Downhole jet pump

One embodiment of a downhole jet pump 10 includes an exterior pump housing 12, power fluid jet nozzle 30, mixing tube 32, and a carrier 40 including a plurality of venturi ports 38. A nose piece 48 is provided fluidly downstream from the mixing tube 32. A diffuser 46 is downstream from the nose piece, and preferably forms a unitary body from the lower end of the nose piece to the side port of the pump housing. An inlet valve 100 passes formation fluid into the pump housing and to the venturi ports.

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 '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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1depicts one embodiment of a downhole jet pump10according 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 pump10includes an exterior pump housing12which defines an elongate housing passageway14therein extending from an upper portion to a lower portion of the pump housing. The exterior pump housing12preferably has a generally outer cylindrical surface16and a generally cylindrical inner surface18which defines the passageway in the pump housing. The pump housing is thus generally tube or sleeve shaped, with its ends welded to a top pin20and a bottom pin22, respectively. A top sub24is adapted for sealing engagement with a tubular string, while the top pin20seals with the tubing string. An inlet valve nut (bottom sub)26may be provided at the lower end of the pin22, and has a passageway28providing an inlet for hydrocarbons into the pump housing.

FIG. 1depicts a power fluid jet nozzle30with a passageway31which becomes axially restrictive in the downward direction, thereby increasing the velocity of power fluid transmitted through the jet nozzle. The jet nozzle30is supported on and has an exterior sealed to the carrier40which contains the venturi ports38. The carrier40is sealed by a metal to metal seal29formed 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 sub24. A mixing tube32is provided fluidly downstream from the jet nozzle, and has an elongate mixing tube passageway34receiving power fluid from the jet nozzle30and formation fluid through venturi ports38. A plurality of venturi ports38also discussed below are provided immediately below the nozzle30and within the upper portion of carrier40. These venturi ports allow entry of formation fluids from within the housing12radially through the venturi ports and into the mixing tube32. For the embodiment shown inFIG. 1, the carrier40which houses the nozzle30and all or at least a portion of the mixing tube32is formed as a unitary component, and is discussed further below. The mixing tube32preferably is formed from a tungsten carbide alloy material to define the mixing tube passageway34.

A nose piece48is provided within the housing12fluidly downstream from the mixing tube32. The nose piece48may be part of carrier40, or may be formed separate from then threaded to the carrier40. The nose piece has a nose piece passageway44in fluid communication with the mixing tube passageway34. The nose piece48is preferably provided with a carbide material liner42along the entire length of that portion of the nose piece which fluidly connects mixing tube passageway34with the interior of diffuser46. In a preferred embodiment, the carbide material liner42is shrink fit within the nose piece. The selected liner material is one of tungsten carbide, silicon carbide, and boron carbide.

The pump as shown inFIG. 1also includes a diffuser46downstream from the nose piece48. The lower end49of the nose piece seals within a bore in the upper end of the diffuser46. The lower portion50of the diffuser46and the upper portion51of the diffuser form a rigid body, with the groove space for weld56to fuse the upper and lower portions of the diffuser together. The upper portion51of the diffuser46includes a conical or otherwise expanding passageway54, and the lower portion50of the diffuser includes a substantially circular curved bore56. The pieces50and51are mated and are welded together to ensure integrity and reduce manufacturing costs.FIG. 1further illustrates that the lower end49of the nose piece may functionally serve as an upper portion of the diffuser, since venturi bore44may also be a conical or otherwise expanding bore to pump the fluids toward the annulus. Interior surface54of both the upper51and lower50portions of the diffuser are preferably clad with a selected metal coating along the entire length of this surface.

The mixing tube passageway34is thus in communication with the interior31of the jet nozzle30and with the interior44of the nose piece48. The carrier40preferably has three venturi ports38A,38B, and38C as shown inFIG. 3each extending through the side wall of carrier40and between the interior passageway in the pump housing and the mixing tube passageway34. The venturi ports38are spaced substantially equidistant circumferentially about the carrier40. 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 legs70A,70B, and70C 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 carrier40has three equally spaced venturi ports38as shown in greater detail inFIGS. 2 and 3. Each of the legs70A,70B, and70C forming the three venturi ports allows each port to have a substantially rectangular configuration defined by substantially parallel left and right side surface74. The cross sectional area of the ports is increased significantly compared to prior art circular ports. As shown inFIG. 3, each of the side surfaces74is also preferably substantially parallel to a central axis76of the respective venturi port. Each port has a central axis76.

The carrier40as shown inFIG. 2preferably has a plurality of annular grooves78for receiving axially spaced sealing members, and has an interior surface80for receiving the nozzle30shown inFIG. 1. Flange82on the carrier engages a stop surface in the sleeve24shown inFIG. 1. The interior cylindrical surface84of the carrier is sized for receiving the mixing tube32shown inFIG. 1, and an enlarged portion86includes interior threads for receiving the upper threaded end of the nose piece48.

The entirety of the carrier40including the venturi ports38is 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.

Carrier40as shown inFIGS. 1 and 2may 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 nozzle30, the mixing tube32, and the nose piece48when 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 valve100as shown inFIG. 4is provided at the lower end of the pump housing, and more specifically within the bottom pin22, as shown inFIG. 1. As shown inFIGS. 4 and 5, the ball cage102engages the bottom pin22which is sealed to the pump housing, and has a metal sealing surface104for sealing engagement with a similar metal sealing surface105in the bottom pin22. The ball cage102is provided with an interior surface106which 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 ball101to limit radial movement of the ball during operation of the valve. The ball cage end surface108has a radius substantially equal to or greater than the radius of the ball101within 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. 6shows 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 pump110includes an exterior pump housing152which defines an elongate housing passageway therein extending from an upper portion to a lower portion of the pump housing. The exterior pump housing152preferably has a generally outer cylindrical surface150and a generally cylindrical surface154which 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 pin140and a bottom pin156, respectively. The sleeve116is adapted for sealing engagement with cap112, and also for sealed engagement with a top pin140, which is supported on the upper end of housing152. Sleeve116includes shoulder120for supporting the carrier122therein. Sleeve116in turn is supported on the top pin140, and includes a plurality of shoulders for receiving the sleeve116. A short component124may include o-ring grooves for sealing with top pin140, and is sealed with the carrier. Cap112supports diffuser114, which has interior frusto-conical wall118. Although not shown inFIG. 6, pump110optionally may include the components of the inlet valve shown inFIG. 1for allowing fluid to enter the interior of the pump housing.

For theFIG. 6application, the pump inlet for the power fluid is formed by the curved sleeve shaped member146, which preferably has its inlet inclined downward relative to the central axis125of the pump housing. Fluid passing from the annulus passes through bore148in member146, then into body144having a frusto-conical inlet, which may be welded at its lower end to the top of curved sleeve146. Body144preferably has its central axis substantially aligned with the central axis125of the pump housing. The upper end of body144has a seat134for receiving the lower end130of carrier122. The curved sleeve146and body144may be formed from materials similar to those used to form the diffuser shown inFIG. 1, and may also have the same configuration as theFIG. 1diffuser.

The carrier122has through ports126circumferentially arranged about the carrier. The materials from which the carrier is formed and the size and relationship of ports126in the carrier may be substantially as discussed for the carrier40shown inFIG. 1.

As with the previously disclosed embodiment, the mixing tube138is 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 inlet146. Mixing tube138, and thus components of the assembly as shown inFIG. 6below the mixing tube138, including the carrier122and the nozzle136supported within the carrier, may thus be temporarily locked within the housing for disassembly at the surface when the entire pump is retrieved. Nozzle136may include a lower flange142for supporting the nozzle within the carrier. Carrier122may include a plurality of vertically spaced flange surfaces132on expanded lower body130each adapted to receive an O-ring or other seal for sealing with the upper end of the diffuser. The lower component of the carrier122may seat with shoulder134on the body144to effectively hold the carrier downward.

Due to the configuration of theFIG. 6embodiment, the inner workings of the pump110cannot be removed by a reverse flow operation. The pump110thus does not include a significant feature of the pump10discussed 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.