US3407830A

US3407830A - Gas lift valve

Info

Publication number: US3407830A
Application number: US572873A
Authority: US
Inventors: James E Reagan
Original assignee: Otis Engineering Corp
Current assignee: Otis Engineering Corp
Priority date: 1966-08-12
Filing date: 1966-08-12
Publication date: 1968-10-29
Anticipated expiration: 1985-10-29

Description

J. REAGAN GAS LIFT VALVE Oct. 29, 1968 2 Sheets-Sheet 1 Filed Aug. 12, 1966 v ENTORS Jom es E. Reagan Wgdk? ATTORNEYS Fig.|-A

Oct. 29, 1968 J. E. REAGAN 3,407,830

GAS LIFT VALVE 2 Sheets-Sheet 2 Filed Aug. 12, 1966 INVENTORS James E. Reagan 'BY Fig .3 %m- United States Patent 71cc 3,407,830 GAS LIFT VALVE James E. Reagan, Dallas, Tern, assignor to Otis Engineering Corporation, Dallas, Tex., a corporation of Delaware 'Filed Aug.'12, 1966, Ser. No. 572,873 17 Claims. (Cl; 137-155) i y This invention relates to well tools and more particularly to air or gas lift valves for controlling the admission of gas or air into a column of fluid in a well to lift the column and to aid in flowing the fluid from the well.

It is one object of the invention to provide a new and improved welltool for admitting fluid into a flow conductor.

- i It is another object of the invention to provide a new and improved well tool for removing fluids produced by wells through an inner well tubing disposed in a casing of a. well wherein gas from an annular flow passage between the casing .and the inner well tubing provides power for transporting the fluids to the surface through the inner well tubing. I

. It isanother object of the invention to provide a well tool for automatically removing well fluids from the bore of a well including a valve which opens intermittently to permit gas flow from an annular flow passage between a well casing and an inner well tubing into the well tubing to aid in lifting fluids present in the well tubing above the valve to the surface. I

It is still another object of the invention to provide a well tool for use in a well having a casing and an inner well tubing telescoped therein including a valve providing communication between the interior of the well tubing and the annular space between the casing and the well tubing which is responsive to the pressure both within the tubing and'within the annular space to permit fluid flow from the annular space into the tubing when the force on the valve resulting from the combined tubing and annular pressures exceed a predeterminedvalue.

.It is another object of the invention to provide a new andimproved gas lift valve connectable in a String of tubing to form a section thereof having a central longitudinal passage or bore of a diameter not smaller than the bore of the tubing.

It is another object of the invention to provide a gas lift valve having a relatively small outside diameter.

, It isstill another object of the invention to provide a gas lift valve of concentric construction connectable in a tubing string to form a section thereof and provided with an internal longitudinal passage having a diameter no smaller than the drift diameter of the tubing with which the valve is connectable and an annular flow passage concentrically disposed about the longitudinal flow passage, port means communicating the longitudinal flow passage with the annular flow passage and the annular flow passage with the exterior of the gas lift valve, and concentric annular valve means in the annular flow passage for controlling the flow of lift gas from the exterior through the annular flow passage into the longitudinal flow passage responsive to the pressure both within the annular flow passage and exterior of the gas lift valve.

l It is still another object of the invention to provide a gas lift valve having an annular valve member movable between open and closed positions by an annular piston member biasedin one direction toward a closed position by ,spring means and movable in the other direction to an open position responsive to a combined predetermined annulus and central bore pressure.

It is still a further object of the invention to provide a concentric type. gas lift valve wherein the operative components of the valve are not exposed either to the interior or the exterior of the valve structure to minimize damage by well tools, flow cutting, erosion, high pressures, or other similar forces. i

It is still a further object of the invention to provide a gas lift valve having a concentric valve member movable by a concentric piston actuated responsive-to a pilot valve housed in a'wall portion of the gas lift valve body structure.

It is still a further object of the invention to provide a concentric type gas lift valve having a concentric flexible check valve member positioned downstream of a concentric valve member in the flow path between the concentric valve member and ports admitting fluid into the central longitudinal flow passage of the valve whereby fluid under pressure is not trapped between the valve member and the exterior of the valve bodystructure.

It is still another object of the invention to provide a concentric type gas lift valve which admits lift gas to a central flow passage from exterior of the valve at relatively high flow rates.

Additional objects and advantages of the-invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIGURES 1 and l-A taken together constitute a longitudinal view partially in elevation and partially in section of a gas lift valve embodying the invention;

FIGURE 2 is an enlarged fragmentary longitudinal view partially in section and partially in elevation showing a major portion of the pilot valve in the gas lift valve of FIGURES l and 1-A;

FIGURE 3 is a fragmentary longitudinal view in elevation of the central and lower mandrel members only of the gas lift valve with its pilot valve assembly and other related components removed;

FIGURE 4 is a view in section along the line 4-4 of FIGURE 1;

FIGURE 5 is a view in section along the line 55 of FIGURE 1-A;

' FIGURE 6 is a view in perspective of one of the flow passage protective screen members illustrated in FIG- URES l-A and 5;

FIGURE 7 is a view in section along the line 7-7 of FIGURE l-A; 7

FIGURE 8 is a fragmentary view in perspective of a portion of the tubular shaped concentric valve assembly of the gas lift valve;

FIGURE 9 is an enlarged fragmentary view in section along the line 99 of FIGURE 2;

FIGURE 10 is an enlarged fragmentary view in section along the line '1010 of FIGURE 2; and,

FIGURE 11 is an enlarged fragmentary perspective view of a longitudinally slotted check valve retainer used in the gas lift valve.

Referring to the drawings, a gas lift valve 20 embodying the invention includes a mandrel 21 having an upper member 22, a central member 23, and a lower member 24. The upper member is externally threaded along an upper end section 25 while the lower member is externally threaded along a lower end section 30 so that the gas lift valve may be threadedly engaged with suitable couplings and included as a section in a tubing string of a Well.

A longitudinal central bore 31 of uniform diameter throughout its entire length extends through the mandrel 21. The central mandrel member 23 is threaded along an upper end portion 32 into an internally threaded lower end portion 33 of the upper mandrel member 22. The upper mandrel memberyhas an internal annular downwardly facing shoulder surface 34 engageable with the upper end face 23a of the central mandrel member limiting its movement into "the upper mandrel member. The

Patented Oct. 29, 1968 internally threaded lower end portion of the upper mandrel member and the externally threaded upper end portion of the central mandrel member have diameters so related that the internal wall surfaces defining their bores join at the connection between them to provide a smooth bore wall surface through the mandrel. The lower mandrel member 24 has a slightly enlarger upper end bore portion 35 which receives a reduced lower end portion 40 on the central mandrel member 23 providing a smooth wall relationship between the bores of the central and lower mandrel members. The lower mandrel member is secured with the central mandrel member by suitable means such as an external annular weld 41.

I A tubular main valve assembly 42 is slidably positioned concentrically within an elongated annular chamber 43 defined between external wall surface portions of the upper and

central mandrel members

22 and 23 and an internal wall surface portion of an outer sleeve 44 secured in concentric spaced relationship around portions of the upper and central mandrel members. The main valve assembly has a head 45 formed on a tubular sleevelikebody portion 50 which is internally threaded along a lower end portion on an externally threaded reduced upper end portion 51 of an annular piston 52. The piston moves the valve assembly between a lower end closed position illustrated in FIGURES 1 and 1-A and an upper end open position responsive to spring force and fluid pressure as explained in detail hereinafter. I

The outer sleeve 44 is telescopically fitted along a lower end portion over a slightly reduced upper end portion 53 of the central mandrel member with the outer wall surface portions of the adjoining sections of the outer sleeve and central mandrel member providing a smooth outer wall surface connection. A lower end surface 44a of the outer sleeve 44 engages an external annular shoulder surface 53a on the central mandrel member limiting the downward movement of the outer sleeve over the central mandrel member. The outer sleeve has an, upper end head portion 54 of reduced internal diameter fitted around an outer wall surface of the upper mandrel member. The sleeve 44 is locked against upward movement on the mandrel members by a nut 55 threaded on the portion 25 of the upper mandrel member until the lower end surface of the nut engages the upper end surface 54a of the outer sleeve. The nut 55 is locked in position by a set screw '60 threaded through a lateral bore 61 in the nut against the external threads on the upper mandrel member. A plastic ball, not shown, may be disposed within the bore 61 between the end of the set screw and the threads on the mandrel member 25 to prevent damage to the threads while holding the nut against rotation on the mandrel member. Two O-rings 62 are disposed in external annular recesses around the upper mandrel member to seal between the mandrel member and the outer sleeve head portion 54. Similarly, two O-rings 63 are disposed in external annular recesses 63a in the reduced portion 53 of the central mandrel member to seal between the outer sleeve and the central mandrel memher.

The annular chamber 43 effectively extends from the internal annular downwardly facing shoulder surface 64 on the head portion 54 of the outer sleeve 44 downwardly around the upper and central mandrel members within the outer sleeve to an external annular shoulder surface 65 on the reduced portion 53 of the central mandrel memher at the base of its reduced upper portion 70.

A plurality of lateral ports 71 are formed in the upper mandrel member 22 to communicate the mandrel bore 31 with the annular chamber 43. The exterior of the gas lift valve is communicated with the annular chamber 43 below the valve head portion 45 through a plurality of ports or slots 72 in the outer sleeve 44 and corresponding ports or slots 73 in the body portion 50 of the main valve assembly 42. The ports 72 in the outer sleeve 73 and in the main valve are equal in number and correspondingly positioned in their respective members so that the valve ports and sleeve ports register with each other to permit fluid flow from around the-gas lift valve through both the outer sleeve and main valve body into the annular chamber 43 within the valve body. The valve body ports 73 are substantially longer than the outer sleeve ports 72 so that the total effective area of each port 72 is available for fluid communication irrespective of the position of the main valve and valve action will be effected at only one location along the main valve and mandrel as discussed below. The main valve body 50 has one longitudinal slot 74 below, aligned with, and communicating with one of the ports 73 in the valve body. The slot 74 receives the outer end portion of a lock pin 75 secured along its inward end portion in a blind outwardly opening hole in the upper mandrel member 22. The slidable relationship of the pin 75 in the slot 74 permits the valve assembly 42 to move longitudinally while holding it against rotation relative to the mandrel and outer sleeve 44 to retain the ports 73 in alignment with the corresponding outer sleeve ports 72.

The upper mandrel member 22 is enlarged along a flange portion 81 providing an upper and outwardly facing annular stop shoulder 82 which is engageable by an internal annular downwardly and inwardly facing stop shoulder 83 formed in the head 45 of the main valve assembly. An O-ring 84 disposed in an external annular recess in the upper mandrel member flange 81 seals between the flange and the head 45 of the main valve assembly when the valve assembly is at its lower end closed position as illustrated in FIGURE 1. The O-ring 84 is preferably cemented in its recess by a suitable material such as an epoxy cement. An O-ring 85 received in an external annular recess around the head 45 seals between the valve assembly head and the inner wall surface of the outer sleeve 44. When the valve assembly is at the lower end position of FIGURE 1 the sealing elfect of the O-

rings

84 and 85 prevents fluid flow upwardly in the annular chamber 43 from below the head of the valve assembly. The shoulder surfaces 82 and 83 are preferably finished as seat surfaces to provide a supplementary seal to the O-ring 84 in the event of leakage past it.

The internal wall surface portion 83a of the head 45 below the shoulder 83 is tapered downwardly and outwardly so that when the valve assembly is at the closed position of FIGURE 1 a sealed relationship exists between the 'O-ring 84 and the surface portion 83a while when the valve assembly is at its upper end open position there is ample clearance around the O-ring 84, and within the surface portion 83a of the head 45 below the shoulder 83 to permit the desired fluid flow upwardly within the valve assembly past the O-ring 84 and then between the spaced

shoulders

82 and 83. Similarly, the inner surface of the head 45 above the shoulder 83 and the outer surface of the mandrel member 22 above its shoulder 82 are spaced apart sufficiently to allow the desired volume of fluid to flow upwardly between the mandrel and the valve assembly head when the valve assembly is at its open position.

An annular flexible check valve is clamped along a lower end portion 91 within the annular chamber 43 above the valve assembly 42 by an annular finned retainer 92. The retainer 92 as shown in FIGURE 11 has a tubular body portion 93 on which are formed a plurality of circumferentially spaced longitudinally extending fins 94 which define longitudinal circumferentially spaced slots 95 extending along the retainer between the fins to allow fluid flow from below the retainer past the retainer within the annular chamber 43. As shown in FIGURES 1 and 11, the fins 94 extend below the lower end surface of the body portion 93 of the retainer. The upper end surface of the head 45 of the main valve assembly at its upper end position engages the lower end surfaces of the fins 94 limiting the upward movement of the valve assembly. The wall thickness of the head member 45 of the valve assembly is reduced along its upper end portion 45a to provide clearance within the head around the mandrel section 22for fluid to flow from within the head member into the space 100 defined within the fins below the retainer body around the mandrel member 22. The outside diameter of the mandrel member 22 is reduced along a portion 22a abovethe shoulder 82 to provide clearance for fluid flow at a desired rate within the head 45 along the mandrel member. The fluid flows from around the mandrel member within the head 45 into the space 100 and then radially outwardly into lower end portion of the slots .95.

When the valve assembly 42 is at its upper open posi tion the clearance between the internal wall surface portion 83a of the head 45 and the O-ring 84 defines an annular orifice for fluid flow which is less in effective area than the total effective area of either of the sets of

ports

71 and 72. The annular orifice between the valv assembly head and the O-ring 84 is sized to effect a pressure drop under normal fluid flow conditions for the gas lift valve to hold the valve assembly at an upper open position as discussed in more detail hereinafter.

The lower end portion 91 of the check valve is disposed within an external annular recess 101 of the mandrel member 22 and an aligned internal upwardly opening annular recess 102 within an upper end portion of the finned retainer. The retainer is secured on the mandrel section by a lock wire 103 received within external and aligned internal annular recesses in the mandrel member 22 and the finned retainer, respectively. The lock wire is inserted into the aligned recesses through a lateral slot 104 opening into the recess of the finned retainer, FIGURE 11. One end of the lock wire is inserted into the slot 104 when the retainer is positioned as in FIGURE 1. The wire is driven around the mandrel member in the aligned recesses until the inserted end is visible in the slot104. The driving end is then cut off and tucked into the slot.

The check valve 90 is formed of a flexible material such as rubber and normally is at the position illustrated in FIGURE 1 so that downward flow within the annular chamber 43 develops a pressure differential across the check valve biasing it outwardly into sealed relationship within the inside wall of the outer sleeve 44 within the chamber 43 preventing downward flow in the annular chamber past the check valve and thus preventing flow from the bore 31 of the gas lift valve to the aligned

ports

72 and 73 leading .to the exterior of the valve. Upward flow within the annular chamber from below the check valve tends to collapse the check valve or fold it inwardly around the mandrel member 22 displacing all or portions of its outer surface away from the inside wall surface of the outer sleeve to allow fluid flow within the chamber 43 toward the ports 71 leading into the bore 31 through the mandrel section 22.

The annular piston 52 of the main valve assembly 42 is slidable within the annular chamber 43 below the lower end face 105 of the mandrel member 22. The piston is biased downwardly from the mandrel member by a spring 110 confined between the face 105 at its upper end and at its lower end an upper end face 111 on the reduced upper end portion of the piston. At its lower closed position shown in FIGURES 1 and 1A the valve assembly is limited against further downward movement by engagement of the stop shoulder 82 on the mandrel member 22 and the stop shoulder 83 within the head of the valve assembly. The piston 52 has upper inner and outer seal rings 112 disposed within internal and external recesses formed in the piston to prevent leakage in a downward direction past the piston along the annular chamber 43. Similarly, leakage past the piston in an upward direction along the annular chamber is prevented by lower ring seals 113 disposed within inner and outer annular recesses formed in the piston along its lower end portion. The ring seals 112 and 113 mayconveniently comprise seals sold under the trademark-Tec-Ring which are ring seals having a cross-sectional configuration in the shape of a C. Such ring seals are positioned within their recesses so that the open portion of the C faces opposite to the direction of flow against which sealing is desired sothat fluid flows into the ring seal, expands it, and thus effects a seal proportional to the pressure differential imposed across the seal. 1

When the valve assembly 42 is at its lower closed position, the lower end surface 114 of the piston 52 is spaced above the upwardly facing shoulder surface on the central mandrel member 23 defining below the piston an annular chamber portion 43a within the outer sleeve 44 around the central mandrel member. The annular chamber portion 43a receives fluid under pressure,-as explained hereinafter, effecting a pressur differential across the piston 52 to move the valve assembly 42 to its upper open position. v 1

Referring to FIGURES 1A, 5, and 6 the reduced mandrel portion of the central mandrel member 23 is provided with a single small lateral port.115 communicating the longitudinal bore 31 through the mandrel member with the annular chamber portion 43a. Also, communicating with the annular chamber portion 43a is alongitudinal flow passage 120 within the wall of the central mandrel member below its shoulder surface 65 spaced 180 degrees from the port 115. Two filter screens 121 are secured within the annular chamber portion 43a over the port 115 and the flow passage 120, respectively, to protect the piston 52 from foreign matter which may flow into the chamber portion from either the bore 31 through the port 115 or the bore 120 from the annulus around the gas lift valve.

Each of the screens 121 includes an arcuate body portion 121a having generally triangular opposite end tabs 121b bent to about a degree angle with the body portion. The screens are suitably secured, as by silver soldering, to the central mandrel member 23, one over the port and the other over the opening of the passage through the surface 65 into the chamber portion 43a. For example, the inside edge 121a of the screen body portion along with the edges 121d of the end tabs are soldered to the outside wall surface of the portion 70 of the central mandrel member. The outside edge 1210 of the screen body portion and the edges 121i of the end tabs are soldered to the mandrel member shoulder surface 65. The screen edge 1210 is circular shaped on a radius equal to the radius of the outside wall surface of the portion 70 of the mandrel member 23 while the edge 121a is circular shaped on a radius equal to the radius of the inside wall surface of the sleeve/l4 at the chamber portion 43a. Debris larger than the screen openings which may flow into the annular chamber portion 43a through the port 115 is trapped within by the screen over that port while similarly debris flowing into the chamber portion from the passageway 120 is trapped by the screen over the opening of the passageway into the chamber portion.

Flow of fluid from the exterior of the gas lift valve into the flow passage 120 is controlled by a pilot valve disposed within an external longitudinal recess or pocket combination 131 in the central mandrel member. The pilot valve is held within the recess by an outer sleeve 132 telescopically fitted over the central mandrel member.

The recess 131 communicates with the flow passage 120 through a cylindrical check valve chamber 133 and a connecting bore 134. The chamber 133, FIGURE 2, is misaligned from or eccentrically positioned with respect to the passage 120 to prevent a ball check valve 135 disposed therein from seating on and closing off the opening of the passage into the chamber. A lateral slot 136 extends perpendicular to and intersects the outer edge of the bore 134 to receive a lock pin as explained hereinafter.

.The; borev 134 opens atits lower end into the recess.

combination 131 which includes a lateral slot 140 defined by a substantially planar or flat bottom surface 141 extending between circular segment end surfaces 142 and 143. The surface 141 is in a plane parallel to the longitudinal axis of the mandrel member 23 and perpendicular to a radius line from such longitudinal axis. The end surfaces 142 and 143 each lies in a plane perpendicular to the longitudinal axis of the mandrel member. The bore 134 opens into the slot 140 through the surface 142. Also included in the recess combination 131 opening through the end surface 143 into the slot 140 is a longitudinal recess 144 defined by parallel side wall surfaces 145 oriented perpendicular to the bottom surface 141 and having a semicylindrical bottom surface 150. The recess 144 has laterally enlarged spaced

portions

151 and 152, FIGURE 3. The recess 144 is open at its lower end through a downwardly and inwardly converging or tapered end surface 23a on the mandrel member 23.

The pilot valve 130 includes a seat member 153 having a reduced upper portion 154 disposed in the bore 134 and an enlarged lower portion 155 extending into the lateral slot 140. The two valve seat member portions are tubular in shape and at their juncture the valve member is provided with an external annular shoulder 160 which seats against the slot surface 142 limiting the movement of the valve seat member into the bore 134. An external annular seal ring 161 is disposed within an external annular recess 162 of the valve seat member portion 154 to seal around the valve member within the bore 134. The valve seat member has an annular downwardly and inwardly convergent upper end seat surface 163 which receives the ball check valve 135 to prevent flow into an upper bore portion 165 in the seat member. The seat member bore portion 165 communicates with an intermediate bore portion 170 which opens into a further enlarged lower bore portion 171 through an internal annular downwardly and outwardly divergent seat surface 172. The lower portion 155 of the valve seat member has lateral bores 173 communicating with the bore portion 171. The upper portion 154 of the valve seat member has an external annular groove 174 which receives a section of a lateral or tangentialy positioned straight lock pin 175 disposed in the lateral slot 135 of the mandrel member 23, FIGURE 3, for locking the seat member 153 within the mandrel. The lock pin 175 is held within the slot 135 by the external annular sleeve 132 fitted around the mandrel member 23.

The pilot valve 130 further includes a head 180 threaded on an upper end portion of a longitudinally extending upper valve rod 181 connected at its lower end to a bellows 182. The head 180 has an upwardly opening blind bore or hole 183 which receives a reduced portion 184 of a valve tip 185 having an enlarged head portion 190 provided with a semispherical surface 191 adapted to engage the annular seat surface 172 to prevent upward flow into the bore portion 165 of the valve seat member. The valve tip 190 is held in the head by a lateral lock pin 192. The upper reduced portion of the head member 180 fitsin sliding relationship within the bore portion 171 of the valve seat member so that the upper valve rod moves the valve head between the closed position of FIGURE 2 and an open position at which the tip 190 is spaced downwardly from the valve seat surface 172 to allow upward flow around the valve tip into the

bores

170 and 165 of the seat member. The sleeve 132 has a lateral port 194 through which fluid flows from the exterior of the gas lift valve into the lateral slot 140. The fluid then flows from the lateral slot 140 through the ports 173 in the valve seat member and around the valve tip 190 into the bore of the valve seat member.

The upper valve rod 181 is enlarged along a lower portion 195 of a square cross-sectional configuration, FIGURE 10. The upper valve rod is further enlarged along a portion 200 having a circular cross section and provided with a reduced end portion 201 which is telescoped into an upper end portion 18211 of the bellows 182 which is suitably secured, as by silver soldering-to the bellows. A lower valve rod 202, FIGURE l-A,'includes a bellows guide rod 203 formed on an enlarged rod portion 204 which has a graduated outside diameter to provide an external annular flange 205. The rod portion 204 above the flange 205 is telescoped into the lower end of the bellows which then is suitably secured as by silver soldering to the rod portion 204 and flange to secure the bellows to and seal it around its lower end on the lower valve rod. The lower valve rod has an intermediate reduced cylindircal portion 206 and an enlarged cylindrical lower end portion 210. The bellows guide rod is fully enclosed within and functions to maintain the longitudinal alignment of the bellows 182 while being shorter than the bellows by a sufiicient amount to permit compression of the bellows to the degree necessary for the upper valve rod to retract the valve head with its tip downwardly to the opened position.

The pilot valve is disposed within the recess combination 131, a major portion of it being within the longitudinal recess 144 with the valve rod portions and 205 aligned, respectively, with the

enlarged recess portions

151 and 152. A C-shaped retainer block 211, FIGURE 10, is locked over the valve rod portion 195 by a lateral straight lock pin 212 extending across the valve rod section between the spaced parallel leg portions of the retainer. A similar C-shaped retainer 213 is held on the lower valve rod section 206 by a straight lateral lock pin 214 extending across the valve rod section between parallel leg portions of the retainer. The spacing between the legs of the C-retainer 213 is slightly larger than the diameter of the valve rod portion 206 while the lock pin 214 is positioned to engage the valve rod surface to firmly lock the retainer on the valve rod. The C-

retainers

211 and 213 are received within the

enlarged recess portions

151 and 152, respectively. Each of the C-

retainers

211 and 213 has an outer arcuate surface engaged by the inside wall surface of the sleeve 132 holding each retainer in its respective enlarged recess portion so that the retainers lock the pilot valve within the recess combination 131. For example, FIGURE 10, the retainer 211 has an outer arcuate surface 211a engaged by the inner wall surface of the sleeve 132.

The pilot valve is held against longitudinal movement within the recess combination by the flange 205 and the enlarged upper end face of the lower valve rod portion 210 which engage the upper and lower faces, respectively, of the lower C-retainer 213. The upper valve rod portion 195 is slidable a short distance through and relative to the C-retainer 211 to permit the pilot valve to move longitudinally between its open and closed positions. A spring 215 on the upper valve rod 181 is confined between a loosely fitting annular retainer 220 on the valve rod and a pair of lock nuts 221 threaded on the valve rod. The lower end face of the retainer 220 is engageable with the upper end face of the C-retainer 211 holding the lower end of the spring 215 so that downward movement of the upper valve rod 181 to move the pilot valve toward an open position effects compression of the spring. The spring 215 bearing against the lower face of the lower lock nut 221 biases the pilot valve upwardly toward its closed position.

The pilot valve is held and enclosed within its recess combination by the sleeve 132 fitting over the C-

retainers

211 and 213. The sleeve is telescopically fitted over the central mandrel member 23 with the upper end surface of the sleeve engaging the external annular downwardly facing shoulder surface 230 limiting the movement of the sleeve over the mandrel section. The sleeve is secured on the mandrel section by a set screw 231 through the sleeve into the mandrel section, FIGURE 1-A.

The recess 131 throughout the operation of the gas lift valve is subjected to the pressure within the space surrounding the valve, such as the annulus space within a well between its casing and the tubing string of whichthe gas lift valve comprises a part. The recess is comunicated with the exterior of the'valve through both the port194 in the sleeve 132 and through the lower open end of the longitudinally extending recess 144. While the pilot valve is supported by the C-

retainers

211 and 213, there are no pressure seals around the valve at the retainers and thus the annulus pressure as applied through both the lower end of the longitudinal recessand the port 194 is communicated to the pilot valve. Preferably the bellows 182 is secured to the upper and lower valve rods with the pressure within it being atmospheric, while it is to be recognized that the fluids sealed within the bellows, whichmay be either air or a desired gas, may be sealed under a pressure above or below atmospheric as desired and determined by the pressure at which the pilot valve is to move to its open position. In order for the pilot valve to move downwardly to an open position the spring 215 and the bellows 182 mustboth be compressed and thus each contribute to a determination of the force needed to open thepilot valve. Thus, the combination of the pressure sealed within the bellows and the strength of the spring 215 and the extent to which it is precompressed by the lock nuts 221 are determinative of the opening pressure of the pilot valve. Since the bellows is a sealed component, its resistance to compression remains a constant while the extent to which the spring 215 is compressed by the lock nuts 221. is varied to accommodate the valve to desired operating conditions.

The gas lift valve is incorporated into a conventional gas lift system comprising well equipment usually including a string of relatively small pipe referred to as tubing which is inserted inside a large diameter pipe called casing. Generally, several of the gas lift valves are connected at different depths along the length of the tubing, each valve comprising a short section of the tubing. Liquids are produced by the well flow through the tubing and gas or air is introduced under controlled pressures and volumes into the annulus between the tubing and casing and subsequently injected from the annulus into the tubing through a gas lift valve to aid in lifting the column of well fluids inside the tubing to the surface.

The pressure of the gas charge sealed within the bellows 182 of the pilot valve and the selection and adjustment of its spring 215 are both determined by the desired operating conditions of the gas lift valve. The pilot valve is: biased upwardly by the-force of the charge within the bellows and by the spring 215. It is also biased down wardly, when in its closed position by the annulus pressure applied over the effective area of the bellows 182 reduced by the effective cross sectional area within the line of sealing engagement between the valve tip 190 and the valve seat surface 172 and by the pressure within the seat member flow passage 165 on the valve tip exerted over an area of the valve tip defined by the line of effective sealing engagement between the tip and the valve seat surface.

Generally, the bellows charge and the adjustment of the spring are established at values at which the annulus pressure at the operating depth of the gas lift valve is slightly below the value necessary to apply a force to the pilot valve sufiicient to depress the valve to its open position against the bellows and spring. When the pilot valve is so adjusted and designed it opens responsive to the pressure of the fluids in the tubing string as explained'further below.

With the pilot valve at its closed positionthe main valve assembly also is closed for reasons explained below. The pressure of the lift gas around the gas lift valve is communicated through the

ports

72 and 73 into the an-' nular chamber j43. The lift gas pressure applies a downward force on the upwardly facing surface portions of the main valve assembly over an effective annular area defined by the line of sealing engagement of the inner and outer ring seals 112 with the outer wall surface of the both the lower open end of the longitudinal recess 144 10 mandrel member 23 and with the inner wall surface of the sleeve 44, respectively, while also exerting an upward force on the downwardly facing surface'portions of the valve assembly over an effective annular area defined be tween the line of sealing engagement of the ring seal 84 with the internal surface portion 83a on the head 45 and the ring seal 85 with the internal wall surface to the sleeve 44. Since the effective sealed 'area of the piston 52 isgreater than the effective sealed area of the head of the main valve assembly, the net effect of the lift gas pressure on the assembly is to exert a downward force. The spring also biases the main valve assembly in a downward direction toward its closed position. The' pressure of the well fluids within theilongitudinal flow pas sage 31 of the gas lift valve is communicated through the port into the annular chamber portion 43a against the lower end of the piston 52 over an annular area de fined by the line of sealing engagement of the inner and outer ring seals 113 with the outer wall surfaceof the mandrel member 23 and the inner wall surface of the sleeve 44, respectively. The pressure of the well fluids also is transmitted through the ports 71 into the annular chamber 43, and since the main valve assembly is closed with no flow occurring and thus no pressure differential across the check valve 90 the pressure is transmitted to the upwardly facing surfaces of the head 45 over an effective annular area defined between the line of sealing engagement of the ring seal 84 with the wall surface portion 83a of the head and the line of sealing engagement of the outer ring seal 85 with the internal wall surface of the sleeve 44. The effective downwardly facing annular area within the ring seals 113 exceeds the effective upwardly facing surfaces on the head 45 sealed by the ring seals 84 and 85 with a net upward force on the main valve assembly due to the pressure of the well fluids in the longitudinal flow passage. The various sealed areas of the main valve assembly together with the spring 110 are so selected that the main valve assembly remains at its" lower closed position until lift gas pressure is admitted through the pilot valve into the annular chamber portion 43a below the piston 52 to lift the piston .to its open position, as discussed below. When well fluids-in the tubing above the gas lift valve rise to a sufiicient level to exert a hydrostatic pressure on the pilot valve which is high enough when combined with the lift gas pressure, the

pilot valve moves to its open position. The hydrostatic pressure within the bore 31 is communicated to the valve tip 190 of the gas lift valve through the lateral port 115, the annular chamber portion 43a, the longtiudinal flow passage 120, the bore 133, and the flow passage 165.

A Well installation in which the gas lift valve is included may have a conventional intermitting device, not shown, which causes lift gas to be injected into the well casing annulus around the tubing string at relatively great rates for short periods of time at regularly spaced intervals of time, or, in the alternative, the lift gas is supplied at a constant rate to the casing annulus through a choke, not shown, Which limits the flow rate into the annulus to a value below the rate at which the lift gas flows from the annulus into the tubing string through a gas lift valve 20 when the gas lift valve is at its open position.

With the gas lift valve in operating position in a well installation, not shown, lift gas is introduced into the casing annulus until its pressure reaches a predetermined maximum which with the preferred form of the gas lift valve, as indicated above, is not of sufiicient magnitude to move the pilot valve downwardly to its open position. The casing annulus pressure is communicated around the pilot valve including its bellows 182 through and through the lateral port 194 of the sleeve 132 opening into the lateral slot 140.

With lift gas pressure established around the gas lift valve at a maximum predetermined value, the pressure acting over the effective area of the bellows 182 tends to collapse the bellows against the holding force of the spring 215. Since the square portion 195 of the upper valve rod is movable through the upper C-retainer 211, the bellows may pull the valve rod downwardly. The lower face of the spring retainer 220 bears on the upper face of the C-retainer 211 while the lower end of the spring 215 rests on the upper face of the retainer 220 with the lock nut 221 on the upper valve rod bearing against the upper end of the spring 215 so that the downward movement of the valve rod by contraction of the bellows is resisted by the spring 215. With the pressure charge within the bellows and the spring and its adjustments selected to hold the pilot valve on its seat at a maximum predetermined lift gas pressure, additional downward force is necessary to move the pilot valve to its open position. This additional force-is supplied by fluid pressure applied to the upper spherical end surface 191 of the valve tip 190 over an area defined within the line of sealing engagement of the tip with the valve seat surface 172. The well liquids within the tubing string rise above the gas lift valve to a height at which the hydrostatic pressure of the liquids as transmitted through the lateral port 115 and along the flow passage 165 of the pilot valve seat member against the valve tip 190 of the pilot valve supplies sufficient force in addition to the lift gas pressure on the bellows to exceed the holding force of the spring 215 and the force of the pressure of the gas sealed in the bellows. The pilot valve is then moved downwardly to its open position. The bellows 182 contracts as the upper valve rod 181 is forced downwardly compressing the spring 215 between the lock nuts 221 and the spring retainer 220 and withdrawing the valve head 180 to an open position at which the valve tip 180 is spaced below the seat surface 172. When the pilot valve moves to its open position the lift gas flowing from the annulus space through the port 194 into the slot 140 flows upwardly around the valve tip into the

flow passage

170 and 165 above the valve tip. The pressure of the lift gas from the annulus is transmitted to the exterior surface portions of pilot valve over the entire effective area of its bellows 182 and since the lift gas pressure must exceed the pressure wtihin the bore of the gas lift valve, the pilot valve is held at its lower open position against the forces of the spring 215 and the pressure within the bellows by the pressure of the lift gas.

The lift gas entering and flowing upwardly through the passage 165 flows around the ball check valve 135 into the longitudinal flow passage 120. The ball check valve is carried upwardly by the flowing lift gas within the check valve chamber 133 to the upper end of the valve chamber at its opening into the flow passage 120. The eccentric position of the flow passage 120 relative to the valve chamber prevents the seating of the ball check valve over the passage and allows lift gas to continue to flow around the check valve into the passage. The lift gas flows from the flow passage 120 upwardly into the annular space portion 43a, through the screen 121 over the passage into contact with the lower end portion of the annular piston 52. The lift gas is prevented from flowing upwardly around the annular piston by the inner and outer ring seals 113 which expand or spread apart to effect a seal within the piston around the mandrel member 23 and around the piston within the sleeve 44. The annular piston is urged upwardly by the force of the lift gas applied over an effective annular area of the piston defined between the line of sealing engagement of the inner ring seal 113 with the outer surface of the mandrel member 23 and the line of sealing engagement of the outer ring seal 113 with the inside wall surface of the sleeve 44. The upper end portion of the main valve assembly, FIG- URE 1, is in communication past the check valve 90 through the ports 71 with the lower pressure of the well fluids within the central bore of the gas lift valve over an annular area defined between the line of sealing en- 12 gagement of the ring seal 84 with the inner wall portion 83a of the head 45 of the main valve and the line of sealing engagement of the outer ring seal 85 with the internal wall surface of the sleeve 44. The upward force of the lift gas pressure on the piston 52 is greater than the downward force of the pressure of the fluids within the bore of the gas lift valve on the head of the main valve assembly which is moved upwardly against the spring 110 to an open position.

At the open position of the main valve assembly the seat surface 83 on the head 45 is spaced above the mandrel seat surface 82 so that the lift gas from the annulus flows inwardly through the sleeve port 72, the main valve assembly ports 73, and around the ring seal 84 within the downwardly and outwardly tapered lower internal surface portion 83a of the valve assembly head. The lift gas flows between the spaced seat surfaces 82 and 83, upwardly around the portion 22a of the upper mandrel member 22 within thesleeve 45 into the annular downwardly opening recess of the slotted retainer 92. The lift gas then flows radially outwardly into the lower end portions of the longitudinal slots 95 in the retainer and upwardly in the slots 95 into the annular space 43 above the retainer, The flowing lift gas collapses the flexible check valve 90 inwardly around the upper mandrel member flowing then inwardly through the mandrel ports 71 into the central bore 31 of the gas lift valve. As the lift gas flows past the head 45 it flows through a slightly restricted annular flow passage between the downwardly and outwardly convergent surface portion 83a within the main valve assembly head and the ring seal 84 thereby producing a zone of slightly reduced pressure within the flowing lift gas above the head 45 within the sleeve 44. Thus with the pressure reduction in the upwardly flowing lift gas there is a pressure differential across the valve head. The upward force of this pressure differential exceeds the force of the spring which is compressed between the upper end piston surface 111 and the lower end surface 105 of the upper mandrel section and holds the main valve open. The upward and downward forces exerted by the lift gas on the piston are now substantially equalized so that as long as the force resulting from the pressure differential across the main valve exceeds the resistance of the spring 110, the main valve remains at its upper open position. The lift gas enters the annulus space 430 below the annular piston 52 at a rate of flow through the passageway 120 which so far exceeds the bleed off of the gas through the port into the flow passage 31 that the pressure within the space 43a is maintained at a value substantially equal to the lift gas pressure above the piston.

The effective area of the ports 71 in the upper mandrel member through which the lift gas flows into the longitudinal bore of the gas lift valve is relatively large so that the lift gas enters the column of well fluids at a substantial rate. The lift gas flows into the column of fluids displacing the fluids upwardly in the tubing string to the surface. The lift gas is introduced into the tubing by the gas lift valve at a rate sufficient to establish a column or slug of gas within the fluid column in the tubing string of sufficient volume and at a sufficient pressure to displace the liquid column in the tubing string above the gas lift valve to the surface and effect its production from the tubing string. As the production fluids flow from the tubing string the pressure within the string at the gas lift valve is progressively reduced due to the shortening of the length of the column of liquid above the gas slug. Since the flow rate into the tubing string through the gas lift valve is greater than the rate at which gas is supplied to the casing, the casing or annulus pressure is re duced. When the pressure of the lift gas within the casing annulus drops to a level at which the force on the pilot valve resulting from such pressure over the effective area of the bellows 182 is below a predetermined level the spring 215 together with the pressure of the confined charge within the bellows expands theibellows liftingthe upper valve rod 181 upwardly until the pilot valve is at its closed position with the tip 190 of the valve seated against the 'seat'surface 172 in the valve seat member 153: The supply of lift gas through the pilot valve to the annular'chamber portion 43a is cut off. The lift gas holding the piston 52 and thus the main valve assembly at its open position bleeds off through; the port 115 into the central bore of the gas lift valve since'the pressure within the central bore is lower than that of the lift'gas in the. annulus and continues to decrease as the well fluids flow from the tubing at the surface. When the pressure below the annular piston reaches a predetermined value, the force exerted by the spring 110 and the effective downward force of the lift gas on the piston 52 is effective to move themain valve assembly downwardly against the effective upward force of the pressure differential of the lift gas across the head 45, until the valve seat surface. 83 on the head 45 engagesthe seat surface 82 of the upper mandrel member closing the main valve.

The gas lift valve remains closed until the pressure of the lift gas within the casing again reaches a predetermined level and the column of well fluids in the tubing string rises above the gas lift valve to a sufficient height that the hydrostatic pressure from it coupled with the pressure of the lift gas is sufficient to move the pilot valve to its open position to repeat the above described sequence. As previously indicated, the lift gas is supplied to the casing at the surface either through a choke at a predetermined rate or through an intermitting device which causes the injection of lifting gas at regularly spaced intervals for short periods of time at relatively great rates of injection. The gas lift valve functions in the same manner irrespective of the way the lift gas is supplied to the casing. With either form of lift gas supply the gas lift valve permits the lift gas to be injected into the-tubing string at a rate which is sufficiently high that it displaces the column of fluids to the surface through the tubing string and as the column is produced at the surface a sufficient volume of lift gas flows from the. casing annulus into the tubing string to reduce the casing annulus pressure to the value which permits the pilot valve to move back to'its closed position and .then permits closure of the main valve of the gas lift valve.

While the pilot valve opens responsive to a combination. of the annulus and tubing pressure and since it is designed and adjusted to remain closed at maximum casing. annulus pressure, it is thus necessary that the liquid column in the tubing string rise to a predetermined level for opening the pilot valve. The pilot valve is therefore operable responsive to the tubing pressure. On the other hand, however, once the pilot valve is open it is held open by a force applied over the entire effective area of the bellows by the annulus pressure and thus it closes responsive to the decline of the annulus or lift gas pressure to a predetermined value.

Numerous variations may be made to change the operating characteristics of the gas lift valve such as varying the effect of the casing annulus and tubingpressures on the opening and closing of the pilot'valve. The effect of the liquid column within the tubing string above the gas lift valve on the pilot valve is reduced by reducing the diameter of the line of contact between the pilot valve tip 190 and the seat 172 so that the pressure within the tubing string as applied against the tip of the pilot valve produces less downward force on the pilot valve relative to the force effected by the pressure of the lift gas on the bellows 182. l

The pilot valve of the gas lift valve may be made operable by use of .only the. bellows 182 thereby eliminating the spring 215. In such a modified form-of the pilot valve,

the bellows --is charged to a pressure. to apply a force within the bellows sufficient to hold the pilot valve closed until the combined forces of the pressure of the lift gas and thehydrostatie pressure from tlie eolumn of liquid within the tubing string above the gas lift valve exceeds, a predetermined value. Such a form of pilot valve is to be less preferred, however, than the form illustrated usingthe spring 115. Controljof the charging pressure and the effective area of the bellows is difficult and thus establishment of the operating conditions of the pilot valve utilizingthefbellows alone is more diflicult than providing the flexibility of control inherent in the use of the spring 215 with the lock nuts 221 so that the compression of the spring is adjusted by the position of the lock nut on the upper valve rod. Further, the use of the spring 215 for effecting adjustment of the opening and closing pressures of the pilot valve provides a valve which is adjustable for .ise under varying conditions and at various depths, whereas, when the bellows alone is employed, the valve is used under operating conditions with no flexibility of adjustment being available.

It will now be seen that an improved well tool has been described and illustrated.

It will :be further seen that there has been described and illustrated a new and improved well too] for removing fluids produced by a well through an innerwell tubing disposed in a casing of the well wherein gas from an annular flow passage between the casing of the well and the inner well tubing provides power for transporting the fluids to the surface through the inner well tubing.

It will also be seen that there has been described and illustrated a new and improved well tool for automatically removing well fluids from the bore of a wellincluding a valve which opens intermittently to permit gas, flow from an annular flow passage between a well casing and an inner well tubing into the well tubing to aid in lifting fluids present in the well tubing above the valve to the surface.

It will be further seen that there has been described and illustrated a well tool for use in a well having a casing and an inner well tubing telcscoped therein including a valve providing communication between the interior of the well tubing and the annular space between the casing and the well tubing, such valve being responsive to the pressure both within the tubing and the annular space to permit fluid flow from the annular space into the tubing when the force on the valve resulting from the combined tulliing and annular pressures exceeds a predetermined va ue.

It will be further seen that a new and improved gas lift valve has been described and illustrated, such valvebeing connectable in a string of tubing to form a section thereof and having a central longitudinal passage or bore of a diameter no smaller than thebore of the tubing.

It will also "be seen that a new and improved gas lift valve having a relatively small outside diameter has been described and illustrated.

It will be further seen that the gas lift valve is. of concentric construction and is connectible in a tubing string to form a section thereof providing an internal longitudinal flow passage having a diameter no smaller than the drift diameter of the tubing with which the valve is connected and an annular flow passage concentrically disposed about the longitudinal flow passage and having port means communicating the longitudinal flow passagewith the annular flow passage and the annular flow passage with the exterior of thegas lift valve and a concentric annular valve member in the annular flow passage for controlling the flow of lift gas from the exterior through the annular flow passage into the longitudinal flow passage of the valve responsive both to the pressure within the annular flow passage and the pressure exterior of the gas lift valve. L

It will also be seen that the gas lift valve has an annular valve member movable between open and closed posi tions by an annular piston biased in one direction toward a closed position by spring means and fluid pressure and movable in the other direction to an open position responsive to a combined predetermined annulus and central bore pressure.

It will be further seen that the gas lift valve includes operative components which are not exposed either to the interior or the exterior of the valve structure thereby minimizing damage by well tools, flow cutting, erosion, high pressures, and other similar forces.

It will be further seen that the gas lift valve has a concentric flexible check valve member positioned downstream of a concentric valve member in the flow path between the concentric valve member and ports admitting fluid into the central longitudinal flow passage of the valve whereby fluid under pressure is not trapped between the valve member and the exterior of the valve body structure.

It will also be seen that the gas lift valve has a concentric valve member movable by a concentric piston actuated responsive to gas admitted to a concentric chamber by a pilot valve housed in a wall portion of the body structure of the gas lift valve.

It will be further seen that the gas lift valve admits lift gas to its central longitudinal flow passage from the exterior of the valve at relatively high flow rates.

It will additionally be seen that the pilot valve of the gas lift valve in its preferred form is biased toward closed position by both the pressure of gas sealed within a bellows connected in the pilot valve and an adjustable spring.

It will also be seen that an alternate form of the gas lift valve includes a pilot valve biased toward a closed position by the pressure of gas sealed within a bellows included in the pilot valve.

While the gas lift valve has been illustrated and described as being used with its main valve assembly 42 at an upward position and its pilot valve 130 at a downward position, it is to be understood that the gas lift valve is not limited to use at such orientation. The gas lift valve is used equally Well at a position inverted from that illustrated, with its main valve assembly downward and its pilot valve upward. This latter orientation of the gas lift valve is preferred under well conditions which may be expected to produce sand which may pass into the flow passages leading to the check valve and affect its operation particularly by collection in the check valve chamber 133. 'It will be apparent that when the gas lift valve is so oriented the ball check valve 135 will normally rest due to gravity along the end surface of the check valve cham; her 133 through which the flow passage 120 opens into the chamber. Otherwise, the check valve and all other components of the gas lift valve function identically as described above.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A gas lift valve adapted to be included in a tubing string positioned in spaced relationship within a well bore defining a central longitudinal flow passage through said well bore and an annular flow passage within said well bore around said tubing string, said valve functioning to control admission of lift gas from said annular space into said tubing string for displacing well fluids to the surface through said tubing string and comprising: mandrel means having a central longitudinal flow passage extending therethrough in communication with said tubing string when said valve is included in said tubing string; sleeve means supported in concentric spaced relation on said mandrel means defining an annular chamber having closed opposite ends and providing an annular flow passage around said mandrel means within said sleeve means; said mandrel means having ports therein communicating said annular chamber with said longitudinal central flow passage; said sleeve means having ports longitudinally spaced v 16 from said mandrel means ports communicating the exterior of said sleeve with said annular chamber; an external annular flange providing an annular valve seat around said mandrel means within said annular chamber between said mandrel means ports and said sleeve means ports; an annular valve member longitudinally slidable within said annular chamber between said mandrel means ports and said valve seat on said mandrel means, said annular valve member having an internal annular valve seat surface adapted to engage said valve seat surface of said mandrel means; annular piston means slidably positioned within said annular chamber on the opposite side of said external valve seat on said mandred means from said annular valve member; connecting means between said annular piston and said annular valve member where in said valve member is movable longitudinally between opposite end positions by said piston; resilient means confined between said piston and said mandrel means biasing said piston away from said mandrel means valve seat surface whereby said annular valve member is biased toward closed position; said mandrel means having fluid flow passage means communicating the exterior of said gas lift valve with said annular chamber between said annular piston (and a first end of said chamber whereby fluid pressure is communicated from said annular flow passage in said well bore into said annular chamber for displacing said piston toward said valve seat on said mandrel means for moving said annular valve member toward open position; a pilot valve supported in said flow passage means communicating the exterior of said mandrel means with said annular chamber for controlling the flow of fluid from said annular flow passage into said annular chamber for moving said annular valve member to open position; and means connected with said pilot valve for biasing said valve toward closed position.

2. A gas lift valve as defined in claim 1, wherein said mandrel means is provided with port means communicating said longitudinal central flow passage with said annular chamber between said piston and said first end of said chamber, said flow passage means communicating said annular chamber with the exterior of said valve being adapted to conduct fluid at a flow rate substantially greater than the rate of fluid flow through said port means communicating said annular chamber with said longitudinal central flow passage.

3. A gas lift valve as defined in claim 2, wherein said pilot valve includes a bellows charged with a compressible fluid to a predetermined pressure for biasing said pilot valve toward closed position.

4. A (gas lift valve as defined in claim 3 wherein said pilot valve also includes adjustable spring means adapted to bias said pilot valve toward closed position.

5. A gas lift valve as defined in claim 4, wherein said pilot valve is operable responsive to a combination of forces effected by fluid pressures communicated from said longitudinal central flow passage and from the exterior of said valve, said pilot valve being adapted to move to open position responsive to a pressure in excess of said pressure exterior of said gas lift valve.

6. A gas lift valve as defined in claim 1 including an annular flexible check valve supported within said annular chamber between said mandrel means and said outer sleeve means between said annular valve member and said mandrel means ports and adapted to expand into sealing relationship with an. inside wall surface portion of said outer sleeve means responsive to a pressure differential across said check valve to prevent fluid flow in said annular chamber in a direction from said mandrel means ports toward said sleeve means ports.

7. A gas lift valve as defined in claim 1, wherein said annular valve member, is in concentric spaced relation around said mandrel means whereby at openposition said valve member defines with an annular wall surface portion of said mandrel means a restricted annular orifice having a cross sectional area less than the effective cross sectional areas of each of said mandrel means ports and said outer sleeve means ports wheneby when fluid flows through said annular chamber from said outer sleeve means ports to said mandrel means ports a pressure differential is elfected across said annular valve member biasing said valve member toward open position.

8. A gas lift valve as defined in claim 7, including an annular flexible check valve supported in said annular chamber between said mandrel and said outer sleeve between said annular valve member and said mandrel means ports to prevent flow of fluid through said annular chamber in a direction from said mandrel means ports toward said sleeve means ports.

9. A gas lift valve as defined in claim 8, including a pilot valve supported in said flow passage means between said annular chamber and the exterior of said gas lift valve for controlling fluid flow from exterior of said valve into said annular chamber between said first end of said chamber and said piston, said pilot valve being biased toward closed position by an adjustable spring and a bellows charged with a compressible fluid to a predetermined pressure level.

10. A gas lift valve as defined in claim 9, wherein said pilot valve also includes a spring biasing said valve toward closed position.

11. A gas lift valve as defined in claim wherein said pilot valve is adapted to open responsive to a pressure in excess of the pressure in said annular space of said well bore around said gas lift valve.

12. A gas lift valve for inclusion in a tubing string positioned in a well bore in spaced relation with the wall of said well bore defining a central flow passage in said well bore through said tubing string and an annular flow passage within said well bore around said tubing string, said gas lift valve controlling flow of fluid from said annular flow passage into said tubing string to displace Well fluids in said tubing string to the surface end of said well bore, said gas lift valve comprising: a mandrel having a longitudinal central fluid flow passage therethrough substantially equal in diameter to and communicating at opposite ends with said tubing string when included in said tubing string; "an outer sleeve positioned in concentric spaced relationship on a reduced upper portion of said mandrel defining between said sleeve and said mandrel an annular chamber closed at opposite ends; said mandrel having port means communicating said annular chamber near a first end thereof with said longitudinal flow passage through said mandrel; said sleeve having port means in longitudinal spaced relation relative to said mandrel port means communicating the exterior of said sleeve with said annular chamber; said sleeve port means, said annular chamber, and said mandrel port means defining an exclusive flow path from exterior of said gas lift valve through said annular chamber into said longitudinal central flow passage; said mandrel having an external annular enlarged portion within said annular chamber providing an annular seat surface within said annular chamber facing said first end of said annular chamber between said sleeve port means and said mandrel port means; seal means supported in an external annularrecess in said enlarged portion of said mandrel; an annular check valve secured within said annular chamber around said mandrel between said mandrel port means and said annular seat surface for preventing fluid flow through said annular chamber in a direction from said mandrel port means toward said seat surface; 'an annular longitudinally slotted retainer secured on said mandrel within said annular chamber around and securing said check valve providing an outer seat surface for a portion of said check valve and defining longitudinal circumferentially spaced flow passages within said annular channber to permit fluid flow past said retainer within said chamber; a main valve slidably positioned within said annular chamber for controlling fluid flow through said annular chamber between said longitudinal central flow passage and the exterior of said gas lift valve through said sleeve port means and said mandrel port means, said main valve comprising an annular head between said mandrel seat surface and said retainer, a tubular connector secured to said head, and an annular piston secured with said connector between said sleeve port means and a second end lOf said annular chamber; said head of said main valve having an internal annular seat surface engageable with said annular seat surface on said mandrel for limiting the movement of said main valve toward said second end of said annular chamber and the upper end of said head being engageable with said annular retainer for limiting the movement of said main valve toward said first end of said annular chamber; said head of said main. valve having an internal annular tapered wall portion engageable with said seal means around said enlarged portion of said mandrel when said valve assembly is at an end position toward said second end of said chamber for preventing fluid flow through said annular chamber, said internal annular wall portion of said head being spaced from said mandrel and said seal means when said main valve is moved toward said first end of said annular chamber defining an annular flow restriction between said head and said mandrel of an effective cross sectional area less than the total effective cross sectional area of each of said mandrel port means and said sleeve port means for effecting a pressure differential across said head for biasing said main valve toward open position when fluid is flowing through said annular chamber between said head portion and said mandrel; said connector of said main valve having port means aligned with said sleeve port means permitting fluid flow through said sleeve port means and said connector port means into an annular space defined around said mandrel within said connector and said head of said main valve; means holding said valve assembly against rotation within said annular chamber while permitting said assembly to move longitudinally within said chamber to maintain said port means in said connector in alignment with said sleeve port means whereby fluid pressure is communicated into said connector at all longitudinal positions of said main valve; spring means secured between said piston and said mandrel biasing said main valve toward closed position; said piston being provided with internal and external seal means effecting fluid seals between said piston and the internal and external surfaces of said sleeve and mandrel; said mandrel having bleed port means communicating said annular chamber between said second end of said chamber and said piston with said longitudinal central flow passage through said mandrel; said mandrel I aving flow passage means communicating the exterior of said mandrel with said annular chamber between said second end of said chamber and said piston for conducting fluid from around said mandrel into said annular chamber to displace said piston toward said first end of said chamber for moving said main valve to an open position; said last mentioned fluid flow passage means being adapted to conduct fluid into said annular chamber at a rate substantially in excess of the flow rate of said bleed port and conducts fluid from said annular chamber into said longitudinal central flow passage through said mandrel; and a pilot valve supported in said last mentioned fluid flow passage means in said mandrel for controlling fluid flow from exterior of said mandrel into said annular chamber between said second end of said chamber and said piston.

13. A gas lift valve as defined in claim 12, wherein said pilot valve is operable responsive to a combination of forces effected by the pressure of fluid within said longitudinal central flow passage and around said gas lift valve.

14. A gas lift valve as defined in claim 12, wherein said pilot valve includes a bellows having sealed therein a charge of compressible fluid at a predetermined pressure level for biasing said pilot valve toward closed position.

15. A gas lift valve as defined in claim 14, wherein said pilot valve also includes spring means biasing said valve toward closed position.

16. A gas lift valve as defined in claim 15, wherein said pilot valve is adapted to open responsive to a fluid pressure in excess of the pressure exterior of said gas lift valve.

17. A gas lift valve as defined in claim 14, including a ball check valve supported in said fluid flow passage connecting said annular chamber between said second end of said chamber and said piston with the exterior of said gas lift valve for preventing back flow of fluids through said pilot valve from said longitudinal central flow passage through said mandrel.

References Cited UNITED STATES PATENTS Lamb 137-155 Lilly 137-155 Canalizo 137-155 Waters 137155 Thrash 137-155 ALAN COHAN, Primary Examiner.

Claims

1. A GAS LIFT VALVE ADAPTED TO BE INCLUDED IN A TUBING STRING POSITIONED IN SPACED RELATIONSHIP WITHIN A WELL BORE DEFINING A CENTRAL LONGITUDINAL FLOW PASSAGE THROUGH SAID WELL BORE AND AN ANNULAR FLOW PASSAGE WITHIN SAID WELL BORE AROUND SAID TUBING STRING, SAID VALVE FUNCTIONING TO CONTROL ADMISSION OF LIFT GAS FROM SAID ANNULAR SPACE INTO SAID TUBING STRING FOR DISPLACING WELL FLUIDS TO THE SURFACE THROUGH SAID TUBING STRING AND COMPRISING: MANFDRL MEANS HAVING A CENTRAL LONGITUDINAL FLOW PASSAGE EXTENDING THERETHROUGH IN COMMUNICATION WITH SAID TUBING STRING WHEN SAID VALVE IS INCLUDED IN SAID TUBING STRING; SLEEVE MEANS SUPPORTED IN CONCENTRIC SPACED RELATION ON SAID MANDREL MEANS DEFINING AN ANNULAR CHAMBER HAVING CLOSED OPPOSITE ENDS AND PROVIDING AN ANNULAR FLOW PASSAGE AROUND SAID MANDREL MEANS WITHIN SAID SLEEVE MEANS; SAID MANDREL MEANS HAVING PORTS THEREIN COMMUNICATING SAID ANNULAR CHAMBER WITH SAID LONGITUDINAL CENTRAL FLOW PASSAGE; SAID SLEEVE MEANS HAVING PORTS LONGITUDINALLY SPACED FROM SAID MANDREL MEANS PORTS COMMUNICATING THE EXTERIOR OF SAID SLEEVE WITH SAID ANNULAR CHAMBER; AND EXTERNAL ANNULAR FLANGE PROVIDING AN ANNULAR VALVE SEAT AROUND SAID MANDREL MEANS WITHIN SAID ANNULAR CHAMBER BETWEEN SAID MANDREL MEANS PORTS AND SAID SLEEVE MEANS PORTS; AN ANNULAR VALVE MEMBER LONGITUDINALLY SLIDABLE WITHIN SAID ANNULAR CHAMBER BETWEEN SAID MANDREL MEANS PORTS AND SAID VALVE SEAT ON SAID MANDREL MEANS, SAID ANNULAR VALVE MEMBER HAVING AN INTERNAL ANNULAR VALVE SEAT SURFACE ADAPTED TO ENGAGE SAID VALVE SEAT SURFACE OF SAID MANDREL MEANS; ANNULAR PISTON MEANS SLIDABLY POSITIONED WITHIN SAID ANNULAR CHAMBER ON THE OPPOSITE SIDE OF SAID EXTERNAL VALVE SEAT ON SAID MANDRED MEANS FROM SAID ANNULAR VALVE MEMBER; CONNECTING MEANS BETWEEN SAID ANNULAR PISTON AND SAID ANNULAR VALVE MEMBER WHEREIN SAID VALVE MEMBER IS MOVABLE LONGITUDINALLY BETWEEN OPPOSITE END POSITIONS BY SAID PISTON; RESILIENT MEAND CONFINED BETWEEN SAID PISTON AND SAID MANDREL MEANS BIASING SAID PISTON AWAY FROM SAID MANDREL MEANS VALVE SEAT SURFACE WHEREBY SAID ANNULAR VALVE MEMBER IS BIASED TOWARD CLOSED POSITION; SAID MANDREL MEANS HAVING FLUID FLOW PASSAGE MEANS COMMUNICATING THE EXTERIOR OF SAID GAS LIFT VALVE WITH SAID ANNULAR CHAMBER BETWEEN SAID ANNULAR PISTON AND A FIRST END OF SAID CHAMBER WHEREBY FLUID PRESSURE IS COMMUNICATED FROM SAID ANNULAR FLOW PASSAGE IN SAID WELL BORE INTO SAID ANNULAR CHAMBER FOR DISPLACING SAID PISTON TOWARD SAID VALVE SEAT ON SAID MANDREL MEANS FOR MOVING SAID ANNULAR VALVE MEMBER TOWARD OPEN POSITION; A PILOT VALVE SUPPORTED IN SAID FLOW PASSAGE MEANS COMMUNICATING THE EXTERIOR OF SAID MANDREL MEANS WITH SAID ANNULAR CHAMBER FOR CONTROLLING THE FLOW OF FLUID FROM SAID ANNULAR FLOW PASSAGE INTO SAID ANNULAR CHAMBER FOR MOVING SAID ANNULAR VALVE MEMBER TO OPEN POSITION; AND MEANS CONNECTED WITH SAID PILOT VALVE FOR BIASING SAID VALVE TOWARD CLOSED POSITION.