US2620741A

US2620741A - Pressure responsive valve and valve system

Info

Publication number: US2620741A
Application number: US80792A
Authority: US
Inventors: Henry U Garrett; Clifford M Peters; Everett D Mcmurry
Original assignee: GARRETT OIL TOOLS Inc
Current assignee: GARRETT OIL TOOLS Inc
Priority date: 1949-03-11
Filing date: 1949-03-11
Publication date: 1952-12-09
Anticipated expiration: 1969-12-09

Description

Dec. 9, 1952 H. u. GARRETT ETAL PRESSURE RESPONSIVE VALVE AND VALVE SYSTEM Filed March 11, 1949 a b M a 3'1 5 May nmmzu 5 M m m w w 5% M R H Ii 0 reCN r M! 1 0 A M0 or 0 d* 2 I y; .W q ff 0 d1 /2 3 f v w a %M f 2 WW 5 3 HCE Patented Dec. 9, 1952 UNITED STAT ES PAT ENT FF 1 CE PRESSURE RESPONSIVE VALVE AND vA'LvE' SYSTEM HenryUl Garrett, Clifford M. Peters, and EVerett" D; McMurry, Houston, Tex.', assignors to Garrett Oil Tools; 1116., Houston, Tex, a corporationof Texas Application Mar-c1111, 1949, Serial'No; 80,792

,14Claims; 1:

This invention relates to improvements" in pressure responsive valves and' a'sys'tei'n of installation of a seriesof s'u'cli valves; and refersmore particularly tovalvesadapted" to-c'ontrol the injectionof' fluid undefp'ress'ure' from 1 one container into another containerin response to variations in the pressures within thetwo containers.

The valve'of this invention especially adapted for usein gas lift operations as they are con'ducted in the oil industry; In many oil producing wells, it is the present daypractice to stimulateproduction by the injection of gas under pressure into thepipe string which conducts'j the well fluids to the ground surface; gas is -injected into the string at a level well belo'wthe'g'round and, due to itsbuoyancy andexpansion, forces" the well liquids upwardly within the pipe string. Control of the injection-of theg a'sinto'the flow string of pipe of the well hasbeen attempted by variousmeans, and this-invention is concerned with the type of operation employing pressure responsive valves for this-purpose; that is, valves that have asealedoffresilient means which hold .them closed when the 'pressure of the gas-to be injected into thefiow'p'ip'eis below a predetermined amoun t, Thi'smeanshasm part exposed to the pressure'of 'thelifting gas and' -when the force due to the'pre'ssure acting-ag'ainstithis part overcomes the resilient means; the valve is opened;

In this method of liftingwell fiuid's to the ground surface, it isdesirab'le, in wellswhich'have ahigh rate offlowof wellifiuids from the producing formation into the well bore, to produce the well'fiuids with-a continuous-flow. On the other hand, in wells wherethe-wellifluids'feed slowly from the producingfi'orma-tion into the bore, it is preferred to intermittently. inject; the lifting gas'into the flow stringaof pipe: Heret'ofore, it has beenimpossible-to usether'samefvalve installations for either'continuous orintermittent production. Also, therehas been no means whereby the wells canbeproducedr continuously which employ pressure-respc msive valves adapted to positively open and close in response to pressures within the two containers or stringsof 'pipel In addition, it is desirable to" employ a valve installation which makes it possible to produce the well fluids through the" working valves or lower valves of the installation at a high pressure. In pressure responsive equipment heretofore used, it has been" necessary successively reduce the 'openingpressures iof succ essivelylower level valves to prevent" the"untimely opening of 21 the upper valves; This greatly reduces the available working pressure at-the working valve. Another problem that has confronted the' industry when employing gaslift-valveinstallations, where the pressurerespOnSiVe'VaIVes-employ a charge of fluid under elevated' 'pressur'es acting through-a benqws-cr otl i'er movable seal element;- h a sbeen that, whrthe bellows of one of thedumping valves fails, the pressure charge will drop and these upper valves will'thenopen during normal operation or working =of the well. When this occurs; the well must beshut down and the upper valves-repa-ired-or replaced. It-is desirable to provide a valve ofthis type wherein the valve will open when the" pressure of the pressure charge within the dumping valves is somewhat less than the-pressure-of thej control fiuid'or a gas'to-be injected into-theflow conduit of' thewell; Then, if the bellows orseal element of the valve-is destroyed, the pressure charge within the dumping valves will equalize with the control pressure and effectively'm'aintain thevalve'closed.

An object of this invention is to provide a'pressureresponsive valve which is especially adapted for use in gaslift production of well-fluids;

Another'object is to'provid'e a pressure-"responsive'valve which may 'beemployed'in gas lift production of well fluids in'both intermittent"- or continuous fiow'operations; p

A further object is' to provideapressureresponsiv'e valve'which makes it possible to equip a well for gas lift production wherein the by drostatic' head of well fluids may bedropped without sustantial' loss of operating pressure at the working valves of the-well.

Still another object is to provid'e'a pressure responsive valve employing a pressure charge as aresilient means formaintaining thevalveclosed' except" at precletermir'ied pressures wherein" the pressure charge is" of lesser magnitude than the control pressure atwhich the valve will open;

A still further object is to provide 'a sys tem for gas lift operations which will provide continuous flow of-liftingfluid'intothefwell at any one of several possibleflworlg'ing valves soas to efficientlyproducethewell fluidsi V Yet 'another'obj act is to" providea gas" lift'system for'wellsfor employing a series of pressure responsive valves, each' having resilient means for maintaining the valve" closed'under predetermined: ratios "of" pressures within the pressure "or gasinjection' string of pipe'andthe flow string of pipe, whereby thewellmay beproduced continuously from the working valve at the same 3 pressures used to dump the well or may be produced intermittently at substantially such pressures.

Yet a further object is to provide a gas liftvalve employing a resilient means for holding the valve closed which is subjected to the pressure of the fluid to be injected into the production string of pipe to provide a force tending to open the valve and having an arrangement whereby the pressure within the production string will influence opening and closing of the valve.

Even another object is to provide a flow fitting which may be employed in conjunction with a pressure responsive motor and adapted to maintain a part of the pressure mechanism tending to maintain the valve open in a pressure zone which will be influenced by the pressure within the container into which the pressure fluid is to be injected.

Other and further objects of the invention will appear from its full description.

In the accompanying drawings, which form a part of the instant specification and are to be read in conjunction therewith, and wherein like reference numerals are used to designate like parts in the various views:

Fig. 1 is a diagrammatic view of a well installation illustrating the invention and equipped with a plurality of pressure responsive valves embodying this invention;

Fig. 2 is a fragmentary sectional view upon an enlarged scale showing the details of the pressure responsive valves shown in Fig. l; and

Fig. 3 is a View taken along the line 33 in Fig. 2 in thedirection of the arrows.

Referring to the drawings, in the illustration of Fig. 1, the numeral 5 designates the usual well casing and the numeral 6 indicates the usual string of Well tubing; With the installation as shown, the tubing 6 constitutes the flow string of tubing and communicates through a screen 1 at its lower end with the producing formation. At its upper end, the tubing string 6 is connected with a flow line 8. The well head 9 provides a seal for the annulus between the pipe strings 5 and B. A connection In is provided for supplying a lifting gas under pressure to this annulus. Usually, a packer seals off this annulus at a lower level beneath the lowest gas lift valve installation and is shown schematically at H. The tubing string 6 has mounted along its length a plurality of pressure responsive valves l2. These valves will ordinarily be installed with the uppermost valve just below the upper level of the accumulated well liquid or hydrostatic fluid head. The lowest valve 12 will be installed at the level where gas is to be injected into the flow string for normal working of the well, if this is known, but where this is not positively determinable, the lower valve or valves will be at a sufliciently low level to insure proper operation through one of the lower valves, that is for example, the lowest one, two or three valves of the installation.

Turning now to a description of the individual pressure responsive valves employed in the installation, reference is made to Figs. 2 and 3. The valve may be considered as made up of the usual pressure responsive motor, which may be of any conventional type employing a resilient means such as a pressure charge, a spring, or a combination of a pressure charge and spring, arranged to force the valve member toward closed position. It -is preferred to use as a motor the arrangement shown in the co-pending application 4 of Henry U. Garrett and Clifford M. Peters for Pressure Responsive Valves, Serial No. 737,600, filed March 27, 1947, now Patent No. 2,519,242, but for further example, the arrangement shown in our co-pending applications for Valves, Serial No. 789,964, filed December 5 1 947,and for Pressure ResponsiveValves, Serial No. 771,160, filed August 29, 1947, now abandoned, may be employed. In conjunction with this motor, a flow fitting is employed, which provides a pressure chamber about the valve member arranged to reflect substantially the pressure of the flow string of pipe of the well, the arrangement being such that this pressure urges the valve member toward open position.

Referring in detail to the valve, it includes a housing l3 made up of a cap or dome M, a nipple I5 threaded thereto, a ported member I6 threaded to the nipple, and a flow fitting made up of a choke support I! and a seated member or valve cage l8. 7 The motor is includedwithin the parts I4, l5 and I6 of the housing and itsfunction and construction is described and explained in great detail in the above-mentioned co-pending application, Serial Number 737,600, but will be described at considerable length herein. The interior of the dome member [4 houses the resilient means whichyinthe preferred form, constitutes a bellows l9; sealed at one end to nipple I 5, and at its other end to the head of valve uide or stem 29. This stem 20 may be made up of tWoor more parts as indicatedin the drawings. A seal is provided between the nipple l5 and cap l4 so that the bellows constitutes a movable part or element, in conjunction with the head of stem 20, sealing off achamber in the housing. This chamber may be charged with a pneumatic fluid under predetermined pressure and the vforce of this fluid chargeagainst the movable part provides a force that will urge the Valve member 21 against the seat 22in port 23. The sealed off chamber'may carry an'apertured partition [4a, the'aperture of which is to'be. engaged by seal washer 24 secured to the upper end of stem 20 by screw 25. A non-compressible liquid such as water may be placed in the sealed chamber in sufficient quantity to completely fill the space between the bellows and the part of the housing beneath partition Ma when the bellows has been expanded or extended sumciently to abut washer 24 on the underside'of partition I la to close. the aperture therein. This provides a non-compressible backing for the bellows to protect it against excessive pressure differentials that may be encountered when equipping a well for gas lift.

With this arrangement, the pressure exteriorly of the device communicates withthe interior of the bellows through ports [6a of ported member I6 and acts'against the inner area of the bellows, which due to the thickness of the bellows, usually about eighteen thousandths of an inch, is less than the effectivegpressure area of the movable element which is subjected tothe pressure of the pressure charge. Therefore, the'pressure exteriorly of the device will. of necessity exceed the pressure charge inorder to open the valve; ,Thus, if in operation a leak should occur in the bellows, the pressure exteriorly of the valves, when increased, will bleed into the sealed-off chamber to increase the pressure'therein and this will effectively maintain the valves closed so. that, if the bellows failure is in one of the dumping valves, production may be continued through the workfing valves without interruption for repair? or replacement of. the faulty dumping valve.

The'valve stem 20, asheretofore indicated, car'- ries the valve member 2| at its lower end and the motor is adapted .to normally maintain the valve closed until the force of the. pressure interiorly of the bellows acting against the movable element, plus the force of the pressure against the valve member across the area of" seat 22",, is sufiicient to overcome the force. of pressure'within dome I4 against the other side of the movable element or the area across theitop of the sealed bellows l9. 7

It is thus seen that the opening of" thevalve", is a function of the ratio. of pressures within, the flow string of pipe 6 and the gas lift ressure within the other string of pipe 5; In order to maintain this relationship when the valve is open, it is necessary to provide a chamber tor the valve member 2| in which theipressure will, remain substantially that of the now tubing. This may be accomplished by providing means for restricting the flow of the pressurefluid. into the interior of valve cage it as compared with "the cross-sectional area of port 23, by providin a constricted portion in the flow passage through the fitting. There will be a pressure drop across the constricted portion of thepassage and the pressure within the cage l8 will be substantially the pressure of the tubing. This may be accom-' plished by providing a series of plugs 26'having choke passages 28a'of predetermined" total areas. The stem 28 extends through a sleeve Ila in the choke support member 11 and preferably carries seal means, which may be O-rings 21, to provide a low friction seal between the stem and sleeve. This seal should be such as to be substantially frictionless. A lubricant material may be provided in the space 28 between the'seal elements 21.

The choke support member I! has a flange-like part which carries the choke plugs 26 and preferably about three of these plugs are employed. An annular space is provided between the'flangelike portion of member I! and the lower end of the ported member IE. It is preferred to surround this space with a screen 29 which may be secured to housing l3 in any suitable manner as by screws 30. This arrangement greatly reduces the likelihood of debris clogging the choke passages 28a. and even though a portion of the screen 29 should become clogged, nevertheless, ample opening will be provided'for'the passage of gas into the passage through the .flow fitting. The upper end or screen'29 may be extended so as to cover ports [6a leading into the interior of the bellows. An external groove in ported member It opens into ports lfia and is covered by the screen.

It is contemplated that this arrangement of the flow fitting may be altered as, for instance, by providing restricted openings in the peripheral wall of choke support member 11' communicating with the interior of the valve cage, or by employing a loose fitting stem 2-!) in the sleeve Ha to provide a constricted annular flow passage therebetween. In the latter instance, of course, the seal elements 21 will be dispensed with. Any other suitable means to provide a resricted flow passage for the flow of pressure fluid through the fitting. so as to give a pressure drop within the valve cage, which willbea func tion of the tubing pressure, may be employed. The advantage 'of' the preferred flo'w' fitting i1- lust'rated in the drawings resides in the freedom from "clogging of the restricted ortion" or the passageand also in the fact that the passages 26a do not impinge a stream of fluid against the valve member 2! or the stem. 20 which would have a deleterious cutting effect thereon.

Referrin to the operation of the device and system of installation of this invention, the operation of the individual valve will be first discussed and then the mode of operating the entire installation will be taken up. Thevalve member is assembled so as-to deliver gas from one pipe string into the other and it is contemplated that the arrangement can be such so that the tubing 6 provides the gas'supply string and the annulus between the tubing and easing 5 provides the how string. However, it is usually preferred to produce through the flow string of tubingt.

The pressure chamber within housing I3 is filled with a predetermined pressure charge of pneumatic fluid except that sufiicient liquid may be employed to completely fill that portion of the sealed off chamber'of the housing residing below partition Ma when the washer 24 provides a seal between the stem and the partition upon complete opening of the valve. This liquid level is indicated in the drawings. Of course, a spring or other suitable resilient means may be employed either exclusive of a pressure charge or in conjunction with a pressure charge. The how of the fluid from eXteriorly of the housing 53 into the interior of the bellows takes place past ports lea and the'loose fitting stem extending upwardly through nipple l5 and interiorly of the bellows. This passage is constructed so as to be substantially non-restricted whereby pressure variations exteriorly of the device are quickly reflected against the movable element to affect its position within housing l3. It is desirable to provide the stem 29 with an'internal axial bore Zta with radial portions 26?) adjacent the connection of the stem with the bellows. This provides a passage through which a suitable lubricant such asv grease may be forced into the space between the bellows and" stem and the space between the nipple and stem. The

grease reduces the likelihood of the space becoming clogged with debris and maintains a free or lubricated action of the valve stem. whereby the motor is very sensitive.

The flow of fluid through the flow fitting takes place through the screen 29- past the restricted portion of the fitting fiowpassage illustrated by passages Eta in the preferred' embodiment, through the interior of the valve cage and through port 23 into the how string of the installation. With the valve 2i engaging seat 22, the forces affecting the position of the valve member and the upper end of the bellows and head of stem 28 includes the pressure of the fiui-ii within. the sealed off portion of housing 53 acting against the upper end. or area across the upper end of the bellows tending to seat. the valve. Opposing this is the force due to the pressure exteriorly of the flow device acting against an area equal to the interior of the bellows where it is sealed to the stem, less the diameter of that portion of stem 20 across the seals 2?. An adidtional force tends to open the valve equal to the force of the tubing pressure against the part of the valve member 2! exposed interiorly of the seat. When these two opening pressures exceed the closing pressure, the valve will shift to open position. When this occurs, flow takes place past screen Z S Q-the refstricted'portion of the passage provided bychokes 25 and through port 23.

. Inasmuch as the total cross-sectional area of the passages 26a is less than the area across port 23, ther will be a pressure drop within the interior of the valve cage or flow fitting as compared to the pressure exteriorly of the device. This pressure drop will be a function of the pressure within the flow tubing adjacent the connection with the flow device. When the column of well fluid within the flow tubing becomes aerated, the force due to the pressure within the flow fitting acting against the valve member and across the stem 20 as it passes through sleeve I! will be reduced because of the difference in weight of the less dense aerated column and the arrangement should be designed so as to produce a substantial drop in the opening force whereby the valve will be closed. It is recommended that the effective area across stem 29, as at seals 21, be such that a drop of tubing pressure of one hundred pounds will produce a reduction of twenty pounds of the force due to the pressure interiorly of the fitting which forces the valve member toward open position. Of course, this may be altered somewhat to meet particular conditions. The cross-sectional area of the port 23 preferably is equal to the cross-sectional area of th stem at seals 21 to substantially equalize the opening force due to tubing pressure with the valve open or closed.

Taking up the operation of the system, it will be assumed for purposes of discussion that each of the four valves shown in Fig. 1 has a pressure charge which, when tested at the ground, will cause the valves to open at six hundred pounds gauge pressure exteriorly of the devices. Where the preferred Valve arrangement, utilizing the bellows having its interior sealed to the stem, is employed, the actual pressure within the pressure dome will be less than six hundred pounds and where the bellows has a cross-sectional area of substantially one inch and a wall thickness of eighteen thousandths of an inch, the actual pressure charge within the dome will be about five hundred twenty-five pounds gauge pressure. The temperature of the well fluids in most of the deep production of today is elevated and will in eifect increase the pressure required to open the valves but each of the valves will open at substantially the same pressures. However, if pressure fiuid is injected into the casing-tubing annulus, so as to raise the pressure within the annulus adjacent the well head 9 to, say, six hundred pounds, the weight of the column of fluid in the lower levels at which the valves are installed will increase the pressure at these levels where the liquid level is therebelow, to substantially evenly counteract the eifect of an increase in temperature.

For purposes of describing the operation of this invention, it will be assumed that the liquid level within the casing-tubing annulus is above the first or uppermost valve [2. The pressure fluid or gas lift medium is introduced into the annulus through conduit [0, and where continuous flow is desired, the fluid will be metered through a choke Illa or other suitable means. The total cross-sectional area of the restricted portions of the passages of the flow fittings of each of the valves 12 is gradually increased at successively lower levels. This is in accordance with the well known fact that a greater volume of lifting gas is required at a lower level than at a higher level. However, the arrangement is such that when any two of the valves are open, the total cross-sectional areas of the restricted porvalves should tions of the flow passages through eachof the valves will be greater than the area of the choke supplying conduit. I0. Thus, when two or more of the valves are open, the casing-tubing annulus pressure will reduce to close at least the uppermost one of the two open valves.

The pressure within string 5 then increases, forcing the liquid level downwardly to uncover the highest valve l2. Inasmuch as the control pressure at each of the valves is greater than six hundred pounds, all of the valves will be open, and when the uppermost valve is exposed to the gas, the gas will flow into tubing 6 aerating the column of fluid. At the same time, the liquid level will be lowered because more gas is being introduced into the casing than the single valve can accommodate. When the second valve has been uncovered, gas will pass into the tubing through both of the top two valves to aerate the column and produce the well fluids. However, this will bleed off the'casing pressure until the total forces tending to open the uppermost valve are not suflicient to maintain the valve open. This closing effect will be due to both a drop in casing pressure and tubing pressure at that valve. The liquid level will then commence to drop toward the third valve. When this Valve is uncovered, the casing pressure will again drop until the second valve is closed and the dumping process will continue until only the lowermost valve is open. 7

When the hydrostatic head has been dumped, the amount of fluid metered into the casing will be that required for producing the well at a continuous flow rate. As long as the gas introduced into the tubing maintains the proper producing condition of the fluid within the tubing 6, the valve member 2| of this lowest valve will remain unseated. However, if the well fluid within tubing 6 becomes too light, due to an excess of gas charged into the tubing, the pressure drop interior of the flow fitting and surrounding valve member 2! will be so great as to cause the valve to close. However, immediately upon an increase of the tubing pressure adjacent the valve, the valve will open. By proper regulation of the amount of gas charged into the casing, the lowermost valve I2 will operate substantially continuously to stimulate production of well fluids.

The continuous flow of Well fluids is desirable in those wells having a rapid rate of production of well fluids into the bottom of the hole. On the other hand, where the rate of production of the formation is not great and it is desirable to permit time to accumulate a head of well fluids, then the device and installation of this invention may be operated on an intermittent basis. The twenty pounds reduction in closing force, due to lightening of the load within the tubing adjacent the working valve, may be relied upon to eifect the intermittent opening of the lower valve. However, it is usually desirable for intermittent operations to drop the opening pressure of the valve or valves, which may be relied upon as intermitters, about twenty-five pounds in addition to this by reducing the force of the resilient means tending to close the valve. By this expedient the well may be produced intermittently with the elimination of any possibility of opening of the upper valves and with but very small reduction in operating pressure at the working valve.

Obviously, if any of the upper or dumping fail so as to open and constantly admit gas to the tubing, itwould throw off the operations and require a pulling of the tubing and repair of the upper valve. Such pulling operations are very expensive and require a shutting in of the well. It is for this reason that the preferred valves are of great value, for if the bellows fails on-an upper valve, the pressure within the bellows will not bleed ofi but .rather the casing pressure will bleed into the bellows, for at the operating level, the casing pressure will be greater than the actual pressure charge within the bellows. Thus, the valve member 2! of the faulty dumping valve will be held firmly against its seat and it will not be necessary to pull the tubing string 6 and repair the valve as long as the working valve is functioning properly.

In going into a well for the first time with gas lift equipment, it is often'impossible to-determine in advance at just what lever the working valve should be installed. In the installations in accordance with this invention if it is determined that thewell can be best, produced atone of the higher lever valves, this may be accomplished at a continuous flow by metering the gas into the casing at a rate equal to the capacity of the choke passages 26a of the higher lever valve.

From the foregoing it will be seen that/this invention is one well adapted to attain all of the ends and .objectshereinabove set forth, together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may 'be employed'without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

.As many possible embodiments may be made of .the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been claimed is:

1. A gaslift valve comprising a housing, an element movably :mounted within the housing and sealing off a variable capacity chamber therein, resilient means within the housing urging the :described, what is 'movable element in a direction to increase the volumeof the chamber, ports in the housing between the interior and exterior of the housing on the side of the movable element remote from the chamber, an outlet port in the housing with a seat thereon axially aligned with the movable elemerit, a valve member engageable with the seat, an actuating connection between the movable element and valve member, said outlet port communicating with the exterior of the valve with a passage having a constricted portion upstream from thevalve member the'si'ze of the constricted portion, relative to the outlet port, being such that substantially all of the pressure reduction in the fiuidpassing through'the constricted portion and outlet port takes'place across the constricted portion.

.2. In a valve of the gas lift type, a housing, a movable element providing a variable capacity sealed off chamber therein, resilient means urging the movable element in a direction to expand the chambenan opening in the housing wall on the side of the movable element remote from the chamber, ,a second chamber in the housing spaced axially from themovable element, an outletport therein with .aseat coaxial with .themovable element,.avalve.member controlling .the seat, an actuating connection between the movable element and the valve member, and port means providing a, constriction between the second chamber and the exterior of the housing, said port means having sufiiciently smaller effective area than that of the outlet port that substantially all of the pressure reduction in the fluid passing through the port means and outlet port takes place across the constriction.

3. A gas lift valve including ,a fitting with a passage .therethrough adapted to provide for fiow of fluid under. pressure from the exterior of the valve into a receptacle to which the fitting may be attached, a port with a seat ,on its upstream side making up part of the passage, a, constriction in the passage relative to the cross-sectional area of the port such'that substantially all of the pressure reduction in fluid passing through the passage takes place across the constriction with the valve 'in operation, said constriction positionedinterm'ediate the-seat and the inlet end of the passage, a valve'member adapted to engage the seat to control flow through the port, and a pressure responsivemotor connected to the valve member 'for actuating same, said connectionxineluding a rod extending from the fitting with a sealed sliding connection therethrough, said motor having a part exposed to the pressure of fluid exterior of the valve and sensitive to variations therein to influence opening and closing of thefvalve member, the arrangement being such that the force of pressure Within the fitting, between the port and constriction, acting against the effective area of the connecting rod at its sliding seal with thefitting, withthe valve member in open position, tends toxmaintain the valve memher in open'position.

'4. 'The'valve of 'claim'3 wherein the cross-sectional area of the valve-member included within the seat with the valve closed is substantially equal to the effective cross-sectional area of the connecting rod across the sliding seal.

5. A pressure responsive gas lift valve comprising a housing, 'a ,port with an upstream seat therein, a valve :member adapted to engage the seat to 'controlfiow therethrough, resilient means within the housing and connected to the valve member to urge it toward seated position, said resilient means having a part movably mounted within the casing providing a variable'capacity sealed chamber therein-with one surface exposed to the fiuid exterior of thevalve, said port being included in a passagesealed ofi-from the resilient means and communicating with the exterior of the valve, a constriction in the passage relative-to the portsuch that substantially all of the pressure reduction in fiuidpassing through the passage takes'place across the-constriction, said constriction being intermediate theportseat and the exterior 'of the valve, the connection between the valve member and resilient meanshaving a moving seal with the housing to seal off the passage, the arrangement being suchthatwith the valve member in open position the pressure of fluid withinthe passagebetween the-portand the constriction urges the connection, across the area of its seal-with the housing, in a direction to hold the valve member'open.

6. A gas lift valve including ;a :flow fitting adapted to provide for flow of fiuidzunder pressure from the exterior of the valve into aifluid container to which the fitting may be attached, a port with an upstream seat therein making up a part Offl'lflllid passage 'of-thefitting, a valve member movable interiorly of the fitting and cooperable with the seat 'to control flow therethrough, a pressure responsive motor connected to the valve member for actuating same, said motor having a resilient element urging the valve member closed and a part exposed to the pressure of fluid exterior of the valve urging the valve member toward open position under the influence of such pressure, said fitting having a constricted flow passage communicating between the exterior of the valve and the port and located upstream from the portion of the fitting housing the valve member, the size of the constricted passage, relative to the outlet port, being such that substantially all of the pressure reduction in the fluid passing through the constricted passage and the fitting takes plate across the constricted passage.

7. A gas lift valve comprising a housing, a flow passage therethrough with a seated outlet port and a valve member controlling same, a pressure responsive motor means within the housing with an operable connection with the valve member, said motor means including a resilient means constantly urging said valve member toward seated position, said motor means adapted to move the valve member to seated and open positions in response to variations in a control pressure to which it is exposed, the pressure to which the valve member is subjected when seated and from downstream of the seat urging the valve member toward open position in opposition to the resilient means, said passage having a constricted portion upstream of the port whereby the pressure between the constriction and port urges the valve member toward open position when unseated the size of the constricted portion, relative to the outlet port, being such that substantially all of the pressure reduction in the fluid passing through the constricted portion and outlet port takes place across the constricted portion.

8. The value of claim 7 wherein the motor means includes a bellows sealing oil a portion of the interior of the housing, said resilient means urging the bellows toward valve seating position against the pressure of control fluid to which the side of the bellows remote from the sealed off portion of the housing is exposed.

9. The valve of claim 8 wherein a charge of fluid under pressure within the sealed oil portion of the housing constitutes the resilient means.

10. A gas lift valve comprising a pressure responsive motor part and a flow control fitting for injecting fluid under pressure into a flow string of well equipment, the motor part having the usual housing with an element movably sealing off a variable capacity chamber therein with a resilient mean urging the element toward full capacity position and the pressure of fluid in the unsealed portion of the housing urging the element toward reduced capacity position, the flow control fitting including a valve cage with an outlet port carrying a seat, a valve member movable within the cage to control the seat, an actuating connection between the movable element of the motor and the valve member including a rod extending from th cage with the pressure in the cage urging the rod toward valve opening position when the valve is open, and port means so constricted relative to the area of the outlet port that substantially all of the pressure reduction in fluid flowing through the fitting takes place across the port means. said port means communicating between the interior of the cage and the exterior of the gas lift valve.

11. In combination inner and outer strings of well pipe, one adapted to produce well fluid and mam , r 12 the second adapted to supply gas under pressure into the first string of pip at selected positions therealong to stimulate flow of the well fluids, a series of pressure actuated gas lift valves positioned at descending levels within one of the strings to control injection of fluid from the second pipe string into the first pipe string in response to pressure within both strings, each of said valves having an outlet port between the interiors of the strings with a valve member controlling same, a constricted opening between the port and interior of the second string, the size of the constricted opening, relative to the outlet port, being such that substantially all of the pressure drop in the fluid passing from the second pipe string into the first takes place across th constricted opening, a resilient means connected to and urging the valve member closed and having a part exposed to pressure within the second string and urged thereby toward valve opening position, the pressure within the first string tending to unseat the valve member When seated and the pressure between the port and constricted opening tending to prevent seating of the valve member when in open position whereby when gas is introduced into the second string at a predetermined velocity, a Well so equipped will be automatically dumped of accumulated hydrostatic head of well liquid and then continuously produced from lower ones of the series of valves.

12. The combination of claim 11 wherein means is provided for metering lifting gas into the second string adjacent the ground surface and the constricted portions of the passage of each of the valves being increasingly large in descending order, the arrangement of these constricted passages being such that with any two of the valves open and passing gas, the pressure within the second string will be lowered to such extent that the uppermost of the two valves will be closed.

13. The combination of claim 12 wherein each of the valves has a charge of fluid under pressure serving as the resilient means for holding the valve members closed and each of the pressure charges for the valves are such as to cause the valve to open under identical pressures when tested under atmospheric pressure conditions.

14. A gas lift valve which comprises, in combination, a housing, a bellows mounted in the housing to provide a variable capacity sealed off chamber therein, said housing having an opening therein placin the side of the bellows situated externally of said sealed off chamber in fluid communication with the exterior of the housing so that pressure externally of the housing urges the bellows to decrease the volume of said sealed off chamber, said housing having a second chamber therein spaced axially from the bellows, an outlet port in said second chamber with a seat coaxial with the bellows, a valve member engageable with the seat, a rod extending through the housing into said second chamber and connecting between the bellows and valve member so that movement of the bellows to increase the volume of said sealed off chamber moves the valve member toward said seat, a sliding seal between the housing and rod, port means between the second chamber and the exterior of the housing having sufficiently smaller eflective area than that of the outlet port that substantially all of the pressure reduction in the fluid passing through the port means and outlet port takes place across the port means, the arrangement being such that fiuid pressure downstream of said valve seat, with the valve member seated, urges the valve member toward open position and, with the valve member unseated, the pressure in said second chamber acting against the efiective area, within said sliding seal, likewise urges the valve member toward open position.

HENRY U. GARRETT. 5

CLIFFORD M. PETERS.

EVERETT D. MCMURRY.

REFERENCES CITED The following references are of record in the 10 file of this patent:

Number 14 UNITED STATES PATENTS Name Date Bryant July 16, 1935 King Jan. 18, 1944 Peters Feb. 22, 1944 Walton Sept. 18, 1945 Carlisle Mar. 22, 1949