US2762308A

US2762308A - Gas-lift pumping system

Info

Publication number: US2762308A
Application number: US336098A
Authority: US
Inventors: Lilburn J Tomlinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-02-10
Filing date: 1953-02-10
Publication date: 1956-09-11
Anticipated expiration: 1973-09-11

Description

Sept- 11, 1956 L. J. ToMLlNsoN GAS-LIFT PUMPING SYSTEM s sneaks-sheet 1 Filed Feb. l0, 1955 'ad ATTO/eme x5- Sept. 11, 1956 l.. J. ToMLlNsoN 2,762,308

GAS-LIFT PUMPING SYSTEM Filed Feb. lO, 1955 3 Sheets-Sheet 2 Q f8 o o 4f f o l Q 4.5' O 44 a2 59 A l INVENTOR. G3 1./1.- BURN J. TOML//vso/v Sept 11, 1956 1 J. ToMLlNsoN GAS-*LIFT PUMPING SYSTEM 5 Sheets-Sheet 3 Filed Feb. l0, 1955 IN V EN TOR. L /LBt/RN J. TOML/NO/V SDU RCE OF CURRENT *GEMM TTO ZZN'EXS,

United States Patent- 2,7 62,308 GAS-LIFT PUMPING SYSTEM Lilburn J. Tomlinson, Long Beach, Calif. Application February` 10, 1953, Serial No. 336,098

3 Claims. (Cl. 10S-52) This invention relates to the production of liquids from wells. More particularly, the invention relates to an improved plunger gas-lift system for pumping oil and/or water from a well by means of a compressed gas.

Essentially, plunger lift equipment comprises a string of production tubing in which a freely moving plunger travels the entire distance from the wellhead to the bottorn of the tubing and back to the wellhead on each stroke.

On each trip to the surface, the plunger lifts a column of liquid, such as oil. The plunger is in turn propelled on its upward trip by the pressure of gas under it in the tubing, which gas is supplied by a parallel string of injection tubing. The production tubing is connected at the surface to a ow head to receive the liquid lifted by the plunger and direct it through flow lines to storage or transport. As soon as the plunger has delivered its load at the wellhead and the lift gas pressure is released thereby, liquid begins to ow from the well into the lower end of the tubing. Release of gas pressure occurs when a valve n the plunger is opened upon striking a wellhead bumper. The plunger falls freely through any uids back into the well string by gravity alone and the valve in the plunger is closed as the plunger falls at the end of the down stroke upon a bumper in the footpiece fitted at'the lower end of the tubing.

Regulatory bodies in some oil producing states have placed restrictions upon the output from oil wells. This makes it necessary to reduce the number of cycles which the plunger makes during any given period if the well is to be kept in continuous production on a limited quota basis, or to shut down the well when the allotted quantity of oil has been produced. A consequence of a shutdown is an expense in returning the shut-in well to production again, as by swabbing or bailing. Restrictions are also placed upon the quantity of gas which may be produced from a gas-oil well with respect to the amount of oil produced in order to conserve the gas and maintain the formation pressure for as long as possible. Where a quota has been set on gas, it may be the controlling limit before the oil quota is reached. In such cases it is desirable to reduce the gas to oil ratio to increase oil production to its maximum. y

The improved gas-lift pumping system of this invention is particularly applicable to producing oil in areas which also produce natural gas. This gas under pressure provides the power for raising the oil. Such gas may flow within the casing from the oil zone being produced, from a separately produced zone in the same Well, or from a neighboring well. If the gas is not obtainable at sufficient natural pressure, it is passed through a booster pressuring pump before use. Although the greatest utility of the improved pump is in gas-oil producing areas, it may be used elsewhere in the absence of natural gas by compressing air, CO2, and the like to the requisite lifting pressure.

It is accordingly one object of this invention to provide an improved time controlled plunger lift system to permit Vontrolledprates of production over a desired period of time heretofore not possible of achievement, thus avoidice ing expensive swabbing to return shut-,in wells'to production.

A further object is to provide an improved gas-lift system by the use of which gas-oil ratios can be kept to a minimum to conserve natural gas.

Another object is to utilize formation gas eiciently to raise a maximum quantity of oil per pressured quantity thereof.

A still further object of this invention is to provide au improved system whereby back pressure of gas in the production string may be reduced to a minimum to facilitate the inow of oil to the bottom section thereof between lifting strokes of the plunger.

Other objects of the invention will tion proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In the drawings: Figures 1 8 are concerned with an embodiment of my invention employing pneumatic controls. Figure 9 illustrates another embodiment of my pumping system employing electrical controls. Each figure of the drawings is further identied as follows:

Figure 1 is an elevation view, partly broken away, showing one form of the improved gas-lift system of this invention.

Figure 2 is a detail view partly in section on an enlarged scale showing the plunger catcher assembly at the wellhead. This same assembly is also shown and, in part, in section, in Figure 2a.

Figure 3 is a detail view, partly in section, of a plungeractuated trip mechanism for controlling shut-off of the lift gas supply.

Figure 4 is a detail view, partly in section, on an enlarged scale of a pressure-spring actuated piston assembly by which the time control mechanism is actuated.

Figure 5 vis a diagrammatic plan view of one form of the time control device which may be used in the syst'em of this invention.

Figure 6 is a diagrammatic elevation shown the piston of the pressure-spring actuated piston assembly and the arm controlling Ia pressure bleed-olf sleeve valve in up position.

Figure 7 is a similar diagrammatic elevation showing the piston and arm in down position.

Figure 8 is a diagrammatic showing of the operation of a time control mechanism used in the system of this invention. V

Figure 9 illustrates the use of electric controls atthe wellhead for` controlling the pumping cycle and lift gas supply.

Brieily summarized, the sequence of the automatic and timed controlled stepwise operations provided in the presentl pumping system are as follows: (1) The lift gas supply is shut oif at a desired point prior to complete delivery at the wellhead of the oil column lifted by the plunger. (2) At pre-set timing device is put into motion upon shutting off the lift gas. (3) The plunger on reaching the wellhead completes the delivery of a column of oil and the valve in the plunger is opened bythe plunger striking a wellhead bumper whereupon the remaining lift gas pressure is diminished by flow of..gas after the delivered oil. (4) The plunger falls back upon a catcher in the wellhead and remains there for a preset time interval. (5) After this time lapse, the timing appear as the descrip- `4device actuates release of the catcher `and the open- .valved plunger falls freely into the production tubing.

1(6)V After a further pre-set time lapse, preferably when .the .plunger has fallen through an accumulated .column of oil in the production tube of the well and the plunger valve has closed upon striking a bottom tube bumper, the gas .supply is ton by 'the ,device rIhus the pumping cycle is continuously repeated. Set- Y-tingfthe .holding time :at `the plunger catcher `:determines the frequency volf pumping and ithus permits ehe relative continuous productivity/ of a well :at allowable .leuels helowils Vnztaxinlum (capacity. Controlling the tion! of .lift gas prevents .ffreefowing wasta'ge .fullest utilization of the pressured gas for lifting oil. Thus, operations .are .maintained at the 4least 'possible gas :to nil natio. Provisions .for accomplishing this `'controlled .operational sequence will be I'seen :in the drawings 4and .the .descpton of the pumping system hereinafter.

Referring more specifically tto the drawings and Amore especial-ly v:to Fig-.ure l., there is here illustrated sa well .provided with a casing generally indicated at 1 vextending into a producing -zone within the earth. Within the ,casing are :two parallel strings lof tubing, tube 2 being a .lift :gas .injection string and tube 3 being a production string. The injection tube and :the .production ltuhe :are :held together byaclamp 4. Atconventional valvedxphmg'er Yindicated v'generally at 5 is freely movable in the production tube, adapted to .travel .the lentire distance from pre- .duction `zone to wellhead A lfootpiece` assembly represented gener-ally at 6 connects the bottom ends `of the two str-,ings of tubing adjacent the production zone .and isrequipped with a spring loaded ball and seat'check salve 7 to prevent flow -of well liquids into the gas injection tube 2. A :conventional bottom lock holdfdown shoe SKA -is positipned in the production tube above the .footpiece 6 to 'hold in place a retrievable bumper zspring :assembly .9 which is employed to jstop :the downward fall o f the plunger 5 .and to shut the valve rcontained said plunger assembly when the plunger falls thereon. Another bottom lock hold-down shoe l .is positioned below .the foot-.piece -.6 in the .production -stringito zhold .in place .a retrievable .spring .loaded ball `and vseat 1standing check valve 11 which prevents the backhow tof the liquid or gas into the well bor-.e Iand lformation `als :the lift .gas pressure ris applied .to lit-t the liquid fload upon the plunger -to vthe surface; Ithus fa .closed .type vof fgaslift plunger pump .is provided. A -tail pipe `1,2 rcan be employed below lshoe .10, :if desired, to permit :the production o'f well liquid from a sumpv at the bottom-.of .the well bore.

Well casing .'1 terminates at its .upper-end at .the earths .surface in an .assembly .comprising generally wellhead 1'3 into which production string 3 leads and from which flow .pipe .K14 .entends to .carryfofft the .well product to a gas-oil separator and .storage vessel or .transport .not :show-n. Within `wellhead 13'is ya top bumperzspring and valve .opener which stops ,plunger .S .at the end .of its upward travel. At the wellhead in production string y3ds a spring loaded catcher assembly 15, .more .fully 4described lhereinafter with .reference to .Figure .2, .to hold plunger '5 at the wellhead after Vdelivery of a column .of oil. The catcher 21 within catcher .assembly `15 is actuated to release the ,plunger by ,pressure changes transmitted through pressure line I6 to .diaphragm housing '17 controlled 'by a pressure-.operated time .cycle -interm'itter lindicated generally at -18 anddescribed more fully hereinafter with reference to Figures 4, 5, 6, 7, and 8. The lift gas supplied under suitable Apressure .from 'a source previously described flows through line 19 to .injec'tio'n tube 2. Flow of gas to .theinjection tube is .conitrolled through valve V20 actuated by time control device 18 'in a manner hereinafter described in detail.

"Referring -now to Figures 2 and 2a, production string 3 is intercepted by the plunger catcher assembly 15. .Catcher 21 is Aslidably .mounted in sleeve 22 .of .-the 'assembly joined .by rod and sliding clevis `arrangement 23 to diaphragm 24 in diaphragm .housing 17. eCoil spring 25 urging against diaphragmk 2.4 causes zzcatcher .21 .to .he retracted .from production .tube 3 as pressure is released from chamber 24a. Pressure line 16 leads to pressure chamber 24a -in diaphragm housing 17.

The trip mechanism, cam 26 et seq., in Figure 3 may be positioned on the production tube either at the wellhead or elsewhere along the upper length of the string. The upward velocity of fthe :plunger will accelerate as soon as the weight of the liquid column thereon starts decreasing by unloading lthrough delivery line 14. The lift pressure, therefore., becomes .decreasingly less than that required initially to move the liquid column up the production tube. To vprevent `,undue acceleration and impact of the plunger against the wellhead, the location of the trip mechanism will be preferably far enough below the wellhead so as to shut off the lift gas supply early enough for expansion-reduction of pressure to meet the decreasing pressures required during liquid unloading. Thus, undue :acceleration :of .the plunger can be avoided. The trip mechanism comprises `cam 26 .pivotall-y mounted at '27 and urged `by coil .spring 28 vattached to arm .29 so fas `to extend a :short distance yinto the-,path .of zplunger assembly 5 in production tube 3. Arm 29 'is joined tto the needle bleed-oit yvalve .30 :which -.i11 Aturn is :connected :through line .31 to pressure chamber :32 in .the rpiston assembly :33 tof Figure l4. Piston 21A-within pressure chamber .S2 is joined .through rod .'35 `to piston head .Gaspressure is `induced in .chamber 32 :through port :37 diro'm the injection gas .supply line. Piston` 34 -is `urged vupward vinit-hin chamber 32 by means of .

coil Jspring

3,8. .Piston assembly :33 is positioned within time cycle intenmit'tcr .18, nas :shown in Figures 5, 6, .and "7. :Cam `iollower .39 .is .pivotally spring mounted above piston and joined 'to frapper vdisc 5.0 (as shown in Figure alf)V in hou's'ing l) to actuate fthe ,gas control -valve :20 in line 19. Timer 1wheel .4-1 is rotatably mounted -within housing 18adjacent`to the 'cam .follower 39 and is driven -by suitablerspring, electric, :or fluid power means. Timer wheel d1 tcarries a plurality tof dapper disc closing lugs '42 :upon Jits .upper surface and va plurality ,of sleeve valveopening .flugs d3 ron rits perimeter. Sleeve v alve 44 lis 'positioned adjacent timer wheel -41 :to permit .fthe spring mounted arm 45 to be contacted by

lugs

4,3.. :Sleeve -valve 44, upon :lifting of .arm 45, bleeds poif pressure (fsupplied rby :control gas pressure line 46) Yrfrom line L6 tto chamber 24a ein plunger catcher diaphragm housing ,-17 iso asato withdraw catcher -21 :and release the pump plunger- In .Figure f8., Control gas pressure line -4.6 supplied :from .lift rges line l1-9=,or :some Iother source, such .as 'compressed aintleadsinto 'housing fill). Within `the housing 40, :the restricted .orice :.48 is smaller :than :or'itice 49. vFlapper disc 50 wattached to the 4cam :follower 39 is :held against orifice@ byfcoil spring 5-1. Housing 40 leads to a .diafphragm housing contain-ing :pressure :chamber 153 'and diaphragm 5 4. '.,Gasrcontrol valveZO is :actuatedlny rdiaphragm' .1,54 through connecting frod 5.6, the valve being .urged :shutfin @the absence of j :mressure *in :chamber :53 ahy .coil spring 55. 'tlime `cycle yintermitters of several types are per se old and available commercially. One type .ottime cyclerinterrnitter .which may be readily `r'nodi'ied .to :be adapted to the @operation :of the :improved gas-litt .pumping systemof this invention, asshown .in 'Figures .5 -to P8, :is ,available as Type 4655B -from the Fisher Y,Gov- .ernor CompanytoflMarshalltoWn, Iowa.

flu zthe oper-ation of fthe :system of this invention, -as in an Soil .well, foil -ows from the subsurface .formation :by :gravity land :formation gas pressure through atail 'pipe d2 .and .checkfvlalve All .into the lower end of :production tuhe V-3 to :form :a column .of :oil therein. The 'valve of plunger v5 being wpen, :the plunger will drop freeily through rauch liquid tto bumper :9-whch .closes theaplunger naive. .Gas .under pressure is :introduced inte the :production tube under' the rplunserirom line 2.19 :through im jectien .tube 'r2 .f ajnd cheek `valve '7 tin-'Afootpiece .6 forcing the L.plunger upward canning before it :the column 0f -nil ccumulated in the production tube. -At thewellhead theoil produced Hows through line 14 to storage or trans"- port. As the plunger passes the trip cam 26 in the pro'- duction' tube, vthe injection gas supply is shut off. This occurs as follows: the plunger depresses cam 26 unseating needle valve 30 causing a Ableed off of pressure through line 31 from Achamber 32 of piston assembly 33 mounted inthe diaphragm case of the pressure operated time cycle intermitte'r 18. The release of pressure from pressure chamber 32 above pressure-spring actuated piston 34 allows coil spring 38 to push the piston upward, piston head 36 in turn raising cam follower 39 to a position riding the rim of the vtimer wheel of the time cycle intermitter, thereby holding apper disc 50 away from orifice 49 thus allowing pressure to bleed from the upper diaphragm pressure chamber 53 faster than it can be replaced through the restricted orifice 48 and at the same time actuating switch 47 to begin the movement of timer wheel 4l. As the pressure in chamber 53 decreased, the coil spring 55 urges diaphragm 54 and connecting rod 56 upward, closing valve 20 and shutting off the injection gas supply.

The plunger after striking the top bumper spring in the wellhead comes to rest on catcher 21 which extends out into the production tube. opened upon the plunger striking the top bumper spring. After being actuated by the piston head 36 through switch 47, the timer wheel 41 driven by motor 47a begins to rotate slowly in a counter-clockwise direction. After a pre-set interval of time as determined by the positioning ofsleeve valve opening lugs 43 on the perimeter of the clock wheel, spring mounted arm 45 on sleeve valve 44 is raised by a lug 43 bleeding olf pressure from the diaphragm chamber 24a in diaphragm housing 17, allowing coil spring 25 to retract catcher 21 thus permitting the plunger to return to the producing zone to begin another cycle. After arm 45 passes over lug 43 and returns to its normal position, the bleed-off port is closed, pressure is supplied to chamber 24a, and catcher 21 returns to catching position in the production tube. When plunger drops through the production tube on its way back to the producing zone, it again actuates piston head 36 by tripping cam 26, unseating4 needle valve 30 causing a bleed off of pressure through line 31 from pressure chamber 32 of piston assembly 33 allowing coil spring 38 to push the piston upward. However, because cam follower 39 is at this time riding on top of timer wheel 41, the piston merely moves up and then falls back down after the plunger has passed cam 26 resetting the release mechanism for. the next cycle and nothing further happens until the next stage of activity is actuated by movement of the timer wheel. After a predetermined longer period of time as determined by the positioning of apper disc closing lugs 42, the cam follower 39 riding the outer rim of timer wheel 41 is forced oif this wheel, actuating switch 47 to halt rotation of the timer wheel and allowing apper disc 50 to close orifice 49 thus permitting pressure to build up in chamber 53 against diaphragm 54 urging connecting rod 56 away to open valve 20 in injection gas line 19 permitting a build-up of gas under the plunger and thus begin a new cycle. Thereafter the cycles are repeated continuously. It will be noted that when the lift plunger 5 is released and dropped into the well, it will again depress the trip cam 26. However, the cam remains inoperative at this point until a time thereafter when a lug 42 on the timer wheel 41 has forced the follower 39 back onto piston head 36.

The length of the pumping cycle, regulated by the positioning of the

lugs

42 and 43 on timer wheel 41, may be varied from a fraction of an hour to several 'hours dependent upon a number of circumstances such as the number of cycles in any given calendar period required to produce the allowable quantity of petroleum fluids, the depth of the well which determines the time of actual plunger travel, the rate of ow of the well The plunger valve has uid ,into the foot of the production tube, and the like.

VThe longer pre-set time interval regulating .resumption of ow of the lift gas must be enough longer'than vthe rst pre-set timel interval for dropping the plunger Yso asf t0 allow the plunger to return to the bottom of the well and close its valve before gas flow is resumed for oil lift.

Referring now to Figure 9, there is shown an electrical arrangement in conjunction with thewellhead section for controlling the pump cycling in my improved plunger gas-lift pumping system. Certain ofthe parts shown in this figure which correspond to like parts'in the preceding description are` designated by like nurnbers'. The operation of the pump with :electrical timing controls is as follows: Plunger 5 'propelled bygas supplied under pressure from line 19through `open 4valve 20 and injection tube 1, as already described, has delivered a column of oil into owpipe 14. In so doing, plunger S'has in passing, depressed lcam 26, thus closing spring switch 57 momentarily whereby relay 58 deenergizes solenoid 59 through circuit 60 to close the lift gas supply valve 20 urged by spring 55.' Valve stem 56 includes a movable armature `shaft extending into solenoid 59. This operation of relay 58 also closes circuit 6 1 to start the timer motor 62, and readiesrelay 63 by closing switch 64 to become operative at a later pre-set time interval. Plunger 5 has completed delivering the oil into flow 'pipe 14,. has struck the bumper spring 13 which opens the plunger valve, and the plunger has come to rest on its vcatcher 15 as shown in thedrawing. Meanwhile, the timer motor 62 is operating, having been started by movement of cam 26 just described; the timer cams 63 and 64 are rotating so that each will come into electrically actuating positionsv at a pre-set time interval. Cam 64 comes into actuating position at a time subsequent to that for cam 63. The pumping cycle waits upon the now rotating timer cam63 with plunger 5 being held on catcher 15 which vis in the production tube 3 by means of yspring 67. The plunger 5 is dropped into the well'when cam 63 has rotated until the notch therein has` dropped spring arm 65 which closes circuit 66 to energize solenoid 68 and withdrawn catcher 15 attached to a movable armature therein. Athough cam 26 becomes depressed again.V as the plunger drops by, there is now no operative effect upon the control mechanism as will be seen from the circuiting thereof. As cam 63 continues to rotate, spring arm 65 is raised, opening circuit 66 to de-energize solenoid 68 and catcher 2 1 is returned by spring 67 tothe catching position in the production tube. Having released plunger 5, the timer cam 64 vat a later pre-set time drops spring arm 69`to close' circuit 70 and energize relay 71 to stop timer motor 62 '(circuit `61 is opened), and to open the lift gas valve 20'(circuit 60 is closed); also relay 71 is simultaneously cle-energized by the opening of switch 72. It may be noted now that cam 26 is operatively ready to function again upon return ofv the plunger from the well. Thus, the timing sequences of the pumping system have been completed and will be automatically and cyclically repeated upon each return of the plunger with a load of oil from the bottom of the well. As an added safety feature, it will be noted that in case of electric power failure solenoid 59 becomes de-energized, thus allowing valve 20 to shut off the lift gas supply from line 19.

The improved gas-lift control system of this invention was experimentally eld tested in a California oilgas well of 6,063 feet depth, having a lift depth of 5,760 feet below which there extended a tail pipe of 186 feet dipping below the surface of accumulating well liquids. The total time of a pumping cycle was 20 minutes, operationally divided as follows: 6 minutes to raise column of oil at a gas pressure of 200 p. s. i., 8 minutes plunger rest on

catcher

21, and 6 minutes time elapse after release and dropping plunger before turning on the gas supply. An average monthly production of 2,232 bararcanos Y"tic'in, vhich preceded the installation of my improved l lt isj-appareiit 'that many modifications and variations offth'e Virive'rition asdhereinbeforeset'forth may be made Without departing from "the spirit and scope thereof. The specific embodiments described are vgiven by Way of 'example` only and the invention is limited only by "fue "farms or the 'appended claims.

'An improved 'gas-'lift Apumping system for use in a Well consisting of: -a gas'injectiontube, a well head, a production tube'exten'clin'g downward from the well head, lungiervvithin'the production tube adapted to travel ffr ly "substantially 'the Vfull length of said production ltube and into'said vvellhead, a footpiece assembly connecting -the Vinjectiontube in direct uid` communication "{vith thefp'roduction Ytube at the bottom thereof, a check Avalve Within ltheprodilc'tio'n tube adjacent'the foot-piece to prevent loss Yof `tiuid tol the"w`ell formation, a lplunger vcatcher in `'the vi'ell `head,-"a lift lgas pressure control Y-valvein said 'gasinjection'tbm means for closing said liftg'as pressure 'control valve by lthe'upward movement vfsaid'plunger consisting of "a trip mechanism actuated lbythe plunger 'and operatively connected to said lift gs'fp'resse vcontrol vlve,"a manually adjustable dual timigfdevice connected to saidpluriger catcher and said @ltr p mechanism "and actuated by saidtrip mechanism :for'felesingtleplnger catheruponthe lapse ofthe `first'time.period setonsaid'tmirig device and said'timing "device also Being opeativelycorinected'tothe lift l'gas pressure control valve `for opening said control valve l"upon the-lapse of the` second' time'period set onsaid timning""clevic'e. v j

:n improved fgasliftlp'ump'ing systemfor use in a tiwi/e vcor'tsi'sting of: a'fgas injction'tube, a Well head, apro- "d" d, on"t"tbefe `rt`riding douinivard'vfrom'the well head, -af`plinger Within therproduc'ton tube dapted'to travel may substantisuynetnneagfh efsatdrpraaeuaa tute and 'into 'Sad-sven tread, attingere-ee assenitily ennecting tire injection tubein direct nu -'corntnunication with'ttre produetonjtube at thebottcm thereof, a 'check valve adjacent the foot-piece tdprevent'ba'c'k newl "if well jnuids into the injection'tube, 'a check valve Within theproduction tube adjacent thefoot-p'i'ece tojprevent loss of Huid to the Vwell formation, a plunger'ctcher in'the well'head,

alift 'gas pressure control vlvein said lgas injection tube, means for 'closing 'saidlift 'gas vpressure control 'valve 4bfy the upward movement of said plunger consisting of a trip mechanism actuated by'the 'plunger and operatively connected to sai'dlift gas pressure -control valve, a manually adjustable dual timing device connected to said 'plunger catcher 'and said-trip mechanism and actuated by said trip mechanism `for releasing the `plunger catcher upon the lapse of thetrsttime periodiset onsaid .timing device and said vtiming 'device also being operatively connected 'to the liftfgaspressfurecontrol valvef'for opening said control valveupon the'laps'e 'of the second time period set on said timing device.

3. YAn improved gasflift pumping system for use in 'a well consisting of: a gas injection tube, a well head, a production'tbe extending downwardifrom the well-head, apl'un'ger withintheproduction tube adapted .to vtravel freelysubstan'tially the flllength of saidproduction vtube and into -said well headfafootfpiece assembly connecting the injection tube in direct Atiuid communication kwith the productiontube-at the bottom thereof, a check valve adjacent the foot-piece to prevent back 'ow of weil tludsinto the injection tube, aplunger catcher in V'the well head, a top bumpery spring-assembly within the-pro duction tube beyond the plungercatcher, a check fvalve within the production tube adjacent the rfoot-piece .to prevent loss offuid to the well formation, .a lift gas pressure control valve in said Lgas injectionrtube, V,means for closing said 4lift gas pressure control valve by Vthe upward movement of--said .plunger consisting ofi-a trip mechanism actuatedby the plunger and operativelyiconnected to said lift gaspressure control `valve, atmanually adjustable dual timing device vconnected `to saidplunger catcherfand said `trip mechanism=and actuated .by jsaid trip mechanism for releasing the-*plunger catcher upon the lapse of the first time periodseton said timing-device and said timing device'alsoibeingl operatively connected to the lift pressure control Yvalve Vfor :opening said-control valve upon the lapse of the second timeperiod setlon said timing device.

A:References Cited-in the tile .of-'this .patent 'UNITED STATES PATENTS v971,612 IHolliday "Oct 4, "1910 2,001,552 vScott May 1`4, 1935 2*,649l738 Tait 'Aug. i"i2/5, i953 v2,699,121 Knox "Jan, `1`1, 'i955