US3675714A

US3675714A - Retrievable density control valve

Info

Publication number: US3675714A
Authority: US
Inventors: George L Thompson
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-10-13
Filing date: 1970-10-13
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11

Abstract

Retrievable valve apparatus for lightening oil being gas lifted through a tubing string. The apparatus includes a valve body having a fishing neck which projects upwardly within the tubing string and valve means proper carried by the body for selectively communicating the tubing string interior with a pressurized gas supply to inject gas into the oil upwardly past the fishing neck in response to a predetermined pressure of oil lifted in the tubing string above the apparatus, the valve body being provided with a port to pass the pressurized gas into the body when the body is selectively positioned within the string.

Description

United States Patent TUBING RICIPROCA Thompson 1 July 1 1, 1972 I54] RETRIEVABLE DENSITY CONTROL 3,045,159 7/1962 Garrett et all ..137/1s5 VALVE 2,275,345 3/1942 3,016,844 1/ 1962 [72] Inventor: George L. Thompson, 3265 W. Andrews 3 0 2 0 5 7 19 2 St., Fresno, Calif. 93705 0 Primary Examiner-James A. Leppink [22] Flled' 1970 Attomey-White, Haefliger& Bachand [21] Appl. No.: 80,340

[57] ABSTRACT [52] US. Cl......; ..l66/224, 137/155, 417/86, R ll'i fl Valve pparatus for lightening Oil being gas lifted 417/117 through a tubing string. The apparatus includes a valve body 1 1m. 1721! 33/00 having a fishing neck which projects upwardly within the tub- [58] Field ofSearch ..166/224; 137/155; 417/86, 108-118 mg t s and valve means P 1 earned y the y for selectively communicating the tubing string interior with a Ci pressurized gas supply to inject gas into the oil upwardly past [56] References M the fishing neck in response to a predetermined pressure of oil UNU'ED STATES PATENTS lifted in the tubing string above the apparatus, the valve body being provided with a port to pass the pressurized gas into the 2,145,918 2/1939 Bryan ..417/1 12 body when the body i selectively positioned within the string 3,375,847 4/1968 Brown 2,314,869 3/1943 Boynton ..137/155 10 China, 8 Drawing Figures SHEET 10F 3 P ATENTEDJHL 1 1 I972 IZ/OMPSO/V M? Mud INVENTO/Q POWER 6A5 OUTPUT meme 1 RECIPROCATO a v I. I v vi 1 r l 1 iii. I Q e M u 7 11 P 7 x r 1 PATENTEDJUL 1 1 m2 75, 4

SHEET 3 0F 3 1&0. 4.

I N vs/vro/z 650265 I 11/014 50 1 RETRIEVABLE DENSITY CONTROL VALVE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention has to do with apparatus for lifting oil from wells and more particularly, with density control valve apparatus and fluid handling systems incorporating the apparatus for the efficient removal of oil from wells such as those requiring a gas lift assist to bring oil to the surface.

The removal of oil from wells has been accomplished by pumping either mechanically or by gas injections into the oil to carry the oil to the surface. In U.S. Pat. No. 2,416,359 to Thompson and Cejka, a gas lift type of pumping operation is described in which gas is injected into a reciprocating inner tubing string, provided with a valve mechanism to receive and transport oil from the depths of a well to the surface under applied gas pressure.

2. Prior Art Gas lift pumps typically employ an inner and outer tubing string or well casing between which gas is forced at a suitable pressure to lift discrete quantities of oil to the surface. As the well depth increases and bottom pressure decreases with depletion of the pool, the weight of oil within the tubing string may be such that gas pressure economically available is not efficient or even adequate to lift the oil slugs to the surface.

In these cases, it has been known to provide means for lightening the oil being lifted by injection of gas thereinto in the course of its upward travel. Means for doing this are termed density control valves. In the patent referred to above, a density control valve is shown fixed to the inner tubing wall by couplings providing for the delivery of pressurized gas into the valve for injection into the lifted oil in response to predetermined weight conditions in the oil.

In practice, the volume of gas injected by the density control valve is desirably varied with changes in bottom conditions; moreover, the valve seat may wear requiring repair. In either instance, with previously known gas control valves, e.g. U.S. Pat. No. 2,416,359, it has been necessary to pull the inner tubing string to replace, repair or adjust the gas density control valve. While pulling the string is at best a considerable inconvenience, in the deep wells now being operated, the effort and downtime required for so doing is likely to be economically prohibitive.

SUMMARY OF THE INVENTION Accordingly, it is a major objective of the present invention to provide a density control valve apparatus which is retrievable from the tubing string for replacement, modification or repair and replaceable in the tubing string without pulling the tubing string, and which particularly introduces gas into the inner flowing string in an upward direction. The valve finds particular usefulness in connection with gas lift pump apparatus in which the inner tubing is reciprocated in pumping oil to the surface with gas supplied to the inner tubing through a gas lift valve.

Specifically, the invention provides a retrievable valve apparatus for lightening oil being gas lifted through a tubing string including above the oil supply level, a valve body having a fishing neck adapted to project upwardly within the tubing string and valve means carried by the body for selectively communicating the tubing string interior with a pressurized gas supply to inject gas into the oil upwardly past the fishing neck in response to a predetermined pressure of oil lifted in the tubing string above the apparatus. The valve body is provided with a port to pass the pressurized gas thereinto when the body is selectively positioned in the tubing string. The valve body may carry laterally projecting means below the fishing neck for supporting the apparatus in the tubing string and may be provided with an internal bore communicable with the body port, e.g., plural upwardly diverging passage means communicating the bore with the exterior portion of the body, which portion may be annularly recessed, located adjacently below the fishing neck. There may further be in- I'Lll cluded an actuator for the valve means comprising an axially movable piston responsive to lifted oil pressure to move downward and to gas supply pressure to move upward, both relative to the fishing neck, the actuator thus being responsive to pressure differences between the oil and pressurized gas supply to actuate the valve means. Added downward pressure may be derived from resilient means arranged to downwardly bias the piston.

The retrievable valve apparatus of the invention may be mounted on a mounting means fixed within the tubing string to locate the apparatus opposite a tubing port, the mounting means typically comprising a sleeve adapted to sealably receive the apparatus in such fishing neck projecting relation that the neck is accessible above the sleeve, and ported between the valve body port and the tubing port for passage of pressurized gas from without the tubing into the valve body interior. The mounting sleeve may be annularly recessed opposite the annular recess in the valve body and passage outlet and apertured to pass fluid from the body bore into the tubing string. The valve body port typically is in open communication with the gas supply; and communicable with the body port, there may be provided an axial gas passing bore. Between the body port and the body passage, a valve seat is typically provided, encircling the body bore. A needle valve is provided below the bore comprising a stem pointed end having a portion which normally engages the valve seat against fluid passage, and also having a valve stem actuator comprising a piston fixed on the stem and movable axially within the valve body relative to the fishing neck thereof, a first pressure port for communicating lifted oil pressure around the sleeve to the piston upper surface and a second pressure port for communicating gas supply pressure outside the tubing to the piston lower surface, said piston being responsive to superior force on its upper surface optionally enhanced by a compression spring centered on the valve stem and engaging the piston in downward biasing relation to unseat the point stern portion and to permit supply gas to flow through the bore into the tubmg.

The valve apparatus is useful in connection with apparatus for lifting oil from a well by gas under pressure through a flow string, e.g., the inner string of spaced concentric tubing strings which may be adapted to be reciprocably movable within the well, the apparatus including means carried at the lower end of the inner string adapted to receive oil, e.g., in response to reciprocation of the inner string to be lifted to the surface through the inner string under pressure of gas surrounding the flow tubing string and at a density controlled by the retrievable valve apparatus described above located within the inner tubing for selectively introducing gas into the flow string. In this embodiment of the invention, pressurized gas is provided between the tubing strings. The mounting sleeve, fixed within the inner tubing string and opposite a port therein, serves to communicate the body port with the gas. The valve body may be provided with a central vertical fluid passing bore communicable with the body port and upwardly divergent passages communicating the bore with passage outlets above the upper end of the bore at the exterior valve body portion adjacently below the fishing neck, with the sleeve being apertured in a manner to form a linear continuation of said passages to smoothly pass fluid from said bore upward into the tubing string radially of said fishing neck. The apparatus may further include upper and lower sets of circularly spaced supports supporting the mounting sleeve at vertically spaced locations and centrally within the inner tubing string, plural members of each support set being ported and alined outwardly with inner tubing ports and alined inwardly with sleeve and body ports to provide fluid communication therebetween. Upper and lower annular seals may be provided between the valve body and the sleeve, the lower seal being located between the first and second pressure ports and the upper seal being located between the first pressure port and said body port.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described as to an illustrative embodiment thereof in connection with the attached drawings in which:

FIG. 1 is a view in section of apparatus according to the invention with the gas lift valve mechanism shown in the ejection cycle;

FIG. 2 is a view like FIG. 1 showing the gas lift valve mechanism in the loading cycle;

FIG. 3a and 3b together comprise an enlarged vertical sectional view of the density control valve with the upper portion thereof shown in FIG. 3a and the lower portion in FIG. 3b, the valve is in the closed position;

FIG. 4 is a view like FIG. 3b with the density control valve shown in the normal open position;

FIG. 5 is a cross-sectional view taken on line 5-5 13 in FIG. 3b;

FIG. 6 is a cross-sectional view taken on line 6-6 in FIG. 3b; and

FIG. 7 is a view like FIG. 1 of an alternate embodiment of the invention apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now to the drawings in FIGS. 1 and 2, a simple, cased single well arrangement is depicted. Well bore 1 carries a common form of well casing 2. The casing 2 extends downwardly into the well bore 1 from a suitable casing landing head 3 provided at the surface or top of the well. The casing 2 is provided opposite the oil bearing formation stratum 4 with a perforated section or line 5 which admits well fluid into the well casing, so that it is available tobe removed by the apparatus provided.

The casing landing head 3 is joined to the upper end of the casing 2 and such as to provide a landing for outer tubing string 7. Concentric inner tubing string 8 which is the flow string in the apparatus, is suspended from tubing reciprocator 9 supported above the casing head 3 by stand 6. Reciprocator 9 is adapted to reciprocate inner tubing string 8. While shown diagrammatically, the reciprocator 9 may be an hydraulic piston connected to inner tubing string 8 for alternately raising and lowering the inner string within the outer string 7, as more particularly described in US Pat. No. 2,416,359 mentioned above, which patent is incorporated herein by reference. Reciprocator 9 operation is at intervals and may be controlled by a clock timed intermitter (not shown). The reciprocation movement of the inner flow string 8 is for the purpose of actuating

slide valves

17 and 18 to control the admission of power gas supplied to annulus 11 between inner tubing string 8 and outer tubing string 7 through conduit 12, leading from a compressor or other source (not shown) of gas under pressure from the annulus to the pump chamber 13. Pump chamber 13 comprises the lower portion of outer tubing 7 below the working barrel 10. The pump chamber 13 is of a diameter limited by the inside diameter of the outer casing 2 or perforated liner 5 but may be as long as required or desired to hold a capacity to produce the well at a desired rate determinable by the standing level of fluid in the hole and the productivity index of the formation at 4 surrounding the perforated liner 5.

Eductor tube 14 hangs inside the pump chamber 13 and its internal capacity comprises part of pump chamber 13; it has its open end near the bottom standing valve 15 and is attached at its upper end to the inner flow string 8 to move with it.

The portion 10 of the outer tubing 7 immediately above the pump chamber 13 forms a working barrel for upper slide valve 17 and lower slide valve 18. The upper slide valve 17 controls the flow of power gas to the pump chamber 13. With reference to FIG. 2, inner flow string 8 is in the down position, the upper slide valve 17 is sealed within working barrel 10, shutting off flow down through annulus 11 of power gas to the pump chamber 13. The lower slide valve 18 is in lowered position to unblock vent windows 20 in the center portion of working barrel 10. Vertical channels 21 are provided in the lower slide valve 18 to provide gas passageways through the lower slide valve regardless of valve position in the working barrel lower portion 16. Venting check valve 22 is located in the upper reaches of the eductor tube 14 to vent the eductor tube when the inner tubing string 8 is down, as shown in FIG. 2, thus enabling filling of the eductor tube with well fluid. Check valve 22 opens into the pump chamber 13 between the eductor tube 14 and the portion of outer tubing 7 defining the pump chamber 13.

When the flow string 8 is in the lowered position (FIG. 2) the power gas is blocked, as described above, from the pump chamber 13 by the position of upper slide valve 17. In the absence of power gas in the pump chamber 13, the venting check valve 22 is free to open. The vent windows 20 unblocked by virtue of the lowered relative position of lower slide valve 18 are open to the annulus 23 defined outwardly by the casing 2 which now contains oil and gas at formation pressure. Pump chamber 13 accordingly fills by submergence in the accumulated fluid in the casing through bottom standing valve 15 to commence the loading cycle.

The loading cycle is timed by the mentioned clock intermitter or other device so that the pump chamber 13 will just fill before the reciprocator 9 lifts the flow string tubing 8. Upward movement of the flow string tubing 8 causes lower slide valve 18 carried thereby to first close vent windows 20 to annulus 23. Sequentially upper slide valve 17 is moved upwardly and out of working barrel 10 which permits flow of power gas downwardly through annulus 11 and lower slide valve channels 21 into the top of pump chamber 13. The gas pressure within the outer portion of pump chamber 13 closes venting check valve 22 as the formation pressure thereon is overcome. Similarly, lower standing valve 15 closes by virtue of pump chamber 13 becoming full or from pressure therewithin. The fluid within pump chamber 13 is thus forced upwardly in the eductor tube 14 past upper standing valve 24 and into the lower end of flow string 8 (see arrows, FIG. 1), whereupon the lifting apparatus, i.e., reciprocator 9, may be recycled to displace another slug or pumping chamber-filling quantity of well fluid into the lower reaches of the flow string tubing 8, by lowering this tubing string to vent the pump chamber 13 as above described, to permit filling with well fluid which has again accumulated through the casing perforated section 5.

This pumping cycle may be repeated at any desired rate, e.g., to have several slugs of production fluid in transit to the surface at any one time, enabling characteristically high production rates with the apparatus described.

The well fluid lifting apparatus thus far described is conventional. In the use thereof there may be employed a density control valve 25 located in the lower reaches 26 of the flow string tubing 8 for the purpose of allowing a determined amount of gas to enter the flow string interior 27 laterally from annulus 11 between

tubing strings

7, 8, so as to lighten too heavy weights of production fluid in the flow string 8 and in response to a predetermined differential of between the flow string 8 interior pressure at the valve 25 and the power gaspressure in the annulus l 1.

The density control valve 25 of the present invention is a departure from valves heretofore employed for like purposes of lightening fluid production. Particularly this valve discharges its gas in an upward direction assisting the upward travel of the fluid being pumped upwardly from pump chamber below. Also the present density control valve is a retrievable apparatus, locatable from a distance, i.e., above ground, within a flow string and removable therefrom by wire line without pulling the string from the well.

With reference to FIGS. 3a and 3b, which depict a single retrievable valve apparatus according to the invention, it will be seen that the density control valve apparatus of the invention includes a valve body 28 having an upwardly, freely projecting fishing neck 29 of slightly lesser diameter than the valve body and carrying suitable annular ribs 30 adapted for engagement with a wire carried retrieval tool (not shown). A

laterally projecting latch 31 such as a Type R latch is secured to the fishing neck 29 for the purpose of supporting the valve body 28 in place. Below the fishing neck 29, the valve body 28 comprises plural sections in pin and box threaded connection including a two part upper annular section 32 defining an axial vertically extended bore 33 and plural upwardly divergent passages 34 communicating the bore with exterior annular portion 35 of the upper valve body section adjacently below the fishing neck. The valve body section exterior portion 35 is annularly recessed as shown at the level of passage outlets 36 above the upper terminus 37 of bore 33. Upper recess edge 38 is beveled to provide a smooth continuation of the flow path through passages 34, outwardly from the valve body 28 and upwardly through ports 81 into flowing annulus 27 carrying production from pump chamber 13 below.

A valve seat 39 is provided in the lower part of the upper annular section 32 of the valve body 28 at the lower terminus 40 of the bore. Valve seat 39 is provided with a restricted opening 41 selected to provide the desired control over gas passage ,through the valve opening when wide open and is replaceable by disconnecting the lower part of annular section 32 and the coupling 42 to vary the restriction on gas flow into the bore Coupling 42 comprises a body 43 having a central annular recess 44 and radial ports 45 adapted for communication with power gas in annulus 11 as will be described below leading from the recess into an axial bore 46 which is suitably of the same diameter as bore 33 in upper and lower parts of upper annular section 32 spaced from bore 46 across the valve seat 39. Bore 46 in the coupling is adapted to receive valve stem 47 from below carrying at its upper end above labyrinth sealing rings 48, a pointed terminal 49 configured as a needle valve to seat fluid tightly on seat 39 around valve opening 41.

Below the coupling 42 to receive and guide valve stem 47 there is provided guide block section 50 of the valve body. Guide block section 50 comprises an elongated cylinder having formed therewithin a downwardly stepped axial bore 51 in which valve stem 47 reciprocates to operate the stem pointed portion 49 with respect to the valve seat 39. Valve stem 47 carries a piston 52 having labyrinth sealing rings 53 and movable within the lower, larger diameter portion 54 of the stepped bore 51 to actuate the needle valve. Radial ports 55 are provided through section 50 at annular recess 56 above the travel of the piston 52 to communicate upper bore portion 57 with flow string tubing interior 27 whereby pressure of lifted'oil about the valve body 28 is transmitted to the upper surface 58 of the piston. A compression spring 59 is provided in the upper bore portion 57 centered on the valve stem 47 and engaged between the bore step 60 and the piston upper surface 58 to bias the piston 52 downwardly to thus resiliently assist depression of the valve stem 47 and opening of the valve at 41. The power of spring 59 is selected to provide a desired preload on the piston 52.

Terminal 61 below the piston 52 terminates lower bore portion 54 and through radial ports 62 in annular recess 63 and axial passage 64 is adapted to communicate the bore below the piston with annulus 1 1 between the outer and

inner tubing string

7 and 8 which is power gas containing so that annulus 11 gas pressure is sensed by the piston 52 at its lower surface 65 in a manner biasing the piston and stem upward.

The valve body 28 is retrievably supported in cylindrical sleeve 66. Latch 31 engaging internal annular recess 67 in the sleeve locks valve 28 into place and prevents it from being blown upward out of position. The sleeve 66 is fixed in the tubing section 8a which is pin and box connected into the flow string tubing 8. Support ribs 68 center the sleeve 66 and serve to guide the valve body 28 into the sleeve. Plug 69 threaded into the lower end of sleeve 66 also supports the valve body 28 and in appropriately registered and selected alinement of its

ports

45, 55 and 62, respectively with upper sleeve apertures 70 intermediate sleeve apertures 71 and lower sleeve apertures 72.

Sleeve apertures

70 and 72 in turn are in open communication with upper rib and

tubing apertures

73, 74 and lower rib support and

tubing apertures

75, 76. Intermediate sleeve apertures 71 are open to fluid within tubing string interior 27. See FIG. 6. Thus piston 52 is simultaneously subjected to a pilot pressure on its upper surface 58 from lifted oil through oil from tubing interior 27 entering aperture 71, the upper pressure port 55 and upper bore portion 57, and pilot pressure on its lower surface 65 from the pressurized gas supply in annulus 11 entering through tubing aperture 75, rib aperture 76. Sleeve aperture 72, the lower pressure port 62, bore 64 and lower piston bore 54. Spring 59 biases the piston downwardly to establish the actuating force differential across the piston required to effect operation of the valve, e.g., 200 pounds.

Middle body and lower body sets of

annular seals

77, 78 and 79, 80 are provided between the valve body 28 and the sleeve 66, with

lower seals

79, 80 being located between the upper pressure port 55 and the lower pressure port 62 to fluid tightly seal the body and sleeve between these ports and with

middle seals

77, 78 being located between the upper pressure port 55 and the body port 45 to fluid tightly seal the body and sleeve between these ports.

Annular seals

82 and 83 seal off power gas at port 45 from escaping upwardly between valve body 28 and sleeve 66 and comingling with controlled gas at 81.

In operation of the invention apparatus and with particular reference to FIGS. 3b and 4, power gas is delivered through annulus 11 to cause fluid to be lifted into inner tubing string 8 as described. Several slugs of fluid may be passing through tubing string 8 at one time. The piston 52 is arranged to oppositely sense lifted fluid pressure and gas pressure as v described. When these pressures are at a predetermined differential, the piston 52 moves down and opens valve opening 41. See FIG. 4. Power gas which has entered the valve body 28 through body port 45 in open communication with annulus 11 through rib support aperture 74 and tubing aperture 73 (see FIG. 5) moves into bore 33 and is jetted upwardly and outwardly by passages 34 through outlets 35 and sleeve openings 81 into tubing interior 27 up between support ribs 68 to rush past fishing neck 29 and into the fluid withinthe tubing to lower the density thereof or to lighten the same. Upon lowering the density of the fluid, the piston 52 moves upwardly and closes the valve opening 41 until a too heavy fluid weight condition again occurs. Production passes upwardly in tubing 8 through reciprocator 9 and out through manifold 84.

The upwardly discharging, retrievable valve of the invention in the described apparatus is believed superior to all other flow valve systems now known. The valve is further useful in conjunction with a conventional well gas lifting apparatus shown highly simplified in FIG. 7 wherein like parts to FIGS. 1-6 are shown with like numerals with the addition of e.g., casing 102. Power gas from line 112 is run down the annulus 1 1 1 to packer 190 so as to not exert pressure on the producing zone inward of stratum 104 in casing 105. Density control valve operating on the differential between fluid in flow string interior 127 and annulus 111 between casing 102 and tubing string 108 is admitting its gas in an upwardly jetting direction and serves to lighten the lifted fluid as described above with the lifting gradient within the tubing controllable by the power gas pressure in the annulus 111. Alternatively packer may be omitted and no power gas used where the formation gas pressure is sufficient to lift the well with the help of the upwardly directed valve 125, if the formation pressure in stratum 104 is sufficient.

I claim:

1. Retrievable valve apparatus for lightening oil being gas lifted through a tubing string including a valve body, a valve body mounting sleeve coaxially within the tubing string and radially spaced therefrom to define an annular passage, said body having a fishing neck adapted to project upwardly within the tubing string and valve means carried by the body for selectively communicating the tubing string interior with a pressurized gas supply to inject gas into oil emerging from said passage and upwardly past said fishing neck in response to a predetermined pressure of oil lifted in the tubing string above the apparatus, said body having a port to pass said pressurized gas into the body when the body is selectively positioned in the string.

2. Retrievable valve apparatus according to claim 1 including also an actuator for the valve means comprising an axially movable piston responsive to lifted oil pressure to move downward and to gas supply pressure to move upward, both relative to the fishing neck, whereby said actuator is responsive to pressure differences between the oil and pressurized gas supply to actuate the valve means.

3. Retrievable valve apparatus according to claim 2 including also resilient means arranged to downwardly bias the piston.

4. The combination according to claim 3 in which said valve body mounting means comprises a sleeve adapted to sealably receive said apparatus in such fishing neck projecting relation that said neck is accessible above the sleeve, and port means between said sleeve and said body for passage of pressurized gas from without the tubing into the valve body interior.

5. The combination according to claim 4 including also a vertically extended bore within the valve body, a valve seat encircling said bore, a valve stem below the bore having a portion normally engaging the valve seat against fluid passage, a valve stem actuator comprising a piston fixed on the stem and movable axially within the body relative to the fishing neck, a first pressure port for communicating lifted oil pressure around the sleeve to the piston upper surface, and a second pressure port for communicating gas pressure outside the tubing to the piston lower surface, said piston being responsive to superior force on its upper surface to unseat the stemhead portion and to permit gas to flow upwardly through the bore in the tubing.

6. The combination according to claim 5 including also compression spring means centered on the valve stem engaging the piston in downwardly biasing relation.

7. ln apparatus for lifting oil from a well by gas under pres sure including spaced concentric tubing strings the inner string of which is adapted to be reciprocably movable within the well, and the outer string of which defines with said inner string a gas pressure chamber, and means carried at the lower end of the inner string adapted to receive oil in response to string reciprocation to be lifted to the surface therethrough by said gas, the improvement comprising retrievable valve apparatus to lighten oil lifted by inner string movement, said apparatus comprising a retrievable valve body above the oil supply level coaxially within the inner tubing string, a valve body mounting sleeve of lesser diameter than the inner tubing, mounting sleeve supports extending between the inner tubing string and the mounting sleeve and carrying the mounting sleeve for reciprocating movement with the inner tubing string in spaced relation to the tubing to define an annular passage circularly of the mounting sleeve within the inner tubing string, said valve body having an upwardly projecting fishing neck, a central fluid passing vertical bore having an outlet adjacently below the fishing neck, first port means communicating lifted oil'pressure at the sleeve to said bore, a second port means extending through said sleeve supports for communicating gas pressure between the tubing strings to said bore, valve means operatively arranged within said bore to be oppositely responsive to lifted oil and gas pressures within the bore and adapted to pass pressurized gas from between said strings into lifted oil above said annular passage in said inner string, in response to a predetermined pressure of lifted oil and during reciprocating movement of said inner string.

8. Apparatus according to claim 7 in which said valve means includes a needle valve stem having a pointed portion normally engaging the valve seat against fluid passage; a valve stem actuator comprising a piston fixed on the stem and movable axially within the body, said first port means communicating lifted oil pressure at the sleeve to the piston upper surface,

said second port means communicating gas pressure between the tubing strings to the plston, said piston being responsive to superior force on its upper surface to move downwardly to unseat the pointed stem portion and to permit gas from between said tubing strings to flow through the bore and upwardly into the tubing.

9. Apparatus according to claim 8 including also compression spring means mounted on the valve stem and engaging the piston in downwardly biasing relation.

10. Apparatus according to claim 9 in which said sleeve supports comprise upper and lower sets of circularly spaced and radially disposed supports at vertically spaced locations on said sleeve and centrally within the inner tubing string, plural members of each support set being ported and alined to provide fluid communication therebetween.

Claims

5. The combination according to claim 4 including also a vertically extended bore within the valve body, a valve seat encircling said bore, a valve stem below the bore having a portion normally engaging the valve seat against fluid passage, a valve stem actuator comprising a piston fixed on the stem and movable axially within the body relative to the fishing neck, a first pressure port for communicating lifted oil pressure around the sleeve to the piston upper surface, and a second pressure port for communicating gas pressure outside the tubinG to the piston lower surface, said piston being responsive to superior force on its upper surface to unseat the stem head portion and to permit gas to flow upwardly through the bore in the tubing.

7. In apparatus for lifting oil from a well by gas under pressure including spaced concentric tubing strings the inner string of which is adapted to be reciprocably movable within the well, and the outer string of which defines with said inner string a gas pressure chamber, and means carried at the lower end of the inner string adapted to receive oil in response to string reciprocation to be lifted to the surface therethrough by said gas, the improvement comprising retrievable valve apparatus to lighten oil lifted by inner string movement, said apparatus comprising a retrievable valve body above the oil supply level coaxially within the inner tubing string, a valve body mounting sleeve of lesser diameter than the inner tubing, mounting sleeve supports extending between the inner tubing string and the mounting sleeve and carrying the mounting sleeve for reciprocating movement with the inner tubing string in spaced relation to the tubing to define an annular passage circularly of the mounting sleeve within the inner tubing string, said valve body having an upwardly projecting fishing neck, a central fluid passing vertical bore having an outlet adjacently below the fishing neck, first port means communicating lifted oil pressure at the sleeve to said bore, a second port means extending through said sleeve supports for communicating gas pressure between the tubing strings to said bore, valve means operatively arranged within said bore to be oppositely responsive to lifted oil and gas pressures within the bore and adapted to pass pressurized gas from between said strings into lifted oil above said annular passage in said inner string, in response to a predetermined pressure of lifted oil and during reciprocating movement of said inner string.

8. Apparatus according to claim 7 in which said valve means includes a needle valve stem having a pointed portion normally engaging the valve seat against fluid passage; a valve stem actuator comprising a piston fixed on the stem and movable axially within the body, said first port means communicating lifted oil pressure at the sleeve to the piston upper surface, said second port means communicating gas pressure between the tubing strings to the piston, said piston being responsive to superior force on its upper surface to move downwardly to unseat the pointed stem portion and to permit gas from between said tubing strings to flow through the bore and upwardly into the tubing.