CA1204382A - Differential gas lift valve - Google Patents
Differential gas lift valveInfo
- Publication number
- CA1204382A CA1204382A CA000438552A CA438552A CA1204382A CA 1204382 A CA1204382 A CA 1204382A CA 000438552 A CA000438552 A CA 000438552A CA 438552 A CA438552 A CA 438552A CA 1204382 A CA1204382 A CA 1204382A
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- Canada
- Prior art keywords
- valve
- flow
- seat
- gas lift
- flow passage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Lift Valve (AREA)
Abstract
ABSTRACT
A gas lift valve device of the differentially operated type, having a straight, non-tortuous flow passage there-through, with a hollow valve stem providing a portion of such passage, said device having a floating seat which automatically moves to valve engaging position to check backflow, the area of said seat being larger than the area of a piston on said stem and arranged so that the valve will close at a first prede-termined differential pressure and will open at a second pre-determined differential pressure which is lower than the first.
A gas lift valve device of the differentially operated type, having a straight, non-tortuous flow passage there-through, with a hollow valve stem providing a portion of such passage, said device having a floating seat which automatically moves to valve engaging position to check backflow, the area of said seat being larger than the area of a piston on said stem and arranged so that the valve will close at a first prede-termined differential pressure and will open at a second pre-determined differential pressure which is lower than the first.
Description
~43~32 VIFFER~:NTIAL GP.S LI~T VI~LVE
BACKGROUND OF ~HE INVENT10 __ _ Field of the Invention Thi6 invention relates to well tools and more particular~y to gas lift valves used in operating oil well~ through practice of gas lift technique~.
Description of the Prior Art -Gas lift valves have been used for many year~ to control the injection of lift gas into a flow conductor from the exterior thereof to aerate a column o liquid therein and aid in lifting it to the surface. While fixed orifices have been used ~uccessfully in lifting liquids from well conduits, they waste lift gas. Gas lift valves, on the other hand, are more efficient in that they need not remain open and passing lift ga~ all the time, but mdy open only when conditions justify their eficient oper~tion.
One type of valve u~ed in gas lift operations is the dif-ferentially operated ga6 lift valve, commonly called "differ-ential valve". Such valve~ are normally open but close upon occurrence of a condition where the difference in pressures between the ~a6 lift colu~n and the production column exceeds predetermined value or which the ga& lift valve has been adjusted t~ clo~e- Becau~e of thiB characteri6tic~ the --1-- ~.
43~2 1 pressure of the lift ga6 is no- critical once the well has been unloaded and placed on PIoduction. Generally, li~t yas jr~
injected into thc tubing-casing annu~us of a well throuyh a choke which i~ sized to p~ss t~le quantity of lift gas which is needed to produce the de6ired volu~e of li4uids from the well.
In ~ome cases, gas i6 injected into the tubing and well products are lifted through the annulus.
Listed here are several U.S. patents which disclose a variety of differential gas lift valves. They are:
10 2,144,144 2,236,864 2,256,70~ 2,288,6~5 2,305,250
BACKGROUND OF ~HE INVENT10 __ _ Field of the Invention Thi6 invention relates to well tools and more particular~y to gas lift valves used in operating oil well~ through practice of gas lift technique~.
Description of the Prior Art -Gas lift valves have been used for many year~ to control the injection of lift gas into a flow conductor from the exterior thereof to aerate a column o liquid therein and aid in lifting it to the surface. While fixed orifices have been used ~uccessfully in lifting liquids from well conduits, they waste lift gas. Gas lift valves, on the other hand, are more efficient in that they need not remain open and passing lift ga~ all the time, but mdy open only when conditions justify their eficient oper~tion.
One type of valve u~ed in gas lift operations is the dif-ferentially operated ga6 lift valve, commonly called "differ-ential valve". Such valve~ are normally open but close upon occurrence of a condition where the difference in pressures between the ~a6 lift colu~n and the production column exceeds predetermined value or which the ga& lift valve has been adjusted t~ clo~e- Becau~e of thiB characteri6tic~ the --1-- ~.
43~2 1 pressure of the lift ga6 is no- critical once the well has been unloaded and placed on PIoduction. Generally, li~t yas jr~
injected into thc tubing-casing annu~us of a well throuyh a choke which i~ sized to p~ss t~le quantity of lift gas which is needed to produce the de6ired volu~e of li4uids from the well.
In ~ome cases, gas i6 injected into the tubing and well products are lifted through the annulus.
Listed here are several U.S. patents which disclose a variety of differential gas lift valves. They are:
10 2,144,144 2,236,864 2,256,70~ 2,288,6~5 2,305,250
2,314,~68 2,323,893 2,541,807 2,5~,715 ~ 11 of the above listed patents, with the exception of U.S.
Patent 2,305,250, have a common basic structural design which is, perhaps, more readily seen and understood when looking at patent 2,144,144 which i~sued to C. S. Crick~er on January 17, 1939. In this patent, and in Figures 11 and 12 in particular, the valve member has a piStOII 41 having its upper end exposed to casing pressure transmitted into the valve housing through lateral ports 46, and has its lower end exposed to tubing pressure transmitted t?-ereto through tubing port 25. A coil ~pring 44 biases the valve oward open position (shown in Figure 11). When the pre~sure in the casing exceeds the pre6sure in the tubing by a ~ufficient margin, the difference between these pressures actiny across the area of the piston 41 will create ~ufficient force to move the valve to closed position (shown in Figure 12), as it overcomes the force of 8pring ~4, and engages seat 6urface 47 with the ~eat to 6top the flow of lift gas from the casing into the tubing- When the difference between the tubin'3 and casing pressure is reduced 6ufficiently, the sprinc3 44 will open the valve, i.e., return the valve to it6 open po~ition (s?own in Figure 11). It is readily seen that t?e pi~ton areas exposed to the tubing pres~ure and the casing pre~sure are equal- Since the~e areas lZ~43t~Z
are equal, the valve both opens and closes at substar,tially the same pressure. ~nderstandably, the valve may quickly cycle between open and closed po6itions several times before ass-lming one position or the other. Thi6 i8 not desirable. It wastes gas and causes unnecessary wear and tear on the mechallism.
The gas lift valve~ disclosed in the other paterlts in this group also have valve mean~ with pistons having equal areas exposed to tubing and casing pressures.
U.S. Patent 2,~56,704 which issued on September 23, 1941 to C. S. Crickmer, et al., discloses a gas lift valve which is similar to those just discussed. In operation, this valve is in the position shown in Figure 2 of the pàtent. Lift gas from the casing enters side purts 37, flows upwardly in flutes 36, flows around the upper portion of valve 30 and past the tapered upper end thereof, and from thence througll port 27. When the pressure in the tubing decreases, the velocity of the gas passing the upper end of the valve increases, and the valve moves up toward the seat, pinching the flow therebetween. This further increases the velocity. The upper portion 34 of the valve acts as a piston and plunges into port 27 until it seats as shown in Figure 3- When liquid rises sufficiently high in the tubing to create sufficient back pressure acting against the upper end of the valve (which acts liXe a piston), the valve will move to open position.
Patents 2,288,605; 2,314,86~; and 2,323,B93 which issued to A. Boynton on July 7, 19~2, March 30, 1943, and July 13, 1943, respectively, each show a gas lift valve with a hollow-stemmed valve, but these valves have their opposite ends formed with equal seal ~urfaces ther~on and are addpted to enyage in equal cup-shaped seats at eit~er end to stop flow through the hollow stem when the differenLial pr~6sure across the mechani6m create~ a force exceedin~ the force of centering spring means associated with the tubular valve stem.
12~43~3z U.S. Patent 2,305,25~ which issued on December 15, 1942 to H. U. Garrett et al., discl(~ses a differeJltial 9a5 lift valve which indeed is opera~e(~ by the differel-ce between tubin~ and casing pres~ures, but i~ vdlve member does not always present equzl areas to the tubirl~ al~d casin~ areas and, therefore, acts differ~ntly from th~ device~ o the pat~ntB jUsL diBCU6Bed.
The device of patent 2,~05,250 has a valve member 21 (~ee Figures 2 and 3) with a conical seat surface 23, 22 on its upper and lower ends and a piston 28 just below the upper end.
Spring 30 biases the valve toward open position (shown in Figure 2). ~he upper end of the valve member can close upper seat 20 which opens to the casing, or its lower end can close lower seat 14 which opens to the tubing. Lateral ports 31 in the valve housing conduct lift gas fro~l the casing into the housing and to lower seat 1~ when the valve is open. The ports 31 have a combined area ~uch smaller than the area of either port }4 or port 20.
When the valve is open and is seated on upper port ~0, ca6ing pressure cannot act upon the upper side of piston 28, but acts upon the upper end of the valve through port 20. Port 20 is smaller than port 14, and the piston is larger than port 14. Thus, when the difference between the casing and tubing pres6ures be~omes 6ufficiently great to unseat the valve from upper 6eat 20, ca6ing pres~ure immediately acts upon the greater area of piston 28, causing the valve to move to fully clo6ed po6ition with a "snap action". This imparts positive operation to the ga~ lift valve and prevent6 the unwanted cycling mentioned above- It also save6 gas and avoids unnece~-6ary wear and tear on the valve mechanism.
It i6 obvious that when the valve is open, the differential pres6ure acts upon the area of upper seat 20, and when it is clo~ed~ the differ~ntial pres6ur~ act6 upon the larger area of lower seat 14- Thi6 difference in port sizefi cau~es the gas lZ~43~2 lift valve to close at a first differential pre6sure valuc and to reopen at a 6ec~r)d diff~rential value whicll is lesser than the first.
~ e present invention ifi an improvement over the differ-ential gas lift valves mentioned hereinabove. It i6 formed with unequal areas acros~ w~lich the differential pressure ~ay act to actuate the valve to open or closed po8i tion so that the valve will close at a first differential pressure value and close at a lesser value without cycling and without need of a special piston to provide snap action because the openiny and closing differentials are 80 ~ifferent. Also, the present invention provides a gas lift valve having a less tortuous flow passa~e through it in that the flow passage passes straight through the valve. The valve stem is hollow and conducts lift ga.s to the ball valve closure member attached thereto, tl-e lift gas exiting the stem througl) lateral ports at the ball and passing aro~nd the ball and through the seat. A choke or flow bean is advantageously provided in the hollow valve stem.
Further, the present invention provides a gas lift valve having novel mean~ for preventing backflow thro~gh it.
There is not found in the known prior art a gas lift valve having a valve stem hollow from end to end which closes at one differential pressure and reopens at a le~ser differential pressure and having a s-raicJht flow pas6age therethrough with only a ~mall but streamlined detour around it~ ball closure.
Neither was there foun~ a gas lift valve in the known prior art having a floating valve seat which also actS-as a check valve and at the same time provides a straight unobstructed flow passage therethrough when in open position- In addition, there was n~t found a ga~ lift valve having a hollow valve stem in which a flow re~trictor i~ provided.
~ le present invention ovcrcomes many of the problems as-sociated with differential ga~ lift valve~ by providing gas lZ~43~32 lift valves haviny a ~Lr~i(3ht-t}lrouc3h flc-w passage, a hollow stem constituting a portion of that strait3ht passage, a flow re6trictor in the h~llow steln, a floating valve seat which also serves to check again~t backflow, a closing differ~nt;al which i8 higher than its operling differential, and simple con-~truction which i~ less coutly to manuf~cture.
SUMMA RY OF' THE I NVENT I ON
~ . .
The present invention is directed to a ~as lift valve for attachment to a well flow c~nductor and having a body with a flow passage therethrough for conducting lift gas between the exterior of the conductor and the interior thereof, a valve ~eat in the body s~rrounding the flow passage, a valve closure in the body engageable with the seat to control fluid flow through the flow passage, a hollow valve ~tem having one end expo~ed to up~tream pre~ure and its other end attached tQ the clo~ure ~ember, lateral port ~ean6 in the stem adjacent the closure membex and means for ~iasing the closure member toward open position to permit fluid flow through the hollow stem, around the valve closure and throu9h the valve 6eat. This invention i8 al80 directed to such gas lift valves having flow restrictor mearls in the hollow ~tem, a floating seat for pre-venting backflow through Lhe valve, and having means whereby ~he valves close in responRe to a first differential pressure and open at a second differential pre~sure which is le~er than the first.
It i~ therefore one object of this invention to provide an improved gas lift valve for controllin9 fluid flow between the interior and the exterior of a flow conductor and which i~
re~ponr,ive to the diff~rerlce between the upstream and the downstream pre6sure~ to which it i~ ~ubjected.
Anothcr object i6 to ~rovide a ga~ lift valve of the i~43~32 character descri~ed whicll will cl~se w~lell Lhe dif~erential pressure incre~ses to a prl!(3eLer~illed val~e but will reope when tl-e diff~r~ntidl prLs~ur-~ d~cre~ses to a ~redetermined value which iB 8Ubstalltially lc~s than the valuo at which the valve closes.
Another o~ject is ~o provid~ a gas liC- valve of the character described ~aving a ~ubstarltially straight, relatively non-tortuous ~low passage therethrough.
Another object is to provi~e a gas lift valve of the character described having a valve closure with a hollow stem providing a portion of a non-tortuous flow passage therethrough.
A further object iu to provide sllch a gas lift valve having flow restrictiny means in the valve stem thereof.
Another object is to provide a gas lift valve of the character descri~ed ~lavillg im~rov~d m~arlR therein ~or pre-venting backflow therethrough.
~ nother object is to provide a gas lift valve of the character described having a f loating seat which upon occurrence of backflow will ~ove into engagement with the valve's closure member to ~reclude further backflow through the device.
Another object of this invention is to provide a gas lift valve of the character described having its inlet provided in the form of narrow slits for precludin9 entrance of larger particles such as sand or debris into the valve ~echanism.
A further object is to provide a gas lift valve of the character described which is attcchable to a lock or latch device to be rè~ovably installed in a seating receptacle, such as, for instance, a side pocket receptacle or a landing nipple formirlg a part of a well Ilow conductor.
Other objects and advanta~es may become apparent from reading the descriptioll which follows and from studying the accompanying drawing w}lereir-,:
1~43~Z
l Brief Descr~t:ion o~ t},c l)rawiu~
_ _ _ _ . _ _ _ Figure l i8 a diagram~ tical view of a gas lift. well having - a 6ingle ~tring of tUbill-J with a plurality of gas lift valves attached thereto;
Figure 2 is a diagrammatical view of a gas lift well having ~ultiple tubing strings therein with a plurality of gas lift valves in each tubing string;
Pig~re 3 is a longitudinal view, partly in section and partly in elevation, 6howing a gas lift valve constructed in accordance with thi~ invention showing the valve in open position;
Figure 4 is a cross-sectiorlal view taken along line 4--4 of Figure 3;
Figure 5 i5 a view ~imilar to ~igure 3 showing the device of Figure 3 with the valve in closed position;
Figure 6 i6 a fragmentary view similar to Figure 3 showing the valve of Figure 3 in po~ition preventing backflow;
Figure 7 is a fragmentary view similar to Figure 6 showing a ~odified form of ga~ lift valve having a spring for biasing the floating 6eat toward backflow preventing position;
Figure 8 i6 a diagrammatical view similar to Figure l but ~howing a well with a single string of tubing which includes side pocket mandrel6 with g2l~ lift valves installed therein; and ~ igure 9 i6 a view si~ilar to Figure 3 ~howing a gas lift valve embodying this invention and adapted for attachment to an anchoring device for retrievable in6tallation in a landing receptacle in a well flow conductor.
Description of the Preferred Embodi~ent~
The device of thi~ invention i 8 u~eful in sas lift wells such a6 the well lO illustrated diagrammatically in ~igure l.
~his well has a casing ll perforated a~ at l2 to provide inlet~
for well product~- A well tubing 13 ~a~ it~ ~ower open end in i2~b43~32 fluid communic~ion with t~e ca~ing near ~he p~rforations. A
well packer 14 closes the tubing-casing arlnulus 15 just above the perforations while a wellhead 16 closes the annulus 15 at the upper end of the casing. The ~pper end of the tubing ~onnects to the wellhead 1~ and a conventional Christmas tree represented by the valve 17. A flow line 18 containing a wing valve 19 ie connected to the Christma~ tree to conduct well product~ to conventional surface equipment (not shown).
The well tubing is equipped with a plurality of gas lift valves only two of whic}l are shown. These are identified by the reference numerals 20 and 22. These gas lift valves are constructed in accordance with this invention and may be identical to the ga~ lift valve ~hown in Figures 2-6.
Lift gas i~ supplied through yas line 23 connected to the casing 11 as shown and includes a valve 24 for controlling flow therethrough. A flow choke (not shown) may be included in line 23 near valve 24, if desired.
All of the gas lift valves described herein and embodying this invention are of tl-e differential type. They are actuated by the difference in pres~ures of the lift gas and the production fluids which act upon them- These valves are ~tructured such that they close at a predetermined differential pres6ure and open at a predetermined differential pressure which i~ con~iderably lower than the closing differential preEisure .
Referring now to Figur~6 3-6 it will be seen tha~ the gas lit valve of this invention is indicated generally by the numeral 25. This valve 25 may be identical to valve~ 20 and 22 6een in Figure~ 2 and function in exactly the same manner and used for the ~ame purpo~e.
Valve 25 include6 a hou~ing or body 28 having a flow pasfiage 29 extending it~ full length, flow normally taking place therethrough in the direction 8hown by the arrow 29. The _g_
Patent 2,305,250, have a common basic structural design which is, perhaps, more readily seen and understood when looking at patent 2,144,144 which i~sued to C. S. Crick~er on January 17, 1939. In this patent, and in Figures 11 and 12 in particular, the valve member has a piStOII 41 having its upper end exposed to casing pressure transmitted into the valve housing through lateral ports 46, and has its lower end exposed to tubing pressure transmitted t?-ereto through tubing port 25. A coil ~pring 44 biases the valve oward open position (shown in Figure 11). When the pre~sure in the casing exceeds the pre6sure in the tubing by a ~ufficient margin, the difference between these pressures actiny across the area of the piston 41 will create ~ufficient force to move the valve to closed position (shown in Figure 12), as it overcomes the force of 8pring ~4, and engages seat 6urface 47 with the ~eat to 6top the flow of lift gas from the casing into the tubing- When the difference between the tubin'3 and casing pressure is reduced 6ufficiently, the sprinc3 44 will open the valve, i.e., return the valve to it6 open po~ition (s?own in Figure 11). It is readily seen that t?e pi~ton areas exposed to the tubing pres~ure and the casing pre~sure are equal- Since the~e areas lZ~43t~Z
are equal, the valve both opens and closes at substar,tially the same pressure. ~nderstandably, the valve may quickly cycle between open and closed po6itions several times before ass-lming one position or the other. Thi6 i8 not desirable. It wastes gas and causes unnecessary wear and tear on the mechallism.
The gas lift valve~ disclosed in the other paterlts in this group also have valve mean~ with pistons having equal areas exposed to tubing and casing pressures.
U.S. Patent 2,~56,704 which issued on September 23, 1941 to C. S. Crickmer, et al., discloses a gas lift valve which is similar to those just discussed. In operation, this valve is in the position shown in Figure 2 of the pàtent. Lift gas from the casing enters side purts 37, flows upwardly in flutes 36, flows around the upper portion of valve 30 and past the tapered upper end thereof, and from thence througll port 27. When the pressure in the tubing decreases, the velocity of the gas passing the upper end of the valve increases, and the valve moves up toward the seat, pinching the flow therebetween. This further increases the velocity. The upper portion 34 of the valve acts as a piston and plunges into port 27 until it seats as shown in Figure 3- When liquid rises sufficiently high in the tubing to create sufficient back pressure acting against the upper end of the valve (which acts liXe a piston), the valve will move to open position.
Patents 2,288,605; 2,314,86~; and 2,323,B93 which issued to A. Boynton on July 7, 19~2, March 30, 1943, and July 13, 1943, respectively, each show a gas lift valve with a hollow-stemmed valve, but these valves have their opposite ends formed with equal seal ~urfaces ther~on and are addpted to enyage in equal cup-shaped seats at eit~er end to stop flow through the hollow stem when the differenLial pr~6sure across the mechani6m create~ a force exceedin~ the force of centering spring means associated with the tubular valve stem.
12~43~3z U.S. Patent 2,305,25~ which issued on December 15, 1942 to H. U. Garrett et al., discl(~ses a differeJltial 9a5 lift valve which indeed is opera~e(~ by the differel-ce between tubin~ and casing pres~ures, but i~ vdlve member does not always present equzl areas to the tubirl~ al~d casin~ areas and, therefore, acts differ~ntly from th~ device~ o the pat~ntB jUsL diBCU6Bed.
The device of patent 2,~05,250 has a valve member 21 (~ee Figures 2 and 3) with a conical seat surface 23, 22 on its upper and lower ends and a piston 28 just below the upper end.
Spring 30 biases the valve toward open position (shown in Figure 2). ~he upper end of the valve member can close upper seat 20 which opens to the casing, or its lower end can close lower seat 14 which opens to the tubing. Lateral ports 31 in the valve housing conduct lift gas fro~l the casing into the housing and to lower seat 1~ when the valve is open. The ports 31 have a combined area ~uch smaller than the area of either port }4 or port 20.
When the valve is open and is seated on upper port ~0, ca6ing pressure cannot act upon the upper side of piston 28, but acts upon the upper end of the valve through port 20. Port 20 is smaller than port 14, and the piston is larger than port 14. Thus, when the difference between the casing and tubing pres6ures be~omes 6ufficiently great to unseat the valve from upper 6eat 20, ca6ing pres~ure immediately acts upon the greater area of piston 28, causing the valve to move to fully clo6ed po6ition with a "snap action". This imparts positive operation to the ga~ lift valve and prevent6 the unwanted cycling mentioned above- It also save6 gas and avoids unnece~-6ary wear and tear on the valve mechanism.
It i6 obvious that when the valve is open, the differential pres6ure acts upon the area of upper seat 20, and when it is clo~ed~ the differ~ntial pres6ur~ act6 upon the larger area of lower seat 14- Thi6 difference in port sizefi cau~es the gas lZ~43~2 lift valve to close at a first differential pre6sure valuc and to reopen at a 6ec~r)d diff~rential value whicll is lesser than the first.
~ e present invention ifi an improvement over the differ-ential gas lift valves mentioned hereinabove. It i6 formed with unequal areas acros~ w~lich the differential pressure ~ay act to actuate the valve to open or closed po8i tion so that the valve will close at a first differential pressure value and close at a lesser value without cycling and without need of a special piston to provide snap action because the openiny and closing differentials are 80 ~ifferent. Also, the present invention provides a gas lift valve having a less tortuous flow passa~e through it in that the flow passage passes straight through the valve. The valve stem is hollow and conducts lift ga.s to the ball valve closure member attached thereto, tl-e lift gas exiting the stem througl) lateral ports at the ball and passing aro~nd the ball and through the seat. A choke or flow bean is advantageously provided in the hollow valve stem.
Further, the present invention provides a gas lift valve having novel mean~ for preventing backflow thro~gh it.
There is not found in the known prior art a gas lift valve having a valve stem hollow from end to end which closes at one differential pressure and reopens at a le~ser differential pressure and having a s-raicJht flow pas6age therethrough with only a ~mall but streamlined detour around it~ ball closure.
Neither was there foun~ a gas lift valve in the known prior art having a floating valve seat which also actS-as a check valve and at the same time provides a straight unobstructed flow passage therethrough when in open position- In addition, there was n~t found a ga~ lift valve having a hollow valve stem in which a flow re~trictor i~ provided.
~ le present invention ovcrcomes many of the problems as-sociated with differential ga~ lift valve~ by providing gas lZ~43~32 lift valves haviny a ~Lr~i(3ht-t}lrouc3h flc-w passage, a hollow stem constituting a portion of that strait3ht passage, a flow re6trictor in the h~llow steln, a floating valve seat which also serves to check again~t backflow, a closing differ~nt;al which i8 higher than its operling differential, and simple con-~truction which i~ less coutly to manuf~cture.
SUMMA RY OF' THE I NVENT I ON
~ . .
The present invention is directed to a ~as lift valve for attachment to a well flow c~nductor and having a body with a flow passage therethrough for conducting lift gas between the exterior of the conductor and the interior thereof, a valve ~eat in the body s~rrounding the flow passage, a valve closure in the body engageable with the seat to control fluid flow through the flow passage, a hollow valve ~tem having one end expo~ed to up~tream pre~ure and its other end attached tQ the clo~ure ~ember, lateral port ~ean6 in the stem adjacent the closure membex and means for ~iasing the closure member toward open position to permit fluid flow through the hollow stem, around the valve closure and throu9h the valve 6eat. This invention i8 al80 directed to such gas lift valves having flow restrictor mearls in the hollow ~tem, a floating seat for pre-venting backflow through Lhe valve, and having means whereby ~he valves close in responRe to a first differential pressure and open at a second differential pre~sure which is le~er than the first.
It i~ therefore one object of this invention to provide an improved gas lift valve for controllin9 fluid flow between the interior and the exterior of a flow conductor and which i~
re~ponr,ive to the diff~rerlce between the upstream and the downstream pre6sure~ to which it i~ ~ubjected.
Anothcr object i6 to ~rovide a ga~ lift valve of the i~43~32 character descri~ed whicll will cl~se w~lell Lhe dif~erential pressure incre~ses to a prl!(3eLer~illed val~e but will reope when tl-e diff~r~ntidl prLs~ur-~ d~cre~ses to a ~redetermined value which iB 8Ubstalltially lc~s than the valuo at which the valve closes.
Another o~ject is ~o provid~ a gas liC- valve of the character described ~aving a ~ubstarltially straight, relatively non-tortuous ~low passage therethrough.
Another object is to provi~e a gas lift valve of the character described having a valve closure with a hollow stem providing a portion of a non-tortuous flow passage therethrough.
A further object iu to provide sllch a gas lift valve having flow restrictiny means in the valve stem thereof.
Another object is to provide a gas lift valve of the character descri~ed ~lavillg im~rov~d m~arlR therein ~or pre-venting backflow therethrough.
~ nother object is to provide a gas lift valve of the character described having a f loating seat which upon occurrence of backflow will ~ove into engagement with the valve's closure member to ~reclude further backflow through the device.
Another object of this invention is to provide a gas lift valve of the character described having its inlet provided in the form of narrow slits for precludin9 entrance of larger particles such as sand or debris into the valve ~echanism.
A further object is to provide a gas lift valve of the character described which is attcchable to a lock or latch device to be rè~ovably installed in a seating receptacle, such as, for instance, a side pocket receptacle or a landing nipple formirlg a part of a well Ilow conductor.
Other objects and advanta~es may become apparent from reading the descriptioll which follows and from studying the accompanying drawing w}lereir-,:
1~43~Z
l Brief Descr~t:ion o~ t},c l)rawiu~
_ _ _ _ . _ _ _ Figure l i8 a diagram~ tical view of a gas lift. well having - a 6ingle ~tring of tUbill-J with a plurality of gas lift valves attached thereto;
Figure 2 is a diagrammatical view of a gas lift well having ~ultiple tubing strings therein with a plurality of gas lift valves in each tubing string;
Pig~re 3 is a longitudinal view, partly in section and partly in elevation, 6howing a gas lift valve constructed in accordance with thi~ invention showing the valve in open position;
Figure 4 is a cross-sectiorlal view taken along line 4--4 of Figure 3;
Figure 5 i5 a view ~imilar to ~igure 3 showing the device of Figure 3 with the valve in closed position;
Figure 6 i6 a fragmentary view similar to Figure 3 showing the valve of Figure 3 in po~ition preventing backflow;
Figure 7 is a fragmentary view similar to Figure 6 showing a ~odified form of ga~ lift valve having a spring for biasing the floating 6eat toward backflow preventing position;
Figure 8 i6 a diagrammatical view similar to Figure l but ~howing a well with a single string of tubing which includes side pocket mandrel6 with g2l~ lift valves installed therein; and ~ igure 9 i6 a view si~ilar to Figure 3 ~howing a gas lift valve embodying this invention and adapted for attachment to an anchoring device for retrievable in6tallation in a landing receptacle in a well flow conductor.
Description of the Preferred Embodi~ent~
The device of thi~ invention i 8 u~eful in sas lift wells such a6 the well lO illustrated diagrammatically in ~igure l.
~his well has a casing ll perforated a~ at l2 to provide inlet~
for well product~- A well tubing 13 ~a~ it~ ~ower open end in i2~b43~32 fluid communic~ion with t~e ca~ing near ~he p~rforations. A
well packer 14 closes the tubing-casing arlnulus 15 just above the perforations while a wellhead 16 closes the annulus 15 at the upper end of the casing. The ~pper end of the tubing ~onnects to the wellhead 1~ and a conventional Christmas tree represented by the valve 17. A flow line 18 containing a wing valve 19 ie connected to the Christma~ tree to conduct well product~ to conventional surface equipment (not shown).
The well tubing is equipped with a plurality of gas lift valves only two of whic}l are shown. These are identified by the reference numerals 20 and 22. These gas lift valves are constructed in accordance with this invention and may be identical to the ga~ lift valve ~hown in Figures 2-6.
Lift gas i~ supplied through yas line 23 connected to the casing 11 as shown and includes a valve 24 for controlling flow therethrough. A flow choke (not shown) may be included in line 23 near valve 24, if desired.
All of the gas lift valves described herein and embodying this invention are of tl-e differential type. They are actuated by the difference in pres~ures of the lift gas and the production fluids which act upon them- These valves are ~tructured such that they close at a predetermined differential pres6ure and open at a predetermined differential pressure which i~ con~iderably lower than the closing differential preEisure .
Referring now to Figur~6 3-6 it will be seen tha~ the gas lit valve of this invention is indicated generally by the numeral 25. This valve 25 may be identical to valve~ 20 and 22 6een in Figure~ 2 and function in exactly the same manner and used for the ~ame purpo~e.
Valve 25 include6 a hou~ing or body 28 having a flow pasfiage 29 extending it~ full length, flow normally taking place therethrough in the direction 8hown by the arrow 29. The _g_
3~3Z
1 body 28 comprises a main housing member 30 which is internally threaded at its lower end (upstream end) as at 32 for attach-ment of the pluy member 33 while its upper or downstream end is internally threaded as at 34 for attachment of sub 36. This connec-tion is preferably sealed by suitable means such as resilient seal ring 35. Sub 3G is externally threaded at its upper end as at 36a for attachment to the lug 37a of a con-ventional lug-type mandrel 37 (shown in dotted lines) rnade up in the tubing string and providing a passageway (not shown) between the tubing bore and the annulus. When the gas lift valve 25 is attached to the tubing via the lug-type mandrel 37, gas may be conducted from the annulus to the interior of the tubing when the gas lift valve is open.
Plug member 33 is bored as at 38 from its upper end, but this bore terminates short of its lower end. An inlet for lift gas is preferably provided by narrow cross slots or slits 39 for excluding sizeable particles of debris, et cetera, which may otherwise enter the valve mechanism and cause damage thereto. These slots 39 can be made as wide or as narrow as desired, but they should provide an inlet of adequate flow capacity (at least as great as bore 38).
The main body member 30 has a main bore 40 having a lower portion thereof much enlarged as at 41 providing a downwardly facing shoulder 42. The upper portion of bore 40 is enlarged as at 43 and further enlarged as at 44 providing an inclined shoulder 45, all for purposes to be made clear later.
The sub 36 has a bore 48 which is enlarged as at 49. The outer end of enlarged bore 49 is flared as at 50 to provide a frusto-conical shoulder whose purpose is soon to be explained.
The device 25 is provided with a valve seat having a seat surface which surrounds the flow passage 29 passing through the body 28. This seat may be formed integrally with the sub 36 or could possibly be formed in the main member 3~. However, in the form illustrated in t~e drawing, and particular~y ~igures 3 and 5, such seat surface i~ provided in a floating valve seat member 60 having a bore 61 therethrough whic}) is enlarged at 62 to provide frusto-conical ~eat surface 63 adapted to be engaged by a valve member, to ~e described later, for controlling flow through the bore 61 of the ~eat member. Enlarged bore 62 of the seat member is flared at its lower end a~ at 64 to streamline the flow passage and to provide a guide surface for the valve member.
The lower portion of the valve seat member 60 is slidable in bGre 45 and has a fairly close fit therewith yet will ~lide freely therein. Its outer ~urface 66 is provided with an external annular rece~6 in wl~ich i~ carried a resilient seal ring 67. The upper portion of seat member 60 i5 reduced in outside diameter a~ at 65 ~nd is telescoped into enlarged borc 49 of ~ub 36 as shown where it is ~reely slidable. The tran-sition between the enlarged and reduced outer surfaces of the seat member 60 provides an external frusto-conical surface 68 in which is formed an external annular reces~ fitted with a resilient seal ring 69.
~ he valve ~eat member 60 is slidable between an upper position, shown in Figures 3 and 5, and a lower pnsition, shown in Figure 6. When the seat member is in its upper position, it~ upwardly facing external frusto-conical surface 68 engages downwardly facing fru~to-conical surface 50 of ~ub 36 and seal ring 69 ~eal~ therebetween to prevent leakage between the sub 36 and seat member 60.
~ he seat me~ber 60 i~ very freely movable to an inter-mediate position wherein its ~eal ring 67 reaches upwardly facing inclined ~houlder 45 in the main hou~ing member, and is further filidable to it~ lower po~ition ~een in Figure 6 wherein its seal ring 67 ~ealingly e~lgages bore 43 in the main housing 12~43~3Z
member, a position w~,ich will be In~l-e ~llly ~xplairled ll~reill-below.
7~
A valve closure mem~r\i~i disl~osed in the main flow passage 29 of -the body c~nd is movable longitudinally relative to tlle seat member 60 between ';~lt~ dnd un~ated positions. T~lis valve closure member m~ly lle c~f any suitdbl~ shape, but th~t illustrated in the drawil~y i~ in the ~nl~C of a ball or sp21ere 72. This ball is eng~lyeable with seat surface 63 to preclude flow through the seat meml~er, and when the ball is thus seated, there is but ~ small clearance between it and the inner wall of - bore 62 of the seat member. The lower portion of the seat member which surrounds bore 62 may be termed a lip and is indicated by the referel~ce numeral 60a.
The ball or valve closure 72 has attached thereto a hollow valve stem 74 which is secured to the ball as by silver soldering or other suitable means. The hollow valve stem 74 has a passage 75 extending the full length thereof. Slot6 76 are formed in the wall of the valve stem adjacent the ball 72 to enable gas flowing upwardly through the hollow stem to exit just below the ball and bypass it before passing through the valve seat. The flow area through slots 76 should be at least as large and preferably larger than the area of flow passage 75 through the stem.
It is preferable to provide flow restrictor means in the passage of the valve stem 74. If the valve stem is formed in one piece, a restriction may be provided in it~ bore. For instance, the sten can be bored from its upper end to within a fraction of an inch, say 3/8 to 1/2 inch, of it~ lower end.
Then this portion can be drilled through with a ~maller drill to provide a bore of de~ired orifice- Alternatively, a screw having an orifice therethrougll could be threaded into the ~tem bore.
12~P43t32 1 In the device illu6~r~ed in Figures ~ and S, the valve stem 7~ is for~led in ~wo pieces: a stem 77 and an adapter 78.
The adapter 7a is tubular, ~laving a bore 7~a, and is internally threaded as at 79. At ur ne~r its upper end it is provided with lateral slots 76 as ~own. The upper end face 78~ is shaped to fit the valve closure or ball 72 which is attached thereto as by suitable means such as silvcr soldering. The stem 77 is threadedly attac~cd as at thread 79 to the lower end of the adapter 78 as shown. 'rhe stem 77 is provided with an external flange B0 near its lower end and below flange B0, the stem is reduced in outside di~meter as shown at ~1 to provide a piston of suitable diameter. If desired, the bore 77a of the stem may be restricted ~y reducil-lg the diameter of the bore, say at one or the other of its ends as previously described, or a screw orifice could be threaded into one of it~ ends.
However, it may be desirable to provide a flow restrictor in the form of replaceable flow bean ~4. Bean B4 is captured in sealing engagement between the upper end of stem 77 and down-wardly facing shoulder 85 formed in adapter 78 below 610ts 76.
The flow bean is provided with a bore 86 therethrough of suitable orifice. The flow l~ean may be readily replaced by another bean when such becomes necessary.
A spring 90, preferably a straig21t helical coil compression spring. is disposed within enlarged bore 41 of the main body member 30 and surrounds the stem 77 with its lower end engaged with the upper side of stem flange 80 and its upper end engaged with downwardly facing shoulder 42 of main body member 30.
Thus the spring applies a bias to the valve ~tem 74 tending t~
maintain it in its lower position as shown in Figure 3 with the lower side of its flange engaged with the upper end of plug 33. Thus, the valve stem's longitudinal movel~ent is limited in one direction by its flan~e B0 engaging the plug and in the lZ~43~3Z
other direction by its bclll closure 72 engaying the seat 60 as clearly sh~wn in Figure 5.
The 6pring 90 can be made of suitable ~trength to provide the characteristics desir~d in the valve. The required load of the spring will be dictated ~rincipally by the size of pi~ton 81 and the differential pres6ure at which the valve will be desired to respond. It is preferably for~ed with a strength ~omewhat less than ~laximum with one or more spacer6 added later if more spring load is needed- Thus, a single spring together with suitable spacers may suffice for many differing instal-lation~. Such 6pacer~ are shown in the drawing and are indi-cated by the numeral B8. The~e ~pacers, like the flow bean 84, are readily replaced by disassembling at least a portion of the device 25 and reasse~bling with the desired bean and/or spacer 6i zes.
It is readily ~een that lift gas may enter the device 25 through the inlet 610ts 39 in the plug, flow upwardly through bore 38, passageway 75 of the valve ~tem 74 and exit through ~lots 76, flow around the ball 72 tbetween the ball 72 and the wall 43 of the body), flow through the bore 61 of valve seat 60, through bore 49, and exit the device through the bore 4~ o~
sub 36. Since the flow pa~ge 29 throu~h the valve conduct~
lift ga6 therethrough. such ga~ is conducted fro~l the tubing-ca~ing annulus into the well tubing through the lug-type mandrel 39.
The flow path through the device is almost perfectly straight, rather than being tortuous a6 i6 t-he case with most BUCh devices. The lift gas only make~ but a 6ingle jog as it veer6 momentarily to bypa~3 the b~ll 72.
The spring 90, a~ previously 6tated, tend~ to maintain the valve in open position ~6~0wn in Figure 3)- Back pressure from the tubing act6 in conjunction with the load of spring gO
t~nding to move the v~lve to open position. The pre6Lure of :12~43~2 1 lift gas in the casing and up~tream of tlle flow restrictor in the valve ste~ applie~ a bia~ to the piston tending to close the valve. Thi~ force is equal to the casing pressure (at the valve depth) times the area of the piston.
The piston is a rather close fit in bore 3~ of the plu~ 33, it~ exterior surface as well as the cylinder, or the wall of plug bore -~, being carefully formed and finished to provide a very close but free sliding fit. At the same time the valve ~tem has a loose fit in body bore 40 above the spring 90.
Thus, the pressure in the spring chamber and exterior of the valve stem will be the same as the pressure existing ~etween the flow restrictor (bean ~4) and the valve seat 60, that is, in body bore 43 below the valve seat 60.
Thus, when the valve is open as ~een in ~igure 3, the difference ~etween tubing and casing pressures acts across the cross-sectional area of piston 81. When the tubing pressure decreases sufficiently, this differential pressure becomes sufficiently high to overcome the bias of spring 90 and the valve will begin to move toward its closed position, seen in Figure 5.
When the valve is clo~ed as seen in Figure 5, the ball 72 i~ sealingly engaged with seat surface 63 of seat 60 and ~eals an area the 6ize of or very ~lightly larger than the cross-eectional area of seat bore 61- Seat bore 61 i5 somewhat larger than cylinder bore 38 of plug 33- Thus, when the valve i8 in closed position, the differential pressure act~ across an area larger than that across which it acts when the valve is in open positi~n.
In a valve manufactur~d according to this invention, the area of the pisto~ was 5/16 inch diameter with a cross-sectional area approximately 0-0767 square inch. The ~eat member 60 had a bore 61 of 3/~" diameter- The valve clo~ure contacted the ~harp corner of thi~ bore to seal the pa~sage %
1 through the s~at. l'he area ~ealed by this contact equaling a cross-sectional area approximately 0.1104 square inch.
When such valve i~ open, the differential pressure acts across the area of pi~torl 81 or the cylinder bore 38 of the plug 33, or 0.0767 square inch. And, when such valve i5 closed, the differential pressure acts across the area of sealing contact between valve and seat, or an area of 0.1104 square inch, an area about 1.44 times as large as the piston.
~ or this reason, the valve, after it has been closed by the differential pressure acting across piston 81, will remain closed without cycling until the tubing pressure rises suf-ficientl~ to reduce the differential pressure between tubing and casing sufficiently, to enable the tubing pressure and the sprin~ load together to move the valve closure to open position. All of this, of course, is assuming that the casing pressure remains constant, as well it might. And, of course, the above figures hold true regardless of the annulus p~essure.
In the example just given, if the casing pressure remains at 600 psi and the spring load is lg pounds, the tubing pressure at the time the valve begins to move toward closed position will be: 600 ~ o Q9767 = 352 psi.
Thus, the tubing pressure is 352 psi, the casing pressure i6 600 psi, and the differential pressure is 600-352 or 248 psi. So, the valve in this example will close when the dif-ferential pressure rises to 248 psi.
Since both the tùbing and the casing pre6sures act across a common area lthe area of the piston ~1), the spring governs the differential at which the valve closes. Note that the ~pring load of 19 pounds acting against the piston area offsets a pressure of o 1967 or 248 psi.
In a similar manner, both tubing and casing pressures act across the sealed area of Lhe seat when the valve is closed.
Thus, if the spring (now mor~ compre6sed) exerts a force of 22 ~4;~
1 pounds against the ~eat ar~a of 0.1104 square inches, the valve will open at a differenti~l pres~ure of ~ = 199 psi.
Thus, the tubing pres~ure nt valve opening will be 600 - 199 or 401 p~i.
Thus, the valve in this example will close at a dif-ferential pressure o~ about 248 psi. It will not cycle, but will remain firmly closed until the differential pressure is reduced to about 199 psi, ~t which differential pressure it will open.
The valve i6 normally open and will pass lift gas from the casing into the tubing to aerate the column of fluids therein to aid in lifting them to the ~urface until the load of such column lightens to the point where the pressure thereof at the valve is so low that it i~ le~s than the casing pressure by the differential required to close the valve, or about 248 psi.
Subsequently, the well fluids must rise in the tubing to ~ufficient height to exert a tubing pressure on the valve of about 401 psi to provide a differential of 199 psi and open the valve again.
lt should be understood that when the differential pressure reaches sufficient value to cau~e the valve to begin its movement toward closed position, it must rise even higher to cause the valve to move farther in that direction. This i8 because 6uch movement increases the co~pression of the spring, thus increasing the resistance to such valve movement. When the valve has moved about half way to closed positisn, however, the annular clearance between the ball 72 and the seat lip 60a which now surround~ it becomes ~o reduced that the flow stream is pinched or throttled, thereby causing a drop in pressure therebeyond while pressure begins to build up upstream thereof. With very little delay, the valve then is moved the other half of its travel to fully clossd po~ition, further compres6ing the spring.
lZ~43~2 1 Now, please refer again to Figure 1 of the drawing.
Gas lift valves 20 an~ 22 are valves of the type described herein, and are considered, for the moment, to be identical to the gas lift valve 25 of E`igures 2-6. ~lso, let us suppose that well 10 has just been completed and that both the tubing 13 and the annulus 15 are full of salt water having a pressure gradient of 0.5 psi per foot of depth. For the sake of simplicity, let us further assu~e hat the well will produce nothing but ~alt water with a gradient of 0.5 pound per foot.
If valves 20 and 22 are each adjusted to close when the differential pressure acting across them is 250 pounds per square inch, then, at closing, the spring load acting against the 5/16" piston (area = 0.0767 square inch) will be: 250 x 0.0767 = 19.175 pounds.
The valve will move an additional 0.21 inch (approximately) before engaging the valve ~eat surface 63, and this additional movement increaqes the co~pression in the spring. lf the rate ~f spring 90 is 12.5 pounds per inch, its load when the valve is fully closed will be: 19-175 + (12-5 x 0.21) = 21.8 pounds.
Accordingly, the differential pressure required to open the valve when the spring i~ ap~lying a load of 21.8 pounds against the valve closure now engaged with the valve seat sealing an area of 0.1104 square inches, will be: o21io84 = 197 psi ~approximately).
It is readily 6een then that the valves 20 and 22 will each close at a differential pressure of 250 psi and will open at a differential pressure of about lg7 psi.
In placing the gas lift valves in well 10, the top valve, valve 20, would be placed at a depth of about (6000 55) =
1100 feet. This allows 50 psi for tubing surface pressure.
The second valve, valve 22, wou~d be placea below valve 20 by a distance equal to the closing differential of the valve divided by the pre~sure gradient of 0- 5, or 0 5 = 500 feet.
1~43~Z
1 Thus the valve 22 would be placed 500 feet below valve 20 or at a depth o-f 3100 + 500 = 1600 feet. Other like valves would also be placed at 500-foot in~ervals below one another.
Lift gas in injected into the well's annulus 15 at the surface throuc3h a small choke. Gas lift valves 20 and 22 are both open becau~e the differential acros~ th~m i~ less thall the closing differential of the valves. Valves 17 and 19 are open and salt water issues from the tubing because as lift gas is slowly and carefully applied to the annulus, thè salt water U-tubes through the open valves. As the salt water U-tubes from casing to tubing and is produced from the well, the fluid level in the annulu~ is d~prcssed and casing pressure is gradually increased to 600 psi. When the fluid level in the casing is depressed to 1100 fect, gas enters valve 20 and aerates the fluid column in the tubing and decreases its density. The gradient in the upper 1100 feet of tubing becomes considerably less than 0.5. Salt water continues to U-tube through valve 22 and any other like valves therebelow. The gas in the annulus reaches valve 22, enters it and aerates the fluid in the tubing thereabove. Now, both valves 20 and 22 are injecting gas into the tubin~- This so decreases the tubing pressure at valve 20 that it exceeds the valve's set dif-ferential pressure, thus it closes. Now, valve 20 continues to inject gas into the tubing to produce more salt water~ If there are other ga~ lift valves below valve 22, they will come into play and will be operated automatically until the working fluid level is reached ~nd the well stabilizes.
After the well has been "kic~ed off" or "unloaded" and placed on production, thc casiny pressure can be reduced if desired, and the 250 psi differential of the valves will continue to enable the valves to operate with their 500-foot spacing.
For more detailed in~tructions in gas lift operation ana 12~43~
] the spacing of various g~u lift valves for th~ n~any types of in~tallations, et cetera, a cJo~d gas lift manual should be consulted. A good ~ook on ga~ lift is that entitled "GAS LIFT
THEORY AND PRACTICE," by Dr. ~ermit E. Brown, Head of the Petroleum Engineering Department at the University of Tulsa, Tulsa, Oklahomat ~ hould bac~flow occur through the ga& lift valve, the floating seat member 60 will move toward the valve closure 72 and seat thereon to stop such backflow. This i 6 shown in Pigure 6, which see.
When backflow develops, the valve closure i8 already in its fully open or lowermost position. Gravity tends to move the valve seat 60 downwards, and this moveMent is aided by the backflow. When the seal ring 67 on the seat reaches 'he lower extremity of bore 44 of the main body member 30, it may lodge momentarily at the upper extremity of bore 43, that i 5, at upwardly facing 6houlder 45. ~owever, at thi~ ti~e, the lip 60a of the seat will be so close to the ball 72 that the flow therebetween is pinched and the differential pressure acting across the seat quickly increa~es and promptly ~oves the seat to its seated position ayainst the ball as seen in Figure 6.
When flow occurs again in the n~rmal direction, the seat will be returned to its normal po5ition shown in Figures 3 and 5.
There is a distinct advantage in having the valve seat 60 slidable in the body 80 that it will serve not only as a seat but also as a check valve- Most check valves have a tortuous flow passage through or hround them- Seat 60 provides a straight-through, non-tortuous, unobstructed flow passage in the form of bore 61.
When the valve 25 i6 installed with its up~tream end looking downward as i6 6hown in the drawing~, gravity applies a constant bia8 to the valve seat member 60 tending to ~ove it to ~20-~Z~43'~2 i backflow checking po~ition. If it i~ desire-l to increase such bia~ or to operate the v~lve in another position, such as an inverted position with it~ upstream end looking upward, a valve ~odified as seen in Figure 7 is to be preferred. In Figure 7, the modified gas lift valv~ i8 indicated generally by the reference numeral 125. lt~ ~ub 13~ is provided with a bore 149 which may be considerably deeper and a little larger than bore 49 of valve 25, and this bore provides a downwardly facing shoulder 150 which is preferably abrupt. The valve seat member 160 is ~ormed with itB upr~er end face 170 perhaps a little broader than that of iti counterpart, the upper end face of seat 60. A seat spriny 171 is placed between downwardly facing ~houlder 150 and the upper end 170 of the seat member 160 to apply a constant bias to the seat member tending to move it toward the valve closure 72 regardless of which way gravity happens to act thereon.
Gas lift valves of the type described hereinabove will operate automatically after the well has been unloaded and will continue to do so even though the pressure of the lift gas in the annulus may vary over a wide range because these valves operate on the difference between the tubing and annulus pre~ures rather than bein9 operated by ~res6ure only.
Such valves as described hereinabove will not only operate automatically as just ~entioned s~ch as well 1~ having valves in a single tubing string, but they are well suited for u6e in multiple wells where they may be used in a plurality of tubing ~trings simultaneously- Thu6, a well ~ay be equipped with any xea60nable n~mber of tubing trings having 6uch ga~ lift valves therein. The valves will be ~paced according to the conditions attendant with each ~tring of tubing, and al~o5t as6uredly their ~pacing will ~e different in each tubing, causing the valves to be located at ~cattered level6 in the well- Al60, the operation of the variou5 valves in the various tubing6 will iZ~3~3Z
1 surely cause the annulu~ pres~ure to vary con~iderably. Even 80, the valves will continue to operate auto~atically.
Whether unloading a ~ingle or a multiple well, it should ~e done unhurriedly with t~e lift ga~ injected into the annulu~
slowly and preferably throu~h a choke to limit ~uch injection, le6t the lift gas be injected too fast, causiny the differ-ential pressures to rise s~lddenly across the valves and close all of them. Should thi B happen, it may be necessary to bleed gas fro~ the annulus to reduce the annulu~ pressure, or com-municate the annulus with the tubing at the surface to equalize pressures across the valves, or to pre6surize the tubing, in order to reduce the differential to where the valves will open before 6tarting the ~nloading process over again.
Referring to Figure 2, it is 6een that a dual well 200 is diagram~atically illustrated. This well iB provided with a casing 201 perforated opposite a lower ~one as at 202 ~nd opposite an upper zone as at 203. A first tubing string 204 communicates with the lower perforations 202 and the second tubing string 205 communicates with the upper perforations. A
single packer 206 seals between the tubing 204 and casing at a location between the two ~et~ of perforations. A dual pacXer 207 ~eals between the tubinys ~204 and 205) and the casing i~mediately above the upper perforations. The annulus 20B
extends to the surface where a wellhead 209 seals the casing around both tubing~. A Christ~as tree represente~d by master valves 210 and 211 connectL the tubing6 204 and 205 to flow lines 212 and 213 having wing valves 214 and 215, respectively.
Tubing string 204 i~ provided with a plurality of gas lift valves such a~ valve6 220 and 221 a~ shown and tubing 205 i~
provided with a plurality of ga6 lift valves 6uch a6 valves 222 and 223. TheBe valve6 are 6paced according to g~od gas lift practices for efficient operation a6 before explained.
A lift ga6 line 224 having a valve 225 i6 connected ~o ~2~438Z
1 the annulus at the ~urface to ~pply gas for this gas lift operation.
Well 200 may be unloaded in the sa~e manner as was well 10 of Figure 1 and either or both tubing ~trings may be used in doing 60, preferably only one. After the well has been un-loaded, the valves will operate as they are needed and will do 80 ~ndependently of each other Rince each valve i5 operated by the differential pressure across it and each is opened by fluid rising in the tubing. T~us, each valve will pass gas only when such gas is needed. And, these valves will continue to operate automatically in spite of excur6ions in annulus presfiure as before explained.
Gas lift valves embodying the present invention are also u~eful in wells equipped with side pocket mandrels. Figure R
diagrammatically illustrates such a well. Well 300 is a single well completed in a conventional manner, having a casing 301, perforations 302, packer 303, tubing 304, wellhead 305, tree 306, flowline 30~, wing valve 308, lift gas supply line 309, and valve 310. The tubing i6 equipped with a plurality of side 20 pocket mandrels 312 and 313 having offset receptacles 314 and 315, communicating with the annulus 316 through lateral port6 317 and 318 and having 9a6 lift valves 319 and 320, respec-tively, in6talled therein to control admi~sion of lift gas into the tubing to aid in liftin9 well product6 to the surface, for thu6 producing the well. The~e ga~ lift valves are spaced in the manner before explained, and the well i~ u~loaded and placed on production in the manner before explained.
Gas lift valves 319 and 320 may contain the 6ame mechanism a6 in the valves previou~ly described, but they must be adapted for use in 6ide pocket mandrels.
Figure 9 illustrate6 a valve such as valve 319 or 320. The valve in Figure 9 i6 indicated generally by the reference numersl 325- ~he innQr workings of the valve 325 are identical 1~43~2 1 to those of valve 25 ~een in Yiyures 2 and 3, but could be like those of valve 125 seen in ~igure 7.
Valve 325 differs from valves 25 and 125 in that its upper and lower end~ are different, being adapted to carry packing rings for sealing above and below the lateral port means of ~ide pocket mandrel receptacles such as tho6e ~een in well 300 illustrated in Figure 8.
The plug 333 at the lower end of gas lift valve 325 i~
threadedly attached as at 332 to the lower end of the main body member 30 and has a blind central bore or cylinder 338 in which the pi~ton 81 at the lower end of valve 74 i6 61idably re ceived. Inlet openings for the upstream end of valve 325 are provided by the narrow filter 610ts or slits 339, as 6hown, through which lift gas enter~ the valve. The plug is reduced in outside diameter in the region of the slits as at 340 to provide for free passage of lift gas therearound flowing between the mandrel ports (317, 318 of Figure 8).
Plug 333 has its lower portion reduced in diameter as at 334 to fit the bore of packing rings 335 and providing a downwardly facing ~houlder 360 shaped to conform to the packing as 6hown to serve as a female packing adapter and save 6pace.
A double male adapter ring 361 i6 disposed between the upper and lower groups of packing rings 335 facing in opposite directions a5 shown to 60al in both directions. A female packing adapter ring 362 i~ placed beneath the lowermost packing ring 335. The lower end of the lug is threaded as at 363 and cap 364 is attached as 6hown to reLain the packing in place and to guide the valve as it i6 lowered into the well as by wireline to be removably installed in a 6uitable landing receptacle.
At the upper end of valve 325, it6 adapter 336 ha6 it~
upper portion reduced in dianleter a6 at 3~0 to fit the upper packing ~et which may be exactly like the packing 6et on the lZ~43~3Z
1 lower portion o~ the valve as just describ~d. This upper packing set i6 indic.,te~ by the reference nullleral 371. Reduced diameter 370 of the aaa~ter provides an upwardly facing shoulder 372 which corlform6 to the ~pper packing as shoulder 335 conforms to the lower packing set.
The upper end of adapter 336 is threaded as at 374 for attachment to device 373 (~hown in dotted lines) by which the valve 325 is anchored in place in the side pock~t mandr0l receptacle or in another ~uitable receptacle, such as a bypass landing receptacle. When the device is in place in the mandrel, its upper and lower packing sets will be disposed above and below the lateral port (317 or 318) of the mandrel to direct lift gas to irllet openings 363. Lift gas entering the mandrel through its lateral ports may flow around the valve at its external annular recess 340 in the region of the inlet openings 339 and enter therein to pass through the valve mechanism in the manner before explained on its way to the well tubing.
It should be understood that tlle valves illustrated and described herein could be readily modified for use in gas lift wells where well products are lifted through the tubing-casing annulus. For such use, the plug 33 at the lower end of valve device 25 would be replaced with a plug in which its central bore ran end to end and the lower end of the plug as seen in Figure 3 would be provided with an external thread not unlike thread 36a seen on the upper end of adapter 36. This modifiea valve could then be inverted and attached ~o the lug 37.
Since, in the inverted valve, gravity would no longer bias the valve seat 60 toward valve closure 72, it would be desirable, even necessary, to spring load the seat as taught with respect to gas lift valve 125 illustrated in Yigure 7. Al~o, since the thread 32 (connecting the modified plug to the housing ~ember 30) in the inverted valve would now be subjected to a greater 3t~2 .~ differential pressure (t?,e s~lme difIerentidl which exists acros6 the flow bean B4), it would be desirable to seal this threaded connectiorl with a resilient seal ring in the manner taught with respect to thread 34 at the opposite end of the housing member 30. Alternatively, the gas lift mandrel 39 could be inverted in the tubing 6tring, in which case the gas lift valve would remain upright. In either case, the valve would control the flow of lift gas from the well tubing into the casing for lifting well products through the annulus to the surface.
Thus, it has been shown that the devices ill.ustrated ana described herein which embody the present invention fulfill all of the objects set forth at the beginning of thîs specification, and changes in the sizes, shape~, and arrangement of its parts may be had without departing from the true ~pirit of the in-vention.
1 body 28 comprises a main housing member 30 which is internally threaded at its lower end (upstream end) as at 32 for attach-ment of the pluy member 33 while its upper or downstream end is internally threaded as at 34 for attachment of sub 36. This connec-tion is preferably sealed by suitable means such as resilient seal ring 35. Sub 3G is externally threaded at its upper end as at 36a for attachment to the lug 37a of a con-ventional lug-type mandrel 37 (shown in dotted lines) rnade up in the tubing string and providing a passageway (not shown) between the tubing bore and the annulus. When the gas lift valve 25 is attached to the tubing via the lug-type mandrel 37, gas may be conducted from the annulus to the interior of the tubing when the gas lift valve is open.
Plug member 33 is bored as at 38 from its upper end, but this bore terminates short of its lower end. An inlet for lift gas is preferably provided by narrow cross slots or slits 39 for excluding sizeable particles of debris, et cetera, which may otherwise enter the valve mechanism and cause damage thereto. These slots 39 can be made as wide or as narrow as desired, but they should provide an inlet of adequate flow capacity (at least as great as bore 38).
The main body member 30 has a main bore 40 having a lower portion thereof much enlarged as at 41 providing a downwardly facing shoulder 42. The upper portion of bore 40 is enlarged as at 43 and further enlarged as at 44 providing an inclined shoulder 45, all for purposes to be made clear later.
The sub 36 has a bore 48 which is enlarged as at 49. The outer end of enlarged bore 49 is flared as at 50 to provide a frusto-conical shoulder whose purpose is soon to be explained.
The device 25 is provided with a valve seat having a seat surface which surrounds the flow passage 29 passing through the body 28. This seat may be formed integrally with the sub 36 or could possibly be formed in the main member 3~. However, in the form illustrated in t~e drawing, and particular~y ~igures 3 and 5, such seat surface i~ provided in a floating valve seat member 60 having a bore 61 therethrough whic}) is enlarged at 62 to provide frusto-conical ~eat surface 63 adapted to be engaged by a valve member, to ~e described later, for controlling flow through the bore 61 of the ~eat member. Enlarged bore 62 of the seat member is flared at its lower end a~ at 64 to streamline the flow passage and to provide a guide surface for the valve member.
The lower portion of the valve seat member 60 is slidable in bGre 45 and has a fairly close fit therewith yet will ~lide freely therein. Its outer ~urface 66 is provided with an external annular rece~6 in wl~ich i~ carried a resilient seal ring 67. The upper portion of seat member 60 i5 reduced in outside diameter a~ at 65 ~nd is telescoped into enlarged borc 49 of ~ub 36 as shown where it is ~reely slidable. The tran-sition between the enlarged and reduced outer surfaces of the seat member 60 provides an external frusto-conical surface 68 in which is formed an external annular reces~ fitted with a resilient seal ring 69.
~ he valve ~eat member 60 is slidable between an upper position, shown in Figures 3 and 5, and a lower pnsition, shown in Figure 6. When the seat member is in its upper position, it~ upwardly facing external frusto-conical surface 68 engages downwardly facing fru~to-conical surface 50 of ~ub 36 and seal ring 69 ~eal~ therebetween to prevent leakage between the sub 36 and seat member 60.
~ he seat me~ber 60 i~ very freely movable to an inter-mediate position wherein its ~eal ring 67 reaches upwardly facing inclined ~houlder 45 in the main hou~ing member, and is further filidable to it~ lower po~ition ~een in Figure 6 wherein its seal ring 67 ~ealingly e~lgages bore 43 in the main housing 12~43~3Z
member, a position w~,ich will be In~l-e ~llly ~xplairled ll~reill-below.
7~
A valve closure mem~r\i~i disl~osed in the main flow passage 29 of -the body c~nd is movable longitudinally relative to tlle seat member 60 between ';~lt~ dnd un~ated positions. T~lis valve closure member m~ly lle c~f any suitdbl~ shape, but th~t illustrated in the drawil~y i~ in the ~nl~C of a ball or sp21ere 72. This ball is eng~lyeable with seat surface 63 to preclude flow through the seat meml~er, and when the ball is thus seated, there is but ~ small clearance between it and the inner wall of - bore 62 of the seat member. The lower portion of the seat member which surrounds bore 62 may be termed a lip and is indicated by the referel~ce numeral 60a.
The ball or valve closure 72 has attached thereto a hollow valve stem 74 which is secured to the ball as by silver soldering or other suitable means. The hollow valve stem 74 has a passage 75 extending the full length thereof. Slot6 76 are formed in the wall of the valve stem adjacent the ball 72 to enable gas flowing upwardly through the hollow stem to exit just below the ball and bypass it before passing through the valve seat. The flow area through slots 76 should be at least as large and preferably larger than the area of flow passage 75 through the stem.
It is preferable to provide flow restrictor means in the passage of the valve stem 74. If the valve stem is formed in one piece, a restriction may be provided in it~ bore. For instance, the sten can be bored from its upper end to within a fraction of an inch, say 3/8 to 1/2 inch, of it~ lower end.
Then this portion can be drilled through with a ~maller drill to provide a bore of de~ired orifice- Alternatively, a screw having an orifice therethrougll could be threaded into the ~tem bore.
12~P43t32 1 In the device illu6~r~ed in Figures ~ and S, the valve stem 7~ is for~led in ~wo pieces: a stem 77 and an adapter 78.
The adapter 7a is tubular, ~laving a bore 7~a, and is internally threaded as at 79. At ur ne~r its upper end it is provided with lateral slots 76 as ~own. The upper end face 78~ is shaped to fit the valve closure or ball 72 which is attached thereto as by suitable means such as silvcr soldering. The stem 77 is threadedly attac~cd as at thread 79 to the lower end of the adapter 78 as shown. 'rhe stem 77 is provided with an external flange B0 near its lower end and below flange B0, the stem is reduced in outside di~meter as shown at ~1 to provide a piston of suitable diameter. If desired, the bore 77a of the stem may be restricted ~y reducil-lg the diameter of the bore, say at one or the other of its ends as previously described, or a screw orifice could be threaded into one of it~ ends.
However, it may be desirable to provide a flow restrictor in the form of replaceable flow bean ~4. Bean B4 is captured in sealing engagement between the upper end of stem 77 and down-wardly facing shoulder 85 formed in adapter 78 below 610ts 76.
The flow bean is provided with a bore 86 therethrough of suitable orifice. The flow l~ean may be readily replaced by another bean when such becomes necessary.
A spring 90, preferably a straig21t helical coil compression spring. is disposed within enlarged bore 41 of the main body member 30 and surrounds the stem 77 with its lower end engaged with the upper side of stem flange 80 and its upper end engaged with downwardly facing shoulder 42 of main body member 30.
Thus the spring applies a bias to the valve ~tem 74 tending t~
maintain it in its lower position as shown in Figure 3 with the lower side of its flange engaged with the upper end of plug 33. Thus, the valve stem's longitudinal movel~ent is limited in one direction by its flan~e B0 engaging the plug and in the lZ~43~3Z
other direction by its bclll closure 72 engaying the seat 60 as clearly sh~wn in Figure 5.
The 6pring 90 can be made of suitable ~trength to provide the characteristics desir~d in the valve. The required load of the spring will be dictated ~rincipally by the size of pi~ton 81 and the differential pres6ure at which the valve will be desired to respond. It is preferably for~ed with a strength ~omewhat less than ~laximum with one or more spacer6 added later if more spring load is needed- Thus, a single spring together with suitable spacers may suffice for many differing instal-lation~. Such 6pacer~ are shown in the drawing and are indi-cated by the numeral B8. The~e ~pacers, like the flow bean 84, are readily replaced by disassembling at least a portion of the device 25 and reasse~bling with the desired bean and/or spacer 6i zes.
It is readily ~een that lift gas may enter the device 25 through the inlet 610ts 39 in the plug, flow upwardly through bore 38, passageway 75 of the valve ~tem 74 and exit through ~lots 76, flow around the ball 72 tbetween the ball 72 and the wall 43 of the body), flow through the bore 61 of valve seat 60, through bore 49, and exit the device through the bore 4~ o~
sub 36. Since the flow pa~ge 29 throu~h the valve conduct~
lift ga6 therethrough. such ga~ is conducted fro~l the tubing-ca~ing annulus into the well tubing through the lug-type mandrel 39.
The flow path through the device is almost perfectly straight, rather than being tortuous a6 i6 t-he case with most BUCh devices. The lift gas only make~ but a 6ingle jog as it veer6 momentarily to bypa~3 the b~ll 72.
The spring 90, a~ previously 6tated, tend~ to maintain the valve in open position ~6~0wn in Figure 3)- Back pressure from the tubing act6 in conjunction with the load of spring gO
t~nding to move the v~lve to open position. The pre6Lure of :12~43~2 1 lift gas in the casing and up~tream of tlle flow restrictor in the valve ste~ applie~ a bia~ to the piston tending to close the valve. Thi~ force is equal to the casing pressure (at the valve depth) times the area of the piston.
The piston is a rather close fit in bore 3~ of the plu~ 33, it~ exterior surface as well as the cylinder, or the wall of plug bore -~, being carefully formed and finished to provide a very close but free sliding fit. At the same time the valve ~tem has a loose fit in body bore 40 above the spring 90.
Thus, the pressure in the spring chamber and exterior of the valve stem will be the same as the pressure existing ~etween the flow restrictor (bean ~4) and the valve seat 60, that is, in body bore 43 below the valve seat 60.
Thus, when the valve is open as ~een in ~igure 3, the difference ~etween tubing and casing pressures acts across the cross-sectional area of piston 81. When the tubing pressure decreases sufficiently, this differential pressure becomes sufficiently high to overcome the bias of spring 90 and the valve will begin to move toward its closed position, seen in Figure 5.
When the valve is clo~ed as seen in Figure 5, the ball 72 i~ sealingly engaged with seat surface 63 of seat 60 and ~eals an area the 6ize of or very ~lightly larger than the cross-eectional area of seat bore 61- Seat bore 61 i5 somewhat larger than cylinder bore 38 of plug 33- Thus, when the valve i8 in closed position, the differential pressure act~ across an area larger than that across which it acts when the valve is in open positi~n.
In a valve manufactur~d according to this invention, the area of the pisto~ was 5/16 inch diameter with a cross-sectional area approximately 0-0767 square inch. The ~eat member 60 had a bore 61 of 3/~" diameter- The valve clo~ure contacted the ~harp corner of thi~ bore to seal the pa~sage %
1 through the s~at. l'he area ~ealed by this contact equaling a cross-sectional area approximately 0.1104 square inch.
When such valve i~ open, the differential pressure acts across the area of pi~torl 81 or the cylinder bore 38 of the plug 33, or 0.0767 square inch. And, when such valve i5 closed, the differential pressure acts across the area of sealing contact between valve and seat, or an area of 0.1104 square inch, an area about 1.44 times as large as the piston.
~ or this reason, the valve, after it has been closed by the differential pressure acting across piston 81, will remain closed without cycling until the tubing pressure rises suf-ficientl~ to reduce the differential pressure between tubing and casing sufficiently, to enable the tubing pressure and the sprin~ load together to move the valve closure to open position. All of this, of course, is assuming that the casing pressure remains constant, as well it might. And, of course, the above figures hold true regardless of the annulus p~essure.
In the example just given, if the casing pressure remains at 600 psi and the spring load is lg pounds, the tubing pressure at the time the valve begins to move toward closed position will be: 600 ~ o Q9767 = 352 psi.
Thus, the tubing pressure is 352 psi, the casing pressure i6 600 psi, and the differential pressure is 600-352 or 248 psi. So, the valve in this example will close when the dif-ferential pressure rises to 248 psi.
Since both the tùbing and the casing pre6sures act across a common area lthe area of the piston ~1), the spring governs the differential at which the valve closes. Note that the ~pring load of 19 pounds acting against the piston area offsets a pressure of o 1967 or 248 psi.
In a similar manner, both tubing and casing pressures act across the sealed area of Lhe seat when the valve is closed.
Thus, if the spring (now mor~ compre6sed) exerts a force of 22 ~4;~
1 pounds against the ~eat ar~a of 0.1104 square inches, the valve will open at a differenti~l pres~ure of ~ = 199 psi.
Thus, the tubing pres~ure nt valve opening will be 600 - 199 or 401 p~i.
Thus, the valve in this example will close at a dif-ferential pressure o~ about 248 psi. It will not cycle, but will remain firmly closed until the differential pressure is reduced to about 199 psi, ~t which differential pressure it will open.
The valve i6 normally open and will pass lift gas from the casing into the tubing to aerate the column of fluids therein to aid in lifting them to the ~urface until the load of such column lightens to the point where the pressure thereof at the valve is so low that it i~ le~s than the casing pressure by the differential required to close the valve, or about 248 psi.
Subsequently, the well fluids must rise in the tubing to ~ufficient height to exert a tubing pressure on the valve of about 401 psi to provide a differential of 199 psi and open the valve again.
lt should be understood that when the differential pressure reaches sufficient value to cau~e the valve to begin its movement toward closed position, it must rise even higher to cause the valve to move farther in that direction. This i8 because 6uch movement increases the co~pression of the spring, thus increasing the resistance to such valve movement. When the valve has moved about half way to closed positisn, however, the annular clearance between the ball 72 and the seat lip 60a which now surround~ it becomes ~o reduced that the flow stream is pinched or throttled, thereby causing a drop in pressure therebeyond while pressure begins to build up upstream thereof. With very little delay, the valve then is moved the other half of its travel to fully clossd po~ition, further compres6ing the spring.
lZ~43~2 1 Now, please refer again to Figure 1 of the drawing.
Gas lift valves 20 an~ 22 are valves of the type described herein, and are considered, for the moment, to be identical to the gas lift valve 25 of E`igures 2-6. ~lso, let us suppose that well 10 has just been completed and that both the tubing 13 and the annulus 15 are full of salt water having a pressure gradient of 0.5 psi per foot of depth. For the sake of simplicity, let us further assu~e hat the well will produce nothing but ~alt water with a gradient of 0.5 pound per foot.
If valves 20 and 22 are each adjusted to close when the differential pressure acting across them is 250 pounds per square inch, then, at closing, the spring load acting against the 5/16" piston (area = 0.0767 square inch) will be: 250 x 0.0767 = 19.175 pounds.
The valve will move an additional 0.21 inch (approximately) before engaging the valve ~eat surface 63, and this additional movement increaqes the co~pression in the spring. lf the rate ~f spring 90 is 12.5 pounds per inch, its load when the valve is fully closed will be: 19-175 + (12-5 x 0.21) = 21.8 pounds.
Accordingly, the differential pressure required to open the valve when the spring i~ ap~lying a load of 21.8 pounds against the valve closure now engaged with the valve seat sealing an area of 0.1104 square inches, will be: o21io84 = 197 psi ~approximately).
It is readily 6een then that the valves 20 and 22 will each close at a differential pressure of 250 psi and will open at a differential pressure of about lg7 psi.
In placing the gas lift valves in well 10, the top valve, valve 20, would be placed at a depth of about (6000 55) =
1100 feet. This allows 50 psi for tubing surface pressure.
The second valve, valve 22, wou~d be placea below valve 20 by a distance equal to the closing differential of the valve divided by the pre~sure gradient of 0- 5, or 0 5 = 500 feet.
1~43~Z
1 Thus the valve 22 would be placed 500 feet below valve 20 or at a depth o-f 3100 + 500 = 1600 feet. Other like valves would also be placed at 500-foot in~ervals below one another.
Lift gas in injected into the well's annulus 15 at the surface throuc3h a small choke. Gas lift valves 20 and 22 are both open becau~e the differential acros~ th~m i~ less thall the closing differential of the valves. Valves 17 and 19 are open and salt water issues from the tubing because as lift gas is slowly and carefully applied to the annulus, thè salt water U-tubes through the open valves. As the salt water U-tubes from casing to tubing and is produced from the well, the fluid level in the annulu~ is d~prcssed and casing pressure is gradually increased to 600 psi. When the fluid level in the casing is depressed to 1100 fect, gas enters valve 20 and aerates the fluid column in the tubing and decreases its density. The gradient in the upper 1100 feet of tubing becomes considerably less than 0.5. Salt water continues to U-tube through valve 22 and any other like valves therebelow. The gas in the annulus reaches valve 22, enters it and aerates the fluid in the tubing thereabove. Now, both valves 20 and 22 are injecting gas into the tubin~- This so decreases the tubing pressure at valve 20 that it exceeds the valve's set dif-ferential pressure, thus it closes. Now, valve 20 continues to inject gas into the tubing to produce more salt water~ If there are other ga~ lift valves below valve 22, they will come into play and will be operated automatically until the working fluid level is reached ~nd the well stabilizes.
After the well has been "kic~ed off" or "unloaded" and placed on production, thc casiny pressure can be reduced if desired, and the 250 psi differential of the valves will continue to enable the valves to operate with their 500-foot spacing.
For more detailed in~tructions in gas lift operation ana 12~43~
] the spacing of various g~u lift valves for th~ n~any types of in~tallations, et cetera, a cJo~d gas lift manual should be consulted. A good ~ook on ga~ lift is that entitled "GAS LIFT
THEORY AND PRACTICE," by Dr. ~ermit E. Brown, Head of the Petroleum Engineering Department at the University of Tulsa, Tulsa, Oklahomat ~ hould bac~flow occur through the ga& lift valve, the floating seat member 60 will move toward the valve closure 72 and seat thereon to stop such backflow. This i 6 shown in Pigure 6, which see.
When backflow develops, the valve closure i8 already in its fully open or lowermost position. Gravity tends to move the valve seat 60 downwards, and this moveMent is aided by the backflow. When the seal ring 67 on the seat reaches 'he lower extremity of bore 44 of the main body member 30, it may lodge momentarily at the upper extremity of bore 43, that i 5, at upwardly facing 6houlder 45. ~owever, at thi~ ti~e, the lip 60a of the seat will be so close to the ball 72 that the flow therebetween is pinched and the differential pressure acting across the seat quickly increa~es and promptly ~oves the seat to its seated position ayainst the ball as seen in Figure 6.
When flow occurs again in the n~rmal direction, the seat will be returned to its normal po5ition shown in Figures 3 and 5.
There is a distinct advantage in having the valve seat 60 slidable in the body 80 that it will serve not only as a seat but also as a check valve- Most check valves have a tortuous flow passage through or hround them- Seat 60 provides a straight-through, non-tortuous, unobstructed flow passage in the form of bore 61.
When the valve 25 i6 installed with its up~tream end looking downward as i6 6hown in the drawing~, gravity applies a constant bia8 to the valve seat member 60 tending to ~ove it to ~20-~Z~43'~2 i backflow checking po~ition. If it i~ desire-l to increase such bia~ or to operate the v~lve in another position, such as an inverted position with it~ upstream end looking upward, a valve ~odified as seen in Figure 7 is to be preferred. In Figure 7, the modified gas lift valv~ i8 indicated generally by the reference numeral 125. lt~ ~ub 13~ is provided with a bore 149 which may be considerably deeper and a little larger than bore 49 of valve 25, and this bore provides a downwardly facing shoulder 150 which is preferably abrupt. The valve seat member 160 is ~ormed with itB upr~er end face 170 perhaps a little broader than that of iti counterpart, the upper end face of seat 60. A seat spriny 171 is placed between downwardly facing ~houlder 150 and the upper end 170 of the seat member 160 to apply a constant bias to the seat member tending to move it toward the valve closure 72 regardless of which way gravity happens to act thereon.
Gas lift valves of the type described hereinabove will operate automatically after the well has been unloaded and will continue to do so even though the pressure of the lift gas in the annulus may vary over a wide range because these valves operate on the difference between the tubing and annulus pre~ures rather than bein9 operated by ~res6ure only.
Such valves as described hereinabove will not only operate automatically as just ~entioned s~ch as well 1~ having valves in a single tubing string, but they are well suited for u6e in multiple wells where they may be used in a plurality of tubing ~trings simultaneously- Thu6, a well ~ay be equipped with any xea60nable n~mber of tubing trings having 6uch ga~ lift valves therein. The valves will be ~paced according to the conditions attendant with each ~tring of tubing, and al~o5t as6uredly their ~pacing will ~e different in each tubing, causing the valves to be located at ~cattered level6 in the well- Al60, the operation of the variou5 valves in the various tubing6 will iZ~3~3Z
1 surely cause the annulu~ pres~ure to vary con~iderably. Even 80, the valves will continue to operate auto~atically.
Whether unloading a ~ingle or a multiple well, it should ~e done unhurriedly with t~e lift ga~ injected into the annulu~
slowly and preferably throu~h a choke to limit ~uch injection, le6t the lift gas be injected too fast, causiny the differ-ential pressures to rise s~lddenly across the valves and close all of them. Should thi B happen, it may be necessary to bleed gas fro~ the annulus to reduce the annulu~ pressure, or com-municate the annulus with the tubing at the surface to equalize pressures across the valves, or to pre6surize the tubing, in order to reduce the differential to where the valves will open before 6tarting the ~nloading process over again.
Referring to Figure 2, it is 6een that a dual well 200 is diagram~atically illustrated. This well iB provided with a casing 201 perforated opposite a lower ~one as at 202 ~nd opposite an upper zone as at 203. A first tubing string 204 communicates with the lower perforations 202 and the second tubing string 205 communicates with the upper perforations. A
single packer 206 seals between the tubing 204 and casing at a location between the two ~et~ of perforations. A dual pacXer 207 ~eals between the tubinys ~204 and 205) and the casing i~mediately above the upper perforations. The annulus 20B
extends to the surface where a wellhead 209 seals the casing around both tubing~. A Christ~as tree represente~d by master valves 210 and 211 connectL the tubing6 204 and 205 to flow lines 212 and 213 having wing valves 214 and 215, respectively.
Tubing string 204 i~ provided with a plurality of gas lift valves such a~ valve6 220 and 221 a~ shown and tubing 205 i~
provided with a plurality of ga6 lift valves 6uch a6 valves 222 and 223. TheBe valve6 are 6paced according to g~od gas lift practices for efficient operation a6 before explained.
A lift ga6 line 224 having a valve 225 i6 connected ~o ~2~438Z
1 the annulus at the ~urface to ~pply gas for this gas lift operation.
Well 200 may be unloaded in the sa~e manner as was well 10 of Figure 1 and either or both tubing ~trings may be used in doing 60, preferably only one. After the well has been un-loaded, the valves will operate as they are needed and will do 80 ~ndependently of each other Rince each valve i5 operated by the differential pressure across it and each is opened by fluid rising in the tubing. T~us, each valve will pass gas only when such gas is needed. And, these valves will continue to operate automatically in spite of excur6ions in annulus presfiure as before explained.
Gas lift valves embodying the present invention are also u~eful in wells equipped with side pocket mandrels. Figure R
diagrammatically illustrates such a well. Well 300 is a single well completed in a conventional manner, having a casing 301, perforations 302, packer 303, tubing 304, wellhead 305, tree 306, flowline 30~, wing valve 308, lift gas supply line 309, and valve 310. The tubing i6 equipped with a plurality of side 20 pocket mandrels 312 and 313 having offset receptacles 314 and 315, communicating with the annulus 316 through lateral port6 317 and 318 and having 9a6 lift valves 319 and 320, respec-tively, in6talled therein to control admi~sion of lift gas into the tubing to aid in liftin9 well product6 to the surface, for thu6 producing the well. The~e ga~ lift valves are spaced in the manner before explained, and the well i~ u~loaded and placed on production in the manner before explained.
Gas lift valves 319 and 320 may contain the 6ame mechanism a6 in the valves previou~ly described, but they must be adapted for use in 6ide pocket mandrels.
Figure 9 illustrate6 a valve such as valve 319 or 320. The valve in Figure 9 i6 indicated generally by the reference numersl 325- ~he innQr workings of the valve 325 are identical 1~43~2 1 to those of valve 25 ~een in Yiyures 2 and 3, but could be like those of valve 125 seen in ~igure 7.
Valve 325 differs from valves 25 and 125 in that its upper and lower end~ are different, being adapted to carry packing rings for sealing above and below the lateral port means of ~ide pocket mandrel receptacles such as tho6e ~een in well 300 illustrated in Figure 8.
The plug 333 at the lower end of gas lift valve 325 i~
threadedly attached as at 332 to the lower end of the main body member 30 and has a blind central bore or cylinder 338 in which the pi~ton 81 at the lower end of valve 74 i6 61idably re ceived. Inlet openings for the upstream end of valve 325 are provided by the narrow filter 610ts or slits 339, as 6hown, through which lift gas enter~ the valve. The plug is reduced in outside diameter in the region of the slits as at 340 to provide for free passage of lift gas therearound flowing between the mandrel ports (317, 318 of Figure 8).
Plug 333 has its lower portion reduced in diameter as at 334 to fit the bore of packing rings 335 and providing a downwardly facing ~houlder 360 shaped to conform to the packing as 6hown to serve as a female packing adapter and save 6pace.
A double male adapter ring 361 i6 disposed between the upper and lower groups of packing rings 335 facing in opposite directions a5 shown to 60al in both directions. A female packing adapter ring 362 i~ placed beneath the lowermost packing ring 335. The lower end of the lug is threaded as at 363 and cap 364 is attached as 6hown to reLain the packing in place and to guide the valve as it i6 lowered into the well as by wireline to be removably installed in a 6uitable landing receptacle.
At the upper end of valve 325, it6 adapter 336 ha6 it~
upper portion reduced in dianleter a6 at 3~0 to fit the upper packing ~et which may be exactly like the packing 6et on the lZ~43~3Z
1 lower portion o~ the valve as just describ~d. This upper packing set i6 indic.,te~ by the reference nullleral 371. Reduced diameter 370 of the aaa~ter provides an upwardly facing shoulder 372 which corlform6 to the ~pper packing as shoulder 335 conforms to the lower packing set.
The upper end of adapter 336 is threaded as at 374 for attachment to device 373 (~hown in dotted lines) by which the valve 325 is anchored in place in the side pock~t mandr0l receptacle or in another ~uitable receptacle, such as a bypass landing receptacle. When the device is in place in the mandrel, its upper and lower packing sets will be disposed above and below the lateral port (317 or 318) of the mandrel to direct lift gas to irllet openings 363. Lift gas entering the mandrel through its lateral ports may flow around the valve at its external annular recess 340 in the region of the inlet openings 339 and enter therein to pass through the valve mechanism in the manner before explained on its way to the well tubing.
It should be understood that tlle valves illustrated and described herein could be readily modified for use in gas lift wells where well products are lifted through the tubing-casing annulus. For such use, the plug 33 at the lower end of valve device 25 would be replaced with a plug in which its central bore ran end to end and the lower end of the plug as seen in Figure 3 would be provided with an external thread not unlike thread 36a seen on the upper end of adapter 36. This modifiea valve could then be inverted and attached ~o the lug 37.
Since, in the inverted valve, gravity would no longer bias the valve seat 60 toward valve closure 72, it would be desirable, even necessary, to spring load the seat as taught with respect to gas lift valve 125 illustrated in Yigure 7. Al~o, since the thread 32 (connecting the modified plug to the housing ~ember 30) in the inverted valve would now be subjected to a greater 3t~2 .~ differential pressure (t?,e s~lme difIerentidl which exists acros6 the flow bean B4), it would be desirable to seal this threaded connectiorl with a resilient seal ring in the manner taught with respect to thread 34 at the opposite end of the housing member 30. Alternatively, the gas lift mandrel 39 could be inverted in the tubing 6tring, in which case the gas lift valve would remain upright. In either case, the valve would control the flow of lift gas from the well tubing into the casing for lifting well products through the annulus to the surface.
Thus, it has been shown that the devices ill.ustrated ana described herein which embody the present invention fulfill all of the objects set forth at the beginning of thîs specification, and changes in the sizes, shape~, and arrangement of its parts may be had without departing from the true ~pirit of the in-vention.
Claims (16)
1. A gas lift valve for controlling flow of gas into a well flow conductor from the exterior thereof, comprising:
a. imperforate elongate tubular body means having a flow passage therethrough with inlet means at one end and outlet means at the other end and being connectable to a well flow conductor with said outlet means in communication with interior of said flow conductor and said inlet means in communication with the exterior of said flow conductor;
b. valve means in said tubular body having a seat surface thereon surrounding said flow passage;
c. valve closure means in said body having a seating surface thereon engageable with said seat surface on said valve seat means and longitudinally movable relative thereto between seated and unseated positions;
d. tubular valve stem means in said flow passage having one of its ends attached to said valve closure means and the other of its ends exposed to pressure from exterior said flow conductor, said stem means having port means in its wall adjacent said valve closure means communicating the bore of said tubular stem means with the exterior thereof, the area of the valve seat subject to pressure interior of said flow conductor being greater than the area of the valve stem subject to pressure exterior of said flow conductor; and e. means biasing said valve stem means and the valve closure means attached thereto toward unseated position.
a. imperforate elongate tubular body means having a flow passage therethrough with inlet means at one end and outlet means at the other end and being connectable to a well flow conductor with said outlet means in communication with interior of said flow conductor and said inlet means in communication with the exterior of said flow conductor;
b. valve means in said tubular body having a seat surface thereon surrounding said flow passage;
c. valve closure means in said body having a seating surface thereon engageable with said seat surface on said valve seat means and longitudinally movable relative thereto between seated and unseated positions;
d. tubular valve stem means in said flow passage having one of its ends attached to said valve closure means and the other of its ends exposed to pressure from exterior said flow conductor, said stem means having port means in its wall adjacent said valve closure means communicating the bore of said tubular stem means with the exterior thereof, the area of the valve seat subject to pressure interior of said flow conductor being greater than the area of the valve stem subject to pressure exterior of said flow conductor; and e. means biasing said valve stem means and the valve closure means attached thereto toward unseated position.
2. The gas lift valve of claim 1 wherein said tubular valve stem means also includes flow restriction means in its bore.
3. The gas lift valve of claim 2 wherein said valve seat means in said body means comprises:
a. a seat member having a straight flow passage therethrough and a seat surface surrounding said flow passage engageable by said valve closure means;
b. coengageable shoulder means in said body and on said seat member for limiting movement of said seat member away from said valve closure means;
c. resilient seal means carried on said seat member and engageable with said shoulder means in said body means to prevent flow around said seat member when said seat member has its shoulder means engaged with said shoulder means in said body;
d. said seat member being slidable in said body means and movable into engagement with said valve closure means upon occurrence of backflow to prevent backflow of fluids through said flow passage of said body.
4. The gas lift valve of claim 3, further including:
a. said flow passage in said body means being slightly enlarged for a limited distance adjacent said shoulder means therein which is engageable by said seat means;
b. second resilient seal ring carried in an external annular recess on said seat means, said second seal ring having clearance therearound due to said enlarged passage when said seat means is shouldered in said body, said seat means being freely movable toward said valve closure until said second seal ring reaches the extent of said flow passage enlargement; and
a. a seat member having a straight flow passage therethrough and a seat surface surrounding said flow passage engageable by said valve closure means;
b. coengageable shoulder means in said body and on said seat member for limiting movement of said seat member away from said valve closure means;
c. resilient seal means carried on said seat member and engageable with said shoulder means in said body means to prevent flow around said seat member when said seat member has its shoulder means engaged with said shoulder means in said body;
d. said seat member being slidable in said body means and movable into engagement with said valve closure means upon occurrence of backflow to prevent backflow of fluids through said flow passage of said body.
4. The gas lift valve of claim 3, further including:
a. said flow passage in said body means being slightly enlarged for a limited distance adjacent said shoulder means therein which is engageable by said seat means;
b. second resilient seal ring carried in an external annular recess on said seat means, said second seal ring having clearance therearound due to said enlarged passage when said seat means is shouldered in said body, said seat means being freely movable toward said valve closure until said second seal ring reaches the extent of said flow passage enlargement; and
Claim 4 continued....
c. a longitudinally extending lip on said seat member surrounding said seat surface which, when said valve closure means is seated on said seat surface of said member, substantially restricts the annular space around said valve closure means;
d. whereby, when backflow occurs and said seat member moves toward said unseated valve closure member and its second seal ring reaches the extent of said enlargement in said flow passage, said extended lip will thereupon restrict the passage of fluids around said valve closure means and will create a differential pressure across said seat member and will force the seat member fully toward said valve closure means so that said second seal ring will move past said enlarged bore and will sealingly engage between said seat member and said housing and said valve closure will be seated on said seat member.
c. a longitudinally extending lip on said seat member surrounding said seat surface which, when said valve closure means is seated on said seat surface of said member, substantially restricts the annular space around said valve closure means;
d. whereby, when backflow occurs and said seat member moves toward said unseated valve closure member and its second seal ring reaches the extent of said enlargement in said flow passage, said extended lip will thereupon restrict the passage of fluids around said valve closure means and will create a differential pressure across said seat member and will force the seat member fully toward said valve closure means so that said second seal ring will move past said enlarged bore and will sealingly engage between said seat member and said housing and said valve closure will be seated on said seat member.
5. The gas lift valve of claim 4 wherein said tubular valve stem means is formed in two sections connected together by a thread and said flow restricting means is a flow bean secured in said threaded connection between opposing shoulders of said two sections of said stem means, said flow bean having a restrictive flow passage therethrough for restricting the flow of gas through said tubular valve stem means.
6. The gas lift valve of claim 5 wherein said biasing means includes:
a. internal shoulder means in said housing;
b. external shoulder means on said valve stem means; and
6. The gas lift valve of claim 5 wherein said biasing means includes:
a. internal shoulder means in said housing;
b. external shoulder means on said valve stem means; and
Claim 6 continue....
c. a coil compression spring in said body means surrounding said stem means and supported by one and applying a bias to the other of said internal and external shoulder means tending to move said valve stem means and the valve closure means attached thereto toward unseated position.
c. a coil compression spring in said body means surrounding said stem means and supported by one and applying a bias to the other of said internal and external shoulder means tending to move said valve stem means and the valve closure means attached thereto toward unseated position.
7. The gas lift valve of claim 6 wherein said biasing means further includes means for varying the force of said spring.
8. The gas lift valve of claim 1, 2 or 3 wherein said elongate body means includes external seal rings thereon and is connecteable to a locking device by which it may be removably installed in a seating nipple in a well flow conductor.
9. The gas lift valve of claim 4, 5 or 6 wherein said elongate body means includes external seal rings thereon and is connectable to a locking device by which it may be removably installed in a seating nipple in a well flow conductor.
10. The gas lift valve of claim 7 wherein said elongate body means includes external seal rings thereon and is connect-able to a locking device by which it may be removably installed in a seating nipple in a well flow conductor.
11. The gas lift valve of claim 1, 2 or 3 wherein said elongated body means includes external seal rings thereon and is connectable to a locking device by which it may be removably installed in a seating nipple in a well flow conductor and said one end of said body flow passage which communicates with the exterior of said flow conductor terminates at narrow slits formed in said body means to preclude the entrance thereinto of sand, debris, and the like substances.
12. The gas lift valve of claim 4, 5 or 6 wherein said elongate body means includes external seal rings thereon and is connectable to a locking device by which it may be removably installed in a seating nipple in a well flow conductor and said one end of said body flow passage which communicates with the exterior of said flow conductor terminates at narrow slits formed in said body means to preclude the entrance thereinto of sand, debris, and the like substances.
13. The gas lift valve of claim 7 wherein said elongate body means includes external seal rings thereon and is connectable to a locking device by which it may be removably installed in a seating nipple in a well flow conductor and said one end of said body flow passage which communicates with the exterior of said flow conductor terminates at narrow slits formed in said body means to preclude the entrance thereinto of sand, debris, and the like substances.
14. The gas lift valve of claim 1, 2 or 3 wherein said one end of said body flow passage which communicates with the exterior of said flow conductor terminates at narrow slits formed in said body means to preclude the entrance thereinto of sand, debris, and the like substances.
15. The gas lift valve of claim 4, 5 or 6 wherein said one end of said body flow passage which communicates with the exterior of said flow conductor terminates at narrow slits formed in said body means to preclude the entrance thereinto of sand, debris, and the like substances.
16. The gas lift valve of claim 7 wherein said one end of said body flow passage which communicates with the exterior of said flow conductor terminates at narrow slits formed in said body means to preclude the entrance thereinto of sand, debris, and the like substances.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000438552A CA1204382A (en) | 1983-10-06 | 1983-10-06 | Differential gas lift valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000438552A CA1204382A (en) | 1983-10-06 | 1983-10-06 | Differential gas lift valve |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1204382A true CA1204382A (en) | 1986-05-13 |
Family
ID=4126243
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000438552A Expired CA1204382A (en) | 1983-10-06 | 1983-10-06 | Differential gas lift valve |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1204382A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111535784A (en) * | 2020-04-17 | 2020-08-14 | 四川轻化工大学 | Negative pressure suction and gas lift combined action pump and operation method thereof |
-
1983
- 1983-10-06 CA CA000438552A patent/CA1204382A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111535784A (en) * | 2020-04-17 | 2020-08-14 | 四川轻化工大学 | Negative pressure suction and gas lift combined action pump and operation method thereof |
| CN111535784B (en) * | 2020-04-17 | 2022-03-01 | 四川轻化工大学 | Negative pressure suction and gas lift combined action pump and operation method thereof |
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| Date | Code | Title | Description |
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| MKEX | Expiry |