/water separation  200 , thereby potentially causing detrimental effects. 
       FIG. 5  shows a configuration to re-inject a water stream to a zone located below the producing zone. A motor  110 , a pump  120 , and an oil/water separator  200  are connected as before. A redirector  250  is connected uphole from the oil/water separator  200 . The redirector  250  is connected to a conduit  260  that extends downhole from the re-injection and through a packer  420 . The packer  420  separates a production area that is uphole from the packer  420 , from a re-injection area that is downhole from the packer  420 . In that embodiment, the water stream travels through a tailpipe assembly  270 . The tailpipe assembly  270  extends though the packer  420  into the re-injection area that is downhole from the packer  420 . 
       FIG. 6  shows a more detailed cross section of an embodiment of the redirector  250 .  FIG. 9  shows a cross section of a redirector  250  and a flow-restrictor  304  in operation with the flow-restrictor  304  positioned in the flow-restrictor pocket  610 . The flow-restrictor pocket  610  is configured to receive a flow-restrictor  304 . The water conduit  206  is configured to be radially outside the oil conduit  204 , i.e., a centrifugal oil/water separation. The oil conduit  204  extends from down-hole of the redirector  250 , through the redirector  250 , and uphole past the redirector  250 , where the oil conduit  204  connects with production tubing  620  (e.g., coil tubing). The water conduit  204  extends from below the redirector  250  and into the redirector  205 . The water conduit  204  merges into a water passage  630  that connects the water conduit  204  with the flow-restrictor pocket  610 . The water passage  630  can extend in a direction substantially perpendicular to the water conduit  204  proximate to the water passage. That is, during operation, the flow of the water makes approximately a 90 degree turn. The water can alternately make as little as approximately a 45 degree turn and as much as approximately a 135 degree turn. A re-injection passage  670  extends from the flow-restrictor pocket  610  downhole past the redirector  250 . The re-injection passage  670  can be connected with completion tubing or other tubing. 
       FIG. 7  shows an embodiment of the flow-restrictor  304 . The flow-restrictor  304  has a body  701  that defines therein an upper inner chamber  725  and a lower inner chamber  720 . The upper inner chamber  725  and the lower inner chamber  720  are divided by a flow-restriction orifice  740 . The flow-restriction orifice  740  and the body  701  can be the same part, or two separate parts fit together. Preferably the flow-restriction orifice  740  has a narrower diameter in a longitudinal axial direction than either the upper inner chamber  725  or the lower inner chamber  720 . However, the diameter of the flow-restriction orifice  740  can be essentially the same diameter of either the upper inner chamber  725  or the lower inner chamber  720 . Passages  710  are located in the body  701  and hydraulically connect the upper inner chamber  725  with an outside of the flow-restrictor  304 . Passage  715  is on the downhole end of the flow-restrictor  304 . When the flow-restrictor  304  is in position in the flow-restrictor pocket  610 , the passages  710  allow fluid to pass from the water passage  630 , though the passages  710  and into the upper inner chamber  725 . The fluid then flows through the restrictor orifice  740 , into the lower inner chamber  720  and out of the flow-restrictor  304  for re-injection. It should be noted that the flow-restrictor  304  can have many internal configurations, so long as the flow is adequately restricted/throttled. 
     The flow-restrictor  304  has an attachment part  702  that is used to connect to a downhole tool (not shown) to place and remove the flow-restrictor  304  from the flow-restrictor pocket  610 . As noted earlier, the downhole tool can be connected to any relay apparatus, e.g., wireline, slickline, or coiled tubing. 
     There are many ways to determine an oil/water content of a well fluid. Well fluid can be delivered to surface where a determination can be made. Alternately, a sensor can be located downhole to determine the oil/water ratio in the well fluid. That determination can be transmitted uphole in many ways, e.g., electrical signals over a wire, fiber-optic signals, radio signals, acoustic signals, etc. Alternately, the signals can be sent to a processor downhole, the processor instructing a motor to set a certain orifice size for the flow-restrictor  304  based on those signals. The sensor can be located downstream from the well fluid intake of the oil/water separator, inside the oil/water separator, inside the redirector, inside the flow-restrictor, upstream of the oil/water separator, outside the downhole device and downhole of the well fluid intake, outside the downhole device and uphole of the sell fluid intake, or outside the downhole device and at the level of the well fluid intake. 
     One embodiment shown in  FIG. 8  has a flow-restrictor  304  having a sensor  800  located in the upper inner chamber  725 . The sensor could be in the lower inner chamber  720 . The sensor  800  can sense temperature, flow rare, pressure, viscosity, or oil/water ratio. The sensor  800  can communicate by way of a telemetry pickup  810  that is integrated with the redirector  250 . The sensor  800  can communicate through an electrical contact or “short-hop” telemetry with a data gathering system (not shown). 
     The preceding description refers to certain embodiments and is not meant to limit the scope of the invention.