US2896547A - Gas lifting dually-completed wells - Google Patents

Description

July 28, 1959 w. R. FRANEY ET AL 2,896,547

@As LIFTING Dumm-COMPLETED wrJLLs 5 Sheets-Sheet l Filed Feb. 14, 1955 INVENTORS WILLIAM R. FRANEY By MALCOYLM C. GILLIS:

ily/wwf@ ATTORNEY FIG.

July 28, 1959 w. R. FRANEY ET AL GAS LIFTING Dumm-COMPLETED WELLS 5 Sheets-Sheet 2 Filed Feb. 14, 195,5

UDIOU OVA 6 WILLIAM R. FRANEY By MALCOLM C. GILLIS ATTORNEY FIG. 2

July 28, 1959 w. R. FRANEY ET AL GAS LIFTING DUALLY-COMPLETED WELLS 5 Sheets-Sheet 3 Filed Feb. 14, 1955 July 28,1959

W. R. FRANEY ET AL GAS LIFTING DUALLY-COMFLETED WELLS Filed Feb. 14, 1955 5 Sheets-Sheet 4 /III IN V EN TORS w|LL|AM R. 'FRANEY YI MALcoLM c GlLus ATTORNEY July 28, 1959 w. R. FRANEY ET AL 2,896,547

GAS LIFTING Dumm-COMPLETED WELLS 5 Sheets-Sheet 5 Filed Feb. 14, 1955 INVENTORS w|LL|AM n FRANE-Y BY MALcoLM c.G|LL|s lHII FIG. 9

ATTORNEY Figure 3;

GAS LIFTING DUALLYfCOMPLETED WELLS William R. Franey, Wichita, Kans., and Malcolm C. Gillis, Oklahoma City, Okla., assignors to Pan American Petroleum Corporation, a corporation of Delaware f ApplicationFebruary 14, 71955, Serial No. 487,731 11 claims. (cl. 10s-23s) This invention relatesV to an apparatus for completing and producing multiplezone wells. More particularly, this invention relates to `an 'apparatus for selectively gas lifting two separate producing'lzones spaced a great distance apart ina dually-completed well.

The use of"dual completions for yoil wells has been found to be desirable in view of the great economic advantage of completing only-one well through which both zones are produced.` The artificial lifting apparatus for suchdually-completed .wells has, however, been found to cause many and varied producing problems not incurred in wells with only one producing zone or where the well fluilds from a number of zones are commingled within the well.' Multiple-zone wells have been produced and the production from each` zonemaintained isolated by the use of two orinore concentrictubing strings `and also by the use of4 parallel tubing strings with their inlets adjacent the respective producing zones. concentric tubing strings permits pumping only one of theproducing zones. In some cases, however, both zones canbe artificially produced using gas lift. Parallel tubing strings are more desirable in most cases in that it is possible to produce two zones both `of which tend to deposit 4paraiiin in the tubing. While the use of parallel tubing strings has been proposed, nodual gas lift ,system has been proposed which permitsthe selective production of each zoneV in dually-completed `wells'where the zones are widely spaced, orl particularlywhere the lower zone has a working liquid level below the `upper zone.

It is, therefore, the object of this invention to provide an improved apparatus for producing multiple-zgone wells. It is a morespecific objective of this invention to provide an apparatus for gas lifting a two-zone well in which the producing zones are spaced a substantial distance vertically in the well. It is still a more specific object of this invention to provide a means forselectively producing separately widely-spacedzones in a dually-completed well employing a common lifting gaslsupply Vin, the well. These and other objects 'of this invention will `become apparent from the following description in which;`

Figure 1 is a schematic diagram of a` two-zone well showing means for selectivelyv producing the two widelyspaced producing zones; t i t p Figure 2 is a cross-sectional view of a preferred embodiment of the wellhead apparatus;

Figure 3 is a cross-sectional view of the upper section of the subsurface apparatus andis a lower continuation of the apparatus shownin Figure 2;

Figure 4 is a cross-sectional view of the` crossover connection and top of the upper zone accumulation chamber and is a lower continuation of the apparatus shown in Figure 5 is a cross-sectional view taken on section 5-5 of Figure 4; t

i Figure 6 is a cross-sectional view of the crossover con- Vnection taken on section 6-6 shown Figure "5;

The use of 2,896,547.. Patented July 28, 1959 ICC Figure 6a is a cross-sectional view lbf a modification of the crossover connection shown in Figure 6;

Figures 7 and 8 are cross-sectional views of the,4 lower end of the upper accumulation chamber, and `of the packer and lower accumulation chamber, respectively, and are lower continuations in series of the apparatus shown in Figure 4; and,

Figure 9 is a cross-sectional view of oneembodiment of a gas lift valve having both upper and lower ycutoif pressures.

From these drawings it can be seen that this invention in brief comprises an apparatus for producing selectively `by gas lift two widely-spaced producing zones exposed in a single well, and, particularly that it `relates to producing simultaneously and selectively two zones which may `cause paraffin deposition on the tubingv and which have low working fluid levels that typically require the use of an accumulation chamber for eiiicient `gas `lift pro- 1 duction.

Referring now more specifically to Figure 1, a schematic system is shown for producing by gas lift a lower zone 9 in a dually-completed well where this lower zone is produced into a lower section 10 of thewell and a lower accumulation chamber 11 and that chamber is emptied intermittently by gas lift. The lower section is isolated by a lower packer 12 from the remainder Vof the well fand from the upper section 13 which extends through the upper zone 14. Oil produced from lower zone 9 enters the lower section well through lower perforations 15 in the casing 16 and enters the lower zone tub ing 17 through standing valve 18. This oil then ows into the lower accumulation chamber 11 through perforation 19 in the lower zonetubing. As oil enters the accumulation chamber, gas therein is displaced out into the lower zone tubing 17 through a small pressure equalizing port 21 located near the top of the accumulation chamber. This lower zone 9 may be located several hundred feet and may be as much as several thousand feet below the upper zone 14. Inasmuch as it isv considered highly desirable to utilize a common source of gas for gas lifting the two zones so that only one gas supply line down to the upper zone is required, and, inasmuch as production from the two zones must be kept isolated, an upper packer 22 is set in casing 16 above upper zone 14 separating the gas conduit or gas chamber in the annular space 23 from the uids in the upper section 13. These uids enter the upper section through upper casing perforations 25 from the upper zone`14. The distance between lower packer 12 and upper packer 22 being typically greater than the dynamic or producing liquid level of the lower zone, gas is transferred from above upper packer 22` down through the upper section to the bottom of lower accumulation chamber 11. This transfer is accomplished by running the small macaroni string 26 down through lower zone tubing 17 from a connection with the annular space 23 above the top packer. This macaroni string is connected with the gas chamber by a lower zone crossover 27 wherein gas from annular space 23 flowing through a gas port 28 enters a pressure operated gas lift valve 29 through an opening 31` in the wall of the valve. This `gas lift valve is sealed in the lower zone crossover by an upper packing 32 and a lower packing 33 so that gas entering opening 31 from the `gas chamber can be controlled by the gas lift valve and discharged through the lower end of the valve into the macaroni string 26.

The upper zone 14, as indicated previously, produces through upper casing perforations 25 into the upper section 13 which may be considered to be an upper zone accumulation chamber. The upper zone tubing 3'4 which may be enlarged to provide a greater volume extends down into this upper section to any desired distance,

Buscar rztlretubing. .Gas from thegas .chamber in annular space 23 ows through .a lgas l.port 36 ginv y upper .zone .crossover .3,7 into .opening 31' tin .the .uppergas lift -,.valve. -Upper diverted through the opening 3.1' tinto the .upper zone igaslift valve 35 where the gasto liftthe well fluids from the upper zone is controlled. Gas from .the upperrgas `f1iltfvalve.flou/ stoutofthe bottom ofthe valve below lower gpackingS and flows, for -example, viagas dip tube38 into the lower end of the upper zone tubing 34. .A standing valve .39 fmay, if tdesired, be installed the .-bottomof .the .upperfzone tubing. :Both the AYupper and ilower zone crossovers ,37 tand .2.7, respectively, .provide .annular wellvfluid g passages l40 .around .the Agas 'lift valves. .Hillier zone .tubing .-34v-and'lower zone tubing 17 extend ,in parallel above :thecrossover fittings through the gas ichamber f to :theesurface'where they pass through a dual ttubinghead 41.

Gas is injected into the gas chamber in annularspace 23 sthroughone vor .more rpressure controllers which Vpermit .Selective operationfor itheupper and Alower zone gas lift .valves .35 :and '29 respectively. Upper zone pressure fcontroller 42 and lower .zone lpressure controller 43 itypically operate in parallel .as .s hown. These v4pressure controllers. are actuatedl either :electrically or pneumatical- .ly byaclockfdriven intermitter 44 which .has -separate y:control .disks 45 and *..46 -for -the .upper zone controller andthedovver :zone controller, respectively. Gas ilovvin g through 'these controllers then passes .through choices 47, which may, iif desired, be ,adjustable, and enters the Aannular space ,2:3 through fgas inlet .line f4.8.

Nariousnneans may be .providedior selectively produc- '.ing :the .two spaced Azones rin `the iwell with the apparatus zShQWn. '.Genera'lly :this selective .control .is accomplished -byjproviding gas lift valves which Aopen and may even iolosecat dierent pressures. Typically, the most producativerzone .isfproduced by the gas .lift valve having the .douter .opening pressure. As is well-known, Vpressure tonerated gas lift-valves, such as :the Garrett Oil Tools, .'Inc.,

productive lower-zonegas .lift :valve 29 would be set to @nennt 1a .pressure slightly lower :than the opening pres- ;Surezfor upper zone :gas .lift `valve .35. For example, assuming a 15.0.0 pound pressure. supply of gas is available, .lower .zonefgas lift Avalve. might :beset to open .at .400 :pounds :and to :close at .350 pounds. Upper zone gas lift "valve 35 .mightthen be set to open at, for example, -425 pounds and :toelose at 325 pounds. It can beseen that reach zone 'cannot only be selectively produced individualily, :but twith .this arrangement, both zones can be produced together. -For example, `with the pressure pre- -:settings as assumedfabove, if pressure in annular space :23 is increased from vbelow 325 pounds at lwhich both tvalves were closed :to 411) pounds, -.the lower zone valve Y isopened but 'the'upper zone gas lift valve lwill not have .opened so lthe .lower zone can be produced selectively. Then, it is desired to produce both zones simultaneously, `the-pressure jin the gas. vchamber is raised to above the yopeningepressure -for vthe upper zone gas lift valve to a pressure of, for example, 430 pounds. 'The ratio of v operating time at 4l0 pounds to time at `430pounds can "be varied to accommodate the actual productivity ratio 'ohe two zones. Periodically, -whenboth zones are dpumped off, the pressure is again reduced to below 325 pounds. Under these conditions it can be seen that since, as stated previously, the lower zone is more productive, the two zones can be produced with maximum elliciency--the lower zone being produced for a longer period of time than the upper zone. Alternatively, it can be seen that even with the pressuresettings as above specified it lise` possible .'selecti-velytto produce :the .upper -rzone alone. 'Ihus, if after producing both zones simultaneously, the pressure in 1the gas chamber within :annular `space 213 Ais lowered toga ,pressurebelow *the .elosingjpressure for the lower zone gas lift valvebut above the closing pressure for `.the .upperzone :gas liftfvalve 3.5., 'for example, 330 pounds, the upper zone will be selectivelyproduced alone. Obviously, various combinations of valves and valve .settings can be arranged to .suit the particular conditions in any well. For example, the upper zone gas lift valve may beset .to. op en .ata ,lower ,pressure and closerat a .higher or even-.a lower ,pressure than theopening and closing-pressures forthellower zone .gas lift valve. "The gas pressure `in .the gas `chamber is controlled as Vindicated above by the pressure controllers 42,and 43. .Since .three pressure ran-ges in .the .annular .space may be desirable for a particular .situation,'.one for .no production, one for production .of .the mostproductive tzone, and one for production .of .both .zones simultaneously, the ypressure `controllers are ...operated 2periodically land the -length .and frequency .of .the .operating periods `are .controlled .by .a

prearrangementof the controlled disks 45 and -46 as is welleknownin this art.

By employing parallel .tubing .strings for producing dually-completed wells, the .tubing from v.each zone can .be cleaned without5pulling the tubing. 'Ihat is, a par- `aiiin -scraperzmay .be ,lowered ,into the .tubing and down tothe gas "lift valve which .is typicallyat adepth .greater than the depth .at v.which paraffin .commences .to V,prec1pitate and .deposit on the .tubing walls. While various ykinds -of Aparaln .Scrapers may .be employed, .the .free piston, .or plunger, as disclosed, for example, in .U.S. Patent 2,688,928 iis I.considered vhighly satisfactory and :preferred .since notspecialzttings or Jconnections .in the .well are required. 2Byattaching suitable liquid separator or .lubricator connections .tothe tops of the two .tubing .Strings it 4will be seen ...that :.both zones may be produced .by .gas ,lift len ipiloying .the ,free piston without .further .modification .and without withdrawing .and modifying the subsurface well apparatus. Furthermore, by employ- Sing lparallel tubing .strings .in these .dually-completed wells, .wire-linearemovable .gas lift .valves .and kick-off valves can `beused Vto advantage. .For example, .it `may he desirable .to `change the A.pressure :setting Von .the oper- .Latin-g gasflift -valves .or to repair them, land `this would Vbe .diiculh tif .not impossible, in asystem employing -con- .centric .tubing strings.

Referring :now to Figures 2 .to 9 :for the l.description of ya preferred .embodiment .of .our invention, :we have shown, in A addition rto the-.fundamentals shown in .Figure 1, improved means for selectively producing yspaced A producing .zones .and -for z operating ffree pistons :in both .tubing strings .of .a .dually-completed well. Reference will be made first to Figure 2 showing a wellhead connection ,suitable .for .installation .of free pistons .as described above.

yLubricators ..50 .are placed -.at-.the ...top of each `string of tubing .1-7 and -34 for .the v.purpose `lof absorbing fthe energy of .the impact .duefto arrival -of .the free .pistons `at the V surface ,under :.ligh velocity. Separate outlets .from the -strings .of tubing .to upper zone flow Aline 51 and lower zone ow line ..52 are .provided below ,the lubricators. Each outlet includes a perforated liner 53 whichapermits the free piston t0 passfreely and allows the liquids ahead of and the gases behind the free ,piston to escape into the flow line. A free 4piston .catcher 54,

' comprising aspiring-actuated latc'h `55 vand an operating lever 57 which selectively inactivates the 'latch,"is adapted zone accumulation chamber.

i to catch the free piston when it arrives at the surface. Full opening valves 58 are placed in each strlng of tubing between the outlet connection and the tubing head 41 so that either zone may be shut in while the other is producing. The bonnet 59 of the tubing head has two spaced Outlets 60 through which the two strings of tubing pass and means such as slips and packing provided for supporting the tubing and sealing the tubing in the openings so that pressure may be maintained in annular space 23. Gas is injected into the common gas chamber in thisannular space through gas inlet line 48.

These two strings of tubing are then extended downward from the tubing head to the crossover assemblies as shown in Figure 3. In most cases, the two strings of tubing are connected together by clamps 61. Upper zone tubing `34 is threaded into upper zone crossover 37 and extension 62, and lower zone tubing 17 is threaded into the lower zone crossover 27 and extension 63. These upper and lower crossovers have central mandrels 64 and 65, respectively, which receive the gas lift valves. The mandrels are connected with the annular space 23 by gas ports 36 and 28. The mandrels extend above and below thesev gas ports for a suicient distance to provide space for an upper packing 32 and a vlower packing-33 on the gas lift valves, which together prevent lifting gas from bypassing the valve-and cause the gas to enter the valve openings 31. The gas lift valves are supported4 at the lower`- end on shoulders 66 in the mandrels which stop the valves with the opening 31 in position opposite the gas ports 36 and 28. Gas from theupper zone `gas lift valve 35 is discharged into a small diameter tube 67 which is connected to the bottom of mandrel 64 in upper crossover 37. Similarly, gas from lower gas lift valve 29 is discharged into a tube 68 which isconnected to the bottom of mandrel 65 in lower zone crossover 27.

Referringnow to Figures 3 and 4, the two strings of tubing and the gas tubes from the discharge of the two gas lift valves are connected into the top of crossover connection 69, The lower zone crossover 27 connects the lower zone tubing 17 to the passage 71 which then connects to the lower zone dip tube 72. This tube, as shownhereinafter in Figure 7, extends to the bottom of the lower zone accumulation chamber 11. The lower zone gas tube 68 connects through a packed slip joint connection 74 with a lower zone gas passage 75 in the crossover connection to a lower zone gas line 76 which conducts gas from the lower zone gas lift valve 29 through the annular space 77 between the lower zone gas line and the dip tube 72 to the top of the lower lift valve 3S passes down through small diameter tube 67 which is `connected to the cross-over connection `with a packed slip joint connection 78 and flows through passages 79 and 81 (see Figures 5 and 6),

which are connected with upper zone gas line 82,` .to annular space 83, thence through a gas port84 into` the top of the upper accumulation chamber 85.

The` upper accumulation chamber is formed in the annular space between the casing 16 and the upper zone dip ftube 86, by providing an upper packer or packers 88,

which are mounted onupper zone gas line 82 above gas port 84, `and lower packer or packers 89 which are mounted on upper zone dip tube 8 6. Oil or other liquid production Vfrom the upper zone entering upper zone casing perforations 25 flows through the annular type standing valve 91 and into the upper accumulation chamber through annular space 92 and perforations 93. The annular space 92 between lower zone gas line 76 and upper zone dip .tube 86 is closed at the bottom ,by packedislip joint 95.`

Gas from the upper gas l passages 97 and 97 in the crossover connection tothe annular uid passage 40' through the upper zone crossover 37. This upper zone production then flows through upper zone tubing 34 through perforated liner 53 in the surface connections and into upperzone flow line 51.

In some instances, where an upper accumulation charnber is not considered necessary, i.e., where the upper zone is more productive or has a higher working fluid head, the crossover connection as described above can be used in a slightly modified form. More speciically, when an upper accumulation chamber is not employed, the upper zone gas is discharged from the gaslift valve 35 `around the lower end 98 of mandrel 64 into the upper zone crossover extension 62 to lift the upper zone uids via the liuid passage 40 directly, into the upper zone tubing 34. In this embodiment upper ,zone accumulation chamber lower packers 89 and the upper zone dip tube 86 on which they are mounted are not required so the liquid from the upper zone enters upper zone casing perforations 25 and passes through annular space 99 between casing 16 and lower zone gas line 76, up through passage 97 and a standing valve 101 which replaces the bridge 102 as `shown in Figure 6a. 'The pas sage 81 may then, ,if desired, be isolated from passage 79 by inserting a plug 103 in the threads 104. This plug yinserted by removing plug 105 and,I being smaller than the diameter-of channel 106, it is lowered and threaded into position to close thefpassage 81. Upper zone packers 88 onthe upper zone gas line `82-are generally employed in this embodiment to isolate the lifting gas in annular space 23 from the upper zone production in annular space 99. Obviously, the standing valve 101 may in some cases be attached, as is WelLknown in the art, to the upper zone gas lift valve 35 so that it can Ibe pulled for `repair whenever the gas lift valve is pulled. Alternatively, means may be provided on the standing valve `for pulling it separately after the gas lift valve has been pulled.

Referring `againto Figure 7 and particularly `to the method of producing liquids from thejlower zone 9, lifting -gas from thecommon gas chamber in annular space 23 passes through gas ports 28 in lower zone crossover 27, owing through @gas lift valve 29, mandrel 65, tube `68, passage 75 inthe crossover connection and annular space 77 into the top of lower4 accumulation chamber 11. Liquid from the lower zone 9 enters the lower section 10 of the well` through lower `casing perforations 15 and enters the lower zone anchor 107 through perfo rations 108. A packer 12 which may be of the anchor type or in some cases a wire-line retrievable packer is set at any point inthe well between the upper and lower casing perforation by applying weight on the lower zone gas line extension 76'gaftcr the anchor strikes the bottom plug 111. Liquidfrom the lower zone, after entering perforations 15 and 108, ows up through packer 12 and lower zone standing valve 18 and thence into the lower end of the lower zone accumulation chamber 11. A drain fitting 113, having, for example, a pressed-in shear disk 114, may be placed in the lower zone accumulation chamber housing above lower zone standing valve 18. The sheardisk may be ruptured by the application of above-normal operating pressure when it is desired to prevent swabbing the well in c-ase cup-type packersare used and to drain liquid out of the accumulation chamber as the producing equipment is pulled from the well. Periodically, as discussed above, lgas is injected into the top of the accumulation chamber, displacing liquid out of the chamber `up through lower zone dip tube 72 `which extends to near the bottom of the lower zone accumulation chamber 11. Lower zone production then ows up throughrthis dip tube, passage 71, annular fluid passage 40 and lower zone tubing 17 to the surface where it is discharged through flow line 52. In order to eliminate flow valve interference between the upper and lower gas litt valves and to providefor below a predetermined value.

' nular space 23 is raised to 500 p.s.i.

selective production fromr the upper and lowery zones, a

'special gas lift valvel may be used instead of either lower zone pressure-operated gas lift valve 29 or upper zone pressure-operated' `gas lift valve 35. In the following ated gas liftvalve shown in Figure 9. This special gas lift valve' comprises an upper pressure-closing gas lift valve 116 connected'i'n series with -a pressure-opening gas lift valve 1'17. This special valve is placed in upper zone crossover 37 resting on shoulder 66 with gas opening 3:1 between upper packing 32' and lower packing 33' in communication with gas ports 36 so that 4gas from annular` space 2,3 is admitted through the pressure-closing valve 118whene1verthe pressure in annular space 23 is This gas flowing through valve 1'18 passesV down through annular space 119 around the' dash pot'120to an' enclosed chamber 121 and thence ltothe gas entrance port 122 of the pressure-opening gas lift valve 117; Gas passes through pressure-opening valve 123 when the pressure in chamber 121 is above aV predetermined value,` thence out' of the bottom of this special gas lift valve through a landing nipple 124 into j the mandrel 64 and small diameter tube 67. Pressure- Vclosing valve 116, of which various types are available,

forv example, the Garrett Oil Tools, Inc., type P reverse-acting valve, is normally maintained open by a high gas pressure in pressure chamber 126; As pres- Ysure is increased' in annular space 23 to a value greater jtype ygas lift valve of which various designs are availablev commercially, for example, the Garrett Oil Tools, Inc., type OBP junior valve. When valve 118 is open as shown in Figure 9 and the pressure in annular space 23. and chamber 121 is Iabove the opening pressure for valve 123, both valves are open and gas passes from annular space 23 through gas lift valves 116 and 117 into upper zone gas yline 82 and thence into the top of the upper zone accumulation chamber 85. As pressure is further increased in annular space 23, valve 118 is closed, thus'providing -a limited operating pressure range 'for the special'. valve `at'the lower limit of which valve 123 isv closedl and at the upper limit of which valve 118 `is closed'. Thus, it can be seen that depending upon the gas pressure maintained in annular space 23, when this specialV gas lift valve is operated in parallel with the `lower zone pressure-actuated valve 29, interference between` the two can be eliminated and the upper and lower zones can be selectively produced.

As an example of the operation of such valves in parallel, assume that lower zone gas lift valve 29 is set to lopen with a gas pressure within the common gas chamber in annular space 23 of 530` p.s.i. and to close when the'pressure drops to 480 p.s.i. Assume also as to the upper zone system that the pressure-closing valve 116 is set to close at' a pressure of 520 p.s.i. and to open when the pressure drops to 490 p.s.i. Assume further that the pressure-opening gas lift valve 117 is set to open when theA gas pressure in the chamber 121 is above 500 p.s.i. and to close when that' pressure is below 480 p.s.i. Under these conditions, both gas lift valve 29 and valve 123 are closed and no gas is admitted to produce either the upper or'lower zones until. the gas pressure in an- Upper zone pressure controller 42: is opened by clock-driven intermitter 44- at predetermined time intervals to increase the pressure in ,annular space 23 to a pressure in the range 500 to '20lpzszi., typically' 510 p.si. At this pressure, `gas is ladmitted to the upper zone accumulation chamber and that.l zone" is produced., After a predetermined time, as

controller disk 46, lower zone pressure controller 43 is opened to raise the gas pressure in annular space 23 to a pressure greater than 530 p.s.i;, typically 540` p.s.i. At this pressure upper zone gas lift valve 29 opens and pressure-closinglvalve 116 closes so that gas is admitted only to the lower zone accumulation chamber 11 to produce the lower zone. After a preselected time interval, controller disks 45 and 46 move to close upper zone pressure controller 42 and lower zone pressure controller 43 so that the pressure declines to 480 p.s.i., the pressure at which both gas lift valves are closed.

Various modiiications of these operating conditions will be apparent depending upon the producing charac teristics of the respective zones. For example, in some cases only one pressure controller may be required and the ratio of producing time intervals for the two zones may be controlled by a choke 47. Thus, the pressure controller may be set to open periodically and to build up a pressure in annular space 23 suicient to open the highest pressure-opening gas lift valve. For example, assuming the various valve settings referred to in the example above, the pressure would be built up to 530 p.s.i., the pressure at which the lower zone gas lift valve 29 opens. As this pressure rises to 530 pounds, it passes through the pressure range under which the upper zone special gas lift Valve is open, namely 500 to 520 p.s.i. The period of time required to pass through this pressure range, 500 to 520 p.s.i., is controlled by the choke 47. Under the assumed conditions of equal production from upper and lower zones, the pressure controller would accordingly be set to remain open for a period approximately two times as long as the period required for the pressure in annularr space 23 to pass through the operating pressure range for the gas lift valve controlling admission of gas to the upper zone accumulation chamber. Equal amounts of gas would thus be admitted to produce each zone selectively. The ratio of gasadmission periods and the length of either or both can obviously be controlled with the apparatus shown.

It will also be apparent that with dual pressure controllers, as described above, other combinations can be provided so that either the upper zone or the lower zone can be selectively produced, or both zones can be produced simultaneously. Furthermore, by proper design of the space- controller disks 45 and 46, the upper or the lower zones may be selectively produced with several producing cycles for one of the zones to each producing cycle for the other zone. For example, if the lower zone is more productive, gas may be injected into the lower zone accumulation chamber for a short period to unload that chamber and the cycle may be repeated at time intervals as required to produce the lower zone most efficiently. If the upper zones does not make sufiicient production to be produced eiciently each time the lower zone is produced, the upper zone gas lift valve might be opened by upper zone pressure controller 42 only on alternate cycles or on every third or fourth cycle that the lower zone pressure controller is actuated.`

Thus, it can be seen that by this invention means have been provided for selectively lifting with a common gas supply down to the upper zone, a multiplicity of widelyspaced zones in a well, that the invention is susceptible of a wide variety of embodiments and that it is not limited by the explanation of certain embodiments which has been given merely for the purpose of description. Instead, this invention should be construed to be limited only by the scope of the appended claims.

We claim:

l. An apparatus for separately producing Widely-spaced upper and lower zones in a multiple-zone producing well comprising a gas chamber including a lower packer in theupper end of saidV well, packer meansV insaid well between and isolating an upper section of said well through said upper zone `from a lower section of said well through said lower zone, a gas inlet to said gas chamber, a gas conduit fromI said gas chamber through said upper section to said lower section, a lower zone tubing extending from said lower section up through said upper section and said gas chamber, rst valve means at the inlet of` said gas conduit to admit gas selectively from said gas'chamber through said gas conduit into said lower section and lift well lluids from said lower section through said lower zone tubing, `an upper zone tubing extending from said upper section up through said gas chamber, a Huid passage between said gas chamber and said upper section of said well, and second valve means in said uid passage to admit gas selectively from said gas chamber into said upper section and lift well fluids from said upper zones through said upper zone tubing.

2. An apparatus according to claim 1 wherein said first valve means and said second valve means includes at least one pressure-actuated gas lift valve.

3. An apparatus according to claim 2 including pressure regulator means in said gas inlet to said gas chamber periodically to change the pressure in said gas chamber and admit gasv selectively to at least one of said sections.

4. An apparatus according to claim 1 wherein said rst valve means comprises a first pressure-actuated gas lift valve and said second valve means comprises. a second pressure-actuated gas lift valve, said iirst pressureactuated gas llift valve and said second pressure-actuated gas lift valve having different operating pressure ranges whereby said valves may be operated to admit gas selectively and produce at least one of said zones separate from the other.

5. An apparatus according to claim 4 including pressure regulator means in said gas inlet to said gas chamber periodically to change the pressure in said gas chamber to the operating pressure range of each of the pressure-actuated gas lift valves.

6. An apparatus according to claim l wherein said lower zone tubing and said upper zone tubing are side by side in said gas chamber.

7. An apparatus for separately producing widelyspaced upper and lower zones in a multiple-zone producing well comprising a gas chamber in the upper part of said well, said gas chamber including an upper packer isolating said gas chamber from an upper section of said well opposite said fupper zone, a lower packer isolating said upper section from a lower section of said well opposite said lower zone, a lower zone tubing extending from the lsurface down through said gas chamber, said upper packer, said upper section and said lower packer into said lower section, an upper zone tubing beside said lower zone tubing and extending from the surface through said gas chamber and through said upper packer into said upper section, a first fluid passage from said gas chamber into said lower section, a first pressureactuated gas Ilift valve in said first fluid passage, a second iiuid passage from said gas chamber into said upper section, a second pressure-actuated gas `lift valve in said second fluid passage, means including a gas inlet to said gas chamber at the surface to inject gas into said gas chamber, and a pressure controller in said gas inlet to said gas chamber for periodically changing the pressure in said gas chamber, said rst pressure-actuated gas lift vvalve and said second pressure-actuated gas lift valve having different operating pressure ranges whereby the pressure in said gas chamber may be changed periodically to operate said gas lift valves and admit gas selectively to produce each of said upper and said lower zones.

8. An apparatus according to claim 7 including a lower zone accumulation chamber in said lower section, said lower zone tubing extending into said accumulation hamber and having an inlet near the bottom of said Vaccumulation chamber, a well liuid inlet in Said accumulation chamber, and a standing valve in said well fluid inlet to admit well fluids into said accumulation chamber but to prevent well fluids from` being discharged from said accumulation chamber back into said lower section when gas. is injected into said accumulation chamber by said first pressure actuated gas lift valve.

9. An apparatus `according to claim 8 wherein said pressure controller comprises a irst clock controlled valve means in said gas inlet to said gas chamber for periodically admitting gas into said gas chamber within the operating pressure range in which said first pressureactuated gas 'lift valve operates, and a second clock controlled valve means in said gas inlet to said gas chamber for periodically admitting gas to said gas chamber within the operating pressure range at which said second pressure-actuated gas lift valve operates.

l0. An apparatus according to claim 9 wherein said second pressure-actuated gas lift valve comprises in series a pressure-closing valve and a pressure-opening Valve, the exhaust of said pressure-closing valve being connected to the intake of said pressure-opening valve so that said gas from said gas chamber passes` irst through said pressure-closing valve and then through said pressure-opening valve, said pressure-closing valve having a closing pressure lower than the opening pressure of said rst pressure-actuated gas lift valve and said pressure-opening valve having a lower opening pressure than the closing pressure of said pressure-closing Valve whereby said upper zone may be selectively produced as the pressure in said gas chamber is raised to the operating pressure of said first pressure-actuated gas 4lift valve and whereby gas injection through said second pressure-actuated gas lift valve is stopped when the pressure is` raised to open said rst gas lift: valve.

l1. An apparatus for separately producing well fluids from upper and lower zones in a dually-completed well comprising a casing in said well extending down through said lower zone, lower perforations in said casing to "admit well fluids from said lower zone into a lower section of said casing, upper perforations in said casing to admit well fluids from `said upper zone into an upper section of said casing, a lower packer between said -lower perforations `and said upper perforations, a gas chamber in said casing above said upper perforations, said gas chamber including an upper packer in said casing isolating said upper 'section from said gas chamber, a tubing head on the upper end of said casing closing the upper end of said gas chamber, a gas inlet line to said tubing head, a clock-controlled pressure regulator in said gas inlet line adapted periodically to inject gas into said gas chamber at different pressures, a crossover connection located in the lower end of said gas chamber, a lower zone tubing extending from the surface through said tubing head down into a lower zone Well fluid passage in said crossover connection, an upper zone tubing extending from the surface paralleli to said llower zone tubing through said tubing head down through said gas chamber and into an upper zone well fluid passage in said crossover connection, a lower zone pressureactuated gas lift valve in the lower end of said lower zone tubing, an upper zone pressure-actuated gas lift valve in the lower end of said upper zone tubing, said upper and said lower gas lift valves having different operating pressures, a gas inlet to each of said lower zone gas lift valve and said upper zone gas lift valve from said gas chamber, a =lower zone gas line extending through said upper section and down into said lower p section, an outlet from said lower zone gas lift valve extending down through a lower zone gas passage in said crossover connection into said lower zone gas line, an outlet from said upper zone gas lift valve extending down through an upper zone gas passage in said crossover connection into said upper section, a dip tube ex- 11 tending from within said lower section below the normal working fluid level of said lower zone up through said upperl section and connecting to said lower zone Well iiuid passage in said crossover connection, said dip tube extending concentrically down through said lower zone gasV line, an upper zone dip tube extending from below the normal working fluid level of said upper Zone within said upper section into said upper zone well uid passage in said crossover connection, whereby the well uids from each of said lower and upper zones may be selectively gas lifted without commingling the well fluids from the twoI zones and whereby by controlling the pressure in said gas chamber with said clock-controlled pressure regulator sad lower end of said upper zones can be selectively'produced.

Y References Cited in the le of this patent UNITED STATES PATENTS 2,213,372 Aucoin Sept. 3, 1940 2,298,834- Moore Oct. 13, 1942 2,642,812 Robinson June 23, 1953 2,678,605 Tappmeyer May 18, 1954 l 2,680,408 Davis June 8, 1954 FOREIGN PATENTS 496,448 Canada Sept. 29, 1953

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