US2656891A - Apparatus for plugging wells - Google Patents

Description

Oct. 27, 1953 L. w. TOELKE APPARATUS F' OR PLUGGING WELLS 2 Sheets-Sheet l Filed March 2, 1948 FIG FIG. I

L. f TOEL KE INVENTOR FIG. 4

ATTORNEY L. W; TOELKE APPARATUS FOR PLUGGING WELLS voct. 27, 1953 2 Sheets-Sheet 2 Filed March 2, 1948 FIG.7 FIG.6

FIG.9

l.. TOELKE JNVENTOR FIGB ATTORNEY Patented Oct. 27, r.1953i UNITED STATES PATENT OFFICE APPARATUS FOR PLUGGIN G WELLS Lester W. Toelke, Houston, Tex. Application March 2, 1948, Serial No. 12,523 3 Claims. (C1. 16S-13) The present invention relates to improvements in apparatus for plugging wells and particularly to improved forms of plugging devices and bridging plugs useful for such purposes.

Bridging plugs are conventionally employed in wells, such as oil or gas wells, for plugging olf one section of a well from another for various operational purposes, as, for example, in connection with the testing of strata at several elevations to determine their respective oil or gas producing characteristics. Most plugs heretofore employed for this purpose use a sealing body composed of rubber or similar resilient material which is compressed or otherwise distended to expand it into sealing engagement with the well casing and require some form of toothed slips or other gripping means to support the sealing body in its expanded position in order to maintain the required seal. These conventional forms of plugs are commonly oi rather complicated mechanical construction; require elaborate setting tools; frequently fail to establish or maintain a uuid-tight seal; are diiiicult to remove when it is desired to clear the well or to return to the portion of the well below the plug; are relatively expensive to construct; and require considerable time and eiiort to set them properly.

The practice of this invention, briefly stated, comprises inserting into a well bore, casing or other pipe in a well to the desired setting depth a hollow metallic plug designed and constructed in accordance with this invention, and expanding the walls of the plug through the application internally thereof of fluid pressure of suicient force to expand the plug into tight plugging engagement with the surrounding casing, the expansive force applied being generally in excess of the elastic limit of the material of which the plug is constructed, whereby the plug becomes permanently deformed and set in its expanded condition.

The fluid pressures employed for setting the plugs may be either pneumatic or hydraulic and may be developed in various ways. One method for developing and applying the requisite force is by setting off inside the plugging device a suitable explosive material which is adapted to rapidly generate gases of suilicient volume and pressure for the purpose. Devices in accordance with this invention possess the important advantages of relative simplicity in operation and high speed in effecting the plugging operation, the ability to attain any desired pressures, and to form seals capable of withstanding high external pressures without leakage. Also, since selected in any the pressure-generating characteristics of various types of explosive materials are well known, the quantity of explosive material required to develop the desired pressure in each case may be readily pre-determined, thereby providing effective control of the plug expanding operation.

The requisite pressures may also be developed hydraulically by the use of generally conventional means for pumping a suitable hydraulic fluid, such as water or oil, into the interior of the plug until the desired expansive pressure is attained. This embodiment will normally require :more time and equipment than the explosive embodiment but may be successfully employed, if desired.

The plugging devices which may be employed in the practice of this invention are of extremely simple design and relatively cheap construction and, in general, comprise a hollow generally cylindrical metallic body, having a normal outside diameter somewhat less than the internal diameter of the well casing in which it is to be inserted. The metallic materials employed for construction of the plugging device may be any metallic material possessing a suflicient degree of ductility or plasticity such that when Subjected to the requisite pressure, the walls thereof will expand to the desired extent without rupture or cracking and will become permanently set in their expanded condition. Many metals and their alloys possess these characteristics, some of the more useful examples cf which are aluminum and magnesium and their various alloys, copper and its alloys including various brasses and bronzes, mild steels, etc. Generally speaking the metallic materials will be employed in their non-heat treated forms which are generally softer and have greater ductility and plasticity than their heat-treated forms. It will also be found more generally desirable to employ metals having a relatively wide spread between their elastic limits and their ultimate strengths, this spread, of course, being to some extent a measure of the ductility or elongation characteristics of the particular metal. Ordinarily, metallic materials capable of elongation of 1.5% or more in two inches, as determined by standard test methods, will be found to be preferable, although materials of lesser elongation characteristics may be used' in particular cases. Generally speaking, the type and character of metal instance will normally depend upon the particular conditions to be met, such as the degree of expansion required, the pressures to be withstood by the seal, etc.

Accordingly, among the principal objects of this invention are the provision of a plugging device for plugging wells which is adapted for simple and quick operation; which effects permanent seals capable of withstanding without leakageV any external pressures which may be encountered in oil or gas wells; which does not require elaborate or expensive setting tools; and which is of relatively simple and cheap constructions.

A further object is; the provision of a device for plugging a well pipe by the expansion therein of a hollow metallic plug through the application to the sufncient to expand the plug intoA permanently set plugging engagement with the well pipe.

An additional object is the provision of a hollow metallic plug which is expandible into plugging engagement with a well bore through the application to the interior of the plug of pressurel generated therein by the use of explosive material.

Other and more specic objects and advantages of this invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate several useful embodiments in accordance with this invention.

In the drawings:

Fig. l is an elevationall view of a bridging plug in accordance with one embodiment of this invention as it appears when suspended in a well casing from a conductor cable preparatory to setting. the plug;

Fig. 2 is a corresponding elevational View showing the plug set inthe casing and the conductor cable removed;

Fig. 3 is an enlarged sectional view through line 3-3 `of Fig. l, showing the parts of the bridging plug in the positions assumed when running into the well` casing and before being set;

Fig. 4 is an. enlarged sectional view through line 4-4 of Fig. 2 showingY the form and position of the parts of the plug after it has been set;

Fig. 5 is a quarter-sectional View of a plug similar to that shown in Figs. l to 4 inclusive which has been set under pressure sufficient to expand the portion` of the casing which is in contact with the plug; I

Fig. 6 is an elevational. view of a plug which has been set opposite a casing coupling;

Figs. 7 and 8 are elevational views, after setting, of a somewhat modified form of plug; and

Fig. 9 is a view similar to Fig. 3 ofy a plugging structure employing hydraulic means for generating the necessary internal pressure.

In accordance with one embodiment of this invention (Figs. l, 2, 3 and 4), the plugging device comprises a generally cylindrical body, designated generally by the numeral LB, having a bore or cavity Il internally thereof enclosed by a circumferential wall l2, and upper` and lower end closures I3` andV I4, respectively. Body I0 may be constructed of a metallic material of the character mentioned above and may be fabricated in any conventional manner, as by forging, casting, machining, etc. While body l0 will normally, and generally preferably, be constructed from a single piece of metal, it will be understood that wall l2 and end closures' i3' and I4 may be fabricated of separate pieces ofV metal and assembled in any conventionalv and wellknown manner. End closures I3 and Hl will normally be made of greater thickness and mass than wall l2v in order that the fluid pressure to be applied, ashereinafter describe d in cavity i' interior of the plug of fluid pressure before and will generally preferentially expand wall l2. Upper end closure I3 is provided with an internally threaded box l5, the lower end of which communicates with the interior of cavity ll through an axial passageway i6. Box l5 is adapted for threaded connection to the threaded pin Il of a connector sub I8, which is provided with an axial passageway I9 registering with passageway It. A sealing gasket lla., of conventional form is interposed between contiguous faces of sub i8 and box |5` to form a tight seal therebetween. The upper end of passageway I3 is enlarged to form a smooth-walled socket 20 which is adapted to slidably receive therein the connection head 2l carried by the lower end of an electrical conductor cable 22 which serves also as a means for suspending and lowering the plugging device in a well to be plugged. A plurality of shear pins 23 extend radially through the wall of socket 20 into suitable recesses provided in head 2l and serve to attach the plugging device to the cable. A seal ring 2:1, of any suitable and conventional form is suitably mounted between socket 2 andy head 2i to prevent entrance of any extraneous fluidsV into the interior of the plugging device through. this connection. Cable 2 contains an Ielectrical lead 25 which is threaded through head 2l and is adapted to make contact with a cooperating' contact carried by the end of a conventional elec.- trically ignitable fuse cartridge or initiator 26 which is suitably mounted in the lower endv of head 2l and. extends into passageway L9. Car.- tridge 26k is of a well known form which is adapted, when set off, to discharge into cavity Il a jet of gases at suiiicient pressure. to, ignite or detonate the main charge of explosive material, indicated generally by the numeral 2, disposed in cavity il. Other more or less conventional initiator arrangements, well known in the explosive art, may be employed for setting off main charge 2. It will also be understood that lead 25 of cable 22 will be connected at its. upper end to any suitable source of4 electric current with conventional switching mechanism (not shown) for setting` off cartridge 26'.. Such mechanisms and their operation are welll known and of 'themselves form no part of this invention.

The main explosive charge 2l may consist, of any of the well known chemical explosive s ubstances including the various d-etonating and deflagrating types. The detonating type explosives may be exemplied by trinitrotoluene, penta-erythritol tetranitrate, Pentolite, .Amy tol, Cyclonite, TetryL Tetrytoh andthe like. Ther deflagrating types include the various smokeless nitrocellulose base explosives and the various black powders. These explosive mate,- rials may be employed in granular, plastic or molded highly compressed pelletized form, the pressure generating characteristics of all such explosive being well understood and, readily determinable for each particular case. It will be understood that the quantity of explosive used will depend in general upon the character of the particular explosive material and the pressures to be developed in each` particular case.

The method of plugging, a well, using the above-described apparatus, may be, as follows: A main charge 2'.' of the selected. explosive mate,- rial in the predetermined quantity to generate the desired pressure, will be introduced` through passageway I6 into cavity Il, of the plug.V Sub I8 will be. screwed tightly intothe plugr body, and head 2l. carrying cartridge 26 willy be inserted into socket 2t of the sub and locked thereto by means of shear pins 23. The plugging device, thus attached to cable 22, will be lowered into the well casing 30 to the desired point in the well at which it is to be set. When the setting point is attained, cartridge 26 will be fired by suitable manipulation of the ring mechanism at the top of the well, and the resulting blast will travel through passageways i9 and i5 into cavity H where it will set off main charge 2l. The gases generated by the explosion of the main charge, being closely conned within cavity Il, will almost instantaneously develop very high pressure inside cavity il. The resulting force will cause wall 2, being the relatively weaker portion of the plugging body, to expand radially outwardly into tight engagement with the wall of casing 3G. The pressure developed in cavity will be substantially uniformly distributed about the interior of the cavity, and the resulting expansion of wall i2 will be generally uniform radially in all directions, so that a tight circumferential seal will be effected between body I and casing 30. Figs. 2 and Il illustrate the general shape assumed by body IG following expansion. As noted previously, the quantity and density of the particular explosive material selected, will be predetermined to develop the pressure necessary to produce the desired expansion of the plug body. This pressure will exert an expansive force on wall l2 such as to exceed the elastic limit of the material of which the wall is constructed but which will not attain the rupture strength of the wall. Under such a force, wall |2 will become permanently deformed and will be permanently set in its expanded position so that a tight seal with casing 3B will be maintained even after the internal pressures are relieved through normal cooling or escape of the explosive gases.

When the plug has thus been set in the casing, an upward pull or jerk will be applied to cable 22 of suicient force to break shear pins 23. Thereupon cable 22 may be withdrawn from the well bringing with it head 2| which can then be re-prepared for use in conducting another plugging operation. Body H) and connector sub IB will remain in the swell and, due to their relatively simple structural form and the relative softness of the metal of which they are normally constructed, may be easily cut or drilled- -out by conventional methods whenever it may become necessary or desirable to clear the well for any purpose.

As noted previously, the known pressure-generating characteristics of the various explosive materials permits pre-determination of the pressure to be developed in each particular case in relation to the physical characteristics of the material of which the plugging device is constructed, so that the degree of expansion of the plug walls may be regulated and controlled Within relatively narrow limits. In determining the pressure to be developed, any pre-existing pressures in the pipe in which the plug is run will be taken into account in arriving at the total pressure load to be applied in the plug. Under the force of the explosion, it is found that the metal of which the plug is constructed will be extruded into any cracks, pits or crevices which may be present in the inner surface of the casing, thereby forming a plurality of nter-engaging abutments for mechanically locking the plug to the casing which, together with the compressive and frictional forces developed, will provide a seal which is suciently tight to withstand any liuid pressures which may be encountered in the well. It may be assumed that the high temperature, which is the normal concomitant of the disintegration of the explosive material, will be a factor in the expansion of the plug and in causing the described flow of plug metal, whereby the outer surface of the plug will accommodate itself more or less perfectly to the exact form and condition of the casing surface against which it is forced. This is suggested merely by way of theoretical explanation of the plugging action and is not intended to be construed as a limitation upon the described method.

A similar result may be obtained in a more positive manner in cases where exceptionally high pressures are anticipated in the well, by employing a quantity of explosive material such as to expand the plug suliiciently to produce some degree of bulging of the surrounding well casing. This modification, illustrated in somewhat exaggerated form in Fig. 5, has the additional advantage that an annular recess 3| will be formed in the casing which is of slightly greater diameter than the normal diameter of the casing. The distended walls of the plug having, of course, a complementary shape, will extend into the recess and will be lodged therein between shoulders, indicated at 32 and 33, formed by the upper and lower edges, respectively, of recess 3|. Thus, in addition to the compressional and frictional forces tending to hold the expanded plug in place, a positive locking means will be provided to prevent dislodgment of the plug along the casing by forces which may be exerted from above or below the plug. In connection with this modication it will be understood that the ultimate strength of the casing will be considered in computing the quantity of explosive to be used so that the total force applied by the expansion of the plug will not attain or exceed the bursting strength of the casing.

Alternative to the modification illustrated in Fig. 5 the plug may purposely be set opposite a joint in the casing and expanded to accomplish a similar result by causing the plug metal to be extruded into the annular crevice normally present between the abutting ends of adjacent casing sections screwed into the usual coupling collar. Fig. 6 serves to illustrate this modification.

Two sections of casing 30 are shown. screwed into a conventional collar 40. Normally, a narrow annular crevice 4| will be provided between the abutting ends of the casing sections when they are made up to a normal degree of tightness in the collar. The plug will be run into the casing to a point opposite a coupling 40 nearest the desired setting point and will be expanded by the application of fluid pressure in the manner previously described. It will be found that the plug metal will be extruded into crevice 4| forming an annular abutment 42 on the outer surface of the plug body which is generally complementary in shape to the seat formed by crevice 4| and is firmly locked therein. The portions of the plug surface immediately above and below abutment 42 ,will be tightly compressed against the adjacent portions of the casing section and the whole forms a tight immovable plug in the casing.

Figs. '7 and 8 illustrate another embodiment of a plugging device in accordance with this invention, which is adapted to be set in the same manner as the previously described form of plug and which includes supplemental means for additionlor other resilient material,

:such that, prior .sure .a very tight seal casing, and the teeth 'the expanded plug.

.ally assuring .tight engagement between-,the plug and the casing. These means include a vcircular 'band .34, which `may be `constructed of .rubber and `which :is seated in va'suitable :groove 35 `cut :in theoutersurface of body I .at a point about mid-way .along wall .|2. Band 34 will generally be :of Va thickness `to expansion of the plug, it Lwill extend somewhat beyondfthe surfacefof'theplug. A `pair of grooves 136 and -311are cut in the-exterior of body |10, respectively abovenand below groove 35 and-generally parallelthereto. 1A number of toothed or wickered segmental :slip imembers 38-38 are mountedin eachof these grooves, lthose vin .upper groove 36 having their teeth pointing generally upwardly and those in lower groove 31 having their teeth pointing generally downwardly. Slip `.members 3.8 are so-disposed .in the respective grooves that the teeth .will ordinarily protrude slightly from the grooves. When this'type of plug .has been set lin-the'same .man-

`nei` as previously described, .bandfd will-'be compressed very tightly between .the exterior=of the `plug and the casing V(see Fig. 8) thereby forming a supplemental seal Awhich will further as.-

.between the plug andthe of slip members .-38 will be driven forcibly yinto 'the |wall of thecasingand maintained therein by the'compressive force of This engagement vwill further assure against slipping of the .plug `under any external 4forces which vmay be-appliedfin the casing against the oppositeends of the'plug.

Fig. 9 illustrates yanother embodiment in accordance with this invention by which expansionof fthe :plug-may be accomplished by means -of Vhydraulic pressure Yinstead of vthe pneumatic pressure employed in the vpreviously described embodiments. In this embodiment -body I0 -will `be :of the same character `and construction as those previously described but connector .sub I8 will be attached to a pipe 39 Ithrough which .any suitab-le .hydraulic fluid, such as vwater or vOil may be .pumped lfrom the surface by any -well known means (not shown) into the interior fof body l0 at sufficient pressure to effect the desired degree of expansion. Or sub .1.8 may contain any suitable and .generally :conventional 4form of compounding mechanism `to build up the pressure oi the hydraulic fluid supplied from the surface to the desired .expansion pressure.

As one specific example ofthe apparatusem- .ployed in accordance with this invention, -a

.plugging device of the iorm illustrated lin Fig. `3 was constructed of an aluminum alloy, having a yield strength o1 about 6000 'pounds ,persquare inch, a tensile strength of `about 16000 pounds per square inch'and'an velongation actor1of'40% in 2 inches. 'This plug was made'41/2 linches :in outside diameter and 1x1/4 inches `inside diameter, thus providing a wall thickness of approximately 1% inches. The overall length of the plug body was about 12 inches :and the internal 4cavity wasabout'/g incheslong. :BOOgrains-.of acommercial smokeless type explosive, .-known 'as Hercules Bulls Eye No. 2, compressed A,into .a single pellet, vwas introduced into the :interior .of the plug. lThe plug was then connected to the sub and `to the ihead of :an electric cable provided withan ignition cartridge, and inserted inside a piece of 51/2 inch, 24 lb. standard casing and the charge set-oit. The plug wall was ex- 'panded so tightly in the casing that no leakage loccurred when the seal was tested with water l*at :a pressure of A(5000'7000 pounds per square inch.

It'will be understood .that the plugging devices lof the character herein described may be used lalone as bridging plugs. They may also serve as La .base or retainer for cement when desired, and may :be Vused in any other connection .in which it may `be desirable to plug a well for 'various purposes.

VIt will be "further understood that various Vchanges 'and alterations may befrnadein the devsaidside wall, said sidewall being constructedof vmetallic material which Ais `expandible under 1internally applied iiuid pressure into permanently set plugging engagement with said well bore without rupture of said side wall, lan explosive vmaterial confined-within -said body adapted upon being setroi to generate said -iiuid pressure within said body, an internally threaded ibo-X in the upper one of said Aend closures, a passageway providing communication between said box and the interior of said body, a tubular sub having its lower Vrend screwed 4into said box'and having an axial bore communicating with said lpassage- Way, an electrically red initiator element extending into -said bore adjacent `its upper end, and connector means for yreleasably connecting said sub `to a lowering 'cable adapted to carry electric current to Asaid initiator element, said initiator being mounted in saidconnectcr means.

2. A well pluggingdevice accordingtoclaim 1 wherein said metallic material is of the class consisting of aluminum, magnesium, copper, `the alloys thereof, and mild Vsteels characterized by Va'n-eiongation factorof from 15% 'to 40% Vin two inches.

3. AWe'll plugging device'according to-claim 1, wherein said connector means comprises Va `plug member carried-by the endof said cable slidably vNumber .Name Date 1,400,401 Allan 1.- Dec..13, 1921 2,212,619 Roe Aug. 27, 1940 v2,214,226 English Sept. 10, 1940

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