US2680408A

US2680408A - Means for dually completing oil wells

Info

Publication number: US2680408A
Application number: US76750A
Authority: US
Inventors: Louis F Davis
Original assignee: Atlantic Refining Co
Current assignee: Atlantic Richfield Co
Priority date: 1949-02-16
Filing date: 1949-02-16
Publication date: 1954-06-08
Anticipated expiration: 1971-06-08

Description

June 8, 1954 F. DAVIS MEANS FOR DUALLY COMPLETING OIL WELLS 5 Sheg'ts-Sheet 1 Filed Feb. 16, 1949 R m m W.

HTTEST Louis F. Davis BY mnM a 5M June 8, 1954 F. DAVIS MEANS FOR DUALLY COMPLETING OIL WELLS 5 Sheets-Sheet 2 Filed Feb. 16, 1949 w Q Q Q INVEN TOR.

mmmmmU Louis F. Davis BY rmaaw H TTES T Hl'tornej June 8, 1954 F. DAVIS MEANS FOR QDUALLY COMPLETING OIL WELLS 5 Sheets-Sheet 3 Filed Feb. 16, 1949 IN V EN TOR.

HTTEST was; a. 4

Louis F. Davis ,yWafM Attorney 5 Sheets-Sheet 4 INVENTOR.

Louis R Davis BY Ma -M Z Hzi'orney L. F. DAVIS MEANS FOR DUALLY COMPLETING OIL WELLS .ET, 64 L 5 \v-\\ Av v JV \W M r17 VVVW. ////V /NV ///M7 JZA/ m m w u m w mww m a m m.

June 8, 1954 Filed Feb. 16, 1949 June 8, 1954 DA s 2,680,408

MEANS FOR DUALLY COMPLETING OIL WELLS Filed Feb. 16, 1949 5 Sheets-Sheet 5 FITTE'ST 6 INVENTOR. b 1144; 6% Louis F. D auz's BY fi MJMZ' 8,

H i'i'orney Patented June 8, 1954 Louis F. -l)avis,'Dallas, Tex assi'gnor to The Al;-

lantic Refining Company, Philadelphia, Pa.,'a corporation of Pennsylvania "Application February 16, '1 9 19,"Serial No. 76,750

9 Claims.

This invention relates to an improved system for producing from a plurality of subterranean oil reservoirs. More particularly, the invention relates to a system includin artificial lift means for-producing from a plurality of oil reservoirs through a single bore hole without commingling of the fluids from the several reservoirs.

The search for oil has led to the discovery in certain oil fields of a number of producing zones. Generally, the characteristics of thes'e'producing zones are dissimilar and frequently both oil and as reservoirs are encountered. In the case of oil reservoirs, to which the present invention is primarily directed, the pressure exerted on the oil contained therein may be attributable to a water drive, for example, or the presence of dissolved gaseous hydrocarbons. Further, there may be a considerable variance in the quantumof pressure exerted on the various reservoirs in the hold.

Joint production of oil from two or more 'producing zones through a single casing, ortubing strin is likely to result in irreparable damage "of the reservoirs and wastage of the fluids contained therein due to drainage'of fluid from one reservoir into a reservoir of lesser pressure and the attendant pressure drive reduction the former. For the above'reasons and the fact that in substantially all'States in which oilis being produced from subterranean petroliferous zones laws have been enacted i posin restrictionson the production of oil and gas, or either, as the case may be, from two or more producing zones in an oil field, efforts have been directed to the development of a method and apparatus for independently producing oil from a plurality of overlying reservoirs.

Obviously, this could be accomplished by producing separately each of the reservoirs through a well or wells communicatin solely therewith; however, relatively high'drilling' costs make desirable the production from the producing zones through a single bore hole. I In this regard, little difficulty is experienced in the 'case of reservoirs having sufficient pressure exertedfthereonfby a water drive, for example, to produce the same without employment of artificial lift means. For this purpose a tubing strin having'a packer provided on the end thereof is run'into a bore hole which traverses the reservoirs and is lihed with a well casing having, perforations therein "communicating with each of the reservoirs. The

well packer is set intermediate an upper and lower plCdllClllg'ZOIle, whereby'fluidffrom the upper producing zone will flow 'intothe 'we11 easing and thence to the well'surface through the 'therethrbugh 'to'th'e well surface. As the reservoirs are produced, the reservoir pressures will be reduced and-this will continue until the pressure drives are insufiici'ei-it to cause fluids co-ntamed therein to flow to the well surface. Natural flow having ceased, the reservoirs may then be put on artificial lift to recover an additional amount of reservoir fluid. The same situation obtains in the case of reservoirs in which the initial pressure is insufficient 'to permit natural flow of reservoir fluid.

A modification of the system described above, which has been proposed for producing separately from two or more reservoirs having pressures such as to require artificial lift means, utilizes gas lift valves operable upon the establishment of a preselected differential in pressure thereacross. In this system, an inner tubin strin is run inside the outer tubing string ina manner to provide an annular space therebetween and a packer is set externally of the inner tubing strin and adjacent the lower end thereof, in a manner sealing the'annu-lar space between it and the outer tubing string, whereby reservoir fluid from the lower reservoir instead of flowing upwardly in the outer tubing string, as in the previous system, will be directed up wardly into the interior of the inner tubing string. Pairs of'opp'ositely'clisposed gas'lift valves are provided at spaced intervals respectively in the wallsof the inner and outer tubing strings for lifting independently reservoir fluid frofn the lower reservoir and the upper reservoir, respectively, The gas lift valves maybe actuated by injection of gas under pressure into the annular space between the innerand outertubing strings. The valves are adjusted so as to be actuated by decreasing pressure differentials from the uppermost down to the lowermost pair of valves. The gas is injected at apressure sufficient to. actuate the uppermost pair of valves whereby the gas will .pass therethrough andv lift to the well surface the reservoir fluids above the uppermost pair of valves. in a similar manner, succeeding pairs of gas lift valves are actuated until the reservoir fluidsabove the lowermost pair of gas lift valves have been raised to the well surface. In

practice, this system is unsatisfactorybecause the gaspressure atwhichthega's liftvalvesare actuated is dependent uponyth'e'pressures of the reservoir fluids in the annular space between the outer tubing string and the casing, on the one hand, and within the inner tubing string, on the other hand, and, therefore, only partial control of this system from the well surface is possible.

The present invention is concerned with an improved system for producing from a plurality of subterranean oil wells and utilizes pressure responsive valve means of the intermitter type for lifting production to the well surface. The pressure responsive valve means are provided at vertically spaced intervals in the wall of the first and second tubing strings. It is necessary to maintain at all times the reservoir liquids in the annular space between the casing and first tubing string and within the second tubing strin at substantially the same level. For this purpose there is connected in the second tubin strin below the lowermost pressure responsive valve means a valve for controlling the level of the reservoir liquid normally standing in the second tubing string. By means of this improved system a plurality of producing zones may be produced through a single bore hole without commingling of the fluids from the several zones.

Other systems have been proposed for producing independently a plurality of producing zones through a single bore hole but none of them are entirely satisfactory for various reasons.

Accordingly, one object of the invention is to provide an improved system for producing from a plurality of subterranean reservoirs through a single bore hole, and a system that will obviate the difficulties above set forth.

Another object of the invention is to provide a system for producing from a plurality of producing zones through a single bore hole without commingling of the fiuids from the several zones.

A further obpect is to provide a system for producing from a plurality of producing zones through a single bore hole, which system includes artificial lift means for lifting independently to the well surface production from the several zones.

A still further object is to provide such a system in which means are provided for controlling the level of production in the well from one of the producing zones.

Other objects and features of the invention will be apparent from the drawings and description which follow.

Figure 1 is an elevational view, partially in section, showing a system constructed in accordance with the invention and including pressure responsive valve means for lifting independently to the well surface fluid from a plurality of reservoirs. ii Figure 2 is another embodiment of the invention in which pressure responsive valve means are employed for lifting to the well surface production from one of the producing zones and mechanically actuated valve means for lifting to the well surface production from another of the producing zones.

Figure 3 is an elevational view, partially in section, showing in detail a suitable gas lift valve for lifting reservoir liquid to the earths surface.

Figure 4 is a sectional view taken along the line 4-4 of Figure 3.

Figure 5 is an elevational view, partially in section, showing in detail a suitable mechanically operated lift valve.

Figure 6 is a sectional view taken along the line 6-B of Figure 5.

Figure 7 is a sectional view taken along the line l'! of Figure 5.

Figure 8 is an elevational view, partially in section, showing asuitable liquid level control valve.

Referring to the drawings, and in particular at this time to Figure 1, the earths surface is designated generally by the numeral I. A well bore traversing an upper oil reservoir 2 and a lower oil reservoir 3 is lined with a well casing 4 which is provided with

suitable perforations

5 and 6,

adjacent reservoirs

2 and 3, respectively. A first tubing string l is disposed within casing :3 in a manner to provide a first annular space 3 therebetween. A conventional permanent type packer 9 is secured between casing 4 and tubing string i, and intermediate of

reservoirs

2 and 3. A second tubing string in is disposed within first tubing string 1 in a manner to provide a second annular space it therebetween, and a suitable anchor packer I2 is secured between tubing strings I and H! and adjacent the lower ends thereof. By this arrangement reservoir liquids from

reservoirs

2 and 3 are directed into first annular space 8 and the interior of second tubing string ill, respectively. It is obvious that conditions'lrequently may arise where it would be desirable to employ a removable type packer in place of permanent type packer 9 and also a hook wall packer in place of anchor packer l2 and it is to be understood that such arrangement is within the scope of this invention.

It is the purpose of this invention to provide artificial lift means of the intermitter type for lifting independently to the earths surface 1 reservoir liquids from

reservoirs

2 and 3 in the event that the pressure drive of the reservoirs, or either, as the case may be, is insufficient for this purpose. To this end pairs of pressure responsive valve means I3, [4, and [5 are provided at spaced intervals in the walls of tubing strings l and ii], the pairs of pressure responsive valve means being responsive to progressively decreasing pressures from the uppermost pair of pressure responsive valve means i3 to the lowermost pair of pressure responsive valve means 15. The pressure responsive valve means, which will be described more fully hereinafter, may be of the conventional type of intermitter gas lift valve operable upon application of a predetermined fluid pressure to the input side thereof to thereby permit the fluid to flow therethrough and lift to the earths surface liquid standing thereabove in the well. Such a device is disclosed, for example, in U. S. Patent No. 2,385,316, issued to R. O. Walton on September 18, 1945, and entitled Well Flow Device."

Any suitable means, not shown, may be employed for intermittently introducing into annular space H through valve controlled pipe 116 fluid under pressure sufiicient to actuate the several pairs of pressure responsive valve means, whereby the fluid is permitted to flow therethrough and lift to the earths surface i the reservoir liquids in first annular space 8 and in second tubing string Ifl above the lowermost pair of pressure responsive valve means IS. The reservoir liquids from annular space 8 and tubing string to pass through valve controlled pipes l1 and 18, respectively, to suitable storage tanks, not shown.

For reasons which will be obvious from the description hereinafter, it is necessary to maintain the reservoir liquid in annular space 8 and second tubing string ill at substantially the same face.

:..l rc1- Accordingly, thereis connected ;inzsegnd etubin strin LIL-below th l w rmost pr s re :re-

spon iv valve mean It liquid level controivalve "means :LQ-for controllin the l ve of reservoir l quid :n rmallyostandine in s nd tubin strin ;,.L0- h l quid l vel ,.control valve means, which zwillbedes rib d in detail hereinaft r, may e o 1 conventional type, such as that disclosedrin Patent ,No. i2,597,193, issuedMay .20, 1952,11i0 Horace M. ,Sta gs and Louis Davis.

in practice, due to thesizes of standard pipe wh chflare employed usually :in dualcompleti n lations, the normalliquidlevel in second nestling L0 is above that of the liquidin first annularspace. ,8, regardless of. the fact that reseryoir' 25 may be somewhat more productive th n reservoir ,3. should level control valve in second, tubingstring .21 li he; liquid standing in the tubing string may b maintained at the same levellas thatof the ,l -i q. u id';in first annular space -8. In some in- Therefore, by suitably placin stances, however, the rate of flow of liquid from -uppcrpr duc ng r s rvoir-2 may be o mu h greater than that from lower reservoir 3, or the tubin em oyed in: the w ll may esuch; that th liquid- -level in first annular space ,8 is at a level L gherthanthatof the liquid in secondtubing -I-l. In suchinstances, in orderto maintain quidlevels-in the well equal, asuitable, conventional flow direction means or crossover pa ker ma be mployed and dispos d in t well annersuCh that liquid from upper reservoir directed into second tubing string ii) and liquidzfrom lowerproduclngreservoir 3 is directed into first annular space 8. It is readily seen that liquid level control means 19 disposed in secondtubing string it} then may be adjusted in a manner to maintain the liquid level in tubing I string Id, at the same height as the liquid level in first annular space 8.

.EigureZ-shows-another embodiment of theinvention which differs from that ofFigure 1 in -,that there issubstitutcd for the'pressure-responsive valve means i3, I4, and IE on second tubing string l0 a mechanically, actuated lift-device connectedin tubing string lllabove liquid levelconlJ IQl valve means l9 for periodically injecting ,iiuid into the reservoir liquid standing in the tubing stringto raise the liquid to {the well sur- One such device, commonlyv termed anv ,sintermitter is disclosed in U. S. Patent No. 1 1,683,930, ,issuedto Horace M. Staggs 0n September ll, 1928, and-entitled Air-eLiftPump. The intermitter, 29, which-is described in detail below, is disposed, asshown, inosecond tubing string In and is actuated by means of a weight 2.!

lperiodicallybrought into contact with cap '22 of the-intermitter, weight2l being alternately raised andlowered'by means of a suitable raising and lowering mechanism 23 located on the earths, surfaceland to which the weight isoperatively i connected by means of wire: line 24.

A suitable gas lift device, connected, for extainedinaseated. position ,on valvelseatgis ;.by;:a pressure. differential that exists thereacross,-.:the

pressurelbeing greater from below, suitablysprovided about'main valve stem 30 connected ;.to

valve 28. Whenvalve I28 is;.opened,,a :manner described hereinafter, the :fiuidgin the :lower end of, housing :25 will flow pupwardly past valves/28 into chamber 34 and thence will pass through-a series of ports 32Hformed in the wall of housing .15 into the .interior,-,.of second "tubing string 19.

The fluid passing out of the valve will lift tothe well surfacereservoirliquid standing in tubin string is above the valve.

For opening valvex28 there is provided bellows o stem .33, which is connected at one of its ends-to floating head :34 and the free end of which is .adapted to contactzthe end of valve stemrz3 8' :in1a

cessive. sections of housingiis and is provide'dwith an axial opening 33in which bellows stem 33 is mounted for slidable movement. When bellows 35 is contracted by, the pressure of fluidionrthe exterior thereof, as described hereinafter, floatinghead 3 and, therefore, bellows stem 33,- will be. caused to move downwardly whereby bellows stem ,33 will impinge upon valve estem13lln0pcning valve 28 and permittingfiuid in the lower part of, housing 25 to flow pastthe valve "and into vsecond tubing string Hi through ports,.32, .as-described hereinbefore.

Forcontrolling the pressure of fluid on thereaterior of bellows 35 and'thustheopeningofvalve 28, there isprovided in theupper end f housing 25. secondary valve 39 WhlCh'iS actuated-bypilot bellows 40. Bellows iii] is secured at oneiof its ends to fixed head 4! providedxatthe up erl'end of housing 25, and terminates at its lower end-in floating head 42 which "normally rests against plate 43 closing one end of bellows housing '55,

which isconnected atits other end to fixed head 4!. Secured to floating, head 4.2 and extending through a suitable aperture 45 in plate-43 0f bellows housing is secondary valve stem 45. Valve 39 is normally maintainedina closed position'by means of helical springifil'l'whichisprovided about valve stem 46 and-which is distended between plate 43 of bellows housingAiand adjustment nut 48 threaded on-valve stem dlip Valvefig is adapted to be seated normally on valve seat 49 which is threaded or otherwise securedin coupling 55} connecting successivesections of housing, 2.5 and carryinga conventional ball check valve 5! for closing passage 52 inqvalve seat la-against fluid pressure from belowl It is readily seen that fluid in second annularzspace l I, as well as entering into-the lowerpartbf housingze through nipple28, will pass through nipple 27 into the upper end-of the housing but normally will be, prevented from passing downwardly through passage 52 by valve 35-3. The fluid, however, enters bellowshousing 44 through rad-ial ports siiprovided therein and impinges upon the exterior of pilot bellows flll thereby causing the bellows to contract against the pressure I of spring 41, thus opening valve 33. The-fluid then, passesthrough opening'52 in .valve seat-.43, past ball check valve 5|, and through passages 54 provided'in coupling50 into that portion-of housing 25 containingbellowsr35; thelpressure-of gas: lift; device, causes 1 bellows 35, to contrao t,

- by threaded couplings thereby opening valve 28, as described hereinbefore. When the pressure in second annular space I I has decreased to a predetermined value by the passage of fluid through ports 32-, the fluid pressure exerted on the exterior of pilot bellows 49 will be insufficient to maintain the bellows in a contracted position; therefore, the force of helical spring 41 will cause valve 39 to close. This is followed by the closing of main valve 28 which 1 results when the fluid pressure exerted on the exterior of bellows decreases below a value sumcient to maintain bellows 35 in a contracted position due to the escape of the fluid out of bleed ports formed in housing 25. It is readily seen that by proper adjustment of nut 48, valve 28 may be caused to be seated or closed when the fluid pressure in second annular space II falls below a predetermined value.

The intermitter 29 of Figure 2, shown in detail in Figures 5, 6, and 7 of the drawings, comprises generally housing 56 secured at its opposite ends to successive sections of second tubing string I9 Valve stem 58 carrying valve 59 is mounted for slidable movement within sleeve 89 secured within axial bore 5i in housing 5% by threaded collar 62. Valve 59 is seated as at 63 and is normally maintained in a closed position by the action of helical spring 6 distended between shoulder 65 of housing 56 and shoulder 66 of cap 61 threaded to stem 58 of I valve 59. Fluid under pressure in second annular space II is normally maintained against the pressure side of valve 59 through interconnecting port 68 and chamber 99. However, upon the opening of valve 59 the fluid will be permitted Valve 59 is mechanically operated intermittently 4 'by the lowering of weight 2! against cap 22, the

action of weight 2I being controlled through the 'medium of wire line 25 and lowering and raising -mechanism 23 located at the earths surface I,

as stated hereinbefore.

The liquid level control valve of Figures 1 and 2 is shown in detail in Figure 8 and comprises generally a housing formed of end sections '19 and threaded as at Bi and 82, respectively, to

central section 83, and as at 8 t and 35, respectively, to successive sections of second tubing string I0. Valve 86 is seated as at 8'? on seat member 99 rigidly secured within end section 83 by threaded collar 89, which collar also serves as a guide sleeve to valve stem 9-6 through axial bore 9I and to provide a series of vertical bores or ports 92 for the passage of fiuid therethrough. Valve 86 is normally maintained in a closed position by helical spring 93 distended between flanged collar 94 and nut 95 threaded on the free end of stem and rigidly secured thereon by 'lock nut 96. Bellows 9? is secured by welding,

or in any other suitable manner, as at 98, to floating bellows head 99 and as at I99 to fixed bellows head I91, the fixed head being rigidly secured as by threading at I02, in one end of cylinder $93 which, in turn, is threaded at its opposite end to flanged member I99 of end section '19 and in a manner providing sealed bellows chamber I and annular space I96 therebetween and the inner wall of central section 83.

Bellows stem I0! is threaded to bellows head 99 and adjacent its opposite end is mounted for slidable movement through axial bore I08 in cap I09 threaded into bellows head lIlI. A series of bores or ports H0 in cap E99 permit the flow of liquid into and from the interior of bellows 9?. Cap III is threaded to the free end of bellows stem I07 and upon compression of bellows 9'! will be caused to move downwardly with stem IIll against cap H2 and through the medium of stem 96 to open valve 86. It will be seen that when bellows 91 is in a distended position, cap I I I is brought to rest against cap H2 but that liquid within space H3 within central section member 83 is at all times free to flow into and from the interior of bellows 91 through openings H4 in cap III, and ports H0 and annular groove H5 in cap I99. It furthermore will be seen that opening movement of valve 86, and, consequently, the compression of bellows 97, is limited by cap H6 threaded into end section 80.

Upon the opening of valve 86 liquid entering through strainer H7 will be caused to flow by reservoir pressure through openings H8 in cap H6, past valve 36, through ports 92 in space H9 in central member 83, and through annular space I06 from which it will flow through interconnecting ports H9 and I29 into tubing I9 to a predetermined level above the liquid level control means. Also, the reservoir liquid entering the liquid level control means will be caused to enter the interior of bellows 91 through ports H4 and H9, and annular groove H5, and thus to exert a pressure against the interior of bellows 93 dependent upon the level of the liquid in tubing I0 above the liquid level control means, as against the pressure of the fluid in annular space H, which is applied against the exterior of bellows 91 through interconnecting ports 12! and I22 providing communication between annular space H and bellows chamber I65.

Upon removal of the reservoir liquid in tubing is by the artificial means associated therewith, a differential in pressure across bellows 91' in favor of the pressure of the fluid in annular space H will be brought about whereby bellows 9? will be compressed and cause bellows stem I97 to be moved in a downwardly direction against cap I I2 and valve stem 98, thereby causing valve 86 to be opened and to admit additional liquid to tubing Hi to the predetermined level at which time the differential pressure across bellows 91 will be reversed in favor or the pressure of the liquid against the interior of the bellows and valve 86 closed.

Referring to Figure 1, a description of the operation of the invention when employing pressure responsive valve means on both tubing strings I and Ill will now be made. The several pairs of pressure responsive valve means provided at spaced intervals in the walls of the tubing strings are adjusted to respond progressively to decreasing pressures from the uppermost pair of pressure responsive valve means I3 to the lowermost pair of pressure responsive valve means 5. The apparatus is then assembled in the well, as shown in Figure 1, with the liquid level control means i9 connected in second tubing string I0 at a position such that the level of reservoir liquid therein is maintained substantially at the same level as that of the liquid contained in first annular space 8. When the apparatus is assembled initially liquid will be entrapped in second annu- 75' larspace II. Fluid under pressure sufficient to ate-6,468

9, eaters-an of the pressure responsive vane-means is introduced then into second annular space I! through valve' controlledpipe s; at this point each of the pressure responsive valve means will open permitting reservoir liquids within second annular space II" to pass th'erethrough into first annularspace S; and second tubing string I0. When the interface between the reservoir liquid and the fluid in second annular space I I reaches the uppermost pair of pressure responsive valve means I3 fluid will pass therethrough intofirst annular space 8 and second tubing string It] to thereby lift to the well surface reservoir fluids contained therein abovetl'ie uppermost pair of pressure responsive valve means I3. The passage of gas through the uppermost pressure responsive valve means I3 will result in a decrease iii-the fluid pressure in second'annular space II, as described liereinbefore, to the pressure at which this pair of valve means has been adjusted to close. This reduced fluid pressure will be maintained until the interfacebetween the reservoi'r liquid and the fluid reaches the next succeeding pair of pressure responsivevalve means I4 which has been adjusted by means of adjustment nut 48, as described hereinbefore, to close at a pressure less than that at which the uppermost pair of pressure responsive valve means ['3' closes. When the interface hasreached this point, fluid will pass through the pair of valve means I4 into first annular space 8 and second tubing string I I, lifting the reservoir liquid there in above the pair of valve means I4 to the well surface and resulting ina decrease in the fluid pressure-in second annular space II to the closing pressure of valve means Hi. This action will be continued until the lowermost pair of pressure responsive valve means has been actuated and the reservoir liquids'thereabove in first annular space 8 and 'se'cond tubingstring Hl' have been raised to the well surface; at'which time the introduction of fluid into secondannular space Iii; through valve controlled pipe I6 is interrupted. The introduction of fluid into second annular space II may be accomplished either manually or automatically by the time-control mechanism, for examplev The flu-id is supplied to second annular space II until reservoir liquid in' flrst annular space 8and second tubing string l above thelowermost pressure responsive valve means IEhas' been reached to-the well surface, at which time the supply isinterrupted. Sufficient time is-allowed for the reservoir liquids to reach their normal standing leveliri' the well before the fluid is again-injected into second annular space II to once again actuatethe" liquid level control valves'and lift to the; well surface liquid standing in the well above the valves.

If theliquidin tubihg string l0 and the liquid in'first annular space E are not maintained at substantially" the same level, only those pressure responsive valvemeanswhich"'are'assoeiated with the-liquid atthe lower level will operate to lift liquid tothe' well surface. Thus} for example; if the liquid intubingst'ring Ianorinally'stands at a level above the uppermost pressure responsivevalve means I 3, and the liquidin first' annular space 8"standsnormally at a level between valve means I land I55 when fluid under pressure sufficiei'i't-to actuateall of the pressure responsive valve means isintroduced into second annular space I the pressure ofthe fluid will decrease rapidlyitoa point below theclosingpressure of pressure responsive valve' means I4 which pressureis belowthe closing pressureof valve means l3, due to the passageof tl'ie fluid through the pressure, responsive valve means I4 disposed in first tubing string I and'into the first annular space 8. Although, obviously, valve means I3 and I I will close almost immediately, the fluid pressure in second annular space I I will be sufficient to maintain the lowermost pair of valve means I5 open, and, therefore, the fluid will pass through the one ofthe pair of valve means I5 which is disposed in first tubing string 7, to lift the liquid standing in first annular space 8 above the valve means to the well surface. However; due to the hydrostatic head of the liquid in second tubing string I0 above the lowermostjvalve means I5, the fluid pressure will be insufii cient to lift such liquid to the well surface,

In view of the above, it is necessary to maintain at all times the reservoir liquids in first annular space 8 and second tubing string II at substantially the same level. This is accorn plished, as pointed out hereinbeiore, by suitably disposing liquid level control valve means I9'in second tubing string, H3.

Operation of the embodiment of the invention shown in Figure 2 is similar to that of the system shown in Figure l, with the exception that intermitter 2B is not actuated by the fluid pres sure, but instead by the periodic lowering of weight M against cap 22 of the intermitter, as described above. The raising and lowering mechanism 23 located at the earthfs surface is adjusted in a manner so that intermitter 2 0 is caused to operate after each unloading o f liquid in first annular space Sby operational the associated pressure responsivevalve means. Inthis embodiment liquid level control valve means I8 functions to maintain the liquid in second tubing string H) at a level such'that the pressure of the fluid in second annular space It is suflicientto cause the liquid in tubing string 10 above inter; m itter 2d to be lifted to the'earths surface. If the liquid entering tubing string Ill is permitted to rise without control the hydrostatichead of the liquid above the intermitter in many instances would be so great as to prevent the unloading of the liquid by fluid passing through the intermitter from second annular space I I.

The fluid introduced periodically into second annular space I I for lifting the reservoir liquidto the earth's surface may be any suitable, available gaseous medium; however, it-is preferable to em-' ploy normally gaseous hydrocarbon mixtures obtained, for examplairom nearby gas wells.

1' claim:

1'. In a well producing from a plurality of oil another of the reservoirs is directed into the in terior of the second tubing strin'gthe cornbina'- tion therewith of marinate]; ommrvaives operatively secured to each of the tubing strings for controlling admission ofliftingfluid'under pres sure into the first annular space and thesecorid tubing string, and liquid'level-control valve means connected-fin onecisaid tubing strings for con; trolling the normal level of" production therein;

2. In a well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular spaces whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of pairs of intermitter control valves responsive to lifting fluid pressure within the second annular space and provided at vertically spaced intervals respectively in the walls of the first and the second tubing strings for controlling admission of lifting fluid under pressure into the first annular space and second tubing string, and liquid level control valve means connected in said second tubing string for controlling the normal level of production therein.

3. In a well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular spaces whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of pairs of intermitter control valves responsive to lifting fluid pressure within the second annular space and provided at vertically spaced intervals respectively in the walls of the first and the second tubing strings for controlling admission of lifting fluid under pressure into the first annular space and second tubing string, means for periodically admitting lifting fluid into the second annular space at a pressure sufficient to actuate the intermitter control valves, and liquid level control valve means connected in said second tubing string for controlling the normal level of production therein.

4. In a well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular spaces whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of pairs of intermitter control valves responsive to lifting fiuid pressure within the second annular space and provided at vertically spaced intervals respectively in the walls of the first and the second tubing strings for controlling admission of lifting fluid under pressure into the first annular space and second tubing string, means for periodically admitting lifting fluid into the second annular space at a pressure sufiicient to actuate the intermitter control valves, and liquid level control valve means connected in the second tubing string for maintaining normally well liquid in the second tubing string at the same level as well liquid in the first annular space.

5. In a well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular spaces whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of pairs of intermitter control valves responsive to lifting fluid pressure within the second annular space and provided at vertically spaced intervals respectively in the walls of the first and the second tubing stringsfor controlling admission of lifting fluid under pressure into the first annular space and secondtubing string, means for periodically admitting ifting fluid into the second annular space at a pressure sufficient to actuate the intermitter control valves, and liquid level control valve means connected in the second tubing string for maintaining normally well liquid in the second tubing string at the same level as well liquid in the first annular space, the pairs of intermitter con-- trol valves being responsive to progressively decreasing pressures from the uppermost pair of intermitter control valves to the lowermost pair of intermitter control valves whereby fluid from the second annular space will be admitted substantially simultaneously through the uppermost pair of intermitter control valves into the first annular space and second tubing string and will lift the well liquid therein above the levels of the respective uppermost pair of intermitter control valves to the earths surface and progressively will be admitted through succeeding pairs of intermitter control valves to lift the well liquid thereabove to the earths surface until the well liquids in the first annular space and the second tubing string above the lowermost pair of inter-v mitter control valves have been lifted to the earths surface.

6. In a well producing from a plurality of oil reservoirs including a well casing communicat ing with each of the reservoirs, a first tubing string disposed in the casing in a manner to pro vide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular spaces whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of intern litter control valves responsive to lifting fluid pressure Within the second annular space and provided at vertically spaced intervals in the wall of the first tubing string for controlling admission of lifting fluid under pressure into the first annular space, a mechanically operated intermitter control valve positioned within the second tubing strong for controlling admission of lifting fluid under pressure into the second tubing string, and liquid level control valve means connected in the second tubing string for controlling the normal level of well liquid therein.

'7. In a Well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular spaces whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of intermitter control valves responsive to lifting fluid pressure within the second annular space and provided at vertically spaced intervals in the wall of the first tubing string for controlling admission of lifting .fluid under pressure into the first annular space, a mechanically operated intermitter control valve positioned within the second tubing string for controlling admission of lifting fluid under pressure into the second tubing string, means operable from the earths surface to periodically actuate the mechanically operated intermitter control valve, and liquid level control valve means connested in the second tubing string for controlling the normal level of well liquid therein.

8. In a well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular space whereby production from one of the reservoirs is directed into the first annular space and production. from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of intermitter control valves responsive to lifting fluid pressure within the second annular space and provided at vertically spaced intervals in the wall of the first tubing string for controlling admission of lifting fluid under pressure into the first annular space, means for periodically admitting fiuid into the second annular space at a pressure sufficient to actuate the intermitter control valves, a mechanically operated intermitter control valve positioned within the second tubing string for controlling admission of lifting fluid under pressure into the second tubing string, means operable from the earth's surface to periodically actuate the mechanically operated intermitter control valve, and liquid level control valve means connected in the second tubing string for controlling the normal level of well liquid therein.

9. In a Well producing from a plurality of oil reservoirs including a well casing communicating with each of the reservoirs, a first tubing string disposed in the casing in a manner to provide a first annular space therebetween, a second tubing string disposed in the first tubing string in a manner to provide a second annular space therebetween, and packing means provided in the first and the second annular space whereby production from one of the reservoirs is directed into the first annular space and production from another of the reservoirs is directed into the interior of the second tubing string, the combination therewith of intermitter control valves responsive to lifting fiuid pressure within the second annular space and provided at vertically spaced intervals in the wall of the first tubing string for controlling admission of lifting fluid under pressure into the first annular space, means for periodically admitting fluid into the second annular space at a pressure sufficient to actuate the intermitter control valves, a mechanically operated intermitter control valve positioned within the second tubing string for controlling admission of lifting fluid under pressure into the second tubing string, means operable from the earths surface to pcriodically actuate the mechanically operated intermitter control valve, and liquid level control valve means connected in the second tubing string for controlling the normal level of well liquid therein, the intermitter control valves being responsive to progressively decreasing pressures from the uppermost intermitter control valve to the lowermost intermitter control valve whereby the fiuid will be admitted through the uppermost intermitter control valve to the first annular space and will lift the well liquid therein above the level of the intermitter control valve to the earths surface and progressively will be admitted through succeeding intermitter control valves to the first annular space and will lift the well liquid thereabove to the earths surface until the well liquid in the first annular space above the lowermost intermitter control valve has been lifted to the earths surface.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,968,633 Boynton July 31, 1934 2,006,909 Boynton July 2, 1935 2,298,834 Moore Oct. 13, 1942 2,385,316 Walton Sept. 18, 1945 2,391,605 Walton Dec. 25, 1945