|Publication number||US3231021 A|
|Publication date||Jan 25, 1966|
|Filing date||Jun 17, 1963|
|Priority date||Jun 17, 1963|
|Publication number||US 3231021 A, US 3231021A, US-A-3231021, US3231021 A, US3231021A|
|Inventors||Greene Jr Haskell M|
|Original Assignee||Greene Jr Haskell M|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (8), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Jan. 25, i966 H. M. GREENE, JE 3,232
FGBMATION OF CLOSURES IN WELL BORES 'Filed June 17. 196s 2 sheets-sheet 1 WAN \L a? SS IN V EN TOR. HQSKELL M. 6/2EENE,JR.
ATTORNEY Jan. 25, 1966 H. M. GREENE, JR
FORMATION OF CLOSURES IN WELL BORES 2 Sheets-Sheet 2 Filed June 17, 1963 INVENTOR. AMS/ELL M. GPEENS, R.
TTOQNEY United States Patent 3,231,021 FORMATION OF CLOSURES IN WELL BORES Hasitell M. Greene, Jr., 671 Galen, La Habra, Calif. Filed .lune 17, 1963, Ser. No. 288,260 3 Claims. (Cl. 166-117) This invention relates to improved methods and apparatus for forming a closure in a well bore at a location spaced beneath the surface of the earth.
In oil wells or other wells, there frequently arise situations in -which it becomes desirable to form a closure serving to block lolf one zone of the well bore from another higher or lower zone. In forming such closures according to prior practices, considerable difficulty has been encountered in instances in which the closure is to be formed at a location spaced above the bottom of the well, and particularly where substantial fluid pressures may be present in the well at the time that the closure is made. If a plug of light construction is used under these circumstances, the plug may not be able to withstand the pressures occurring in the well, and therefore may be ruptured soon after positioning of the plug in the well. Further, if one of the known types of heavily or strongly built bridge plugs is utilized, having a strong metal body, a heavy rubber packer sleeve, and numerous actuating parts, this bridge plug has the decided disadvantage that it is extremely diliicult to drill out at a later date to reopen the well. Also, such a bridge plug normally must have an outside diameter so close to the inside diameter of the well casing or bore that the plug frequently becomes stuck in the well before reaching the zone to be treated.
A major object of the present invention is to provide an improved type of method -and apparatus which is capable of forming an effective closure in a well bore, at any elevation in the -well either spaced above the bottom `or at the bottom, and which can form this closure under difficult pressure conditions, and in a manner enabling the ultimate closure to withstand virtually any hydrostatic load in the well to which the closure may be subjected after formation. Further contemplated is an arrangement of this type in which the closure, though capable of withstanding high pressures in use, does not contain the heavy metal or other parts usually required in bridge plugs, but instead is formed of materials which are much easier to drill through than is the usual bridge plug, so that the bore may be easily reopened at any time. -In addition, the closure structure is of such a character that the entire closure may be formed at any point in the well by a single run of a unique tool to the desired zone, with that tool preferably being of a small diameter as compared with the size of t-he pipe or bore into which it is lowered.
The above advantages are attained in large part by the use together of a very simple type lightly constructed plug and a large number of discrete solid bodies or particles positioned in the well above the plug. The plug itself may be so lightly constructed that it could not possibly withstand, by itself, the high hydrostatic or other downlWard pressures which are encountered at the zone to be closed; or in some other respect is ineffective to form a proper closure by itself. A major purpose of the plug is then to support in the well, above the plug, the mentioned ymass of discrete solid bodies. These bodies may take the form of gravel or sand, preferably consisting of several different layers of such material, with the solid bodies progressively decreasing in size toward the top of the mass (through at least -a portion of the vertical extent of the mass), from la relatively coarse gravel forming a first portion of the mass to a very fine sand forming a higher portion of the mass.
To maximize t-he effectiveness and strength of the overall closure structure formed in accordance with the invention, I prefer-ably utilize in conjunction with the discussed plug and mass of discrete solid bodies, a quantity of an initially partially liquid substance which is received in the well above `the solid bodies. This substance is desirably cementitious in character, and for best results takes the form of initially uncured Portland cement. The tool acts to deposit this cement in the well above the solid bodies, so that the cement may harden or set in a manner confining the gravel and/or sand or its equivalent between the plug and cement, to thereby form an loverall closure struc,- ture of great effectiveness, and yet one which can very easily be drilled out when desired.
Suitable means are provided for releasing the plug, solid bodies, and cement or its equivalent from the tool body after the entire unit has been lowered to a proper location within a well. The most desirable method of release involves the use of a gas producing charge, adapted to develop a substantial quantity of high pressure gases within the Well. This charge may be a combustible propellant charge, or if preferred may be a container of carbon dioxide or other releasable gas under high pressure. The cement may be supported in the tool by a frangible disc or element which is broken by tiring of the propellant charge.
The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiments illustrated in the accompanying drawings in which: v
FIG. l is a View showing a tool constructed in accordance with the invention positioned Within a well, and partially illustrated in section;
FIG. 2 is an enlarged fragmentary vertical section through a portion of t-he FIG. 1 tool;
FIG. 3 is an enlarged fragmentary vertical section through a second and lower portion of the FIG. l tool;
FIG. 4 is a view similar to FIG. l, but showing the apparatus after ring of the propellant charge;
FIG. 5 is a view representing the closure structure after the charge has been tired and the tool body has then been Withdra-wn upwardly;
FIG. 6 is an enlarged fragmentary perspective View showing a portion -of the chain which connects the plug and upper frangible disc of the FIG. l apparatus;
FIG. 7 is an elevational view of the FIG. 6 chain, taken on line 7-7 of FIG. 6;
FIG. 8 is a fragmentary vertical section taken on line 8 8 of FIG. 7;
FIG. 9 is a view similar to FIG. 3 but showing another forni of the invention; and
FIG. 10 is a horizontal section taken on line 10-10 of FIG. 9.
With reference first to FIG. l, I have represented at 10 a portion of the casing of a well within which a tool 11 embodying the invention is positioned. The illustrated portion of the casing may be at a zone deep within the earth, with the tool being supported at that location by a convenional wire line 12 extending upwardly to the surface of the earth and connected to suitable raising and lowering equipment.
The tool has a vertically extending tubular body 14 which may be closed at its upper end by a top structure 15 `connected to and suspended by wire line 12. The top structure 15 may carry, at the inside of the tool, a gas producing charge 16, adapted upon actuation to suddenly release into the interior of the tool body and from the charge a large volume of high pressure gases. Charge 16 is preferably a combustible propellant charge, such as any `riiie powder (for example E. I. DuPont de Nemours powder No. 4320 or 4350), adapted to be fired from the surface of the earth by closure of a control switch 17 connected into an energizing circuit from a power source 18 to charge 16 through electrical leads represented diagrammatically at 19. It is also contemplated that, if desired, the gas producing charge 1e may be a cartridge of carbon dioxide or other substance in liquid, solid, or a highly compressed gaseous form, and capable of being released from the cartridge when desired.
The vlower end of hollow cylindrical rigid metal body 13 terminates at a bottom circular edge 2i), at which the body is open for downward displacement of the contents of the body therefrom. Within the lowermost portion of the body, there is contained a plug 21 which is adapted to engage the bore wall or casing of the well, and grip the casing in a manner holding the plug at a predetermined location therein. As seen best in FIG. 3, this plug has a vertically extending elongated shaft 22, extending along the main vertical axis 23 of the tool and body 14, and carrying at a vertically central location a series of circulariy spaced upwardly flaring relatively movable support fingers 24, pivoted at their lower ends 124 to a typically circular carrier part 125 secured rigidly to shaft 22. The fingers 24 may be connected to part 125 by any conventional type of pivotal connection, for allowing radial swinging movement of the lingers, such as for instance a wire 126 extending circularly about and located relative to element 125, and passing through openings in the various fingers 24 (see FIG. 8). Fingers 24 are initially held in their radially constricted or contracted positions of FIGS. 1 and 3 by engagement with the side wall 13 of the tool body. When ultimately freed from the tool body, fingers 24 expand radially outwardly to the condition of FIG. 5.
At its lower end, shaft 22 carries a series of gripping fingers 25 which are pivotally mounted to a bottom carrier part 26 secured to shaft 22, so that fingers 25 may swing radially between the inactive positions of FIG. 3 and the active gripping positions of FIG. 5. Fingers 25 are initially retained in their inactive positions by reception within a short counterbore 27 at the lower end of tool body 14. The ngers are yieldingly urged radially outwardly, toward their FIG. 5 positions, by a coil spring 28 disposed about shaft 22, and bearing upwardly against part 125. The lower end of spring 28 bears downwardly against a fiat ring which is disposed about shaft 22, and engages the inner surfaces 31 of ngers 25 in a relation camming the fingers outwardly upon downward spring induced movement of ring 30.
The upper end of shaft 22 carries a Second set of gripping lingers 32, which are pivoted to a carrier part 33 secured to shaft 22, and are urged radially outwardly by the camming action of a part 34 under the inuence of a spring 35. The extremities 36 of fingers 25 and 32 are of sharp pointed configuration, to bite into casing 1li in the FIG. 5 condition, and lock the plug against either upward or downward movement. The outer surfaces of the fingers are desirably somewhat rounded at 37', adjacent pointed tips 36, so that when the fingers are in their retracted FIG. 3 positions, the curved surfaces are substantially tangent to the inner surface of wall 14, and therefore the pointed tips 36 do not bite into wall 14 of the tool body in a manner preventing vertical movement of the plug from the tool.
Above plug 21, tool body 14 contains a mass of material 38 formed of a multitude of discrete or separate solid bodies, with the mass extending vertically between .the locations 39 and 4@ in FIG. l. This mass 33 may be formed of several layers, including a lower layer 41 of relatively large gravel, a second layer 43 formed of liner gravel, a third layer 43 formed of relatively coarse sand, and an upper layer 44 formed of very ne sand. Desirably the gravel and sand is formed of a material presenting sharp edges on each of the particles or bodies of the mass, so that these sharp edges will tend to grip the casing 11i in the ultimate condition of the mass 38, and assist in preventing downwardmovernent of the overall closure structure. Tol attain this result, the gravel 41 and 42 may be made of limestone. The gravel or rock 41 in the lower' portion of mass 38 is large enough that the individual 'rocks can not fall downwardly through the relatively small spaces formed between fingers 24 (even in the expanded FIG. 5 position of the fingers), with the result that the entire mass 38 is supported by fingers 24 within the tool body.
At an elevation above the upper end of mass 38, the tool body 14 contains a horizontally extending imperforate frangible disc 45, above which there is carried withing the body a mass of cementitious material, desirably taking the form of uncured fiowable Portland cement mixture. Disc 45 may be formed of any material adapted to be ruptured by firing of charge 15, such as aluminum or a suitable resinous plastic material. FIG. 2 represents the manner in which the disc 45 may be secured in position at the threaded joint 46 between two sections of tubular body 14. As illustrated, the disc may have an outer or peripheral flange 47, received within a counterbore 4S formed in the lower section 14u of the body, and clamped in position by engagement with the lower end of upper section 14h, when the two parts are screwed together.
The plug 21 and the mass of material 38 are initially supported in their FIG. 1 positions within the tool by means of a chain 49 connected at its upper end 50 to the center of disc 45, and connected at its lower end 51 to element 33 of plug 21. The chain is protected against contact with the mass of sand and gravel 38 by means of a rigid tube or pipe 52, formed of metal or the like, and resting at its lower end 53 on the upper surface of part 33, in a relation allowing downward movement of part 33 relative to part 53 upon tir-ing of the apparatus.
Chain 49 may be formed of a series of links 54 of the known type illustrated in FIGS. 6 and 7. Each of these links is made of a piece of sheet metal appropriately apertured and doubled back to engage the adjacent links in a manner forming a composite chain. At one point 55, the two meeting links do not engage in the same manner as do other adjacent links, but instead are interconnected only by a wire 56, which is accessible for setting through an access opening 156 in wall 14 of the tool body, and which extends through two links and connects them together, but releases them for relative separating movement upon withdrawal of the wire from its position of engagement with the links. The wire 56 is connected to the sidewall 14 of the tool, as at 57 in FIG. 2, so that downward movement of the chain will pull the chain away from interlocking engagement with the wire, and thereby separate the upper portion ofthe chain from the lower portion at the point 55.
The upper end of tool body 14, above the level of cementitious material 46, may contain one or more apertures 58 for placing the inside of the tool in communication with the well about the tool, but with a check-valve 59 being associated with each of the apertures for preventing the flow of gases outwardly from the tool, while permitting subsequent inward fioW of gases or liquids into the tool after the tiring operation.
To now describe the operation of the tool of FIGS. l through 7, assume first of all that the tool is in the condition of FIG. 1, and has been lowered to an appropriate zone within casing 10 at which a closure is to be formed. Preferably, the iiuid conditions are controlled so that there is a downward fluid movement (or no movement at all) at this Zone during the actual cementing operation. With the tool in the FIG. l condition, the operator closes switch 17 at the surface of the earth, to fire propellant charge 16. This produces within the tool body a large volume of gases acting to exert a sudden downward force against the uncured body of cement 46. The shock of 5. charge 16 thereby acts through cement body .46 to rupture frangible disc l45, so-that the cement falls downwardly. The Vrupturing of disc 45frees chain 49 and its connected plug -21 for downward movement, and enough of the force of the propellant charge is transmitted downwardly through tube 52, by compression of well fiuid within that tube, to force plug 21 downwardly relative to the tool body to the FIG. 4 position. Upon such displacement of the plug, the lower fingers 25 of the plug are freed for radiallyV outward expansion to the FIG. 4 condition, in which they engage and bite into the casing to lock the plug against subsequent upward movement relative thereto. It is also noted that, upon downward movement of chain 49 with the plug and relative to wire 56, the two lengths of the chain which a-re initially connected by wire 56 move away from the wire and are thereby disconnected, so that the lower portion of the chain may move downwardly through tube 52 without requiring corresponding movement into or through the tube of any remaining portion of frangible disc 45. The tube 52 holds the mass of sand and gravel 38 out o'f contact with the chain, so that this sand and gravel can not interfere with downward movement of the chain'or plug. In the absence of a tube such as that shown at 52, there is a decided tendency for the sand and gravel to grip the chain in a manner preventing downward movement of the plug. Preferably, tube 52 is in some way connected to the tool body 14 for removal from the well therewith, as by means of a spider 152 secured rigidly to body 14 by circularly shaped radial arms 153, and carrying a ring 154 engageable in supportingrelation with an upper fiange 155 on th-e tube. Aftertlie apparatus has reached the FIG. 4 condition, the operator pulls upwardly on wire line 12, to lift tool body 14 upwardly and withdraw it from the well.v As the toblbody moves upwardly, plug 21 is restrained by fingers 25 against corresponding upward movement, and is thereby retaindat the set position in the well, so that the plug ultimately 'assumes the condition shown in FIG. 5. Also, the movement of the tool body allows the gravel and` sand, and the cement above the sand, to fall out of the bottom end of the tool body, and form with plug 21 the composite closure structure illustrated in FIG. 5. This closurefstructure consists of the plug 21, supporting gravel and sand 38 with cement 46 received thereabove. TheV cement sets-up soon after being deposited in the well, to form a closure which will not open until purposely drilled through when it is desired to reopen the well.
A majorV advantage resulting from the use of the mass ofjdiscrete particles 38 in the FIGS. 1 through 7 form of the invention resides in the fact that these particles, together with plug 21 (and even before movement of cement 46 into contact with the mass of discrete particles) form a composite closure structure which is capa-ble of withstanding extremely high downward uid pressures, such as are frequently encountered in wells. More specifically, the arrangement of sand and gravel in mass 38 results in the transmission to plug 21, through mass 38, of only a very small portion of any pressure which may be exerted downwardly against the upper surface of mass 38 by the well fluid. To illustrate this fact, assume that the apparatus is in the condition of FIG. 5, and that a fluid pressure of 2000 pounds per square inch is exerted downwardly against the upper surface of the top layer of sand 44. Also, assume that the void space within the body of sand 44, between the particles of sand, and for a selected unit height (say one inch of height of the sand column) is one unit, while the corresponding void space within a corresponding height in gravel 41 is 200 units, that is 200 times greater than the void space within sand 44. It these conditions do occur, then the liuid pressure within the void space in gravel 41 will be only one 200th of the pressure exerted downwardly against sand 44. Thus, assuming the pressure at 44 to be 2000 pounds per square inch, and equating the product of pressure times volume within sand 44 to the product of pressure times volume within gravel 41, we have:
Pressure at 44 times void volume at 44 equals pressure at 41 times volume at 41.
P (pressure in gravel 41)=10 p.s.i.
From this calculation, it will be apparent that, so long as fluid is flowing downwardly through the sand and gravel, the pressure within gravel 41 will be only 10 pounds per square inch when the downward fluid pressure exerted against upper sand layer 44 is 2000 pounds per square inch. Consequently, the relatively high downward fluid pressure exerts very little downwar-d force against plug 21, and as a result a very lightly built plug, in combination with the sand and gravel mass, may withstand a very large downward fluid force.
This discussion ofthe fluid pressure conditions applies to any downward force exerted against the composite plug structure prior trs-effective closure of the well above the sand an-d gravel mass by cement 46. As soon as this cement settles onto the upper surface of sand 44, across the entire horizontal area of that surface, the cement positively closes all of the spaces between the sand particles at the upper surface of mass 44, to completely seal thewell against further downward fluid flow. The passages between the individual particles of sand within the top layer of fine sand 44 are so small as to prevent the cement itself from flowing downwardly through the sand and gravel, though well fluid itself may pass downwardly through these passages until the cement reaches its final bore closing position. After the cement has completely sealed the bore, fluid pressure exerted against the upper surface of the cement is transmitted downwardly therethrough in the manner of a piston against the sand and gravel. This force exerted downwardly compresses the sharp gravel against plug 21 and forces the gravel and sand laterally outwardly against the casing 10, in a manner such that the gravel and sand (particularly the sharp gravel) bite into the casing wall and lock the entire mass in position, to again prevent the transmission of excessive downward forces to the plug.
FIGS. 9 and l0 show another form of plug 21 which is the same as that of FIGS. 1 through 8 except as to the manner of construction and retention of lower gripping fingers 67. In FIGS. 9 and 10, these fingers are pivoted at their lower ends 68 to a carrier element 69 secured to sha-ft 76 of the plug, and are retained in their inwardly retracted full line position-s of FIG. 9 by a wire 70 which extends about the ends of the fingers. The opposite ends 71 and 72 of the wire are looped about a combustible propellant charge 73, which is connected by electrical leads 74 to the surface of the earth, so that the charge may be fired remotely, to destroy the looped ends 71 and 72 of the wire, and thereby free fingers 67 for radially outward expanding movement to the broken line positions of FIG. 9, under the influence of actuating spring 75. In this form of the invention, the fingers 67 may be initially received somewhat beneath the lower end of tool body 14 (corresponding to body 14 of FIG. l), :so that the plug does not have to be displaced downwardly in order to allow fingers 67 to engage casing 10'. Near their pointed tips, lingers 67 may have small recesses at 77 to receive wire 70 and assure proper retention of the lingers by this wire.
Above the level of plug 21', the device of FIGS. 9 and 10 may be identical with that of FIG. l, except that it is not necessary that the arrangements of FIGS. 9 and l0 include the propellant charge 16. In using the tool of FIGS. 9 and 10, the device is of course first of all lowered to the proper location within casing 10', following which explosive 73 is fired to release fingers 67 for locking contact with casing 10 (see broken line positions of FIG. 9). The tool body 14 is then pulled upwardly, with the plug 21 being retained against upwith the tool.
ward movement by virtue of engagement of fingers 67 with the casing. Thus, the plug remains in position within the well, and acts by virtue of its connection to chain 49' (corresponding to chain 49 of FIG. 2) to retain frangible disc 45 of FIG. 2 against upward movement As a result, the frangible disc is broken, freeing the cement 46 to fall downwardly, and simultaneously the upward movement of the tool body causes wire 56 of FIG. 6 to break the connection between the upper and lower portions of the chain, just after the disc has been broken. Further upward movement of the tool body allows all of the gravel and sand 38' to fall downwardly from the tool body, and allows the cement to fall downwardly on top of this gravel, to form an ultimate composite closure very similar to that shown at FIG. 5.
In both forms of the invention, it is desirable that plug 21 or 21 be constructed to pass iluid downwardly in order to lattain the discussed reduction in pressure resulting from such downtlow through rst the fine sand and then a coarse gravel. More specifically, the plug should be adapted to pass fluid downwardly past the plug at a fluid pressure which is small enough that that pressure can not force the plug downwardly in the well, against the resistance or" locking fingers 132, `after those fingers have engaged the casing in locking relation. Thus, though it is possible (but not usually desirable) to utilize a plug having a sealing cup -or the like initially preventing any downflow of liquid past the cup, it is preferred that any such cup be designed to rupture or pass fluid downwardly at a pressure less than that required to force the plug downwardly, so that after such rupture a downow may be established to set up the previously discussed pressure differential conditions resulting in a lower pressure at the plug than at the top of the sand,
1. Apparatus for forming a closure in a well bore comprising a tool body to be lowered into the well to a predetermined zone therein and having a discharge opening, a mass of discrete bodies of material in solid form carried within said tool body and adapted to fall downwardly therefrom in the well through said opening, a plug carried by the tool body beneath said mass of discrete bodies, said tool body having means detachably holding said plug for release from the body at a location to remain in the well beneath said bodies, said plug being constructed to close the bore suiciently to support said bodies above the plug, said plug having gripping means retained in a retracted position during lowering of the tool and expansible into gripping engagement with ,the wall of the well to lock the plug against vertical movement, means releasably `holding said gripping means in retracted position, a mass of uncured cementitious material in the tool body above said mass of discrete bodies, a frangible closure beneath said cementitious material and above said discrete bodies, a propellant charge carried by the body above said cementitious material and adapted to exert downward force thereagainst acting to rupture said closure and to free the cementitious material to move downwardly from the tool above the plug and discrete bodies, said means detachably holding the plug including a chain extending vertically between and interconnecting said plug and said frangible closure and having a parting section, means for automatically releasing said parting section upon `downward movement of the chain, and a tube extending vertically through said mass of discrete bodies and containing said chain and protecting it from contact with said bodies.
2. Apparatus for forming a closure in a well bore comprising a tool body to be lowered into the well to a predetermined zone therein, a plug detachably carried by said body at a lower end thereof and engageable with the well in a relation to support the plug at a fixed location therein, means detachably mounting said `plug to the tool body for release therefrom in the well, said body containing a chamber above said plug, a mass of discrete bodies contained in said chamber above the plug, and releasable from the tool body, said plug being constructed to close the well bore suciently to support :said discrete bodies above the plug in the well, a mass of cementitious material contained in said tool body above said discrete bodies to be supported in the well thereby, a frangible closure carried by said tool body at the lower end of said cementitious material and higher than said discrete bodies and retaining the cementitious material in the tool body, and a propellant charge means for exerting force against and rupturing said closure to release said cementitious material, said plug mounting means including a connector extending upwardly between said plug and said closure and past said discrete bodies for connecting the plug to the closure until the closure is opened, and a tube extending upwardly through said discrete bodies and containing said connector and shielding it against contact with said discrete bodies.
3. Apparatus for forming a closure in a well bore comprising a tool body to be lowered into Athe well to a predetermined zone therein, a plug detachably carried by said body at a lower end lthereof and engageable 'v with the well in a relation to support the plug at a xed location therein, said body having a tubular side wall dening and containing a chamber above said plug, a mass of relatively large discrete bodies contained in said chamber above the plug, Said plug being constructed to close the well bore sufficiently to support said discrete bodies above-the plug in the well, a mass of particles smaller than said discrete bodies contained in said chamber above said discrete bodies, said side wall of 1the tool body 'having a lower portion releasably lcontaining said plug and having a bottom opening through which said discrete bodies and lparticles may fall downwardly from the tool body into the well for support in the well by said plug, a mass of cementitious materialcontained in said tool body above said particles to be supported in the well thereby, a frangible closure carried by said tool body at the lower end of said cementitious material an-d higher than said particles and retaining the cementitious material in the tool body, a gas emitting propellant charge above said cementitious material operable upon firing to exert downward force against said closure through said material and thereby open the closure and release said cementitious material, a Vexible `connector extending upwardly through said discrete bodies and discrete particles and interconnecting said plug and closure until the closure is opened, and a tube ,disposed about said connector, said connector including a chain having two releasably interconnected sections, and a joining element forming a link between said sections and connected to said tool body in a relation to detach said vsections from Vone another in response to downward movement of the sections relative to said body and said joining element. i
References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Scott, Robert W.: How Through-Tubing Bridge Plugs Work, in World Oil 149(5), pp. 141-149, October 1959, TN 860.041. v
CHARLES E. OCONNELL, Primary Examiner.
BENJAMIN HERSH, Examiner.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|US5579843 *||May 18, 1995||Dec 3, 1996||Loitherstein; Joel S.||Resilient spider for well installation|
|US5623993 *||May 22, 1995||Apr 29, 1997||Baker Hughes Incorporated||Method and apparatus for sealing and transfering force in a wellbore|
|WO1995009964A1 *||Oct 4, 1993||Apr 13, 1995||Baker Hughes Inc||Method and apparatus for sealing and transferring force in a wellbore|
|WO1996037682A1 *||May 16, 1996||Nov 28, 1996||Baker Hughes Inc||Method and apparatus for sealing and transferring force in a wellbore|
|U.S. Classification||166/117, 166/63|
|International Classification||E21B33/13, E21B33/134|