US2678605A

US2678605A - Gas-lift apparatus for producing multiple zone wells

Info

Publication number: US2678605A
Application number: US177990A
Authority: US
Inventors: Ronald A Tappmeyer
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1950-08-07
Filing date: 1950-08-07
Publication date: 1954-05-18
Anticipated expiration: 1971-05-18

Description

R. A. TAPPMEYER 2 Sheets-Sheet l a} T 0 AM R May 18, 1954 GASLIFT APPARATUS FOR PRODUCING MULTIPLE ZONE WELLS Filed Aug. 7. 1950 w in: n ll 4 4 A I Te 8 e o o 8 A B W m B 5 3344 M%4 q. JLI b 1 Qlikllf E R. A. TAPPMEYER GAS-LIFT APPARATUS FOR PRODUCING MULTIPLE ZONE WELLS Filed Aug. 7, 1950 May 18, 1954 2 Sheets-Sheet 2 FIG. 8

a a a u m P u a P e x a n a F F 1 A b 4 b 7. E A. s r W b n e vu m5 Patented May 18, 1954 GAS-LIFT APPARATUS FOR PRODUCING MULTIPLE ZONE WELLS Ronald A. Tappmeyer, Houston, Tex., assignor to Shell Development Company, San Francisco, Galifl, a corporation of Delaware Application August 7, 1950, Serial No. 177,990

13 Claims. 1

This invention relates to apparatus for producing oil from a plurality of oil-bearing formations traversed by a single borehole, and pertains more particularly to apparatus for producing a multiple-zone well by injecting a gas into the oil streams within the well to facilitate the flow of oil to the surface.

Gas-lift methods of producing either single or multiple-zone oil wells are well known to the art. When sufilcient gas and pressure are no longer available from the oil reservoir to maintain natural flow, either due to depletion or because the flow column loads up with water, a volume of extraneous gas necessary to maintain flow may be introduced into the oil flow stream at the proper depth within the well. The gas, such as air, carbon dioxide, natural gas and the like, acts to decrease the weight of the oil column sufficiently so that it may be forced upwardly by the pressure available in the producing zone.

In wells having a single producing zone, gas for lifting the oil to the surface is pumped into the well head, usually into the annular space between the production tubin and the well casing. In multiple-zone wells, where three ormore concentric pipes are employed to produce from a plurality of formations simultaneously, the gas may be introduced through the center pipe or any of the annular spaces between the pipes. Gas-lift flow from a multiple-zone well is usually accomplished with the aid of flow valves placed at calculated intervals on the two inner pipes of a three-pipe system. Ihe flow valves are designed to control automatically the volume of gas introduced into the flowing oil streams.

.While such a system isoperable, it is difficult and expensive to service in that it is necessary to remove both of the tubing strings from the well in order to adjust or replace any of the valves carried on the outer of the two tubing strings. Another important disadvantage to the system is that any liquid used to kill a well, before re moving .the tubings therefrom comes in contact with the reservoir faces, thereby subjecting them to contamination or possible plugging action.

It is therefore a primary object of the present invention to provide a valved gas-lift system of three concentric pipes whereby a gas may be injected into any two of the three pipes through valves mounted on the central pipe only.

t is also an object of this invention to provide a valved gas-lift system of three concentric pipes for injecting a gas through valves into any two of the pipes, all of said valves being removable from said system upon removal of the central pipe therefrom.

Another object of this invention is to provide a valved gas-lift system adapted to isolate the reservoir faces in the well borehole from any contaminating fluid introduced for killing the well prior to servicing the gas-lift equipment.

With the above and other objects and advan tages in view, the invention has particular relation to certain novel features of construction, operation and arrangement of parts, examples of which are given in this specification and illustrated in the accompanying drawing, wherein:

Figure 1 is a longitudinal view, partly in cross section, of the present gas-lift apparatus illustrated as being positioned in a well borehole which traverses two producing zones.

Figures 2 and 3 are longitudinal views, partly in cross section, of alternative arrangements of the present gas-lift apparatus.

Figure 4 is a longitudinal view, partly in cross section, of one embodiment of a dual-valve and iby-pass assembly employe in the present system.

Figures 5; 6 and 7 are cross-sectional views taken along the lines 5--5, 66 and 1-7, respectively, of Figure 4.

Figure 8 is a longitudinal view in cross section illustrating an alternative method of packing 01f the lower ends of the concentric pipe strings.

Referring to Figure l of the drawing, a well borehole II is shown extending downwardly through two vertically-spaced producing formations generally indicated at l2 and I3. A well casing I4 is positioned in the borehole H and cemented therein. The casing or liner [4 has perforations I5 and it at the levels of the upper and lower oil zones 12 and I3, respectively, through which oil from both zones enters the casing.

A casing head ll is mounted on the upper end of the casing Hi and a string of large diameter tubing or pipe i8 is suspended therefrom in a conventional manner, said pipe string [8 extending downwardly in the borehole l l to a point below the upper oil zone [2 and preferably adjacent the lower oil zone i3, as shown in Figure 1. A packer i9 is secured to the pipe string I 8 and run into the casing it to a point intermediatethereby preventing the oil in one zone from flowhaving inside diameters slightly smaller than that of the rest of the pipe string i8, are secured in the pipe string, as by threaded couplings 22 and 23. Each sub 2! is provided with one or more fluid ports 25 which are preferably formed at a point substantially equidistant from the ends of the sub. As the pipe string I8 is being made up and lowered into the well, a special sub 2! is connected therein at each predetermined point at which a gas-lift valve assembly is to be later installed. A line 25 is secured to the casing head ll at the surface, said line being in communication with the annular space 29 between the well casing l4 and the pipe string l8. In like manner, the pipe string is is provided at the surface with a fluid flow line 2? which may. lead to conventional tanks, separators or other equip-ment.

Arranged concentrically within the pipe string I3 is a pipe string or string of tubing having an outside diameter substantially smaller than th inside diameter of the larger pipe string 18, as for example, a 1% inch pipe nested within a 3 inch pipe. The upper end of the pipe string 28 is provided with a'flow line 45 and is'secured to the casing head ll above the ground in a conventional manner, while the lower end of the string 28 may be positioned in a seating nipple The seating nipple 29 is affixed to the inner surface of the larger pipe string l8, in any suitable manner, as by welding, and installed at a point which is preferably intermediate the two producing zones l2 and I3 when the string i8 is positioned in the well. One or more grooves 36 may be formed or cut, in the inner surface of the seating nipple 29 to accommodate packing whereby a fluidtight seal is formed with the lower end of pipe string 28. 7

Thus, the seatin nipple 2% actually forms a packer which closes the annular space a! between the pipe strings l8 and 28 at a point be tween the two oil zones i2 and it. Instead of employing a seating nipple 28 affixed to the inner surface of pipe line l8, a packer ti carried on the outer surface of the smaller pipe string 23 near the lower end thereof may be used as shown in Figure 8. Such a packer would be preferably one which was expansible by either vertical or rotary movement of the pipe string 28 as is well known to the art. As shown in Figure 2, the pipe string l8 may. also be alternatively provided with a nipple 32 having a downwardly tapering bore 33 adapted to receive and seal therein a tapered shoe 36 secured to the lower end of the inner pipe string 23. Sealing rings 35 may be carried on the outer surface of the shoe 3%. It is realized that the expansible packer 61' of Figure 8 may be used interchangeably with the

seating devices

29 and 32 shown in the embodiments of Figures 1, 2 and 3. 7

At predetermined fixed distances, the smaller pipe string 28 is provided with dual-valve assemblies, the distance between these assemblies being equal to the distance between the special subs 2| in the outer pipe string !8. As shown in Figure 1, each valve assembly may comprise a pair of spaced

packing elements

31 and 38 having axial bores 39 and as therethro ugh, respectively. The

axial bores

39 and 69 are in communication with the inner pip string 28, the packing elements being fixedly secured thereto by any suitable means such as by welding, screw-threads, etc. If desired, swaged

nipples

52 and 53 may be welded to the packing elements 3? and 38 and then coupled to the inner pipe string 28 by screw threads.

The outer diameter of the packing elements is substantially equal to the inner diameter of the special sub 2! into and through which the packing elements may be moved in slidin sealing engagement. The packing elements 3? and 38 are also provided with auxiliary conduits ll and 52 extending therethrough which are in communication with each other through a small-diameter by-pass conduit 43. Another short section of small-diameter conduit is is fixedly secured, as by welding, to the adjacent faces of the packers 31 and 353, said conduit being in communication through the axial bores 39 and it, with the inner tubing string 28 above and below the valve assembly. The conduits $3 and id maintain the

packing elements

37 and 38 in rigid fixed" spaced relationship, said elements 3? and 38 being lo cated on either side of the fluid ports 25 in the wall of the special sub 2 I when the valve assembly is positioned therein for gas-lift operation.

Fixedly mounted in the adjacent faces of the packing elements 31 and 3B are a pair of

gaslift valves

45 and 47 of conventional design. Since the construction and operation of gas-lift valves are well known to the art and since their structure does not form any part of the present invention, they will not be further described in this application. It is suiiicient to state that the valves may be pre-set to open when the desired pressure differential exists between a gas filled space or conduit and a liquid filled space or conduit, whereby gas is injected into the liquid, thus reducing its density and allowing it to how upwardly to the surface more readily. The valve 56 in the upper packer 3T communicates with the annular passageway 3| between the pipe strings i8 and 28 through a conduit 48 extending through the packer. The other gas-lift valve fill communicates with the axial bore of the inner pipe string 28 through a conduit 49 in the lower packing element 38.

A preferred embodiment ofthe gas-lift valve assembly is shown in Figures 4, 5, 6 and '7. lnthis embodiment the packing elements 3? and 3 3 are secured, as by screw-threads l6 and H, to nipples 52 and 53 which are coupled to the inner pipe string 28. Conduits l8 and is through said elements 3'? and 38 are offset in order to employ as large a conduit 44 as possible alongside the gaslift valves is and s1. Similarly, in order to accommodate as large a flow as possible in the annulus 3! (Fig. 1) outside the pipe string 23, the valve assembly is provided instead of a single conduit 43 with .a pair of by-pass conduits 33a and 332), said conduits being positioned on opposite sides of conduit 54 and preferably being curved in cross section similar to the contour of the packing elements 3! and 38. Conduits ite and @312 are mounted in communication with conduits Ma, 4! b, 42a and 42b in the packing elements 3? and 38.

Oil from the lower producing zone it enters the inner pipe string 28 through a standing valve 59 which is preferably mounted on the lower end of the pipe string l8. This valve 58 may be a balltype check valve as shown in Figure 1, which allows the inflow of fluid while preventing backflow of any fluid in the pipe string is and 28 when the well is being killed. Similarly, the how of oil from the upper zone !2 into the annular space 3! between the pipe strings l8 and 28 preferably enters through a plurality of check valves 5! carried on the outside of the larger pipe string i8 between the packers l9 and 24, although, if desired, these valves may be dispensed with the string I8 having perforations instead. When check Valves are used, fluid in the annular space 3| is prevented from coming in contact with the reservoir face of the upper oil zone 12 when the well is killed.

With the equipment positioned in the borehole of a well as illustrated in Figure 1, simultaneous production of oil from both producing formations l2 and i3 may be accomplished by gas-lift in the following manner. Oil from the lower producing zone 3 flows through the perforations [6 in the well casing l4 and into the bore of said casing. Since the lower packer |9 on the pipe string it prevents the fluid from rising in the casing M, the fluid pressure forces the ball valve 50 off its seat allowing the fluid to flow into the inner pipe string 28 with the packer or seating nipple 29 preventing any flow from entering the annular space 3|.

Simultaneously, oil from the upper producing zone |2 enters the casing l4 through the perforations and thence through the check valves 5| into the annular space 3| between the pipe string is and 23. Hence, it will be seen that oil from the upper zone |2 flows upwardly in the annular space 3! while oil from the lower zone l3 flows through the inner pipe string 28.

When the oil in the annular space 3| rises to the packing element 38 of the valve assembly, it passes upwardly through by-pass conduits 42, t3 and 4| and into the space 3! above the upper packing element 31. At this point the oil is subjected to the lifting action of a gas being injected into the flowing oil stream.

Gas is pumped from some suitable compressor or storage vessel (not shown) into the flow line leading to the casing head I! above the ground. The gas is forced down the annular space 2!) be tween the well casing l4 and the pipe string Hi. Since thelower end of this annular space 25 is closed by the upper packer 24 carried by pipe string IS, the gas flows through inlet ports '25 in '18 special sub 2| and thence into the gas-

lift valves

35 and 41. Gas is discharged through valve G5 and passageway 48 into the oil in the annular space 3| above packing element 31, whereby the density of the oil is reduced so that it is forced to the top of the well and out flow line 2"! to suitable storage facilities (not shown).

In a like manner, as the oil stream rises in the inner pipe string 28 and passes through by-pass conduits ill, 44 and 39, gas is discharged through gas-lift valve l'itand passageway 49 into the flowing oil stream as it passes through conduit 40. The oil stream then rises in the inner pipe string 28 and is discharged at the surface through flow line 45.

Qne outstanding advantage of the present gaslift system for producing a two-zone well is that all of the gas valves are fixedly secured to the innermost pipe string 28 whereby they may be readily withdrawn from the well for adjustment and/or servicing by the simple operation of pulling or removing the pipe string 23. This operation may be accomplished in the following manner. Blowout preenters, diagrammatically represented at 54 in Figure 1, may be installed on the casing head I? at the surface to surround the inner pipe string 28. The pipe string 28 is then lifted through the preventers 54 to a height sufficient to pull the lower end of the pipe string 28 out of the seating nipple 29 and the packing elements 3i and 38 of the valve assembly out of the special sub 2|. In the eventthat a packer is used in place of the nipple 29, the pipe string 28 may be lifted and/or rotated to disengage the packer. Water or any other liquid to be used for loading the well may be then pumped through the flow line 45 and down the inner pipe string 28.

The standing valve 5|! prevents the water from flowing out of the bottom of the larger pipe string l8 and thus prevents it from contaminating the lower oil zone i3. On reaching the lower end of thepipe string 28, the water is forced up the annular space 3| to fill the larger pipe string l8, and from there is then flows out the open ports 25 to fill the annular space 20 above the packer 24, said packer preventing the water from coming in contact with the upper zone l2. The check valves 5| prevent water in the annular space 3| from coming in direct contact with the reservoir face of zone |2, also. When the inner pipe string 28 and the annuli 2i] and 3| have been loaded, the inner string 28 can be removed upwardly from the well in the conventional manner without further use of the blowout preventers 55.

In the event that it is desired to circulate a fluid through the concentric tubular system Hi, [8 and 28 for any purpose, e. g., to remove accumulations of paraffin, the inner pipe string 28 is again raised a short distance, as previously described, to pull it out of the seating nipple 2i and to pull the valve assembly from the special sub 2|. By shutting off the flow line 26 at the surface, circulation of a fluid can be established down through the pipe string 28 while the opening of flow line 25 permits the circulation of fluid down pipe lines 28, up the annulus 3|, out ports 25 and up the annulus 20.

When the fluid volume to be produced from one oil zone exceeds the capacity of either pipe string 28 or the annulus 3| between pipe strings I8 and 28, it may be desirable to utilize the relatively large cross-sectional area of the annulus 26 between the well casing l4 and the pipe string I8 to handle the flow from the formation having the greater production. As shown in Figure 2, in producing a well in this manner the oil from one zone l2 may be lifted through the larger annulus 20 while the oil from the other zone i3 is lifted through the smaller pipe string 28. The annulus 3|, between the two pipe strings I3 and 28, is then employed to supply gas to gas-

lift valves

55 and 56 carried on the outside of the inner pipe string 28.

In the embodiment shown in Figure 2, the

gaslift valves

55 and 56 are secured to a pair of expansible packers 5! and 53 carried on the pipe string 23 in spaced relationship. These packers are preferably of the type that may be expanded against the inner surface of the pipe string 23 by vertical or rotary motion of the string 28, or in any other manner well known to the art. If desired, the packers 5! and 58 may be separated by a considerable distance to insure proper positioning on either side of fluid ports 52 which are provided in the wall of the pipe string H3 at a point where the gas-lift valve assembly is to be positioned.

The

packers

57 and 58 are provided with a bypass conduit fiil in communication between the space above packer 51 and the space below packer 58. One gas-lift valve'55 is mounted on the top of the upper packer 5'! to control the flow through a conduit 6| which is in communication with the opposite sides of said packer 51. The other valve 56 is mounted preferably on the lower side of the bottom packer 58 to control the flow through a 7. conduit 52 which is in'communication between the bore of'the pipe string 28 and the annulus 3! below the packer 58.

In this embodiment the larger pipe string is (Fig. 2) is provided with a pair of spaced packers i9 and 24 carried outwardly for closing the annulus 23 above and below the upper producing zone l2 as described with regard to Figure 1. Additionally, a by-pass conduit 63 is provided which a is in communication between the check valves i and the annulus above the upper packer 24, whereby the fluid from the greater producing zone I2 may flow into the larger annulus An alternative arrangement may be a conduit 58 through the upper packer 24 which is closed by a check valve 65.

Thus, with the present valve assembly mounted on the inner pipe string 28, it is lowered within the larger pipe string l8 until the shoe 3% seats in the nipple 32 with the packers 5i and 58 being located on either side of the ports 5% in the pipe string is; Fluid from the lower zone l3 enters the casing 14 and flows upwardly through pipe string E8 and into pipe string 28 at the nipple 3'2. Simultaneously, gas is forced down the annulus 31 between the pipe string l8 and 23, down past both packers 5'! and 58 through conduit til to be discharged through valve 56 and conduit 62 into the flowing stream of oil in the inner pipe string 28.

Gil from the upper oil zone i2 enters the casing i4 through perforations l5 and thence through valves 5i and by-pass 63, or through valves 65 and conduit 64, into the annulus 26 above the top packer. As the oil flows upwardly in the annulus 20 past the ports 59 in the pipe string i8, gas from annulus 3| is discharged through valve 55, conduit GI and ports 59 into the flow stream, thus facilitating its rise to the surface, the well may be killed or loaded with a liquid during servicing of the gas-

lift valves

55 and 56 without the liquid coming in contact with the reservoir faces of zones l2 and i3 as previously described.

If precautionary measures against such contamination need not be taken, the upper packer 24,

check valves

50, 5i and 65 and conduit 63 of the embodiment of Figure 2 may be dispensed with and the intake ends of the concentric pipe lines 1 8 and 28 may be arranged as shown in Figure 8. In this embodiment a single packer 65 i carried on the outside of the pipe string I8 near the lower end thereof, said packer being adapted to be set to seal the annulus 20 intermediate the two producing zones 12 and i3. Another packer t? is provided on the outside of the inner pipe string 23 near the lower end thereof for sealing the annulus 3!. Thus oil entering the casing is from the upper zone [2 flows directly upward in the annulus 20 while oil from zone It flows in the inner pipe string 28, the streams in both conduits having gas injected into them when they pass a gas-lift valve assembly as described in the embodiment of Figure 2.

Another embodiment of the apparatus of the present invention is shown in Figure 3 wherein the outer pipe string I8 is provided with packers is and 24 carried outwardly thereon. Ports 555, similar to those shown in Figure 2, are formed in the wall of said pipe string i8 at each level where gas-lift valves are to be employed. The upper packer 24 in this embodiment is different from those previously described in that it is provided with a transverse wall member 63 through which extend a pair of crossover conduits 59 and l'ii. Fluid entering the bottom of pipe string it rises to the wall 68 and then flows through conduit 65 which is in communication between the space inside said pipe string l8 below the packer 24 and the annulus 20 above said packer 24. Fluid from the upper producing zone l2 entering the check valves 5| flows through conduit 10 which is in communication between the space outside the pipe string :8 below the packer 24 and the bore of the inside pipe string 23 above said packer 24. Packers of the above-described type are well known to the art as crossover packers.

A packer 24 having crossover conduits 69 and is employed when the production from the lower oil zone It is greater than that of zone l2 whereby the larger annulus 20 may be utilized to handle the larger flow. The annulus 3| between pipe strings I8 and 28 may be closed byeither' a nipple 32, or by a packer as previously described. Thus, fluid being discharged from conduit 10 enters the lower open end of pipe string 28 and is conducted upwardly.

The gas-lift valves H and 12 of this embodiment are fixedly mounted on an upper side of a single expansible packer '!3 being carried on the outside'of the pipe string '28 at a height sufiicient so that it is above the outlet ports 55 when the lower end of said pipe string 28 is seated in the nipple 32 in a fiuidtight manner. Valve H controls the flow of gas through a conduit M in communication between either side of said packer 13 while valve '52 controls the flow through a conduit it in communication between the annulu 3i above the packer l3 and the bore of pipe string Alternatively, gas valves F5 may be mounted directly on the inner pipe string 2%, said valves being auxiliary to or a substitute for valve 12.

In the operation of this embodiment of the present gas-lift system, gas is pumped .down the annulus 3| and through the gas-lift valves ll and i2. Gas flowing through valve '52 and conduit 75 is injected directly into the oil stream in pipe string 23. On the other hand, gas flowing through valve '1! and conduit id is discharged into the annulus 3| below the packer '13, but since the annulus is also closed by the packer or nipple 32, the gas in the annulus isforced out ports 59 into the oil stream flowing within the annulus 2E).

From the above description, it will be readily seen that various modifications may be made in the arrangement of the packers and gas-lift valves on the three concentric pipe strings without departing from the new and novel feature of the present system which provides for all the gas-lift valves to be mounted on the innermost pipe string.

I claim as my invention:

1. For use in a well having a perforated casing in communication with two producing formations traversed by the well, a gas-lift installation comprising concentric outer and inner tubings arranged within the casing whereby annular spaces are formed between said tubings and between the outer tubing and said casing, first packer means carried by the outer tubing to seal the annular space between said outer tubing and the casing at a level between said two formations, second packer means sealing the space between said two tubings at a level between said two formations, said inner tubing being open to the lower forma tion below said two packer means and said outer tubing being open to said upper formation above said two packer means, and at least one gas-lift assembly arranged above said upper formation, said assembly comprising two spaced packer elements carried on the inner tubing to form there- *9 between a chamber within the-outer tubing by sealing the annular space between the two tubings, the outer tubing having lateral ports opening to said chamber, by-pass conduit means extending axially through said two packer elements and said chamber, and gas-lift injection valves in said chamber opening from said chamber to said inner tubing and the annular space between said outer and said inner tubings, whereby pressure gas supplied to said chamber through said lateral ports and the annular space between the casing and the outer tubing can be injected into said tubings.

2. An assembly for a two-zone gas-lift installation having two concentric tubings, forming an annular space therebetween, said assembly comprising inner and outer packers traversed and supported by the inner concentric tubing in axially spaced relationship with each other, said packers sealing the space between said two packers within the outer tubing, conduit means extending co-longitudinally of said inner tubing through said two packers and the space there between, said conduit means being in communication with the annular space within the outer tubing to either side of the space sealed between said two packers, port means through the wall of said outer tubing in communication between the space outside said outer tubing and the annular space between said two packers, and a gaslift injection valve supported by each of said packers in the space therebetween, one of said yalves opening for gas-injection from the space sealed between said packers to the annular space within the outer tubing adjacent the space sealed between said packers, and the other valve opening for gas-injection from said space sealed between said packers to the inside of the inner tubing.

3. A two-zone gas-lift installation, comprising two concentric tubings forming an annular space therebetween and extending into. a well, first packer means carried by the outer tubing for separating the liquid entering said well from said two zones, second packer means carried by the inner tubing above the first packer means to I within the outer tubing.

4. A two-zone gas-lift installation, comprising two concentric tubings forming an annular space therebetween and extending into a well, first packer means carried by the outer tubing for separating the liquid entering said well from said two zones, second packer means carried by the inner tubing above the first packer means to seal the annular space between said two tubings and means comprising gas-lift valve means for separately injecting gas into theliquids entering said well fromsaid two zones, at least one of said gas-lift valve means being carried by said second packer means, all of said gas-lift valve means and said second packer means being carried by said inner tubing and being removable from the well by pulling the inner tubing-from Within the outer tubing.

5. An assembly for a two-zone gas-lift installation having two concentric tubings, forming an annular space therebetween, said assembly comprising inner and outer packers traversed and supported by the inner concentric tubing in axially spaced relationship with each other, said packers sealing the space therebetween within the outer tubing, conduit means extending colongitudinally of said inner tubing through said two packers and the space therebetween, said conduit means being in communication with the annular space within the outer tubing to either side of the space sealed between said two packers, port means through the wall of said outer tubing in communication between the space outside said outer tubing and the annular space between said two packers, and gas-lift injection valve means supported by at least one of said packers, said valve means opening for gas-injection from one side of said packer to the other.

6. An assembly for a two-zone gas-lift installation having two concentric tubings, forming an annular space therebetween, said assembly com prising inner and outer packers traversed and supported by the inner concentric tubing in axially spaced relationship with each other, said packers sealing the space between said two packers within the outer tubing, conduit means extending co-longitudinally of said innertubing through said two packers and the space therebetween, said conduit means being incommunication with the annular space within the outer tubing to either side of the space sealed between said two packers, port means through the wall of said outer tubing in communication between the space outside said outer tubing and the annular space between said two packers, and a gaslift injection valve supported by each of said packers, one of said valves opening for gas-injection from the annular space within the outer tubing adjacent the space sealed between said packers to the space sealed between said packers, and the other valve opening for gas-injection from the annular space between the inner and outer tubing to the space within the inner tubing.

7. For use in a well having a perforated casing in communication with two producing formations traversed by the well, a gas-lift installation comprising concentric outer and inner tubings arranged within the casing whereby annular spaces are formed between said tubings and between the outer tubing and said casing, first packer means carried by the outer tubing to seal the annular space between said outer tubing and the casing at a level between said two formations, second packer means sealing the space between said two tubings, said inner tubing being open to the lower formation below said two packer means and said outer tubing being open to said upper formation above said two packer means, and at least one gas-lift assem bly arranged above said upper formation, said assembly comprising two spaced packer elements carried on the inner tubing to form therebetween a chamber within the outer tubing by sealing the annular space between the two tubings, the outer tubing having lateral ports opening to said chamber, by-pass conduit means extending axially through said two packer elements and said chamber, and gas-lift injection valve means carried by at least one of said packers, said valve means opening from said chamber to said inner tubing and the annular space between said outer and said inner tubings, whereby pressure gas can be injected through said valves into the liquid flowing through said inner tubing and one of said annular spaces.

8. For use in a well having a perforated cas- 11 ing in communication with two producing formations traversed by the well, a gas-lift installation comprising concentric outer and inner tubings arranged within the casing whereby annular spaces are formed between said tubings and between'the outer tubing and said casing, first packer means carried by the outer tubing to seal the annular space between said outer tubing and the casing at a level between said two formations, second packer means sealing the space between said two tubings, third packer means carried by the outer tubing to seal the annular space between said outer tubing and the casing at a level above said second packer means, said imier tubing being open to the lower formation below said packer means and said outer tubing being open to said upper formation above said first and second packer means, check valve means closing said openings to said inner and outer tubings, and at least one gas-lift assembly ar ranged above said upper formation, said assembly comprising two spaced packer elements carried on the inner tubing to form therebetween a chamber within the outer tubing by sealing the annular space between the two tubings, the outer tubing having lateral ports opening to said chamber, by-pass conduit means extending axial- 1y through said two packer elements and said chamber, and gas-lift injection valves in said chamber opening from said chamber to said innor tubing and the annular space between said outer and said inner tubings, whereby pressure gas supplied to said chamber through said lateral ports and the annular space between the casing and the outer tubing can be injected into said tubings.

9. Gaselift apparatus, for flowing oil from a well passing through a plurality of oil-produce ing formations, said apparatus comprising a casing arranged within said borehole provided with means of communication with at least two of said producing formations, a first string of tubing arranged inside the casing whereby an annular space is formed between said casing and said tubing string, packer means arranged for sealing the annular space between said casing and said tubing string at a point'above the lower of two producing formations, a second string of tubing arranged inside said first tubing string to form an annular space between said tubing strings, second packer means arranged in the annular space between said first and second tubing strings, port means in said first tubing string above said second packer means, and valved packer means arranged in the annular space between said first and. second tubing strings at a point above said port means, said valved packer means including gas-lift valve means for injecting a gas into one of said annular spaces.

10. Gas=lift apparatus for flowing oil from a well passing through a plurality of oil-producing formations, said apparatus comprising a casing arranged within said borehole provided with means of communication with at least two of said producing formations, a first tubing string arranged inside the casing whereby an annular space is formed betweensaid casing and said tubing string, packer means arranged for sealing the annular space between said casing and said tubing string at a point above the lower of two producing formations, a second tubing string arranged inside said first tubing string to form an annular space between said tubing strings, second packer means arranged in the annular space between said first and second tubing strings, port means in said first tubing string above said second packer means, and valved packer means arranged in the annular space between said first and second tubing strings .at a'point above said port means, said valved packer means comprising first gas-lift valve means for injecting a gas into one of said annular spaces and second gas-lift valve means for injecting the gas into said second tubing string.

11. Gas-lift apparatus for fiowing oil from a" well passing through a plurality of oil-producing formations, said apparatus comprising a casing arranged within said borehole in communication with atleasttwo of said producing formations, a first string of tubing arranged inside the casing whereby an annular space is formed between said casing and said tubing string, packer means "arranged for sealing the annular space between said casing and said tubing string at a point above the lower of two producing formations, a second string of tubing arranged inside said first tubing string to form an annular space between said tubing strings, second packer means arranged in the annular space between said first and second tubing strings, first gas-lift valve means carried by the second tubing string above said second packer means for injecting a gas into said second tubing string, port means in said first tubing string above said second packer means, and valved packor means arranged in the annular space between said first and second tubing strings at a point above said port means, said valve packer means including second gas-lift valve means for injecting a gas into one of said annular spaces.

12. In a multiple-zone gas-lift well installation including three substantially concentric tubular strings, said strings forming inner, intermediate and outer tubular strings with annular spaces therebetween, gas-lift valves carried by said inner string for injecting a gas into the inner and intermediate strings, said valves being upwardly removable from said well with said inner string and port means through said intermediate tubular string adjacent said valves for conducting gas to said valves.

1 3, In a multiple-zone gas-lift well installation including three substantially concentric tubular strings, said Strings forming inner, intermediate and outer tubular strings with annular spaces therebetween, gas-lift valve means carried by said inner tubular string for injectin a gas thereinto and into, one of the annular spaces be tween the concentric strings, said valves being upwardly removable from said well with said inner tubular string and port means in the wall of said intermediate tubular string in communi-,

Nu e Name Date 2, 3% 7 Moore "ans-via. 0012.13, 1942-