claim: 1. An apparatus for gas liftiiig liquid comprising a vertical liquid conduit, a gas conduit, a -as chamber between said liqliid conduit and said gas conduit, the 15 volume of said gas chan-lber being substa-@it:ially less than the volume of said gas conduit, an orifice between said gas cor@du-it and said gas chamber to meter gas from said conduit into said gas chamber, a gas outlet from said gas chamber leading into said ver'tical liquid conduit, the flow 20 capacity of said outlet being siibstantially -reater than the flow capacity of said orifice, and valve means to close said outic when the pressure in said gas ebamber is below a predetermined pressure and to open said outlet when the pressure in said gas chamber is above said predeter25 mined presstire. 2. An apparatus for gas liftin.- liquid coniprising a vertical 1:.quid conduit, a gas conduit, a .-as chamber between said liquid conduit and said gas conduit, the volume of said gas chamber being substantially less than 30 the voluriie of said gas conduit, an orifice between said gas conduit and said gas chl@mber to meter gas from said gas conduit into said gas chamber, a gas outlet from said gas chamber leading into said vertical liquid conduit, the flow capacity of said gas otitlet being substantially greater 35 than the -iqow capacity of said orilice, a valve me@-nber adapted to close said gas outlet, and a pres sure-se-iisitive valve aettiator in fluid communication with said gas chamber to operate said valve member, said valve actuator bein-, adapted to open said -as outlet when the pressure 40 in said gas chamber is above a preset opening pressure a-@id to close said gas olitiet when the pressure in said gas chamber is below a preset closin- pressure. 3. An apparatus for -as lifting liquid from a well comprising a casi-iig in sa;d well, a production conduit i-ii said 45 casing, the annular space between said casing and said productio@i conduit forming a gas conduit, an upper packer iTi 'he said annular space at the lower end of said gas condiiit and near the lbwer end of said production conduit, a lower packer in said annular space below said upper @ro packer, said lower packer and said upper packer forming wit'i said annular space a gas chamber, an orifice in said upper packer to meter fluid frorn said gas conduit into said g,,is chamber, a gas outlet from said gas chamber into said production conduit, the flow capacity of said gas 55 o-atlet bein.a substantially greater than the flow capacity of said orifice, aiid a pressure-sensitive valve means to open and close said otitlet, said i7alve means being actiated to close said -as outlet when the pressure in said gas chamber is below a preset closiqg pressure aiid to open said gas 60 outlet when the pressure in said gas chamber is above a preset openin@ pressure, said preset opening pressure being higher than said preset closing pressui,e. 4. A-ii apparatus for -as lifting liqtiid from a well comprising a ttibiiig, a cross-over fitting near the lower end 65 of said ti-ibing, a gas conduit extending down into said well to said cross-over fitting, a fluid bypass longitudinally through said cross-over fitting, a radial opeiiing in said cross-over fittin.- to admit gas from said gas conduit into said tubin---, a gas lift valve in said cross-over fitting, a gas 70 chamber in said gas lift valve, an orifice in said gas chamber in comrnunication with said radial opening to meter @as iito said gas chamber, an outlet from said gas chamber to said tubing, the flow capacity of said outlet be.;ng subs.tantiall,y greater than the flow capacity of said 75 orific-1, a valve member to close said outlet, and pressuresensitive motor means L'Or actuating said valve member, said motor means being ii commun;cat:oii with said gas chamber and adapted to close said outlet when the pressure in said gas chamber is below a preset closing pressure and to open said outlet when the pressure in said gas chamber is above a preset opening pressure. 5. A gas lift valve assembly comprising a pressure acttiated valve means, a gas chamber enclosin.- said valve means, an oi-ifice to meter .-as into said chamber, an outlet fi:om said gas chamber, the flow capacity of said outlet bein.- substantially greater than the flow capacity of said orifice, said valve means being adapted to close said outlet, a fluid motor conriected to said valve means, said fluid rnotor being actuated to move said valve means in one direction and close said outlet when the pressure in said gas chamber is below a preset closing pressure and bein- actuated to move said valve means in another direction and open said outlet when the pressure in said gas chamber is above a preset opening pressure. 6. A gas lift valve according to claim 5 wherein said preset opening pressure is greater than said preset closing pressure. 7. A gas lift valve according to claim 5 wherein said fluid motor comprises an enclosed variable volume chamber having one movable head, said movable head beiiig in fluid communication with said gas chamber and being connected to said valve means, and an expansible fluid 'in said variable volume chamber whereby the volume of said variable volume chamber and 'Lhe pbs,'@tion of said valve member is controlled by the pressure in said gas chamber. 8. A retrievable gas lift valve for injecting slu.-s of gas into a production conduit within a well at high frequency, said well having a casing and a production conduit therein, a cross-over fitting at the lower end of said production conduit, the annular space between said production cont and said cas ng forming a gas conduit in said wel down to said cross-over fitting, a radial opening in said cross-o-ver fitting to admit gas fro-m said gas conduit into said production conduit, a packer in said annular space between said casin-, and said production conduit below said radial opening, a fluid bypass longitudinally through said cross-over fitting providing separate fluid ccmmunication along said production coiiduit, said fluid bypass including an inilet port below sa-ld radial opening, an outlet port above said radial opening, r-qearis to separate fluid in said fluid bypass from the gas in said radial open ng, aiid shoulder means on the inside of said crossover fitting, said retrievable gas lift valve comprisliig an elongat@d cylindi-ical body, means including said body forming a gas chamber in said valve, an orifice in said chamber providing fluid communication betw@-en said gas conduit aiid said gas chamber when said gas lift valv-- is anchored in operating position in said crossover fittiilg, a gas outlet in said chamber, the flow capacity of said -as outlet being substantially greater than the flow capacity of said orifice so that the pressure variation within said gas chamber is substantially greater than the pressure variation ir, said gas conduit, valve means to close said gas outlet, motor means in fluid communication with said gas chamber coiinected to said valve means to move said valve means and open and close said gas outlet, said valve means being raised by said motor means to . open said gas outlet when the pressure in said gas chamber is above a preset opening pressure and being lowered to close said gas outlet when said pressure in said gas chamber is below a preset closing pressure, packing means on said body above and below said orifice adapted to form a fluid seal with said cross-over fitt-ing above and below said radial opening, and resil-'@ent latch mearis on said body adapted to cooperate with said shoulder means aiid anchor said retrievable gas lift valve in said operating position in said cross-over fitting. 9. An apparatus for gas lifcing I:Aquid from a well

3,016,844 9 comprising a production coiduil, a cross-over f@tting at the lower end of said production conduit, a radial openiig through the wall of said cross-over fitting, a gas conduit extending i-rom the surf,-,ce down thro-agh said well to said rad@,,il ope@iing, a well fltiid inlet to said - production cof,- 5 dii',t, a standing vaive in said well flu@.d inlet, a fluid pass',Igo from said radial ope-nin.- into s aid productior. conduit, an a-Lixil@ary valve in said il@uid passa,@e, 2ii atixiliary valve fluid motor to open indclose said alixiliary valve, a-@id a pilot gas lift valve for controlling said fli-iid motor 10 to open and close said fltiid passage, said pil-ot gas iift valve inellidipg a gas cha@iiber, an orifice connecting said gas cliamber Nvith said gas c.6nduit to meter gas from said gas condi-i-I'L into said gas chamber, an outl@et from said gas chq,mber to said fluid motor, an exhaust opening froin 15 said flu,.d motor to said prodtiction cond,,i:@t, the flow cappcity ol. said exhaast opening bein.- greater thati ',he f i.low cipacity o' said orifice but less than @he flow capacity of said olitlet. a valve member adapted -to open and close said oiitlet, a seal--d variable volume Dressurized bellows 20 havin.- one er@d fixed to said -as chamber and a movable end connected to said valve me-tuber and in fluid comniunication -,vit-h the gas in said gas chamber fcr opetiing saicl otillet when tlle pressure in said gas chamber is greater than a preset opening pressure and for clos;ng said 25 outlet when the pressure in said gas chamber is below a preset closing pressure. 10@ A retrievib'@e gas lift valve comprisng an elongated cylindrical body, means including said body and a lower head formiug a first gas chamber in said body, an orifice 30 in th,- wall of said body to meter gas into said first gas c.hamber, a-@i outlet in said lower head, the flow capacity of said outlet being substantia.Ily greater than the flow r,apacity of said orifice,,a valve member normally closing said outlet, an expa-@idable sealed bellows within s,,iid first 35 ,,as chamber liaving one end fixed to said frst gas chamber a,.id a movable end connected to said valve member to raise said valve member and open said outl@et when the press,,jre in said first gas chamber is above a preset openi-ig pressure, an auxiliary valve gas chamber in said body 40 below said lower bead and incl@uding a piston in fluid commr.nication with said outlet, ayi at-lxiliary fitiid passa.-e tbrotigh said body below said piston, said auxili-,iry fluid passage includirg an @.'nlet D.-rt iii the wall of said body and an outlet port in the bottom of said body, ai atixiliary 45 v?,Ive member contiected to said piston and adapted to seat oq said outlet port and close said a,,ixiliary fluid passage, resilient means normally -urgiiig said auxiliary valve member to close said outlet port, and an exhaust opening through said piston apd auxiliary valv-- member, the flow 50 capacity of said exhaust open;ng being greater than the @low cai)acity of said oi-ifice but less than the flow capacity of said outlet whereby gas i'rom a hi,-h-pressure sotirce in f@uid comir@unication with said orifice metered into said first gas cbamber wilt build up a pressure in said first gas 55 chamber as great as said preset oper.-i,.ig pressure to i'aise said valve member -and open said outlet, and when said outlet is open the gas in said first gas chamber is discharged through said outlet into said auxiliary valve gas chamber to move said piston and said auxiliary valve 60 member and open said auxiliary fluid passage. 10 11. An apparatus fc,,r gas liftin.- liquid from a wellcomprisin.- a casing i-@i s-aid well, a tubing iii said well, a cross-over fitt;ng Tiear the lower eiid of said tubitig below the working liquid level in said well, a radial opeii-@ig through said cross-over the aipular space between said tubiiig and said casin.- a gas conduit in said well d@-vi-i to said ,:adial opeiir,-, an o,-lter shell or, said cross-over fitting, an iniaer sleeve in said cross-over fitting, a longitudinal v!ell fluid passa.qe between said orter shell and said inner sleeve, a bottom port conriecting the inside of said tlbin.@ to said well f@iiid passage be'ow said radial opening, an upper port coiinecl,ing said well fluid passage to the inside of said tubin.- above said radial openi-@ig, an upper and a lower shotilder on tiie i-.Qside <)f said iiiner sleeve, and a retrievable gas lift valve in sa@,'d cross-over -@ittirig, s@lid gas lift valve -liaiiing an clon.-:-,ted cyl,@'r@drical bc@dy adapted to Qt in said ir@--ic-,r sleeve and rest o-Ti said tidper shoulder, resilient latch meaiis on said body adapted to oooperate with said lower slioulder @@C) anchor said gas '@ift valve -in said cross-over filtiiig, me,,i:.,is including said body ard a lower gas chamber head formin-.@ a first aas ch,,)mbr-r in said gas lift valve, an ori'fice through Ilie wall of said gas clianiber in fluid cona,-nunic-,tion when said body rests on said upper shoulder with said radial opening, a - as outl,-t in s,@id ower gas cliamber head, a valvo member for opeii-.ng alid closing s-,iid outlet, an -xpandable sealed bcllc,,v,,s v-@ithiii said iirst gas chamber having one end fixed to said first gas chamber !and a movable end connected to said valve mei-iber for actuating said valve member to oper and close said outlet, an auxiliary -as valve cb amber '@ii said body bclow said lower gas chamL-,-r head i-tic!uding a pistoii in one end of said auxil;ary gas valve said auxiliary gas valve chamber being in fluid com-munication with said gas outlet, an auxiliary gas i)assage @hrougli said retrievable gas lift valve havi.,ig an itilet port in fluid comniunication with said radi@,l opening a-tid an outlet port in ffuid comrnunication with the ins;de of said tubing, En auxiliary valve member connected to said piston and ada-Dted to seat on and close said outlet port, resilient means urging said auxilia,@-y valve member nornially to close said outlet port, and an exhaust openirg in said iuxiliary valve n-iember providing a fltiid from said auxiliary valve gas chapiber into said tubing, said exhaust opening having a f .low capacity greater than tLe - flow capacity of said orifice but less tha-ti the flow cai)acity ot said first gas chamber outlet whereby said auxiliaryfluid passage is intermittently opened and closed by the in'Lerniit'Lent bu.ildup and release of pressure in said first .@as chambei- and sl)ugs of gas can b.- injected at high freque@icy fro@n said gas conduit into said tubing. References Cited in the file of this patent UNITED STATES PATENTS 2,339,487 King ----------------- Jan. 18, 1944 2 465,060 Carlisle --------------- Mar. 22, 1949 2:620,740 Garrett et al - ----------- Dec. 9, 1952 2,620,741 Garrett ---------------- Dec. 9, 1952 2,642,889 Cummings ---------- -- June 23, 1953 2,672,827 McGowen -------------- Mar. 23, 1954 2,845,940 Garrett et al - ------------ Aug. 5, 1958

3 , 0 1 6 9 8 4 4 United States Patetit Office atented J,sn. 16, 1962 3,016,844 GA,S ]LIFT APPAPATUS Reiiac P. VPce;a,@, Tuls.-a, assigrier to Pin Arnerican Corporation, Tulsi, Okla., a corporation of 5 Delav@,are Filed Feb. A' O, 1,958, Ser. No. 714,103 11 Cl,,iirns. (Cl. 103-232) Th,'s inventio@i relates to an improved apparatus for gas liftin; a well, aid, more particularly, it relates to a - means 10 for increasing the lifting efficiency of a continuous gas lift system. 1 ha@,e found that the lifting -as/prodticed liquid ratio and ttic lifting efficiency of a gas lift well, particul arly a gas lift weil vvhich produces continuously, 15 can b-- substaitially increased by reducin.- heading or slug. -ing of the liquid near the surface in the producing cond uit. "Heading" as the term is used h--rein r-.fers to th-. ir@termittent production from a well of separately detacta ble slu.-s of liquid and gas. As the length of a slug 20 of liquid in a gas lift well i-icreases, the ]on.-er the slug of gas beneath that slug of liquid must be to lift the liqui d. As the len-th of the gas slug is thus increased, the grcater the blowdown of gas following the product@"o n of each slu- of liquid and consequently the greater 25 tiae loss of ener'gy and th-. lower the lifting efficiency. This lif,ina e-qlciency can be increased, I have found by providi-@i.- a continuous gas lift system in which the lengt hs of the intermittent slug of liquid and gas are redu ced to a rpiniri-lum or the two are so uniformly blend- 30 ed @-@ the top of a well that there is apparently no s'.ug-.1n.- or headirg of the produced fluid. This can be accomplished by producing sbort alternate slugs of liquid a-@id gas in the producing conduit at or iiear the bottom of a well. That is, by injecting short 35 slugs of the lifting gas interrnittently into the liquid in the produc-@'ng conduit at a rate sufficient to halt tempora rily the flow of liquid into the producing conduit, slipp age of liquid in the tubing or other producin.- conduit can be substantially reduced and the lifting efficiency 40 can be materially increased, - It is therefore an object of this invention to provide an improved -as lift system, It is a more specific object of this invciition to provide an apparatus for - injecting @-as into a liquid producing conduit intermittently at 45 relati vely high frequency for the purpose of increa sing the lifting efficiency of the -as. It is a still inor e specific object oj' this invention to provide a gas li-ft valve v,/hich will periodically inject at high freqiien cy, a large volume of gas into a production conduit 50 ol' a conti@-iuoiis gas lift well. Other objects of this invent: @o@i will become appareit froril th-, following - description. In this d,-scription reference will be made to the acco mpanyin.- drawings in which: FIG URE 1 is a cross-sectional view of a gas lift well 55 appa ratus showing scbematically the elements of this inventi oii; FI,G URE 2 is a cross-sectional view of part of a well aiid one embodiment of a gas lift valve particularly adap ted to inject gas p,-riodically at rapid rate into a pro- 60 duci r@- conduit, and; F16 URE 3 i, a ross-sectional view of a preferred emb odiment of a gas lift valve which intermittently injec t large qua-Titities of gas into a well tubing aL rapi d rate and at any desired frequency. 65 This i-ii-ve@ition may be described in brief as a gas lift sys,c ern of the continuo-isly producing type wherein the liqui d is lift-,d in short sltigs by injecting gas into the liquid in the producl'ton conduit at high rate and in shbrt bursts to prodlce a colurnn having several alternate slugs of To litaid a@ad gas in the prod@action conduit at one time. In its more particular aspects, this invention is directed 2 to a gas lift valve which will 'ntermittently inject gas into a production conduit at a frequency high -.nough to provide frorn about 2 to about 100 or more separate aiid distinct slugs of liquid i.1 the production conduit at one time For more detailed description of this invention reference will now be made to the drawings. FIGURE I of the drawings shows schematically the -elements of the invention and one embodiment of a suitable apparatus for continuously gas lifting liquid from a well. In this embodiment, the well is represented by a casin- 10 which is equipped with a gas inlet 11 and a casing head 12 through which a production conduit or tubirig 13 extends. The tubing has a fltiid outlet 14 at the surface above the casipg head and extends down into the -asing 10 to an elevation which is desirably substantially be'low the working level of the liquid in the well. A standina valve 15 is typically provided in the lower end of the tubing below the working liquid level of the well to prevent backflow of the we:l fluids from the tubing into the well when a high pressure is imposed on the @ubin.- during a gas injection cycle. A lower casing packer 16 in the annulus between the tubin.- and casing closes or seals this annular space and prevents well fluids from entering the gas chamber 17 between the lower packer 16 and the upper casing packer 18. This upp.-r casing packer has an offset opening 19 connecting the gas chamber 17 with the gas conduit 21 which is typically the annular space between the tubing and casi@ig above the upper casing packer 18. A removable orifice 22 in this offset opening permits gas to be metered into the gas chamber from the gas conduit at at-ly desired rate. The volume of the gas conduit is many tinies greater, typically 100-1000 or more @reater than the volurpe of the gas chamber. That is, the spa@e and volume between casing packers 16 and 18 are relativeiy sma'il in comparisoil to the space aiid volume between the upper casin.- packer and the well head 12. One or more gas lift valves commonly referred to as "kick-off" valves 23 are connected to the vertical production conduit or tub,.-@i,- 13 at spaced points for the purpose of removing excess liquid in the well when gas lift operations are conune-@iced, A high flow capacity, preferably sr@ap-acting, gas lift valve 24 preferab.,y near the 5tanding valve controls the flow of gas from the gas chamber 17 into the lower end of the production conduit. This -as lift valve is operated, i.e., opened and closed, primarily by the presstire in the gas chamber. Gas lift valves of this type are available coinmarcially from a number of sources. Typically, theseso-called "work-ing" gas lift valves are opened when the pressure of the liftiiig -as is high enotigh to inject gas into the production conduit, i.e., when the gas pressure is above a preset opening pressure. They are then closed when the pressure of the lifting gas is at sonie lower valve; namely, the preset closing pressure, thereby preventing the lifting gas from bein.- wasted after sufficient gas has been inject,-d into the production conduit to lift the slug of liquid which has accumulated since the previous lifting cycle. The volw-@ie of the gas chamber 17, th,e flow capacity bf the orifice 22, and the spread, i.e., opening and closing pressures, of the operatin.- valves are selected so that the valve is open from about I to about 10 times or rnore per minute. The frequency of gas ir@jection cycles and the len.ath of each cycle can usua'ily be determin6d best by trial-and-error, the best settings being those at which the lifting efficiency or the weil productivity is highest. In every case the iqow capacity of valve 24 when open is substantially greater, e.g., about two times -reater, than the flow capacity of orifice 22 so that a high-pressure gas from gas conduit 21 flows into the gas chainber 17 substantially continuous and the gas lift valve 24 opens

3 and closes as the pressure in the gas chamber rises and falls. The size of the orifice, other things being coiistar,t, is selected to control the ratio of gas-on/gas-off cycles, the larger the orifice the shorter the time the operating valve is closed and the higher the gas input and the injection frequency. The freqiiency can also be controlled by varying the volume of the gas chamber and by other means such as by varying the mean differential pressure across the orifice, i.e., by controlling the pressure in the gas conduit. In operation, th-. bottom end of the production conduit is lowered to a stibstantial distance below the working or dynamic level of the liquid in the well so that the liquid will rise in the tubiiig to an elevation above the working or operating gas lift valve 24. After the packers are set gas is injected ijito the gas conduit throu.-h gas inlet -11. The kick-off valves 23 first admit .-as to the tubing and allow liquid in the gas conduit to be displaced irito the tubin,@. Eventually the workin-, valve 24 takes over control of gas ipjection. Due to the differellces in pressure across orifice 22 gas is nietered at reasonably co,nstant rate into gas chamber 17. When the pressure within that chamber is increased to the preset opening pressure of the operating valve 24, that valve snaps open and discharges fltiid from the gas chamber into the lower end of the production conduit. When the operating valve opens, the presstire in the tubin,a rises rapidly. Desirably the fluid pressure in the tubing wlien the operating valve opens is greater than the pressui@e iii the well at the standing valve 15 so it closes. This causes the slug of liquid in the tubing above the operating valve to be lifted by the gas. Since the flow of gas throu.-h the operating valve is substantially greater than the flow of gas throu,-h ori.qce 22, the pressure in the gas cbamber 17 is immediately reduced to 'Lhe preset closiiig pressure of the operating valve. When this closing pressure is reached and the valve closes, the gas conlinues to flow from the gas conduit through orifice 22 into the gas chamber and builds the .@,is chamber pressure back up to the pres--t openin- pressure of working gas lift valve. During the time that this valve is clos.-d the pressure within the production conduit is less than the well pressure and liquid flows into the lower end of the tubing through the sta,iding valve. This liquid displaces the slug of gas and the slug of liquid above it bi_eher -.nto the production condliit. When the pressure in the gas chamber again reaches the preset openin.@ pressil-re of the working g@s lift valve, that valve agai-.i opens and injects another short slug of gas into the production conduit displacing the pi-evious gas slugs and the alteriiate liquid slugs further toward the surface. This intermittent operation is cOntinued at such a rapid rate that in effect the production is substantially continuous eveil at the bottom of the well. The optimum frequency of the injection cycles is the frequency at wliich the surface ttibi@-ig pressure is low and is substantially uniform or steady. This condition is attained when ',he alternate slugs of liquid and gas arrivin@ at the surface are so short that the stream issuitig frill, the fluid outlet 14 is substanlially hon-iogencous. Un-der this condition there is no excess gas and, therefore, the well is operating at maxirnum efficiency. Since a frequency lower than the optimum will iiot l@'.ft liquid from the well or will lift liq,,iid by heoding, it is generally desirable in determining the optimum frequency to first try a high freauency and thei to decrease the freque,icy of gas injectioi until the well is just on the thresbold of headin- The frequeiley of gas injection can thus best be determined by trialand-error. TI-ic workina g@is lift valve 24 may be fixed to the ttibing ar.d located in the anilulus b.- tweed the tubing and casing as shown in FIGURE 1. Alternatively, this valve may be of the iiisert or retrievablc type as is well known in th;s art so that the valve can b-, removed as desired vvithotit pulliiig the production conduit. An apparatus oi. this type,is shown in FIGURE 2. In this embodiment 3,016,844 4 the gas chamber 17' is also retrievabic so that either the volume of gas chamber or the flow capacity of the orifice 22' can be changed or the valve can olhe@-wise be repaired w-ithout p,,illing the tubin.- 13. A cross-over fitting 25 is pl@iced i-q th-. production conduit at the elevation where tic retrievable working gas lift v,,ilve 24' is to be seated. This cross-over fi@'ting comprises in part an outer shell 26 a-.id a valve se-,itin- or iiner sleeve 27. The inside diameter of sleeve 27 is si-rialler thaii the 10 inside diameter of tubing 13 so that retrievable valves can be easily lowered througli the tubin- and will seat in the slee-ve. The sleeve has means to aiiehor a retrievable valve in operating position. This may corinprise an Lipper shoulder 2,3 smaller in diam@-ter than the body 29 15 of the retrievable operating valve 24'. The shoulder stops the retrievable operating valve in operating posillion with the orifice 22' at the elevation of an annular receq-s 31 in the etoss-over fitting. This annular recess is iTi fluid communication with the gas conduit 21 through radial 20 openings 32 in the outer shell 26. Gas can thus flow from the gas conduit in the annular space bc@tweeri 'Lhe casing 10 and the tubing 13 via the openings 32 and the orifice 22' into the gas chamber 17'. In some cases it is desirable to lock th-. retrievable @Norking valve iii this 25 op--rating position. In one emb diment of such a lock a spring latch 33 is connected to th-, lower end of the valve body 29. Tapered catches '124 on the lower end of the cantilever sprin.@s 35 cooperate @vith a lower shoulder 36 -@n sleeve 27 to hold the retrievable operating valve 30 down in this operating position against the force of well fluids rising in the tubing. However, due to the taoer either on the c@-@tches as show-@i or on the lower shoulder, the retrievabl@ valve can be i-inseated and removed from the tubing by use of a flshing tool which exerts a force 35 greater than the force of the well fluids. Since the retrievable operating valve fills the sleeve 27, a fluid bypass through bbttom port 37, annular passage 38, and upper por-L 39 is provided in the cross-over fitting 25. This bypass does not communcate with the annular recess 4o 31 or tiie radial operiings 32. An upper fluid seal 41 and a lower fluid seal 42 on the bo,dy '@9 are spaced above and below the annu'@ar recess 31, respectively, when the valve is in operating position with the orifice 22' opposite the gas inlet opening 32 to thereby seal the 45 space between the valve body ard the inner sleeve ofcross-over fitting 25 and cause the well fluids, as well as the gas discharging through the operating valve, to pass upwardly through the annul,,ir passage 33 around the valve. Flow of gas from the gas chamber outlet 43 50 into the production conduit is controlled by a valve member 44 ' Normally, this gas outlet and, ther,-fore, the gas lift valve 24', is closed by the valve r@iember due to the action of compression spring 45 which, acting against the bottom of the bellows housing 46, urges the 55 valve member down. The valve member is connected at the upper end to a pressure-sensitive valve actuator or motor which includes, for exaiiiple, the lower movable piston br head 47 of a variable volume chamber such as a bellows 48. This bellows is attached at the upper 60 end to the upper gas chamber head 49. The bellows is filled with a compressible fluid such as Freon. The force of this compressible fiuid is co@nbined with the force of compression spring 45 to hold the valve member 44 down, counteract the upward force on the lower end 65 piston due to the pressure in the gas chan-lber, and close the gas outl--t 43. In some cases the upper head 49 is prov:ided with a number of perforatioiis 50 ar@d a. suppl@eniental gas chamber 17" is attached to the upper end of the body 29. The volunic of the gas chamber 17' 70 may thus be enlarged as a means of varying the operatiii.- frequer@cy of the valve. A knob 51 at the upper end 0L' ihe retrievable valve is provided for the purpose of iis,erting and removing the valve with a-,i attachable ov-,rshot fishing device. 7.5 In operation the cross-over fitting is lowered into the

3,016,844 5 casing 10 on the prodtiction conduit to the elevation at ivhich it is desired to inject gas into the production conduit and the casin- head 12 is attached. Obviously, two or more of these or similar cross-over fittings may be installed at spaced points along the production cotiduit so that, if desired, retrievable kick-off valves can be installed at preselected elevations. The size of orifice 22' is then selected hand a removable nipple 52 containing the orifice is threaded into the wall of the valve body 29. The removable valve 24' is then either dropped or lowered by a wire line tool into position in the cross-over fittin@ as shown. Gas is then injected into the -as conduit 21. After excess liquid is displaced out of the tubiag and the gas conduit, gas passes through the openiig 32, the orifice 22', and thence into the gas chamber 17'. Gas flows from the high-pressure gas conduit into the - as chamber until the pressure in the gas chamber is as great as the pres,-t openin.- pressure of the valve. When this opening pressure is reacbed the downward force on the valve member dlic to the compression spriii- and the compressible fluid in the bellows 48 is overcome by the pressure of the gas acting on the lower bellows head 47 plus the pressure of the well fluids acting on the lower end of the valve member 44 via -as outlet 43 and the valve member is thus raised, openin,- the outlet. The pressure in the gas chaniber when the valve opens is greater than the pressure in the tubing so that as the valve member ris,-s it is exposed on the end to increasing pr.-ssure causin,@ the valve to snap open. The gas in the gas ch,,)mber being at a higher pressure than the tubing and the bottomhole pressures is then discharged throtigb gas outlet 43 into the production conduit below the operating valve raising the tubing pressure to a point at which flow of well fluids into the tubing is temporarily stoppcd. The liquid level of the well fluids is thus beld at the crossover fitting bottom port 37 and -as passing tbrougb this port raises the well fluids and displaces them as a slug up through the aniiular fluid passage 33, out throul,.h the upper port 39 and the annular space 54 into the production conduit. Gas outlet 43 is substantially larger, typically 2-5 times larger in cross-sectional area than orifice 22'. The gas witbin the gas cbamber thus escapes mucb more rapidly than gas enters the cbamb,-r through the orifice. This rapidly reduces the pressure within the gas chamb@-r. When the pressure is reduced to the preset closilig pressure of the ivorking valve, the force of compression spring 45 and of the expa-@isible fluid therein on the lower bellows head 47 is great enough to overcome the upward force o@@i the movable lower wall of the bellows due to the gas pressure in the gas chamb.-r and, therefore, the valve closes. The valve rnember also snaps shut due to greater differential forces on the end of the valve member as it approaches the gas outlet 43. When the valve closes, the gas continlies to be metered into the gas cliamber through the orifice, building up the presstire in the gas chamber until the opening pressu@-c of the valve is a.-ain reached. During this time when the valve is closed, well fluids are entering the lower end of the production conduit and flowing upwardly throiigh the bottom port 37, the bypass fitting, etc., displacing the previous slug of liquid ar@d the intermediate gas slua upwardly in the production c6pduit toward the stii-fice. The valve coiltinlies to operate, i.e., open and close, as the pressure oscillates in the gas chamber tbereby intermittently injecting into the tubing at high frequency slugs of gas and slugs of liquid. Since the volume of the gas conduit is many times greater than the volume.of the gas chamber, the pressure in the gas conduit remains substantially constant. It can thlis be seen that the working valve, which is in fluid communication with the gas chamber and is primarily sensilive only to the presstire the.-ein, can be made to open and close at hi.-h frequency even though the pressure in the relati)rely high volume gas conduit remains substantially constant. Due to the importance of injecting -as into the production conduit at a rapid rate, it is sometimes desirable ,5 to increase the capacity or rate of gas inject@on of an apparatus of the type described above. A preferred type of gas lift valve for injectin.- gas into th,e tubing in highfrequency, high-volume slugs is shown in FIGURE 3. In this preferred embodiment, an auxiliary gas valve 61, 10 actuated by a pressure-sensitive pilot valve operatin.@ like the abovedescribed retrievable gas lift valve 24', is attached to the lower end of modified valve body 29'. There are a number of inlet gas ports 62 in the wall of the valve body below the lower gas chamber head 63. 15 When the retrievable valve is in operating position in the bypass fitt@:ng 25 with its lower end resting on the upper shoulder 28, these gas inlet ports are aligned and @@'n fluid cor@imu-@iication with the opening 32 in the bypass fitting. The orifice 22' is also in fluid cornmunication ,o with this opening so that gas from the gas conduit 21 enters both the gas charnber 17' and the auxiliary gas valve 61 througii the sarne opening. A lower head 64 in the auxiliary valve has an axial outlet port 65 with a valve seat 66. The auxiliary valve member 67 is 25 connected to an auxiliary v,@ilve fluid motor includin.- a piston 63 and both are held in an upward position with the auxiliary valve closed by compression spring 69 which rests at the lower end on the lower auxiliary valve head 64. The area of pisto@i 68 is desit-ably about equal to 30 the area of valve rnember 67 so that the auxiliary gas valve is insensitive to upstream pressiire. The valve stem 71 of the auxiliary valve member and the valve memb-,r -@'tself have an axial exhaust opening 72 tbrough which aas from the gas chamber 17' and the auxiliary s5 valv.- gas chamber 73 passes down intc), the production conduit. The crosssectional area of this exhaust opening is less than thecross-sectional area o gas cham er outlet 43 and is larger than the cross-sectio@ial area of orifice 22'. 40 This retrievable valve which includes the auxiliary valve 61 is lowered into and seated in position in the bypass fitting 25 in the same manner as the retrievable gas lift valve shown in FIGURE 2. When the valv,- is in operating position, gas injected into the well through 45 eas conduit 21 passes through the opening 32 ar@d thence throu,Lh orifice 22' irito the pilot gas chamber 17'. As the pressure in the pilot gas chamber increases and reaches the preset opening pressure of the pilot valve, valve member 44 is raised as above described. Gas in 50 the gas cbamber then flows through the gas chamber out'@.-t 43 into the auxiliary valve gas chamber aiid theice through th.- exhaust opening 72 into the procluctio,.i conduit. However, since the cross-sectional area a@-id th,,is the flow capacity of the openipg 72 is less than the cross55 sectional area and the flow capacity of gas elitlet 43, the pressure ill the auxiliary valve gas chamber 73 is stibstantially eqtialized with the gas pressure in ',he gas chamber 17'. Th;s pressure, actin,@ ag,-,inst the pisto@i 68, is sufficient to overcome the force oL compression 60 spr;ng 69 and.the auxiliary valve memb.-r 67 is moved downwardly openin.- the auxiliary gas valve 61, Viith this auxiliary valve open the gas in the gas ebamber 17' flowina into the production conduit is suppleme-@ited by gas flowing dii-ectly into the sarne conduit ',rom the gas 65 conduit 21 via gas inlet ports 62 ajid the oil-@llet port 65. it can be seen that by thus eniployin- an auxiliary gas valve actuated by a rapid acting pressure-seiisitil/c pilot valv--, the rate of gas injection and the quaiitity of -as inject-d ipto the production conduit during a short gas 70 injection. cycle can b.- substaptially iicreased in comparison to the rate and quantity of gas injected tbroi-igh the pilot gas lift valve alone. This facilitates 'che separation of the gas and liquid into discrete sILgs. From the j'ore,-Oing it can be seen that various modi75 fications caii be made in the gas lift s3istem disclosed.

3)0161844 7 For example, while the gas chamber and the operating or working valve may both be placed in the an-@lular space between the casing and the tubing or they may both be placed within the tubiiig as retrievable equipment, in some cases it will be desirable to employ the external 5 type gas chamber and the retrievable valve, or vice versa. This invention being thrs susceptible to wide variation of embodiments should not be construed to be lim-1 ed to the embodiments specifically described above. It should instead be cons.trued to be limited only by the 10 scope of the appended claims. I