Abstract:
A downhole jet pump wherein pressurized gas from an outside portion of a string of tubing is directed through a nozzle having a venturi which causes fluids to be sucked from an outside portion of the string of tubing and ejected through an inside portion of the sting of tubing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to and the benefit of the filing of U.S. Provisional Patent Application Ser. No. 60/645,806, entitled “Downhole Well Pump”, filed on Jan. 21, 2005, and the specification and drawings thereof are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to a pump for removing fluids from a cased hole, i.e. a well bore. More particularly, the present invention relates to a novel downhole, gas-driven pump, with no moving parts, particularly suitable for removing fluids from hydrocarbon producing wells.  
       BACKGROUND OF THE INVENTION  
       [0003]     Increasing production demands and the need to extend the economic life of oil and gas wells have long posed a variety of problems. For example, as natural gas is produced, from a reservoir, the pressure within the reservoir decreases over time and some fluids that are entrained in the gas stream with higher pressures, break out due to lower reservoir pressures, and build up within the well bore. In time, the bottom hole pressure will decrease to such an extent that the pressure will be insufficient to lift the accumulated fluids to the surface. In turn, the hydrostatic pressure of the accumulated fluids causes the natural gas produced from the “pay zone” to become substantially reduced or maybe even completely static, reducing or preventing the gases/fluids from flowing into the perforated cased hole. In such cases, the well bore may log off and possibly be plugged prematurely for economic reasons.  
         [0004]     The oil and gas industry has used various methods to lift fluids from well bores. The most common method is the use of a pump jack (reciprocating pump), but pump jack systems have given rise to additional problems. Pump jack systems require a large mass of steel to be installed on the surface and comprise several moving parts, including counter balance weights, which pose a significant risk of serious injury to operators. Additionally, this type of artificial lift system causes wear to well tubing due to pumping rods that are constantly moving up and down inside the tubing. Consequently, pump jack systems have significant service costs, which negatively impact the economic viability of a well.  
         [0005]     Another known system for lifting well fluids is a plunger lift system. The plunger lift system requires bottom hole pressure assistance to raise a piston, which lifts liquids to the surface. Like the pump jack system, the plunger lift system includes numerous supporting equipment elements that must be maintained and replaced regularly to operate effectively. This adds significant costs to the production of hydrocarbons from the well. In addition, plunger lift systems eventually become ineffective due to lower reservoir pressures than are required to lift the piston to the surface to evacuate the built up liquids.  
         [0006]     Yet another system for lifting well fluids from a well bore is disclosed in PCT International Application No.: PCT/US02/32462, which is hereby incorporated by reference. In that system gas from the well is used to power a downhole pump. The disclosed pump design uses pressurized gas to rotate impeller or turbine-type blades, which lift well fluids from the well. While this design does not have the above-described drawbacks inherent in the pump jack and plunger lift systems, it still includes moving parts (impeller/turbine blades) which increases the potential for wear and malfunction.  
         [0007]     Thus, there is a need for a safe, durable and cost effective pump system that is less susceptible to mechanical failure and that effectively removes liquids from well bores that do not have sufficient bottom hole pressure to lift the liquids to the surface.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention relates to a downhole jet pump having a plurality of elongated openings disposed circumferentially about a central jet nozzle, the plurality of openings communicable to an outside portion of at least one piece of an inner tubing string, a chamber providing a passageway from said plurality of elongated openings to an inlet of said central jet, said central jet comprising an outlet communicable to an inside of said inner tubing string.  
         [0009]     The downhole jet pump can also have a venturi disposed near the outlet of the central jet and/or an outer tubing string disposed between an inner tubing string and a well casing. The venturi can be in fluid communication with an outside of the inner tubing and/or an area between the outer tubing string and well casing. The plurality of elongated openings can be communicable to a backside of a well and/or an annular space between the inner tubing string and the outer tubing string.  
         [0010]     The downhole jet pump can also have a diffuser with an opening which is disposed between the central jet outlet and the inside of the inner tubing string. The diffuser opening can have a substantially conical shape.  
         [0011]     In an embodiment of the present invention, pressurized gas preferably flows from an outside of the inner tubing string, through the venturi, wherein the venturi causes an area of reduced pressure to be created which in turn draws liquids and/or gasses from an outside of the inner tubing string to an inside of the inner tubing string. In another embodiment of the present invention, pressurized gas flows between an outside of the inner tubing string and an inside of the outer tubing string, through the venturi, wherein the venturi causes an area of reduced pressure to be created which in turn draws liquids and/or gasses from an outside of the outer tubing string to an inside of the inner tubing string.  
         [0012]     The jet pump can be comprised of a plurality of subparts which connect to form the jet pump. One or more pins and pin openings can be provided for enabling proper alignment of the subparts. In one embodiment, pressurized gas is provided by a natural formation. In a preferred embodiment, pressurized gas is provided by injecting a pressurized gas between an area between an outer diameter of the inner tubing string and an inner diameter of the outer tubing string.  
         [0013]     The present invention can be used on wells of virtually any depth. As such, the inner tubing string as used in the present invention can have virtually any length, including lengths of at least 100 feet, at least 250 feet, and at least 500 feet.  
         [0014]     The present invention also relates to a method for removing fluid from a well having the steps of providing a string of casing tubing having at least one opening which is communicable to a hydrocarbon producing formation; providing an second string of tubing disposed within the casing tubing; positioning a jet pump on a terminal portion of the second string of tubing; and allowing a pressurized gas to travel between the casing tubing and the second string of tubing and through the jet pump wherein venturi action causes fluid to be sucked from outside the second string of tubing and ejected through an inner portion of the second string of tubing.  
         [0015]     The method can be used to remove fluid buildup from a natural gas producing well. Optionally, in the method, at least one of the openings can include at least one perforation in the casing.  
         [0016]     The present invention also relates to a method for removing fluid from a well having the steps of providing a string of casing tubing having at least one opening which is communicable to a hydrocarbon producing formation; providing an outer tubing string disposed within an inside diameter of the casing tubing; providing an inner tubing string disposed within an inside diameter of the outer tubing string; positioning a jet pump on a terminal portion of an element selected from the inner tubing string, the outer tubing string and combinations thereof; and allowing a pressurized gas to travel between an outside diameter of the inner tubing string and an inner diameter of the outer tubing string, through the jet pump wherein venturi action causes fluid to be drawn from an area outside of the outer string of tubing and ejected through an inner portion of the inner string of tubing. The method can be used to remove fluid buildup from a natural gas producing well.  
         [0017]     The present invention also relates to a downhole jet pump having a substantially conically-shaped diffuser opening a venturi disposed such that an outflow of the venturi is communicably coupled to an inlet of the diffuser opening, an annulus for the transport of a pressurized gas to the venturi, the annulus comprising at least one central axis disposed substantially parallel with a central axis of the opening, and a liquids inlet disposed at or near a terminal portion of the jet pump which is opposite that of an outlet of the diffuser opening.  
         [0018]     The diffuser opening outlet can be communicably coupled to at least one piece of tubing. The liquids inlet can be communicably coupled to a backside of a well. The be a hydrocarbon-producing well, a water well, or the like.  
         [0019]     The annulus is communicable to an area between an inner tubing string and an outer tubing string.  
         [0020]     Objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     For a more complete understanding of the present invention and for further advantages thereof, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:  
         [0022]      FIGS. 1A-1C  depict, respectively, a side view, perspective view and exploded cross-sectional view of the downhole pump assembly of the present invention.  
         [0023]      FIGS. 2A-2E  depict, respectively, a left end view, side view, right end view, perspective view and cross-sectional view of the pump housing section of the downhole pump assembly of the present invention.  
         [0024]      FIGS. 3A-3D  depict, respectively, a left end view, side view, right end view, and cross-sectional view of the upper flow adapter section of the downhole pump assembly of the present invention.  
         [0025]      FIGS. 4A-4E  depict, respectively, a left end view, side view, right end view, perspective view and cross-sectional view of the lower flow adapter section of the downhole pump assembly of the present invention.  
         [0026]      FIGS. 5A-5D  depict, respectively, a side view, right end view, exploded perspective view and cross-sectional view of the diffuser section of the downhole pump assembly of the present invention.  
         [0027]      FIGS. 6A-6E  depict, respectively, a side view, right end view, perspective view, first cross-sectional view and second cross-sectional view of the mixing chamber section of the downhole pump assembly of the present invention.  
         [0028]      FIGS. 7A-7C  depict, respectively, an end view, cross-sectional view and perspective view of the downhole parallel section of the downhole pump assembly of the present invention.  
         [0029]      FIGS. 8A-8C  depict, respectively, a side view, cross-sectional view and perspective view of the jet nozzle section of the downhole pump assembly of the present invention.  
         [0030]      FIGS. 9A-9B  depict, respectively, a side view and cross-sectional view of the downhole pump assembly of the present invention indicating the flow paths for motive gases and well fluids through the pump.  
         [0031]      FIGS. 10A-10D  depict, respectively, a side view, an end view, a perspective view and a cross-sectional view of the downhole diffuser of the present invention.  
         [0032]      FIG. 11  is a drawing which depicts a preferred embodiment of the present invention wherein the jet pump is disposed at or near terminal portions of inner and outer tubing strings which are themselves disposed within a well casing. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     The term “tubing” as used throughout the specification and claims is intended to include all elongated elements having at least one opening extending the length of said element. As such, the term “tubing” includes any and all pipes, tubes, extruded hollow members, cast hollow members, collars, nipples, reducers, couplers, and the like, as well as combinations and multiples thereof. The term “tubing string” as used throughout the specification and claims is intended to include one or more pieces of tubing.  
         [0034]     The present invention is a novel downhole pump for use in the removal of fluids from wells, especially, but not limited to, wells that have insufficient bottom hole pressure to lift the well liquids out of the well bore and to the surface. In its typical use, the pump is disposed downhole in a well adjacent the bottom of the well or the hydrocarbon-producing formation. Referring now to  FIGS. 1A-1C , there is shown a preferred embodiment of the pump assembly  10  of present invention. Pump assembly  10  includes as its main components a downhole diffuser assembly section  100 , an upper flow adapter section  200 , a pump housing section  300 , a lower flow adapter section  400 .  
         [0035]     Referring to  FIGS. 2A-2E , the pump housing section  300  shall be described. Pump housing section  300  includes an outer surface  310 , a lower end  312  disposed further downhole when installed, and an upper end  314 . (The use of the term “lower” herein generally refers to the portion of the pump structure positioned further downhole when the pump is installed. The term “upper” is used to refer to the opposite end of the subject pump structure positioned further up hole when the pump is installed.) Pump housing  300  is substantially cylindrical in shape and can be constructed out of any material suitable for use in a down hole wellbore environment, such as stainless steel. The outer diameter of the housing is about 3.5 inches in the preferred embodiment. Pump housing  300  includes a plurality of openings  320  (for motive gas flow) that extend longitudinally through the housing from upper end  314  to lower end  312 . In addition to providing a conduit for the flow of motive gas, elongated openings  320  serve to reduce gas turbulence, thereby enhancing the efficiency of the pump. Another larger opening  330  also extends longitudinally through the housing. Opening  330  is disposed in the approximate center of the housing and has a slight taper from the upper end to the lower end. A flange  340  extends around the periphery of upper end  314 , creating a recess  342 . A dowel pin opening  316  is also formed in the upper end  314 . Still referring to  FIGS. 2A-2E , housing  300  further includes a lateral opening  370  which extends from opening  330  through the outer surface  310  of the housing. During pumping operations, opening  370  is plugged with plug  380  ( FIG. 1C ). Lower end  312  includes a flange  350  which extends around the periphery of lower end  312 , creating a recess  352 . Also disposed at the lower end of the housing is tube opening  360  which extends from lateral opening  370  into recess  352 . In a preferred embodiment, as shown in  FIG. 2E , openings  330 ,  316 , and  360  have chamfered edges to allow for easier mating with other pump assembly components to be described hereafter. In a most preferred embodiment of the invention, the pump housing  300  has the dimensions and specifications indicated in  FIGS. 2A-2E .  
         [0036]     Referring to  FIGS. 3A-3D , there is shown the upper flow adapter section  200  of the pump assembly. Upper flow adapter section  200  has an upper end  212  and lower end  214 . Opening  220  extends longitudinally through the center of the flow adapter. The diameter of opening  220  is greater at upper end  212  and tapers down to a lesser diameter at the lower end  214  to substantially correspond to the diameter of the opening  330  in pump housing  300 . A plurality of openings  230  (for motive gas flow), which surround opening  220  at lower end  214 , extending longitudinally through the flow adapter. In addition to providing a conduit for the flow of motive gas, elongated openings  230  serve to reduce gas turbulence, thereby enhancing the efficiency of the pump. When the components of the pump are assembled, openings  230  will align with the motive gas openings  320  in the pump housing section  300 . A dowel pin opening  240  is included at the lower end  214  and corresponds with the dowel pin opening in the pump housing, allowing for the proper alignment of the upper flow adapter section  200  with the pump housing  300 . Lower end  214  has a reduced outer diameter allowing lower end  214  to be seated in recess  342  ( FIG. 2E ) at the upper end of the pump housing. Upper end  212  has a reduced outer diameter to allow the upper flow adapter to be connected to an outer tubing string that extends to the surface. Preferably upper end  212  includes threads and is threaded to the outer tubing string. The preferred dimensions and specifications for upper flow adapter  200  are shown in  FIGS. 3A-3D .  
         [0037]     Referring to  FIGS. 4A-4E , there is shown the lower flow adapter section  400  of the pump assembly. Lower flow adapter section  400  has an upper end  412  and lower end  414 . A tube opening  410  extends longitudinally through the lower flow adapter. Upper end  412  includes a recess  420 . Upper end  412  also has a reduced outer diameter, allowing upper  412  to be seated within recess  352  at the lower end of the pump housing  300 . Lower end  414  has a reduced outer diameter to allow for the attachment (preferably threaded attachment) of an additional tubing section(s) below the lower flow adapter. When the pump is assembled, a tube  450  will extend through opening  410  in the lower flow adapter and will be seated within opening  360  in the pump housing (see  FIGS. 1C and 9B ). The preferred dimensions and specifications for lower flow adapter  400  are shown in  FIGS. 4A-4E .  
         [0038]     Referring to  FIGS. 5A-5D , there is shown the diffuser assembly  100  of the pump. Diffuser assembly  100  includes a diffuser section  102 , a parallel section  120 , a mixing chamber section  140 , and a jet nozzle  160 . As shown in FIGS.  5 D and  10 A- 10 D, diffuser section  102  has an upper end  104  and a lower end  106 . In the preferred embodiment, the upper end of the diffuser section is attached to a tubing string (not shown) that extends to the surface of the well. As shown in  FIGS. 5D and 10D , an opening  110  at the center of the diffuser section extends longitudinally through the section. As shown, opening  110  tapers outwardly (i.e., expands in diameter) from the lower end  106  to the upper end  104 . Dowel pin openings  112  are provided at the lower end of the diffuser. As shown (FIGS.  5 A,  5 C- 5 D and  7 A- 7 C), parallel section  120  is seated on the lower end  106  of the diffuser section and has a centered opening  130  which extends longitudinally through the section. Dowel pin openings  140  extend longitudinally through the parallel section and are aligned with the dowel pin openings  112  on the diffuser when the pump is assembled. The preferred dimensions and specifications for the diffuser section are shown in detail in  FIGS. 10A-10D . The preferred dimensions and specifications for the parallel section are shown in detail in  FIGS. 7A-7C .  
         [0039]     Referring to  FIGS. 5A-5D  and  6 A- 6 E the mixing chamber section  140  of the diffuser assembly  100  shall be described. Mixing chamber  140  has a lower end  142  and upper end  144 . Mixing chamber  140  is generally cylindrical and tapers to a slightly smaller diameter from its upper end  144  to lower end  142 . The degree of taper corresponds with the tapered opening  330  in pump housing  300  ( FIG. 2E ) so as to provide a metal to metal taper fit when the mixing chamber section is disposed within the pump housing. As shown in  FIGS. 6D and 6E , the mixing chamber section has a centered opening  150  that extends longitudinally through the section. Opening  150  has (a) a first portion  152  adjacent lower end  142  having a substantially constant diameter and (b) a second portion  154  having a diameter which tapers downward toward the upper end  144 . At the upper end  144  there are a pair of dowel openings  146  which align with the dowel openings  140  in the parallel section  120  (see e.g.,  FIGS. 1C and 5C ). At the lower end  142  there are a plurality of lateral inlet openings  180  about the periphery of the mixing chamber section. Openings  180  extend through the mixing chamber walls into the first portion  152  of opening  150 . At the lower end of the mixing chamber there is also a ledge or flange  190  on which the nozzle will seat when the pump is assembled. A notch  192  is provided about the periphery of opening  150  at the lower end  142 . Seated within notch  192  is a ring  194  (e.g., a stainless steel snap ring) ( FIG. 5C ). When the pump is assembled, dowel pins  180  ( FIG. 5C ) extend into the dowel pin openings  146  (mixing chamber section), through dowel pin openings  140  (parallel section), and into dowel pin openings  112  (diffuser section). The preferred dimensions and specifications for the mixing chamber section are shown in detail in  FIGS. 6A-6E  and the detailed drawings corresponding to  FIGS. 6A-6E .  
         [0040]     Referring to  FIGS. 5C-5D  and  FIGS. 8A-8C  the jet nozzle  160  of the diffuser assembly  100  shall be described. Jet nozzle  160  includes a lower end  162  and upper end  164 . As shown, the nozzle has a centered opening  166  that extends longitudinally through it. Opening  166  has (a) a first portion  168  adjacent lower end  162  having a substantially constant diameter and (b) a second portion  170  having a diameter which tapers downward toward the upper end  164 . A flange or ledge  172  extends about the outer periphery of the nozzle at the lower end  162 . Flange  172  is designed to rest upon the ledge  190  in the mixing chamber section, thus seating the nozzle within the mixing chamber. The exterior surface of the nozzle includes (a) a first portion (adjacent the lower end  162 ) which is substantially untapered and (b) a second portion (adjacent upper end  164 ) which tapers downwardly toward the upper end  164 . As depicted in the drawings, the shape of the exterior surface of the nozzle is designed to substantially correspond with the shape of the opening  150  in the mixing chamber section  140 . The preferred dimensions and specifications for the mixing jet nozzle are shown in detail in  FIGS. 8A-8C .  
         [0041]     When the pump  10  is fully assembled, as depicted in FIGS. IA and  9 A- 9 B, upper flow adapter  200  is connected to pump housing  300 , which is connected to the lower flow adapter  400 . Any suitable means can be used to connect these components. Most preferably, these components are removably connected, such as by threaded connection.  
         [0042]     The assembled pump and the flow of fluids within and about the pump (i.e., the operation of the pump) are depicted in  FIGS. 9A-9B . In its typical use, the pump is disposed downhole in a well adjacent the bottom of the well or the hydrocarbon-producing formation. In the preferred embodiment depicted, the upper flow adapter  200  is attached to an outer tubing string  880  that extends to the surface and the diffuser  102  is attached to an inner tubing string  890  that also extends to the surface. As shown, motive gas (i.e., the gas that operates the pump) is injected into the annulus between the inner and outer tubing strings and then enters the annulus  800  between outer surface of the diffuser  102  and the inner surface of the untapered portion of opening  220  in the upper flow adapter  200 . The motive gas then flows through openings  230  in the upper flow adapter  200  and into openings  320  of the pump housing  300 . From openings  320 , motive gas then flows into the chamber  810  created between the recess  352  (in the pump housing) and the upper end  412  of the lower flow adapter  400 . Next, the pressurized motive gas enters the opening  166  in the jet nozzle  160  and passes into the opening  130  in parallel section  120 . The flow of the motive gas into the parallel section  120  creates a region of reduced pressure within and adjacent opening  130 , causing water and other well fluids to flow from the wellbore through tube  450 , then through opening  370 , then through openings  180 , then through the annulus  850  between the exterior surface of the nozzle  160  and the inner surface of the opening  330  in pump housing  300 , and then into the opening  130  in parallel section  120  where such well fluids mix with the motive gas. Finally, as indicated in  FIG. 9B , the motive gas and water (well fluids) mixture enters the diffuser opening  110  where the pressure is such that the mixture flows to the surface through the inner tubing string  890  attached to the upper end of the diffuser.  
         [0043]     The motive gas needed to operate the pump can be from any source so long as the pressure and flow of gas is adequate to lift the fluids from the well. In a preferred embodiment of the invention, the pump would be driven by the natural gas produced from the well. In some cases the natural pressure of the gases produced from the well will be sufficient to effectively operate the pump without the need to compress the gas. For many wells the natural gas pressure will be insufficient. In such cases, a compressor can be utilized. Such compressor should be selected to provide pressures and motive gas flow sufficient to lift the motive gas/well fluid mixture from the wellbore through the inner tubing string. Additionally, the compressor preferably would be versatile enough to adapt to a wide range of inlet and discharge pressures. This versatility would allow the operator to adjust the discharge pressure or gas volume that feeds the pump, thereby allowing the operator to achieve optimum well bore protection and gas/fluid flow. Preferably, the pressure rating of the pump or compressor will be in excess of 1,000 PSIG.  
         [0044]     A preferred embodiment of the present invention is illustrated in  FIG. 11 . As illustrated therein, jet pump  900 , as mechanically and functionally illustrated in the preceding paragraphs is preferably disposed at or near terminal portions of outer tubing string  910  and inner tubing string  920 . Inner tubing sting  920  is preferably disposed within outer tubing string  910  which itself is preferably disposed within well casing  930 . Motive gas is preferably injected in annular space  925  at or near an upper end of the tubing strings. Motive gas then travels through annular space  925 , through jet pump  900 , thus causing fluid  940  to be drawn into inlet  960 , through jet pump  900 , and ejected as atomized fluid through an inner portion of inner tubing string  920  such that it may be collected and/or separated at or near an upper portion of the tubing strings. Those skilled in the art will readily recognize that fluid  940  is produced at, near, or otherwise travels through production zone  950  before it accumulates at a bottom of well casing  930 . When fluid  940  builds to such an extent that it travels up the well casing to a distance above perforation  975 , at some point, depending upon the gas pressure generated by the specific production zone for each specific well, the hydrostatic pressure of fluid  940  equals the ambient pressure of gas which originates from formation  950 ; when this occurs, production of gas from formation  950  ceases. Injecting motive gas through annulus  925 , and thus removing fluid  940 , enables gas production to continue  
         [0045]     It is also preferred that the components of the pump be constructed of materials suitable for prolonged use in a well environment, such as stainless steel. In a preferred embodiment, the pump is constructed out of 316 Stainless Steel to reduce the corrosive effects of exposure to carbonic acid and to reduce erosion from formation sand particles.  
         [0046]     The invention has been described herein to enable one skilled in the art to practice and use the invention. It is understood that one skilled in the art will have the knowledge and experience to select suitable components and materials to implement the invention. Moreover, although the present invention has been described with respect to preferred embodiments, various changes, substitutions and modifications of this invention may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, substitutions and modifications. For example, although the diffuser assembly  100  (see  FIG. 5C ) is depicted and described herein as being constructed of multiple components (i.e., a diffuser section  102 , a parallel section  120 , and a mixing chamber section  140 ), it is understood and intended that the assembly could be constructed as a single part (e.g., by casting the structure). The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.