US2665759A

US2665759A - Method and apparatus for completing multiple production zone well bores

Info

Publication number: US2665759A
Application number: US67346A
Authority: US
Inventors: Roscoe O Childers
Original assignee: Baker Oil Tools Inc
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1948-12-27
Filing date: 1948-12-27
Publication date: 1954-01-12
Anticipated expiration: 1971-01-12

Description

INVENTOR. 0. CLI/Loses, i

oscos CHlLDERs TION ZONE WELL BORES /QTroQA/Exs PPARATUS FOR COMPLETING MULTIPLE PRODUC [III 4. 1

R. METHOD'gAND A Filed Deo.

Jan. 12, 1954 Pa'ten'ted Jan. 12, 1954 METHOD AND APPARATUS FOR COIVIPLET- ING MULTIPLE PRODUCTION ZONE WELL BORES Roscoe 0. Childers, Oklahoma City, Okla., as-

signor to Baker Oil Tools, Inc., Vernon, Calif., a corporation of California Application December 27, 1948, Serial No. 67,346

(Cl. 16S- 2) 14 Claims.

'The present invention relates to the completion of well bores having a plurality of producing zones, and the conducting of the production from such producing zones to the tops of the well bores.

In view of conditions encountered in certain areas, the cost of completing and producing a well bore having a plurality of oil and/or gas producing zones has been exorbitant. A triple zone completion ordinarily involves the running and utilization of three separate tubular strings, one within the other. Heretofore, the outermost casing string was run and secured in place. This casing string contained perforated areas opposite each of the three producing horizons. The intermediate casing string, with two longitudinally spaced packers thereon, was then run in the outermost casing string. The packers were set in the outermost casing string between the three sets of perforations to isolate the respective productions from the three zones. Prior to setting of these packers, the uppermost producing zone was caused to flow, which necessitated the landing of the intermediate casing string and setting of the packers under pressure. This could only be done by the use of expensive surface control equipment. The two lower zones were then killed, as by pumping drilling mud into the intermediate casing string, and an innermost tubing string run in conjunction with a dividing packer that was set in the intermediate casing string to prevent comingling within the latter between the productions from the lower and intermediate zones.

The foregoing prior systems of completion were not only expensive, but they also entail hazards incident to completing wells under high pressure conditions.

Accordingly, an object of the present invention is to reduce substantially the cost of making multiple zone well completions.

A further object of the invention is to minimize the hazards attending the making of multiple zone well completions.

Another object of the invention is to eliminate the necessity for running a tubular string under pressure in making multiple zone, and particularly triple zone, well completions.

Still another object of the inventions is to complete a multiple zone well bore by installing all essential equipment in the well bore before any of the zones is conditioned for flowing.

Yet a further object of the invention is to provide an` improved arrangement for producing three zones in a well bore independently of each other.

This invention possesses many other advantages and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. A form of apparatus. and method of completion and production, are shown in the drawings accompanying and forming part of the present specication, which will now be described in detail, for the purpose of illustrating the general principles of the invention. It is to be understood, however, that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best deiined by the appended claims.

Referring to the drawings:

Figure 1 is a somewhat diagrammatic longitudinal section through a multiple zone production apparatus located in a well bore, with the parts arranged for conditioning the upper zone;

Fig. 2 is a view similar to Fig. 1, with the parts arranged for conditioning the intermediate and lower zones;

Fig. 3 is a view similar to Fig. 1, with the parts arranged for producing each of the three zones independently of one another; and

Fig. 4 is a cross-section taken along the line 4-4 on Fig. l.

As disclosed in the drawings, a well bore has longitudinally spaced upper. intermediate and lower producing zones A, B, C from which oil and/or gas, as the case may be, are to be conducted individually to the top of the hole. An outermost casing string IIJ is run in the well bore and is cemented in place, as by depositing cement I I around the casing string between the producing zones A and B and B and C, in a known manner. The cement sheath thus formed separates the zones and prevents comingling of their production by flowing along the exterior of the outermost casing string IIJ.

The casing string is provided with three sets of perforations I2, I3, I4, the upper set of perforations I2 being disposed opposite the upper zone A, the intermediate set I3 opposite the intermediate zone B, and the lower set I4 opposite the lower producing zone C. A tubular plug or production packer I5 of a known type may then be run in the outermost casing string Il) and anchored in packed-oli condition within this casing between the intermediate and lower sets of perforations I3, I4. The particular tubular plug or packer employed has a central cylindrical passage I6 therethrough terminating in an upper` tapered seat Il.

An intermediate casing string I8 is then run in the well bore. This intermediate casing string includes a lower head i9 adapted to rest upon the tapered seat Il in the tubular plug I5. When the head engages the seat, a tubular extension Ic, xed to the head it, extends downwardly through the plug i5. This extension has perorations ite through which production from the lower zone C may iiow. Leakage between the extension and wall of the passage Iii is prevented by a suitable side seal ite onrthe extension. The intermediate string also carries a suitable packer or hanger 2t, such' as -a hook wall packer, adapted to form an annular seal between the intermediate and outermost tubular strings I8, lil above the intermediate perforations I3. This packer 2@ is disposed above a set of perforations 2i in the intermediate string communicating with the intermediate set of p'e'rv:orations I3 in the outermost casing string IE! when the head I9 engages its companion seat I7.

TheV intermediate casing string iii also contains a tubular plug 22 suitably secured thereto between the periorations iti and the head i9. This plug has .a central cylindrical passage 23 therethrough, terminating in an upper tapered portionl 24, inv order to cooperate with an innermost tubular string 25, to be reierred to hereinafter.

Above the location of the hook wall or set-down packer 2Q, the lower portion 48a of the intermediate casing string i3 is suitably attached, as by threading, onto the lower end of a production member or collar it. The upper end of this collar is suitably secured to the upper portion Ib of the intermediateY casing string, which extends to the top of the well bore.

The production member or collar is designed to permit iow of duid from the upper zone A to the interior of the intermediate casing string I3 under certain operating conditions, and also to permit now of production from the intermediate zone B through the intermediate sets of perforations I3, 2i to a point in the intermediate string' above the production collar 25. To enable these purposes to be accomplished, the production member is formed with longitudinal passages 2l extending therethrough, and also with lateral passages or ports 28 extending between its interior and exterior.

g As specifically shown in the drawings, the production member includes a cylindrical outer member 2S "and a cylindrical inner member 3G spaced from each other. These members are held in spaced relation by a plurality of longitudinally extending radial ribs 3l, 32 that are suitably securd, as by welding material it, to the members, as most clearly shown in Fig. Zl. The meinber`s 129, Silare provided with aligned radial ports 351, which communicate with ports t in the ribs 32, thus forming the lateral ports Y25S between the exterior of the production member 26 and its central passage contained within the inner cylindrical portion t@ orn this member. The lateral ports 23 are preferably disposed intermediate the ends of the inner members to so as to allow uninterrupted sealing surfaces on the inner member on both sides of the ports for engagement by suitable sealng elements later to be described.

It is apparent that the construction of the production member or collar 26 provides spaced ribs 3|, 32 forming arcuate longitudinal passages 2i extending completely through the member, and also lateral ports 23 extending between the interior and exterior of the collar.

The innermost tubular string 25 is composed `4 of sections of tubing containing a lower portion 25a of smaller external diameter than the internal diameter of the inner ported cylinder 30. rihe lower end of this section 25a carries one or more suitable sealing elements 3l, which may be in the form oi chevron packing, adapted to engage the wall of the passage 23 through the tubular plug 22 and prevent uid from owing through the plug 22 around the exterior of the tubing` string Eta. The lower portion 25a of the tubular string also carries spaced sealing members 38, 3S, which can be constituted by suitable packing rings oi the chevron type, adapted to make sealing engagement with the inner wall of the inner cyiindrical member of the production collar 26. These spaced seal-

ing elements

33, 38 are disposable on opposite sides o the lateral ports 28 when a locating head iii) on the tubing string 25 engages the tapered upper end or seat di! of the production collar. vi/'hen such engagement takes place, the lower sealing member 3l is disposed within the central passage 23 through the tubular plug 22.

Above the locating head 39, the tubing string 25 is provided with a side door choke device, of Known design, which has a plurality of radial ports il that can be closed by a shiftable sleeve valve element This sleeve valve member 42 is either disposed across the ports 4I, to close them, or it may be moved upwardly above the ports A l, to open them.

As stated above, the outermost casing string il! is run in the well bore and is cemented in place with its upper, intermediate and lower sets 'of perforaticns iii, iii, Il disposed opposite the corresponding production zones A, B, C. The packer i is then set in this casing string between the lower and intermediate perforations I4, I3, and the intermediate casing string I8 run in the well bore, with its hooi?. wall packer 2i! in retracted position. This packer 2i) is suitably manipulated, in a known manner, to bridge the annulus 50 between the outermost and intermediate casing strings IQ, i3, to engage the lower head I9 with the tapered seat il ci the tubular plug I5. With the parts in this position, the depending perforated pipe or tubing ic, secured to the head I9 extends below the tubuiar packer I5, with its sealing member ide ciosing the clearance space between the tubing itc and packer i When the intermediate casing I3 is located in this manner, the periorations 2| through the in termediate casing string are located opposite, or in communication with, the intermediate set of perforations i3 in 'the outermost casing string` I0. The hook wall packer 2e has been set above the last-mentioned set or perforations and below the upper set or perforations iii. The tubing string 25 is then run in the well bore, 'usually' with the sleeve valve alii of the side door choke in closed position over the tubing ports 4I.

During the running of all of the foregoing equipment in the well bore, the latter is ordi-v narily filled with drilling mud, or the like, which prevents the production from all of the zones A, B, C from flowing through the perforations` E2, I3, 'Ill into the various casing strings. The tubing string 25 is then located in a position in which the spaced packing members 38 are 'disposed above the production collar 25, as shown 1n Fig. 1. With the parts in this position, the upper zone A can be vbrought in. This is usually easier performed by unloading the well above this zone. One method of performing this action is to pump high pressure gas down the annulus 50 between the intermediate and outermost casing strings, the fluid being forced ahead of the gas down this annulus and through the lateral ports 28 in the collar 26 into the clearance space between the tubing string 25a; and production collar cylinder 30. From this clearance space, the uid iiows to the top of the well bore through the annulus 5i between the intermediate casing string I8 and the tubing string 25.

When the annulus 50 between the outermost casing string I and intermediate casing string I8 has been thus unloaded, the upper zone A has been conditioned for flowing, since the hydrostatic head of the drilling mud in the annulus 50 has been removed. If desired, the annulus I between the intermediate casing string i3 and tubing string 25 may alsobe unloaded during this operation, assuming that suincient gas pressure is available for this purpose. Ordinarily, however, this does not occur, since the gas pressure is employed for the purpose of unloading only the annulus 59 between the intermediate and outermost casing strings.

As soon as the outer annulus 5B has been unloaded, the tubing string 25 is lowered until its head 39 engages the seat 40 at the upper end of the production collar 26. In this manner, the spaced sealing members 38 are located on oDlJosite sides of the lateral ports 23, closing these ports against the lateral ilow of fluid, and preventing any production from the upper zone A I from passing through the ports 28 to the interior of the intermediate casing string I8. At this time, the lower seal member 3l is disposed within the tubular plug 22, so as to prevent intercommunication between the intermediate zone B and lower zone C.

The sleeve valve element 42 of the side door choke is now elevated, in a known manner, to open the portsltl (see Fig. 2), and the two lower zones B, C are brought into production, as by unloading the tubing string 25 and the intermediate casing string I8. This unloading action can take place as a result of swabbing the tubing 25, which will remove the drilling mud from the tubing string 25, and also from the intermediate string I8 as well. After the swabbing operation has been completed, the sleeve valve member 42 is again shifted to a position over the side ports 4I to prevent comingling between the fluid from the intermediate zone B and lower zone C (see Fig. 3)

The apparatus is now in condition for flowing the three zones independently of each other, as shown in Fig. 3. Thus, the production from the lower zone C can flow through the lower perforations I4, and through the perforated tubing I8c into the intermediate casing string I8, passing upwardly through the tubing string 25 to the top of the well bore.

The production from the intermediate zone B passes through the aligned sets of perforations I3, 2I in the outermost and intermediate casing strings I0, I8, into the annulus 52 between the tubing string 25 and intermediate casing string I8, flowing upwardly through this annulus and through the arcuate longitudinal passages 2'! in the production collar 26 to a position above the latter, from where the intermediate zone production can continue ilowing upwardly through the `annulus 5I around the tubing string l25 to the top of the well bore.

The production from the upper zone A passes through the upper set of perforations I2 into the annulus 50 between the outermost and intermediate casing strings IIJ, I8, flowing upwardly therethrough to the top of the well bore.

Thus, it is apparent from an inspection of Fig. 3, that the production from each of the three zones pursues a separate path to the 'top of the well bore. The various plugs and packing members prevent their comingling in any particular.

By virtue of the apparatus and production method described above, it is apparent that all elements of the equipment, with the exception of the tubing string 25, are set in the well bore in cooperative relation before any of the producing zones is to be conditioned for flowing. After having been set in place, neither the outermost casing string Il nor intermediate casing string i8, and the apparatus attached thereto, need be shifted. The unloading of the various annuli 50, 5I and tubing string 25 can occur through the simple expedient of shifting the tubing string 25 to either the position shown in Fig. 1, or the position shown in Figs. 2 and 3, and by appropriately manipulating the sleeve valve element 42 of the side door choice. Thus, the unloading of the annulus 5U of the heavy fluid acting upon the upper zone A can take place, and this zone then easily shut in merely by lowering the tubing string 25 and closing the connections for this annulus at the top of the Well bore. Manipulation of the intermediate casing string I8 is not required thereafter, since this casing string has previously been set in packed-olf condition within the outermost casing string I0. Opening ol' the side door choke 4I, 42 enables the intermediate and lower zones B, C to be conditioned for iiowing simply by running the usual tools. which are well known, on a wire-line (not shown) to elevate the sleeve valve `42. After the swabbing operation has occurred, the sleeve valve 42 may be relocated across the ports 4I.

As a result of the operations described above, special control heads at the top of the well bore are not needed to enable the well to be completed, as under pressure, since the only parts requiring manipulation are the tubing string 25 and the sleeve valve member 42 of the side door choke. The equipment at the well surface necessary for operation of these parts is comparatively inexpensive, and is usually found on multiple zone wells. Accordingly, the cost of the installation for completing the multiple zone well bore is substantially reduced, which is also true of the hazards attending the operation of equipment under high pressure conditions.

The inventor claims:

1. In apparatus of the character described: an outer casing string having upper, intermediate and lower longitudinally spaced openings; an

intermediate casing string within said outer string` having upper and lower longitudinally spaced `openings communicatingwith said intermediate and lower openings, respectively, of said outer string; a first plug means between the intermediate and lower openings of said outer string and between the upper and lower openings of said intermediate string for bridging the annular space between said outer and intermediate casing strings; a second plug means between said upper` and intermediate openings of said outer string and located above the upper opening of said intermediate string for bridging the annular space between said outer and intermediate casing strings above said upper opening of said interaccusa mediate string; said. intermeliatejyeasing string having a port above'v sa-id second plug means a.

third plug Ymeans in said intermediate `casing string between the upper and lower openings of.

said intermediate string, saidf thirdplug meansY having a passage therethrough; and alongitudinally' movable tubular stringrwith'in 'said''ifr'iter-Y and around the exterior of the `tubular string.

said-tubular string having alowerfopeningicomfmunicating with the lower opening of. saidintermediate casing string. Y e, 1 H y 2. In apparatus of the, character described: an

outerv casing string having'upper, yintermedlatel and lower longitudinallyv spaced openingsi an intermediate casing string Y withinlsaid outer string having upper and klower longitudinally spacedfopenings communicating ywith said intermediate and lower openings, respectively, or saidk outer string; a first plug.meansbetweentheinten mediate and lower openingsof said outer string and between the upper and lower op'eningsof said intermediate stringior bridging the 'annular space between said outer and intermediate casing. strings; a second plug means-between said' upper and intermediate openingsof said outer string,Y

and located above` the upper opening of said intermediate string fior bridgingthe annular. between said outer and intermediate casing strings above said upper opening of. said intere mediate string; said intermediate casing string havinga port above said second plug means; and means including arlongitudinally movable tubu'f lar string within said intermediate string adapted to close said port and having Valower,opening for the entry of iiuid flowing through the lower openings in said outer and intermediate Acasingstrings.

3.y In apparatus of the character described: anY

outer casing stringhaving upper, intermediate and lower longitudinallyA spaced openings; an interrr'ief'liateV casi-ng string within said outer string having upper and lower longitudinally spaced openings communicating withM said interfv mediateand lower openings, respectively, of said outer stringa first. plug means Ybetween the intermediate andlower. openings of said outer string and4 between the upper andlower openings of Vsaid intermediate stringY for bridging the annular space betwe'enrsaid outer and intermediate casing strings a second plug means between said upper 'and intermediate openings of said outer string and located above lthe upperr opening of said intermediate string for bridging the annular space between said outer and' intermediate'casing strings above said upper opening ofjsaid'ihtermediate string; said intermediate casingstring having a port abovesaidsecond plug means; and means including a tubular string within said intermediateVstringadapted to close said port and having a lower opening for the entry ofiluid owing through saidlower openings in said outer and intermediate casing strings. Y v V 4; In apparatus of the character described: an outer casing string having upper, intermediate and lower longitudinailyspaced openings; n an intermediate casing string within said outer string having upper `and lowery longitudinally spaced openings communicating with said interm'ed-i'ate and lower openings, respectively, of said outer string; a rst plug means between the inte'rr'ne'diate and lower Vopenings of said'fouter string and between-the 'upper and lower openings CIK ofsaidintermediate string for bridgingthe annu-a larfspace betweensaid outer and intermediate. casingst'rings; asecond'plug ymeans between sa'i'd upper landinterm'ediate openings of said outer string and'l'ocated above the upper opening of saidinterme'diate string for bridging the annular space between said' outer and intermediate casingstrings above said upper opening of said intermediate string; a third plug means in said intermediate string above said upper opening in said intermediate string and having a central passage therethrough, said third plug means having a port above said secondrplug meansestablishi'ng communication between the interior and exterior of said intermediate casing string, and' said third plug means having a longitudinal passage disposed'to one side of said central passage and extending throughout the length of said third plug means; and means including a tubular string within said intermediate string and ex tending through said central passage for selectively closing or opening said port and for conducting fluid owing through said lower openingsvof said outer and intermediate easing strings, said tubular string having a lower opening cornmunicati'ng with thellower opening' of said intermediate casing string.

5. In apparatus of the character described: an outer casing string having upper, intermediate and lower longitudinally spaced openings; an intermediate casing string within said outer string having upper and lower longitudinally spaced openings communicating with said inter.- mediate and lower openings, respectively, of said outer string; a first plug means between the intermediate and lower openings .of said outer string and between the upper and lower openings or said intermediate string for bridging the annular space between said outer and intermediate casing strings; aV second plug means between said upper and intermediate openings of said outer stringV and located above the upper opening of said intermediate string for bridging the annular space between said outer and inter.- mediate Vcasing strings above said upper opening of said intermediate string; a third plug meansY in said intermediate string above said upper opening in said intermediate string and having a central passage therethrough, 'said third plug means having a port above said second plug means opening into said central passage and the exterior of said intermediate casing string, and said third plug means having a longitudinal passage disposed to Vone side of said central passage and extending throughout the length of said third plug means; and means including aV longitudinally movable tubular string within said intermediate string and extending through said central passage for selectively opening or closing said port and for conducting fluid flowing through said lower openings of said outer and intermediate casing strings, said tubular string having a lower opening communicating with the lower opening of said intermediate casing string.

6. 'In apparatus or" the' character' described: an outer casing string having upper, intermediate and lower longitudinally spaced openings; an intermediate casing string within said outer string having upper and lower longitudinally spaced openings communicating with said intermediate and lower openingsgrespectively, of said outer string; a first plug means between the intermediate and lower openings of said outer string 'and betweenthe upper and lower openings of said intermediate string for bridging the an- W, 9 nular space between said outer and intermediate casing strings; a second plug means between said upper and intermediate openings of said outer string and located above the upper opening of said intermediate string for bridging the annularvspace between said outer and intermediate casing strings above said upper opening of said intermediate string; said intermediate casing string having a port above said second plug means establishing communication between the interior and exterior of said intermediate casing string; a third plug-means in said intermediate casing string between the upper and lower openings of said intermediate string, said third plug means having a passage therethrough; a longitudinally movable tubular string within said intermediate string adapted to close said port and to engage said third plug means in leakproof lrelation when said port is closed to prevent now of iiuid through the passage of the third plug means and around the exterior of the tubular string; said tubular string having a lower opening communicating with the lower opening of said intermediate casing string, said tubular string having a port above said intermediate string port; and sleeve valve means within said tubular string adapted to be disposed over said tubular string port to close the same.

'7. In apparatus of the character described: an outer casing string having upper, intermediate and iw'er longitudinally spaced openings; an intermediate casing string within said outer string having upper and lower longitudinally spaced openings communicating with said intermediate and lower openings, respectively, of said outer string; a rst plug means between the intermediate and lower openings of said outer string and between the upper and lower openings of said intermediate string for bridging the anhular space between said outer and intermediate casing strings; a second plug means between said upper and intermediate openings of said outer string and located above the upper opening of said intermediate string for bridging the annular space between said outer and intermediate casing strings above said upper opening of said intermediate string; said intermediate casing string having a port above said second plug means establishing communication between the interior and exterior of said intermediate casing string; means including a tubular string within said intermediate string adapted to close said port and having a lower opening for the entry of fluid flowing through said lower openings 1n said intermediate and outer casing strings, said tubular string having a port above said intermediate string port; and sleeve valve means within said tubular string adapted to be disposed over .said tubular string port to close the same.

8. In apparatus of the character described: an Aouter casing string having upper, intermediate and lower longitudinally spaced openings; an intermediate casing string within said outer string having upper and lower longitudinally spaced openings communicating with said intermediate and lower openings, respectively, of said outer string; a first plug means between the intermediate and lower openings of said outer string and between the upper and lower openings of said intermediate string for bridging the annular space between said outer and intermediate casing strings; a second plug means between said upper and intermediate openings of said outer string and located above the upper opening of v said intermediate string for bridging the annular space between said outer and intermediate casing strings above said upper opening of said intermediate string; a third plug means in said intermediate string above said upper opening in said intermediate string and having a central passage therethrough, said third plug means having a port above said second plug means establishing communication between the interior and exterior of said intermediate casing string, and said third plug means having a longitudinal passage disposed to one side of said central passage extending throughout the length of said third plug means; means including a tubular string within said intermediate string and extending through said central passage for selectively closing or opening said port and for conducting fluid iiowing through said lower openings of said outer and intermediate casing strings, said tubular string having a lower opening communicating with the lower opening of said intermediate casing string, said tubular string having a port above said intermediate stringr port; and sleeve valve means within said tubular string adapted to be disposed over said tubular string port to close the same.

.9. In the method of completing a well bore having upper, intermediate and lower producing zones: locating an outer easingr string in said well bore with upper, intermediate and lower openings communicating with the upper, intermediate and lower producing zones, respectively; placing a plug with a longitudinal passage therethrough in said outer casing string between said intermediate and lower openings; locating an intermediate casing string in said outer casing string in leakproof relation to said plug, said intermediate casing string having an opening communicating with said intermediate opening in said outer string; providing a leakproof annular bridge between said casing strings which is disposed between said upper and intermediate outer casing string openings; providing a lateral opening between the interior of said intermediate string and the annulus around said intermediate string above said annular bridge; unloading fluid from said annulus above said bridge by forcing fluid through said lateral opening; closing said lateral opening; and then unloading fluid from said intermediate easing string.

10. In the method of completing a well bore having upper, intermediate and lower producing zones: locating an outer casing string in said Well bore with upper, intermediate and lower openings communicating with the upper, intermediate and lower producing zones, respectively; placing a plug with a longitudinal passage therethrough in said outer casing string between said intermediate and lower openings; locating an intermediate casing string in said outer casing string in leakproof relation to said plug, said intermediate casing string having an opening communieating with said intermediate opening in said outer string; providing a leakproof annular bridge between said casing strings which is disposed between said upper and intermediate outer casing string openings; providing a lateral opening between the interior of said intermediate string and the annulus around said intermediate string above said annular bridge; locating a tubular string within said intermediate string; shifting said tubular string to open said lateral opening and enable fluid in the annulus above said annular bridge to be unloaded through said lateral opening; shifting said tubular string to close said lateral opening; unloading the fluid in said intert:agis-::1115e 11 mediate string and tubular string; and causing well'fluid to'pass from` said lower zone through Y said tubular string, from said intermediate zone through the annulus between said tubular and intermediate strings, and from said vupper Zone through the annulus between said intermediate and outer strings.

11. In apparatus of the character described: an outer casing string having upper, intermediate and lower longitudinally spaced openings;

an intermediate casing string within said outer string having upper and lower longitudinally spaced openings communicating with said intermediate and lower openings, respectively, `on said outer string; a rst plug means between the -intermediate and lower openings of said outer string and between the upper and the lower openings of said intermediate string for bridging the annular space between said outer and'intermediate casing strings; a'second plug means between said upper and intermediate openings of ksaid outer string and located above the upper opening of said intermediate string for bridging the annular space between said outer and intermediate casing strings above said upper opening of said intermediate string; a third plug means in said intermediate string above said upper opening in said intermediate string and having a central passage therethrough, said third plug means having a port above said second plug means establishing communication between the interior and exterior of said intermediate casing string, and said third plug means having a longitudinal passage disposed to one side of said Vcentralpassage and extending throughout the length of said third plug means; means including a tubular string within said intermediate string and extending through said central pas- Ysage for selectively opening or closing said port and for conducting 'uid iiowing through said Vlower openings of said outer and intermediate yan intermediate casing string withinrsaidouter Vstring having upper and lower longitudinally spaced `openings communicating with said in- `termediate and lower openings, respectively, of said outer string; a first plug means between the intermediate and lower openings of said'outer string and between the-upper and lower openings of said intermediate string for bridging the annular space between .said youter and intermediate-casing strings; asecond plug means between said upper and intermediate openingsof said outer string and located above the upper opening of'said intermediate string'for bridging the annular space between said outer and intermediatecasing strings above said upper opening 'of said intermediateA string; a third plug means lin'said intermediate string above said vupper lopening in said intermediate stringY and having -a'centralpassage therethrough, said third plug `means having a port above said second plug 1 means opening into said central passage and the 75" exterior oi! saidv intermediate casing. string, aand said third *'plugrmeans-having a longitudinal -passage disposed'to one-'side of vsaid central passage and extending throughout the length of said third Vplug means; and means including va longitudinally movable tubular string within said intermedi-ate string andextending through sai-d central passagefor selectively opening or closing said port and for .conducting'uid flowing through said lower openings ofsaid outer andintermediate casing strings, said tubular string having a lower openingcommunicating with .the

lower opening of said intermediatecasing string,

vsaid tubular string ,being imperforate along `a portion extending through said central passage Iand being movable longitudinally toport opening position to allow fluid ilow from the exterior of said intermediategcasing string, thro-ugh said port, into said central passage and thegannular space :above said third `[plug rneansA between Said Vtubular string and intermediate casing string.

13. In apparatus viof :the character described: anouter vcasing stringhaving upper, intermediate and lower longitudinally spaced openings; anintermediate casingstring within said outer string vhaving :upper vand lower longitudinally Vspaced openings communicating with said intermediate and lower-openings, respectively, of said louter string; a rstplug means between the intermediate and lower openings of said outer string and between the upper and lower openings of said intermediate string for bridging the annular-space betweensaid outer and intermediate icasingstrings; a second fplug means bef tween Ysaid l upper and intermediate openings of said outerstringandlocated `above the upper opening ofsaidintermediate string for bridging the annular-space betweenfsaid ou-ter and intermediate casingstr-ingsabeve saidA upper opening of said intermediate string; a third plug means in said Vintermediate Astring above said upper opening insaid intermediate string and having a 'central passage therethrough, said -third plug ,means having la port above said second plug means establishing communication between the Vinteriorand exterior of said intermediate casing string, and said third plug means having a longitudinal passage disposed to one side of said ,central passage and .extending Ythroughout the v,length of said thirdplug means; a. fourth plug means in said lintermediate casing string between theupper and lower openings ofv said intermediate string, said fourth plug means having a passage therethrough; .and a Vlongitudinally movabletubular string within, said intermedi- `ate string .and V,extending through said central passage for selectively closing or opening said port, saidtubular string-being engageable with said Afourth `plug means Vrin leakprocf relation when said port is closedto prevent iiowof liiuid through the passageotthe fourth plug means and around the exterior uof v,the tubular string, Vsaid tubular string having aklower openingcom- ,municating with the lower opening of saidintermediate casing string.

.14. In apparatus of the character described: an outer casingstring having upper, intermediate and lowerlongitudipally spaced openings; `an,intermediatev casing string within said outer stringV having ,upper and f lower V longitudinally spaced openings Vcoirimuniating with Ysaid intermediate and lower openings, respectively, of

said outer string; a a'rst plug means between the 4intermediate and lower openings of said outerstring and betweenl the upper and lower openingsV of f said Jintermediate string-for br-idgopening of said intermediate string; a third plugmeans in said intermediate string above said upper opening in said intermediate string and having a central passage therethrough, said third plug means having a port above said second plug means establishing communication between the interior and exterior of said intermediate casing string, and said third plug means having a longitudinal passage disposed to one side of said central passage and extending throughout the length of said third plug means: a fourth plug means in said intermediate casing string between the upper and lower openings of said intermediate string, said fourth plug means having a passage therethrough; and a longitu dinally movable tubular string within said intermediate string and extending through said central passage for selectively closing or opening said port, said tubular string being engageable with said fourth plug means in leakproof relation when said port is closed to prevent flow of uid through the passage of the fourth plug means and around the exterior of the tubular string, said tubular string having a lower opening communicating with the lower opening of said intermediate casing string; said `tubular string having a port -above said intermediate string port; and sleeve valve means within. said tubular string adapted to 'be disposed over said tubular string port to close the same.

ROSCOE O. CHILDERS.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,189,701 Bur-t Feb. 6, 1940 2,277,380 Yancey Mar. 24, 1942 2,368,428 Saurenman Jan. 30, 1945 2,380,022 Burt July 10, 1945 2,403,987 Lewis July 16, 1946 2,465,344 Bennett Mar. 29, 1949 2,537,066 Lewis Jan. 9, 1951 OTHER. REFERENCES The Oil Weekly-June 27, 1938-pages 46 and 48 "A Review of Multiple Well Completions in California, Proc. of American Petroleum Institute-vol 22 (IV), pages 14-17 (1941).