Patent Publication Number: US-7909089-B2

Title: Downhole jet pump

Description:
FIELD OF THE INVENTION 
     The present invention relates to jet pumps and, more particularly, to jet pumps commonly used downhole in wells to pump formation fluids, which may be either hydrocarbons, water, or another liquid, to the surface. The downhole jet pump as disclosed herein is capable of a substantially longer and more reliable life than prior art jet pumps. 
     BACKGROUND OF THE INVENTION 
     Those skilled in the hydrocarbon recovery industry recognize the increasing significance of jet pumps in recovering formation fluids. The potential for jet pumps for pumping formation fluids from a well to the surface is enhanced by its relatively low cost compared to systems which use a reciprocating or rotating rod string to pump fluids to the surface. For many applications, jet pumps are preferable compared to electric submersible pumps, which are frequently not considered reliable for use in producing high solid content formation fluids. 
     Various problems have limited the success of jet pumps in the hydrocarbon industry. More particularly, manufacturers have not recognized the components of jet pumps which should be better protected in order to enhance the pump life and reliability. Many jet pump components are subjected to a unique combination of conditions which enhance corrosion and/or abrasive wear. Jet pumps have been manufactured for decades, but the prior art has not recognized the fluid flow characteristics of jet pumps which have limited their efficiency and reliability. 
     A downhole jet pump which was retrievable by reverse flow is disclosed in U.S. Pat. No. 5,083,609. Further improvements to a downhole jet pump are disclosed in U.S. Pat. No. 5,372,190. The &#39;190 patent discloses a pump with a retrievable nozzle and mixing tube. The mixing tube may be pressed within two carriers by a chemical adhesive. 
     U.S. Pat. No. 4,603,735 discloses another type of jet pump having a reverse up flow. U.S. Pat. No. 4,790,376 discloses a pump wherein power fluid may be injected down the annulus and produced up the tubing string, or power fluid may be injected down the tubing string and produced up the annulus. U.S. Pat. No. 5,055,022 discloses a type of downhole jet pump with a retrievable nozzle assembly. U.S. Pat. No. 4,658,893 also discloses a downhole jet pump with a reverse flow ejection nozzle. 
     The disadvantages of the prior art are overcome by the present invention, and an improved jet pump is hereinafter disclosed. 
     SUMMARY OF THE INVENTION 
     In one embodiment, a downhole jet pump is provided for positioning in a well from a tubular string to pump formation fluids from the well into the annulus surrounding the tubing string. The jet pump includes an exterior pump housing defining an elongate housing passageway therein extending from an upper portion to a lower portion of the pump housing, and a power fluid jet nozzle having an exterior sealed to the pump housing. The jet nozzle has a central passageway therein for increasing fluid velocity of the power fluid transmitted downhole through the tubular string and to the jet nozzle. The pump also includes a mixing tube positioned downstream from the jet nozzle and having an elongate mixing tube passageway for receiving fluid from the jet nozzle. A plurality of venturi ports are provided in a carrier for drawing formation fluids from within the pump housing radially through the venturi ports and into the mixing tube. A nose piece within the housing downstream from the mixing tube has a nose piece passageway in fluid communication with the mixing tube passageway, and a diffuser downstream from the nose piece has a lower end passing through a side port in the pump housing for discharging the mixture of power fluid and formation fluids to the annulus surrounding the pump housing. An inlet valve, commonly referred to as a standing valve, is provided for passing formation fluid into the pump housing and to the venturi ports. In another embodiment, the components of the jet pump are arranged for pumping a power fluid down the annulus, and receiving power fluid and formation fluid through the tubing string. 
     These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a suitable embodiment of a downhole jet pump according to the present invention. 
         FIG. 2  is a cross-sectional view of the carrier with venturi ports generally shown in  FIG. 1 . 
         FIG. 3  is an end view through the ports in the carrier shown in  FIG. 2 . 
         FIG. 4  is a cross-sectional view of the ball cage generally shown in  FIG. 1 . 
         FIG. 5  is an end view of the ball cage shown in  FIG. 4 . 
         FIG. 6  is a cross-sectional view of a downhole jet pump for recovery of formation fluid through a tubing string. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  depicts one embodiment of a downhole jet pump  10  according to the present invention for positioning within a well from a tubular string to pump formation fluid from the well to an annulus surrounding the tubing string, and then from that annulus up to the surface. Those skilled in the art will appreciate that a downhole jet pump may be used for pumping liquid hydrocarbons from a well, but may also be used for pumping other fluids, such as water, to enhance the production of gas or other valuable fluids. Also, the jet pump disclosed below is adapted for receiving power fluid from a tubular, and pumping both the power fluid and the formation fluid to the surface from the annulus. Various functional components of a jet pump may alternatively be arranged for reverse flow, as explained subsequently, so that the power fluid is transmitted down the annulus and the formation fluid and power fluid are recovered at the surface through the tubular string. 
     The jet pump  10  includes an exterior pump housing  12  which defines an elongate housing passageway  14  therein extending from an upper portion to a lower portion of the pump housing. The exterior pump housing  12  preferably has a generally outer cylindrical surface  16  and a generally cylindrical inner surface  18  which defines the passageway in the pump housing. The pump housing is thus generally tube or sleeve shaped, with its ends welded to a top pin  20  and a bottom pin  22 , respectively. A top sub  24  is adapted for sealing engagement with a tubular string, while the top pin  20  seals with the tubing string. An inlet valve nut (bottom sub)  26  may be provided at the lower end of the pin  22 , and has a passageway  28  providing an inlet for hydrocarbons into the pump housing. 
       FIG. 1  depicts a power fluid jet nozzle  30  with a passageway  31  which becomes axially restrictive in the downward direction, thereby increasing the velocity of power fluid transmitted through the jet nozzle. The jet nozzle  30  is supported on and has an exterior sealed to the carrier  40  which contains the venturi ports  38 . The carrier  40  is sealed by a metal to metal seal  29  formed by the shoulder on the carrier and the matching shoulder the top sub. Another seal is provided as a backup and comprises conventional O-rings sealed with the top sub  24 . A mixing tube  32  is provided fluidly downstream from the jet nozzle, and has an elongate mixing tube passageway  34  receiving power fluid from the jet nozzle  30  and formation fluid through venturi ports  38 . A plurality of venturi ports  38  also discussed below are provided immediately below the nozzle  30  and within the upper portion of carrier  40 . These venturi ports allow entry of formation fluids from within the housing  12  radially through the venturi ports and into the mixing tube  32 . For the embodiment shown in  FIG. 1 , the carrier  40  which houses the nozzle  30  and all or at least a portion of the mixing tube  32  is formed as a unitary component, and is discussed further below. The mixing tube  32  preferably is formed from a tungsten carbide alloy material to define the mixing tube passageway  34 . 
     A nose piece  48  is provided within the housing  12  fluidly downstream from the mixing tube  32 . The nose piece  48  may be part of carrier  40 , or may be formed separate from then threaded to the carrier  40 . The nose piece has a nose piece passageway  44  in fluid communication with the mixing tube passageway  34 . The nose piece  48  is preferably provided with a carbide material liner  42  along the entire length of that portion of the nose piece which fluidly connects mixing tube passageway  34  with the interior of diffuser  46 . In a preferred embodiment, the carbide material liner  42  is shrink fit within the nose piece. The selected liner material is one of tungsten carbide, silicon carbide, and boron carbide. 
     The pump as shown in  FIG. 1  also includes a diffuser  46  downstream from the nose piece  48 . The lower end  49  of the nose piece seals within a bore in the upper end of the diffuser  46 . The lower portion  50  of the diffuser  46  and the upper portion  51  of the diffuser form a rigid body, with the groove space for weld  56  to fuse the upper and lower portions of the diffuser together. The upper portion  51  of the diffuser  46  includes a conical or otherwise expanding passageway  54 , and the lower portion  50  of the diffuser includes a substantially circular curved bore  56 . The pieces  50  and  51  are mated and are welded together to ensure integrity and reduce manufacturing costs.  FIG. 1  further illustrates that the lower end  49  of the nose piece may functionally serve as an upper portion of the diffuser, since venturi bore  44  may also be a conical or otherwise expanding bore to pump the fluids toward the annulus. Interior surface  54  of both the upper  51  and lower  50  portions of the diffuser are preferably clad with a selected metal coating along the entire length of this surface. 
     The mixing tube passageway  34  is thus in communication with the interior  31  of the jet nozzle  30  and with the interior  44  of the nose piece  48 . The carrier  40  preferably has three venturi ports  38 A,  38 B, and  38 C as shown in  FIG. 3  each extending through the side wall of carrier  40  and between the interior passageway in the pump housing and the mixing tube passageway  34 . The venturi ports  38  are spaced substantially equidistant circumferentially about the carrier  40 . A feature of the invention is to provide three venturi ports, although in the past pumps of this type have had four or more ports. Providing three venturi ports results in three legs  70 A,  70 B, and  70 C spaced respectively between the ports, thereby providing high structural integrity with very little mass. Secondly, the venturi ports conventionally are provided with a circular cross-section. The three venturi ports according to the present invention preferably are provided with a curved corner, generally rectangular cross-section, which significantly reduces the drag and thus increases the efficiency of the process. 
     The carrier  40  has three equally spaced venturi ports  38  as shown in greater detail in  FIGS. 2 and 3 . Each of the legs  70 A,  70 B, and  70 C forming the three venturi ports allows each port to have a substantially rectangular configuration defined by substantially parallel left and right side surface  74 . The cross sectional area of the ports is increased significantly compared to prior art circular ports. As shown in  FIG. 3 , each of the side surfaces  74  is also preferably substantially parallel to a central axis  76  of the respective venturi port. Each port has a central axis  76 . 
     The carrier  40  as shown in  FIG. 2  preferably has a plurality of annular grooves  78  for receiving axially spaced sealing members, and has an interior surface  80  for receiving the nozzle  30  shown in  FIG. 1 . Flange  82  on the carrier engages a stop surface in the sleeve  24  shown in  FIG. 1 . The interior cylindrical surface  84  of the carrier is sized for receiving the mixing tube  32  shown in  FIG. 1 , and an enlarged portion  86  includes interior threads for receiving the upper threaded end of the nose piece  48 . 
     The entirety of the carrier  40  including the venturi ports  38  is preferably formed from a powdered metallurgy material, which leaves a high percentage of voids in the material which can be coated with a vapor deposition material to enhance abrasion and wear characteristics. 
     Carrier  40  as shown in  FIGS. 1 and 2  may functionally serve as a carrier, in that the carrier may be retrieved to the surface while leaving the pump housing in place, and may also carry both the nozzle  30 , the mixing tube  32 , and the nose piece  48  when pulled to the surface, or when the subassembly including the carrier is lowered back into the well to engage the remaining downhole components of the pump. In other applications, the carrier includes a plurality of through ports, but otherwise does not serve as a retrievable component separate from the pump housing, and/or does not support other components as the carrier is run into or out of the well separate from the pump housing. The term “carrier” as used herein is thus intended to refer to the component which functionally includes the venturi ports, and optionally also serves as a carrier for other components. 
     An inlet or standing valve  100  as shown in  FIG. 4  is provided at the lower end of the pump housing, and more specifically within the bottom pin  22 , as shown in  FIG. 1 . As shown in  FIGS. 4 and 5 , the ball cage  102  engages the bottom pin  22  which is sealed to the pump housing, and has a metal sealing surface  104  for sealing engagement with a similar metal sealing surface  105  in the bottom pin  22 . The ball cage  102  is provided with an interior surface  106  which acts as a guide to limit movement of the ball between the open and closed positions to substantially linear movement, which in this application is substantially vertical movement. The cross-section of the fluid passageway for the ball from the open to the closed positions may not need to be straight, but a majority of the entire length of the passageway should have a cross-sectional diameter substantially no greater than 150% of the diameter of the ball  101  to limit radial movement of the ball during operation of the valve. The ball cage end surface  108  has a radius substantially equal to or greater than the radius of the ball  101  within the ball cage. The ball cage is preferably formed M-4 machine tool stainless steel formed from powdered metal technology, and is then preferably boron coated. 
       FIG. 6  shows an alternate embodiment of the jet pump adapted for receiving power fluid from the annulus of a well and pumping the power fluid and the formation fluid to the surface through a tubular string. The jet pump  110  includes an exterior pump housing  152  which defines an elongate housing passageway therein extending from an upper portion to a lower portion of the pump housing. The exterior pump housing  152  preferably has a generally outer cylindrical surface  150  and a generally cylindrical surface  154  which defines the passageway in the pump housing. The pump housing is thus generally tube or sleeve shaped, with its ends threaded, welded, or otherwise secured to a top pin  140  and a bottom pin  156 , respectively. The sleeve  116  is adapted for sealing engagement with cap  112 , and also for sealed engagement with a top pin  140 , which is supported on the upper end of housing  152 . Sleeve  116  includes shoulder  120  for supporting the carrier  122  therein. Sleeve  116  in turn is supported on the top pin  140 , and includes a plurality of shoulders for receiving the sleeve  116 . A short component  124  may include o-ring grooves for sealing with top pin  140 , and is sealed with the carrier. Cap  112  supports diffuser  114 , which has interior frusto-conical wall  118 . Although not shown in  FIG. 6 , pump  110  optionally may include the components of the inlet valve shown in  FIG. 1  for allowing fluid to enter the interior of the pump housing. 
     For the  FIG. 6  application, the pump inlet for the power fluid is formed by the curved sleeve shaped member  146 , which preferably has its inlet inclined downward relative to the central axis  125  of the pump housing. Fluid passing from the annulus passes through bore  148  in member  146 , then into body  144  having a frusto-conical inlet, which may be welded at its lower end to the top of curved sleeve  146 . Body  144  preferably has its central axis substantially aligned with the central axis  125  of the pump housing. The upper end of body  144  has a seat  134  for receiving the lower end  130  of carrier  122 . The curved sleeve  146  and body  144  may be formed from materials similar to those used to form the diffuser shown in  FIG. 1 , and may also have the same configuration as the  FIG. 1  diffuser. 
     The carrier  122  has through ports  126  circumferentially arranged about the carrier. The materials from which the carrier is formed and the size and relationship of ports  126  in the carrier may be substantially as discussed for the carrier  40  shown in  FIG. 1 . 
     As with the previously disclosed embodiment, the mixing tube  138  is preferably formed as a unitary component formed from a tungsten carbide material with an expanding fluid passageway therein for discharging upward fluids entering the pump housing and passing radially through the venturi ports, as well as power fluid entering the pump through inlet  146 . Mixing tube  138 , and thus components of the assembly as shown in  FIG. 6  below the mixing tube  138 , including the carrier  122  and the nozzle  136  supported within the carrier, may thus be temporarily locked within the housing for disassembly at the surface when the entire pump is retrieved. Nozzle  136  may include a lower flange  142  for supporting the nozzle within the carrier. Carrier  122  may include a plurality of vertically spaced flange surfaces  132  on expanded lower body  130  each adapted to receive an O-ring or other seal for sealing with the upper end of the diffuser. The lower component of the carrier  122  may seat with shoulder  134  on the body  144  to effectively hold the carrier downward. 
     Due to the configuration of the  FIG. 6  embodiment, the inner workings of the pump  110  cannot be removed by a reverse flow operation. The pump  110  thus does not include a significant feature of the pump  10  discussed above. 
     Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations, and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.