Abstract:
An apparatus for selectively controlling fluid flow. The apparatus includes a body member having a throughbore formed therein. The apparatus also includes at least one bypass port formed in the body member and a rotatable member arranged for insertion and rotation within the throughbore of the body member. The rotatable member in the throughbore creates first and second annular portions. The apparatus further comprises a moveable member, wherein the moveable member is moveable between a first configuration which defines a first fluid flow path between the first and second annular portions and a second configuration which defines a second fluid flow path between the first annular portion and the at least one bypass port. The moveable member is typically moveable between the first and second configurations in response to fluid flow along the first fluid flow path.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of United Kingdom Patent Application No. GB0616555.9, titled “Apparatus and Method”, filed Aug. 19, 2006.  
       BACKGROUND  
       [0002]     The present invention relates to an apparatus and a method for selectively controlling fluid flow. In particular, the invention relates to an apparatus and method for use in downhole operations in the hydrocarbon production industry. The invention also relates to a progressive cavity pump comprising a fluid flow control apparatus.  
         [0003]     During extraction of resources from beneath the surface of the earth and especially in the oil and gas exploration and production industry, it is often necessary to overcome a pressure differential (hydrostatic head) between a subterranean fluid reservoir and the surface. This can be achieved using a pump such as a progressive cavity pump (hereinafter a “PCP”).  
         [0004]      FIG. 1  is a cut away side view of part of a typical prior art PCP  12 . PCPs  12  typically comprise a helical steel rotor  16  and a rubber stator  14  having a double screw profile matching the helical rotor  16 . The stator  14  is formed to allow rotation of the inserted rotator  16  therein and this arrangement results in a series of cavities  18  along the length of the PCP  12  between the rotor  16  and the stator  14 . The stator  14  is usually encapsulated within a tubing section (not shown) that typically forms part of a tubing string running from the reservoir to the surface. The rotor  16  is typically connected to a rod string (not shown) having a smaller diameter than the tubing string where the rod string is admitted within the throughbore of the tubing string and positioned such that the rotor  16  is located within the stator  14 . The rod string is then connected to a rotary motor at the surface to power rotation of the rod string and attached rotor  16  at the appropriate speed.  
         [0005]     When the PCP  12  is in use, rotation of the rotor  16  within the stator  14  creates a positive displacement that causes fluids in the cavities  18  to progress upwards due to a gradual build-up of pressure from the inlet to the discharge of the PCP  12 . The build-up of pressure causes positive displacement of fluid within the cavities  18  and provides the necessary lift to extract fluid from the reservoir and pump it towards the surface thereby overcoming the hydrostatic head.  
         [0006]     PCPs  12  are often used in wells that produce high quantities of sand along with the produced fluids due to the material selection of the pump  12  and use of the rubber stator  14  against the steel rotor  16 , PCPs  12  are also suitable for production of heavy hydrocarbons and are commonly used in wells for extraction of high viscosity fluids. An important factor in determining the lifetime of the PCPs  12  is the quantity of sand and solids present in the hydrocarbon and fluid mixture passing through the pump  12 .  
         [0007]     Stopping operation of the PCP  12  can result in the sand (that is entrained in fluids within the production tubing above the PCP  12  having already been pumped) settling above the stator  14  and creating a sand plug in the tubing string. Once the PCP  12  is restarted, the rotor  16  may run dry within the stator  14  for a period of time until the requisite pressure accumulates to blast away the sand plug. During this period, the PCP  12  rotor  16  running dry within the stator  14  can tear up or otherwise cause severe damage to the stator  14  resulting in destruction of the pump  12 . The PCP system would then require replacement with the associated high cost due to lengthy down time and loss of well production. Conventionally, this situation is avoided by dissipating the sand plug using a rig to pull the rod string and attached rotor  16  out of the stator  14 . Sand can then fall through the stator  14  and out of the lower end of the pump  12  after which the rod string and attached rotor  16  can be repositioned within the stator  14 . However, this operation is both costly and time consuming and results in undesirable downtime.  
         [0008]     Since the PCP  12  is a positive displacement pump, there is no method for allowing fluids to free flow through the pump  12  from the reservoir to the surface in the event of pump  12  failure. Additionally, there is no method by which fluids from the surface can be forced into the reservoir through the pump  12  to conduct reservoir treatments. These operations are conventionally conducted by pulling the rod string and attached rotor  16  from the wellbore and allowing fluids to free flow through the stator  14 . Again, this is a costly and time consuming operation and results in undesirable downtime.  
       SUMMARY  
       [0009]     According to a first aspect of the present invention, there is provided an apparatus for selectively controlling fluid flow. The apparatus includes a body member having a throughbore formed therein, at least one bypass port formed in the body member, a rotatable member arranged for insertion and rotation within the throughbore of the body member thereby creating first and second annular portions, and a moveable member. The moveable member is moveable between a first configuration which defines a first fluid flow path between the first and second annular portions and a second configuration which defines a second fluid flow path between the first annular portion and each bypass port.  
         [0010]     Typically, the moveable member is moveable between the first and second configurations in response to fluid flow along one of the fluid flow paths, preferably the first fluid flow path.  
         [0011]     Preferably, the apparatus is downhole apparatus for controlling the flow of naturally produced fluids, injected fluids or pumped produced fluids.  
         [0012]     According to the first aspect of the present invention, there is provided a method of controlling fluid flow. The method includes providing a body member having a bypass port and a throughbore, inserting a rotatable member within the throughbore of the body member and thereby providing a first fluid flow path between a first annular portion and a second annular portion between the body member and the rotatable member and a second fluid flow path between the first annular portion and the bypass port in the body member, and providing a moveable member that is moveable between a first configuration in which flow is directed along the first flow path and a second configuration in which flow is directed along the second flow path. The moveable member moves between the first and second configurations in response to fluid flow along the first fluid flow path.  
         [0013]     Typically, fluid flow along the first fluid flow path is provided by a pump. Preferably, sufficient fluid flow along the first fluid flow path moves and maintains the moveable member in the first configuration and insufficient or no fluid flow along the first fluid flow path results in movement of the moveable member to, and maintenance in, the second configuration. When the moveable member is in the second configuration, fluid flow is directed along the second fluid flow path, where the fluid flow is driven typically as a result of relatively high reservoir pressures.  
         [0014]     Preferably, the method is directed to controlling the flow of naturally produced fluids, injected fluids or pumped produced fluids downhole.  
         [0015]     Preferably, the method of controlling flow of fluid comprises diverting flow of fluid between the first and second flow paths and preferably comprises permitting the moveable member to move in response to fluid flow conditions within a downhole wellbore.  
         [0016]     Typically, the moveable member is moveable in response to a pressure differential within the throughbore. The moveable member can be moveable in response to a pressure differential between the first and second annular portions.  
         [0017]     The movable member can be biased towards the second configuration. The movable member can be biased by a resilient means towards the second configuration.  
         [0018]     Biasing the moveable member in the second configuration allows fluid in the throughbore above the apparatus to circumvent the second annular portion, should the pressure differential between the first and second annular portions be insufficient to overcome the biasing force of the resilient means.  
         [0019]     The moveable member can translate between the first and the second configuration by movement in a direction substantially parallel to a longitudinal axis of the body member. The movable member can comprise a cylindrical sleeve coupled to an inner surface of the body member and movable relative thereto.  
         [0020]     The moveable member can be arranged in the first configuration to permit fluid flow in the first fluid flow path and prevent fluid flow in the second fluid flow path. The moveable member can be adapted to open the bypass port(s) when in the second configuration and to obturate the bypass port(s) when in the first configuration. The moveable member can comprise a sleeve having one or more openings provided in the sidewall. The openings can be aligned with the bypass port(s) in the second configuration and the sidewall of the sleeve can obturate the bypass port(s) in the first configuration.  
         [0021]     The moveable member can, in the second configuration, be adapted to permit fluid flow in the second fluid flow path and prevent fluid flow in the first fluid flow path. The moveable member can be adapted to close the annulus between the first and second annular portions when in the second configuration and can be adapted to permit fluid flow in the annulus between the first and second annular portions when in the first configuration.  
         [0022]     The movable member can comprise a protrusion extending radially into the annulus. The rotatable member can comprise an enlarged portion such that translation of the moveable member into the second configuration comprises movement of the radial protrusion of the moveable member into contact with the enlarged portion of the rotatable member to substantially close the annulus therebetween. Preferably, the radial protrusion of the moveable member only permits flow of fluid through the second annular portion when the bypass port(s) is/are substantially obturated by the sidewall of the moveable member. Preferably the radial protrusion is arranged such that fluid flow can act on a face of the radial protrusion to maintain the movable member in the first configuration when the fluid exerts a force on the face that is above a predetermined force.  
         [0023]     Preferably, the moveable member and the rotatable member are coupled to a pump such as a PCP. Preferably, the moveable member translates from the second configuration to the first configuration when the pump is activated and remains in the first configuration whilst the pump means remains in operation. The moveable member can be actuated to move from the first configuration to the second configuration when the pump is deactivated and can remain in the second configuration whilst the pump remains deactivated.  
         [0024]     The rotatable member can be coupled at one end to a rotor for use in a progressive cavity pump. The other end of the rotatable member can be coupled to a motor for driving rotation of the rotatable member. An end of the body member can be coupled to tubing having a stator disposed therein.  
         [0025]     Embodiments of the present invention have the advantage that the PCP pump does not have to blast away a solids or sand plug in the production tubing above the apparatus on reactivation. This is because no sand plug is created, since when the PCP is inactive, the moveable member can occupy the second configuration and the second fluid flow path is open allowing solids to settle outwith the tubing in which the rotor/stator of the PCP are located.  
         [0026]     The method can include latching the rotatable member in a predetermined position relative to the body member.  
         [0027]     The apparatus can further be provided with a latch device for correctly positioning between the rotatable member relative to the body member. The latch device can ensure the correct position of the enlarged portion relative to the radial protrusion and/or of the rotor relative to the stator. The latch device can comprise corresponding engagement portions provided on the body member and the rotatable member. The engagement portions can comprise intermitting splines. The rotatable member can be rotatable relative to the engagement portion provided on the rotatable member.  
         [0028]     The engagement portion of the rotatable member can be provided on the enlarged portion. An inner surface of the body member can be provided with a fastener formed with corresponding engagement portions and having a throughbore for accommodating the rotatable member therebetween.  
         [0029]     The rotatable member can also be provided with a driver for driving the engagement portions of the rotatable member and the body member into secure engagement with one another. The driver can comprise a rigid band attached to the rotatable member that is capable of contacting and driving the engagement portions into secure engagement. The driver can also be utilised to provide an indicator means for positioning the rotor correctly into the stator.  
         [0030]     Preferably, the apparatus comprises a first sealing means that is adapted to seal the bypass port(s) from the first annular portion when the moveable member is in the first configuration. The apparatus can comprise a second sealing means that is adapted to seal the annulus between the first and second annular portions when the moveable member is in the second configuration.  
         [0031]     The sealing means can comprise annular seals or annular sliding seals. The first sealing means can comprise at least one annular seal provided on each side of the bypass port(s) on an inner surface of the body member to seal against a surface of the moveable member. The second sliding seal can comprise an annular sealing means provided on an outer surface of the radial protrusion.  
         [0032]     Alternatively, at least one of the first or second sealing means can comprise a pressure locked sleeve, such as those described in United Kingdom Patent No. GB2411416B, the full disclosure of which is incorporated herein by reference.  
         [0033]     When in the second configuration, preferably, the bypass port(s) formed in the body member are adapted to encourage solids present in fluids downstream of the moveable member to settle out with the body member rather than the solids falling through the first and second annular portions to settle within the body member.  
         [0034]     According to a second aspect of the invention, there is provided a body member for use with a rotatable member, wherein the body member has a throughbore for receiving a rotatable member and at least one bypass port formed through a sidewall of the body member; and wherein the body member is further provided with a moveable member that is moveable between a first configuration in which the bypass port(s) are substantially obturated and a second configuration in which the bypass port(s) are in fluid communication with the throughbore.  
         [0035]     The moveable member can be coaxial with the body member and sealed thereagainst. The body member can be coupled to tubing having a stator for use in a PCP formed therein.  
         [0036]     According to the second aspect of the invention, there is also provided a rotatable member for insertion into a body member, wherein the rotatable member comprises an enlarged portion releasably coupled thereto, which enlarged portion is arranged for engagement with a part of the body member to thereby attach the rotatable member to the body member such that the rotatable member is rotatable relative to the body member.  
         [0037]     The rotatable member can also be provided with a driver attached thereto, as described with reference to the first aspect of the invention. The rotatable member can be coupled to a rotor for use in a PCP.  
         [0038]     According to a third aspect of the invention, there is provided a progressive cavity pump comprising a fluid flow control apparatus for selectively controlling fluid flow through the progressive cavity pump and selectively diverting fluid flow around the progressive cavity pump.  
         [0039]     The body member, rotatable member and fluid flow control apparatus of the second and third aspects of the invention can comprise any features of the apparatus described with reference to the first aspect of the invention, where applicable. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0040]     Embodiments of the present invention will now described by way of example only and with reference to the accompanying figures in which:  
         [0041]      FIG. 1  is a side view of a part of a progressive cavity pump;  
         [0042]      FIG. 2  is a sectional view of a body member of an apparatus according to a first aspect of the present invention;  
         [0043]      FIG. 3  is a sectional view of the apparatus of  FIG. 2  having a rotatable member disposed therein in a second configuration;  
         [0044]      FIG. 4  is a sectional view of the apparatus of  FIG. 3  in a first configuration; and  
         [0045]      FIGS. 5-10  are perspective views of the apparatus of  FIGS. 3 and 4  with a portion of the moveable member cut away and showing consecutive steps of the assembly and operation of the apparatus. 
     
    
     DESCRIPTION  
       [0046]     A body member of the apparatus according to the invention is shown generally at  11  in  FIG. 2 . The body member  11  is substantially cylindrical and has a throughbore  13 . The body member comprises a lower sub  20 , a middle sub  40  and an upper sub  60 .  
         [0047]     A lower end  20 L of the lower sub  20  is arranged to be coupled to production tubing (not shown) via a conventional screw threaded pin connection. The production tubing attached to the lower sub  20  typically extends to a hydrocarbon reservoir. A part of this production tubing is provided with the rubber stator  14  of the PCP  12  attached to an inner surface thereof. An upper end  60 U of the upper sub  60  is also adapted to be connected to production tubing via a conventional screw threaded box connection such that hydrocarbons can be produced from the reservoir through the progressive cavity pump  12 , the production tubing, the body member  11  and further production tubing up to the surface.  
         [0048]     A substantially cylindrical latching device  22  is provided on the inner surface towards the upper end  20 U of the bottom sub  20  where the latching device  22  is coupled to the sub  20  by means of three attachment points  22   a  (one of which is shown in  FIG. 2 ) that project radially into the throughbore  13  from the inner surface of the lower sub  20 . The latching device  22  has splines  23  provided at its upper end and a centrally disposed passageway to accommodate a rotatable member.  
         [0049]     The upper end  20 U of the lower sub  20  has a screw threaded pin connection that is arranged for insertion into a screw threaded box connection at a lower end  40 L of the middle sub  40 . At this connection point  30 , the throughbore  13  is fluidly isolated from the exterior of the body member  11  by an annular seal  24  recessed into an outer surface of the pin connection at the upper end  20 U of the lower sub  20 .  
         [0050]     The middle sub  40  is substantially cylindrical having box connections at its upper and lower ends  40 U,  40 L. An inner surface of the middle sub  40  is provided with an annular step  46  in a substantially centrally disposed location. Towards the upper end  40 U, the middle sub  40  also has a plurality of downwardly extending bypass ports  42  formed through a sidewall thereof. The inner surface of the middle sub  40  adjacent the bypass ports  42  has recessed annular seals  44 ,  45  on either side thereof. The box connection at the upper end  40 U engages with a pin connection at a lower end  60 L of the upper sub  60 . The ends  40 U,  601  of the middle and upper subs  40 ,  60  are connected by a screw thread  50  and an outer surface of the lower end  60 L is provided with an annular seal  64  to fluidly isolate the exterior of the body member  11  from the throughbore  13 .  
         [0051]     A moveable member  80  is coaxially located within the body member  11 . The moveable member  80  is substantially cylindrical and sealed against the inner surface of the body member  11  and is moveable in a direction parallel to a longitudinal axis of the body member  11 . A lower end  80 L of the moveable member  80  has an end face  80   e  that is shown in  FIG. 2  in its second configuration abutting an end face of the lower sub  20 . An inner surface of the moveable member  80  at its lower end  80 L has a radial protrusion  84  that projects radially inwardly into the throughbore  13  of the body member  11 . An outer surface of the moveable member  80  adjacent the radial protrusion  84  has an annular step  86 . Openings  82  are provided through a sidewall towards an upper end  80 U of the moveable member  80 .  
         [0052]     Movement of the movable member  80  is limited at its lower end by the end face  20   e  of the lower sub  20  and at an upper end by the annular step  46  of the middle sub  40  abutting the annular step  86  of the movable member  80 . A spring  88  is retained in the chamber defined between the annular step  46 , the annular step  86 , the outer surface of the movable member  80  and the inner surface of the middle sub  40 . The spring  88  biases the moveable member  80  into the configuration shown in  FIG. 2  such that the end  80   e  of the movable member  80  abuts against the upper end face  20   e  of the bottom sub  20 .  
         [0053]     A rotatable member in the form of a rod string  100  is shown in  FIGS. 3 and 4 . The rod string  100  is provided with a conventional steel rotor  16  at its lowermost end and can be rotated from surface as will be subsequently described. The presence of the rotatable member within the body member  11  forms an apparatus  10 . Both the rod string  100  and the rotor  16  have an outer diameter less than the central passageway of the latching device  22  and are adapted to fit therethrough. The rod string  100  has a collar  102  arranged therearound. The collar  102  has a splined end  103  for engaging with the splines  23  provided on the latching device  22 . The collar  102  also has an inner bearing surface  102   b  that allows rotation of the rod string  100  therethrough when the collar  102  is in its latched position engaged with the splines  23  of the latching device  22 . A lower end  100 L of the rod string  100  is coupled to the steel rotor  16  for insertion into the rubber stator  14  within the production tubing to thereby form the progressive cavity pump  12 . An upper end  100 U of the rod string  100  is coupled to a drive motor for driving rotation of the rod string  100 . The presence of the rod string  100  within the throughbore  13  creates a first annular portion  110  that is an annular space between a part of the rod string  100  and the inner surface of the body member  11 . A second annular portion  120  is also created between another part of the rotatable member  100  and the inner surface of the body member  11 .  FIG. 3  shows the apparatus  10  in its second configuration wherein the first annular portion  110  is in fluid communication with the bypass ports  42  in the middle sub  40 , since the openings  82  of the movable member  80  are aligned therewith and the first annular portion  110  is obturated from the second annular portion  120  by the seal between the radial protrusion  84  and collar  102 .  FIG. 4  shows the apparatus  10  in a first configuration wherein the first annular portion  110  is in fluid communication with the second annular portion  120  and the bypass ports  42  are obturated by a sidewall of the moveable member  80 .  
         [0054]     Before use of the apparatus  10 , a lower end of the production tubing carrying the rubber stator  14  is positioned within a wellbore, with the body member  11  included in the tubing string downstream (vertically above) of the stator  14 . The upper end of the body member  11  is attached to production tubing that leads to surface as shown in  FIG. 5 .  
         [0055]     A rod string  100  commencing with the rotor  16  is fed through the body member  11  and the passageway in the latching device  22  until the collar  102  is located within the body member  11  (illustrated in  FIG. 6 ). The splined portion  103  of the collar  102  latches with the splines  23  on the latch member  22  as shown in  FIG. 7 . The rod string  100  continues to be fed through the collar  102  until the hammer  104  contacts an upper end of the collar  102  to compression fit the latch device  22  and the collar  102  into secure engagement by driving the interfitting splines  23 ,  103  together ( FIG. 8 ). The rod string  100  can then be backed off such that the hammer  104  is moved away from the collar  102  as shown in  FIG. 9 . The total length of the rod string  100  below the collar  102  is calculated such that the rotor  16  is correctly positioned within the stator  14 . The spring  88  ensures that the default position of the apparatus  10  is in a second or closed configuration to allow flow from the second annular portion  110  through the opening  82  in the sidewall of the moveable member  80  and the bypass ports  42  in the sidewall of the middle sub  40 .  
         [0056]     Fluids and hydrocarbons can be produced naturally from the reservoir, (through the second fluid flow path) if the well pressure is sufficient to overcome the hydrostatic head following installation of the PCP  12  and apparatus  10 . Since the moveable member  80  is biased into the second configuration, the rod string  100  can be held against rotation so that the PCP  12  is inactive and fluids can be produced from the reservoir, through the bypass ports  42 , the openings  82  and the first annular portion  110 . Thus, the apparatus  10  provides a fluid flow path that circumvents the pump  12 , when the moveable member  80  is in the second or closed configuration.  
         [0057]     When it is required to provide fluid such as hydrocarbons from the wellbore with artificial lift (for example, when the natural well pressure drops), the progressive cavity pump  12  is activated by driving rotation of the rod string  100  from the surface. This causes the rotor  16  to turn within the stator  14  thereby positively displacing fluids within cavities  18  and providing the fluids such as hydrocarbons with the necessary lift to overcome the hydrostatic head. Following actuation of the progressive cavity pump  12 , hydrocarbons are lifted through the annulus and enter the annular portion  120 . The hydrocarbon flow acts on the lower face of the protrusion  84  and creates a pressure differential across the protrusion  84 . Above a predetermined level, the pressure overcomes the biasing of the spring  88  at which point the moveable member  80  is pushed upwardly within the body member  11 . Upward movement of the moveable member  80  causes the bypass ports  42  in the middle sub  40  to be obturated by the sidewall of the moveable member  80  and thus the first annular portion  110  is no longer in fluid communication with the bypass ports  42 . Once the radial protrusion  84  clears the collar  102 , the protrusion  84  no longer acts as an impediment to fluid flow within the annulus and there is fluid communication between the second or lower annular portion  120  and the first or upper annular portion  110 . Therefore, hydrocarbons can be produced through the annulus  110 ,  120  when the progressive cavity pump  12  is in use.  
         [0058]     Should the progressive cavity pump  12  cease to function, hydrocarbons are no longer displaced upwardly within the annulus and there is no lift to overcome the hydrostatic head. As a result, the urging of the spring  88  becomes the dominant force acting on the moveable member  80  and the moveable member  80  returns to its default position under the urging of the spring  88  such that the radial protrusion  84  contacts the collar  102  and the openings  82  in the side wall of the moveable member  80  are once again positioned adjacent the bypass ports  42  to open the second fluid flow path and bypass the pump  12 .  
         [0059]     The invention allows fluids to circumvent the progressive cavity pump  12  without the conventional removal of the rotor  16  and consequent downtime in the wellbore. As a result of the apparatus  10  according to the invention certain procedures are facilitated. For example, chemicals, well treatments, etc. can be injected through the second fluid flow path into the reservoir by passing the progressive cavity pump  12 . Additionally, the invention has the advantage that once the progressive cavity pump  12  is no longer in use, the second fluid flow path allows sand downstream of the pump  12  to travel through the bypass ports  42  by means of gravity fall back, such that the sand settles outwith the production tubing and without creating a sand plug above the progressive cavity pump  12 .  
         [0060]     Modifications and improvements can be made without departing from the scope of the invention.