US3135327A - Telescopic bridging plug-pressure set - Google Patents

Description

June 2, 1964 v D, HANEs A3,135,327

TELESCOPIC BRIDGING FLUG-PRESSURE SET 7/Imlllll Il June 2, 1964 v. D. HANEs 3,135,327

TELESCOPIC BRIDGING PLUG-PRESSURE SET Original Filed July 22, 1957 3 Sheets-Sheet 2 Fig.4

Jun 2, 1964 v. DJHANES TELESCOPIC BRIDGING PLUG-PRESSURE SET Original Filed July 22|, 1957 3 Sheets-Sheet 3 j www o llf/IIr\ l.v. u\

3,135,327 TELESCOPIC lilllDGlNG PLUG-PRESSURE SET Vaughan Dean Hanes, West Covina, Calif., assignor to Aerojet-General Corporation, Azusa, Calif., a corporation of Ohio Original application `luly 22, 1957, Ser. No. 673,339, now Patent No. 3,029,872., dated Apr. 17, 1962. Divided and this application Feb. 26, 1962, Ser. No. 185,177 2 Claims. (Cl. 16o-63) This invention relates to oil well tools. More particularly, the invention relates to oil well packers of the type commonly known as bridging plugs. This is a divisional application of my co-pending application, Serial No. 673,339, led July 22, 1957, now Patent No. 3,029,872 patented April 17, 1962, entitled Telescopic Bridging Plug-Pressure Set.

Bridging plugs are employed in oil wells for the purpose of forming a barrier in the well bore. The barrier may be either permanent or temporary, and may be located either in the well casing or in the uncased portion of the well bore. The barrier, thus formed, serves to separate the well bore into upper and lower sections which are isolated from each other. A pressure diiferential may exist across the bridging plug and may vary from a few pounds per square inch to several thousand pounds per square inch.

- The bridging plug of the present invention is intended for use primarily in those cases where the pressure differential across the plug is high.

Heretofore, it has been the practice, when establishing a high pressure barrier in a well, to employ bridging plugs which are relatively large and which therefore contain a large amount of metal which must be drilled up when it is desired to remove them from the well. Such bridging tire job. In recent years, the development of propellantactuated setting tools has made 'possible the running of the plugs on a wire line instead of on pipe, with a consequent large saving in expense.

It is an object of the present invention to provide a bridging plug of the propellant-actuated type, for wire line operation.

Propellant-actuated bridgingplugs of the high pressure type, as heretofore constructed, require the use of separate, detachable setting tools containing the propellantactuated mechanism, which adds to the cost and expense of setting the plugs.

It is an object of the present invention to provide a high pressure bridging plug of the wire line typewhich does not require a separate setting tool and thus reduces the cost and expense of setting the plug.

Heretofore, wire line bridge plugs of the propellant-set type have required the use of insulated electric lines and the associated expensive mobile hoisting equipment for use therewith. The use o f such specialized equipment requires the services of a service company. Ordinary well servicingV crews do not operate such equipment.

It is anobject of the present invention to provide a propellant-set, wire-line bridging plug which does not re-v quire the use of an insulated electric line nor a specially equipped mobile hoisting unit. The bridging plug of the rUnited States Patent O 3,135,327 Patented June 2,` 1964 present invention can be run on the common stranded steel cable which is available on all drilling rigs, workover rigs or well-pulling rigs. No special service crews are required for operation of the bridging plug of the present invention.

Other objects and advantages will be apparent from the following description and drawings disclosing several embodiments of the invention.

FIG. 1 is an elevation, partly in cross section, illustrating one embodiment of the invention in the running-in posiltion, and having only one set of slips.

' FIG. 2 is an elevation, partly in cross section, of the device shown in FIG. 1, in the set position.

FIG. 3 is an elevation, partly in cross section, illustrating the device of FIGS. 1 and 2 equipped with a second set of slips.

FIG. 4 is an elevation, in cross section, of a mechanically actuated firing system for use with the bridging plug,A shown in FIGS. 1, 2 and 3.

FIG. 5 is an elevation, in cross section, of an electrical tiring system for use with the bridging plugs shown in FIGS. 1-3.

FIG. 6 is a continuation of the bridging plugs of FIGS. 4 and 5, showing the lower end thereof.

Referring to FIG. 1, the numeral 1 indicates a well casing. Disposed within the well casing 1 and supported by a wire line, not shown, is bridgingplug 2, in the runningin position. Thebridging plug 2 comprises live major parts which `are movable relative to each other. These parts are: a piston 3; acylinder 4; afloating body 5;wedge slips 6; and acompressible packer sleeve 7.

The piston member Sis provided at its upper end with an enlargedhead 8 forming a downwardly facing annular shoulder 9, a tubular body 11i having a downwardly depending tubular shank 11 of still further reduced diameter, to which is connected, as by thethreads 12, an enlarged,tubular combustion chamber 13.

The edge 13a ofcombustion chamber 13 forms an out` inwardly turned ilange 15 at its upper end, slidably engalging the exterior surface of the tubular shank' 11. A suitable sealing means, such as an `O ring 16 is mounted` 1n theflange 15 in sealing relation with the outersurface of the shank 11. The lower portion of the cylinder mem-1ber 4 is enlarged as indicated at 17 to provide an upwardly facingannular shoulder 18 which supports thewedge slips 6 when in their retracted position, as shown in FIG. 1. The'interior of thecylinder 4, below theflange 15 is enlarged to slidably engage the exterior surface of thecombustion chamber 13 and to form the pressure chamber 19. Sealing means, such as the 0 ring Ztl,

is positioned in the exterior surfacev of thecombustion chamber 13 in sealing engagement between the, walls of thecylinder 4 and thecombustion chamber 13.

The pressure chamber 19 communicates with the in-v pellant charge '23. Acompression spring 25 vmay be placed between the end of thepropellant charge 23 and the end of thecombustion chamber 13 to prevent movement of the propellant charge with the attendant danger of breaking the charge. The upper end of thepassageway 22 is closed by a Valve member in the form of asmall piston 26, slidable in thepassageway 22.

' Thefloating body member 5 is tubular in form with itsinterior surface 27 in slidable engagement with the exterior surface of thetubular body 10. Auid relief chamber 28 is formed between theinterior wall 27 Vof the floating body member and the exterior wall of the shank 11.Ports 29 in the wall of thefloating body member 5 communicates thechamber 28 with the exterior of thebody vmember 5. The lower portion of thebody member 5 is tapered downwardly and inwardly to form a frusto-conical seat 30 for thewedge slips 6. Thewedge slips 6 are normally held in their retracted position, resting upon the shoulder 1S, by any suitable means, such asshear pins 31 attached to thebody member 5.

The upper end of thefloating body member 5 terminates in an upwardly facingannular shoulder 32 which serves as a seat for the lower end of the cylindrical,resilient packer sleeve 7.

In order to lock themembers 4 and 13 in extended position, the outer surface of thecombustion chamber 13 is provided with a series of vertically spaced, upwardly facing,teeth 33. Theteeth 33 are adapted to engage a series of vertically spaced, downwardly facingteeth 34 formed on the inner face ofwedge locks 35 mounted inrecesses 36 formed in the lower end of thecylinder member 4. Thebearing wall 37 of therecess 36 is tapered upwardly and inwardly. Acompression spring 33 mounted in arecess 39 in the back ofwedge lock 35 tends to force the wedge lock inwardly toward the outer surface of thecombustion chamber 13.

Thepassageway 22 in shank 11 has anupward extension 40 of reduced diameter. Thepassageway 40 extends to the top of the shank 11 where it communicates with the interior of atubular housing 41 which is attached to the piston 3 by any suitable means such as thethreads 42. Thetubular housing 41 contains the mechanism for acuating a firing pin 43 which contacts thepercussion cap 24. The firing pin 43 depends from the lower end ofpiston valve 26. On the upper end ofpiston Valve 26 is an upwardly extendingpush rod 44, the upper end of which extends in'to thehousing 41. Any suitable means for actuating the firing pin 43-'44 may be utilized, for example, the mechanism illustrated in FIG. 1 that is substantially the same actuating mechanism shown in FIG. 4 and described in detail below.

FIG. 2 illustrates the device of FIG; 1 in set position in the well casing 1. Upon downward movement of the ring pin 43 (FIG. l), thepercussion cap 24 is red,

initiating the burning of the propellant charge`23. High spect to the piston 3 pushes the floatingbody member 5 upwardly. Thecompressible packer sleeve 7, being restrained by the shoulder 9 on thepiston head 8, is compressed and expanded laterally by upward movement of theupper shoulder 32 onv theoating body 5, until thepacker sleeve 7 is tightly engaged with the inner wall of the well casing 1. At the same time, upward movement of thecylinder member 4 with respect to the piston 3 causes theteeth 34 on theWedge lock 35 to engage the teeth 3 on the piston, to lock the cylinder against any subsequent downward movement, and thus maintaining thepacker 7 in sealing engagement with the well casing 1. Continued build-up of pressure in thechambers 19 and 13 will cause the bottom of thechamber 13 to be blown out,

releasing the pressure in these chambers. The bottom wall of thechamber 13 is intentionally weakened as indicated at 45, Lfor this purpose. The expandedpacker sleeve 7 together with the expanded wedge slips 6 will enable the bridgingplug 2 to withstand high differential pressures of several thousand pounds per square inch.

Theinterior passageways 22 and 40 are closed by thepiston valve 26 and also by thehousing 41 so that fluid cannot pass through the interior of the bridging plug.

Thelarge metal parts 3, 4 and 5 of the bridging plug are preferably made of a metal which is strong but easily drilled up, for example, cast iron or aluminum. Thepacker sleeve 7 is preferably made of an oil resistant rubber. The wedge slips 6y are provided with hardened teeth to better engage the interior walls of the well casing 1.

FIG. 3 illustrates a variation of the bridging plug shown in FIGS. l and 2. The plug shown in FIGS. l and 2 has only one set of wedge4 slips 6, these being so positioned as to prevent downward movement of the bridgingplug 2 in the well casing 1. Sometimes there exists an upward pressure below the bridging plug which is greater than the downward pressure` from above. In this case it is customary to provide the bridging plug with two sets of wedge slips, one set engaging in a downward direction and the other set engaging in an upward direction. The only changes from the design shown in FIGURES 1 and 2 are: an elongation of thepiston body 10a to make room fortubular Wedge seat 46 which slidably surrounds thebody extension 10a with its base standing on the packer sleeve '7 and has litsouter surface 47 tapered downwardly to form a seat for wedge slips 48. The wedge slips 48 are normally held in the retracted position by means of shear pins 49. Upward movement of theoating body member 5 relative to thepiston body 10a causes thepacker sleeve 7 to shear thepins 49 and move the Wedge slips 48 outwardly into engagement with the well casing 1.

FIGURE 4 illustrates one form of actuating device for the bridging plugs shown in FIGURES 1-3. The actuator is of thego-devil type wherein aweight 50 is dropped from the top of the well slidably mounted on thehoisting line 51. The weight 5t) strikes the top of atubular sleeve 52, forcing it downwardly. Thesleeve 52 has a lostmotion connection with atubular release member 53 which is slidably mounted within thesleeve 52. by means of across pin 54 extending radially throughsleeve 52 and through avertical slot 55inthe release member 53. The lower end of thehoisting line 51 is secured to the upper end of therelease member 53 by any suitable means, such as babbitting it into theline socket 56. Suspended on thecross pin 54,.within thetubular release member 53, is a Ycylindrical striker weight 57. Thetubular release member 53 is formed with an .upwardly facing externalannular shoulder 58 on which is seated ahelical compression spring 59. Below theshoulder 53 Vthetubular release member 53 has anenlarged cavity 60 which releasably receives the upper end of the bridgingplug 61. The bridgingplug 61 is generally similar to the plugs shown in vFIGURES 1-3 except as to the actuating means for the propellant, as will be described below.

Thetubular release member 53 is releasably attached to the upper end of the bridgingplug 61 in the following manner. Atubular neck 62 on the upper end of the bridgingplug 61 passes slidably through anopening 63 in the lower end of the wall of enlarged cavity .60. An

opening 64 in the wall of theneck 62 receives a retaining surface of aplunger member 67 having acircumferential recess 67a. scribed later.

The cable releasing operation will be depiston members10 and 10a of FIGURES 1-3.

As4 shown in FIGURE 4, initiation of the firing device is accomplished before the releasing of the bridgingplug 61 fromtherhoisting line 51. This initiation is accomplished in the following manner. When theplunger 67 is pushed downwardly by the striker weight 57 (which is accomplished by the falling go-devil 50 striking the sleeve 52), the downward movement of the plunger actuates a tiring pin 69 which strikes apercussion cap 70 in the upper end of an igniter 71 in the upper end of the combustion chamber 72 within thetubular member 73, igniting the propellant (not shown). The upper end ofmember 73 is attached to the lower end of tubular housing 74 by suitable means such as thethreads 75. The tubular housing 74 is Slidably mounted within the bore of a tubular extension 76 whichcorresponds to the tubular The upper end of the tubular extension 76 is counter bored andprovided with a series of vertically spaced, downwardly facing, circumferential `teeth 77 which engage upwardly facingteeth 78 on the outer face of a lockingmember 79. Lockingmember 79 has upwardly facing, vertically spacedratchet teeth 80 which engage a series of vertically spaced, downwardly facingratchet teeth 81 formed onV the outer surface ofthe tubular housing 74. Ashear pin 82 normally locks the members 74 and 76 against relative movement. The tubular housing '74` is provided, near its lower end, with suitable means for sealing the space between the members 74 and 76, such as the vO` rings 83.

The Ytubular housing 74, which is attached to the combustion chamber 72 is divided into upper andlower compartments 84 and 85 by means of a transverse wall 86 having acentral opening 87. Theplunger 67 is Slidably mounted in theupper chamber 84 and is supported upon acompression spring 88 which rests upon the top of the transverse wall 86. The purpose of thespring 88 is to otiset any tendency for the iiuid submergence pressure to depress theplunger 67 and release the ring pin 69 and tiring the igniter 71, prematurely. Theplunger 67 is provided with adownwardly depending'push rod 89 which passes through theopening 87 in the barrier 86. Sealing means, such as the O rings 90 seal the space between thepush rod 89 andopening 87. Theupper chamber 84 is provided withvent ports 91 to permit the escape of uid as theplunger 67 moves downwardly in thechamber 84. The lower end ofpush rod 89 is provided with an enlarged, tubular head 92 having a circular opening 93 in its lower end. Slidably received within the opening 93 is a tubular sleeve 94 which houses the iiring pin 69. In the lower chamber 85, between the enlarged head 92 and the under side of the barrier 86 is a compression spring 95 which determines the cable release pressure, as will be explained. t

` The iring pin 69 has an enlarged head 96 having an annular beveled downwardly facingshoulder 96a which normally bears against the upper surface of a ball detent 97 positioned within an opening 98 in the wall of the sleeve 94. A barrier 99 is provided midway of the sleeve 94. There is an opening 100 through the barrier 99 through which the shank of the tiring pin 69 extends. The lower end of the firing pin shank terminates in an enlargedhead V101 which serves as an abutment for acompressed spring 102, the other end of which seats against the under side of the barrier 99. The sleeve 94 is provided with aradially extending flange 103 which is secured between adjoining shoulders on the threadedly joinedmembers 73 and 74. The firing pin 69 is so positioned as to strike thepercussion cap 70 when thecompressed spring 102 is released'.

The operation of iiringmechanism of FIGURE 4 is as follows: When the go-devil 50 is dropped into the well bore and strikes member S2 theplunger 67 is driven downwardly by thestriker weight 57, thus moving thepush rod 89 and its enlarged, tubular head 92 downwardly with, respect to the sleeve 94. Theupper portion 104 of the interior of the tubular head 92 is of larger diameter than the lower opening 93, with the result that when the ball detent 97 enters theenlarged chamber 104 it releases the head 96 on the upper end of the firing pin 69. Thecompressed spring 102 then drives the tiring pin downwardly, striking thepercussion cap 70 in theigniter 71 and igniting the propellant (not shown) in the combustion chamber 72.

High pressure gas generated by the combustion of the propellant passes upwardly through the combustion chamber 72, outwardly throughports 105 in thewall 73 of the combustion chamber, and into the space between the relatively movable members 74 and 76, causing these members to move in an axial direction with respect to each other.' Such axial movement continues until thepacker sleeves 106 and 107 (FIGURE 6) have been expanded by axial compression and wedge slips 108 and 109 have been set. The wedge slips 108 and 109 are normally held in retracted position byshear pins 110 and 111, respectively. Engagement of theratchet teeth 80 and 81 prevents return movement of the members 74 and 76. Continued generation of pressure in the combustion chamber 72 results in the shearing of the lower end of the combustion chamber 72, as indicated in FIGURES l and 2. The release of thehoisting line 51, carrying the go-devil 50, from the bridgingplug 61 is accomplished in the following manner.

The increasing pressure within the combustion chamber 72, due to the burning of the propellant within the chamber, causes the spring 95 to be compressed upward due to the increasing `pressure forcingpush rod 89 upward throughopening 87. The upward movement ofpush rod 89moves plunger member 67 upward. This upward movement continues as the pressure in chamber 72 increases until therecess 67a carried by theplunger member 67 is opposite thecable releasing ball 65 as indicated bydotted lines 68 allowing theball 65 to fall inwardly into therecess 67a and thereby releases thetubular member 53` fromthepacker neck member 62. The entire release member is then withdrawn from the well bymeans of the hoistingcable 51.

FIGURE 5 illustrates an embodiment of the invention in which the bridging plug is adapted to be set by electrical initiation. Electric current is conducted through an insulatedelectric hoisting line 112 from the top of the well. The bridging plug is shown in the running-in position, with two sets ofslips 108 and 109 and twosleeve packers 106 and 107. Aspacer ring 113 may be used to separate thesleeve packers 106 and 107, if desired. The lower set ofslips 109 are supported on atubular shoe 114, the outer surface of which is tapered downwardly and inwardly as indicated at 115 to provide a seat for the' wedge slips 109.Shoe 114 is Slidably mounted on atubular body member 116 which is part of the piston assembly. Thetubular body 116 has apartition 117 approximately midway between its ends. Atubular piston rod 118 serves'also as acombustion chamber 119 for thepropellant 23a. Thepiston rod 118 is attached to thepartition 117 by any suitable means such as thethreads 120 and extended upwardly therefrom. Attached to the upper end ofpiston rod 118, as by thethreads 121, is a tubular"piston 122 of enlarged diameter. Theend 122a ofpiston 122 forms an outwardly projecting ange in conjunction' 125, are mounted between the walls offlange 126 androd 118. High pressure gas from the burningpropellant 23a in thecombustion chamber 119 passes through ports 127 in the `wall of thetube 118 and intoexpansion chamber 123 below thepiston 122 and within thecylinder 123, thus forcing thecylinder 123 to move downwardly with respect. to thepiston 122. Ashear pin 129 secures thepiston 122 to thecylinder 123 and prevents premature relative movement between these parts. vRatchet type locking means 136 is provided between thepiston 122 andcylinder 123 similar to the locking means described in connection with the device shown in FIGURE 4. A second tubular shoe 131 (46 in FIGURE 4) is slidably mounted on the lower end of thecylinder 123 at which flange 126 is formed and on the upper end of thepiston body member 116. is tapered downwardly and outwardly as indicated at 132, to provide a seat for the wedge slips 108. The lower end ofshoe 131 rests upon the top of the upper packerv sleeve 1416.Fluid ports 133 are provided in the Wall of theshoe 131 intermediate the ends thereof to permit well Huid to pass in or out of thechamber 134 between theshoe 131 and the tube 118'. In order to force the wedge slips 168 and 169 into engagement with a well casing, thecylinder 123 is provided with an outwardly directed flange 135 having a downwardly facingshoulder 136 which bears The outer surface of theshoe 131 on top and supports the wedge slips 108, and thepiston body 116 is provided at its lower end with a similar outwardly directedflange 137 Vhaving an upwardly facing shoulder 13S which bears and supports the lower end of wedge slips 169.

The ignition system shown in FIGURE 5 is different from that shown in FIGURE 4 in that, in FIGURE 5, ignition is accomplished by passing an electric current downwardly through the insulatedelectric hoisting line 112. The lower end ofline 112 is connected to anigniter 139 positioned adjacent the upper end of thepropellant 23a. serves also as a piston rod, the lower end, of which is attached to anenlarged guide 141, the latter containing theigniter 139. Theguide 141 is normally contained within acylinder 142 formed by counter boring the upper end' of thetube 118. Theguide 141 is normally held in l its lowermost position, as shown, by means of a compression spring 143, the lower Yend of which bears against the top ofguide 141 and the upper end of which bears against' Y the extension 143 to seal the space between the inner wall of a bore 152 in theextension 148 and the outer Wall of the tube 14d. The purpose of theseals 150 and 151 is to prevent the passage `of uid to the interior of the bridging plug, past themembers 145 and 148. To the upper end of tube 140 is attached anenlarged head 153 which provides means for sealing the inside of tube 140 from outside pressure and also provides means for releasingcollar 154 frompiston 122. The upper end of thehead 153 contains astufiing ybox 155 having packing means 156-surrounding theline 112 and a threaded follower157 for tightening the packing 156.

When high pressure gas generated by thepropellant 23a of FIGURE 5 pushes the tube 140 upwardly, against the pressure of spring 143, through itsguide 141theenlarged head 153 is also pushed upwardly with respect to thetubular piston 122. The upper end of thetubular piston 122 is provided with means for allowing the releasingcollar 154 to be detached therefrom. For this purpose, the upper end of thetubular piston 122 is provided with atubular neck 153 which is slidably received within anopening 159 in the lower end of the releasingcollar 154. Anopening 160 in the wall of the neck 15S contains aball detent 161 which has a diameter greater Theline 112 is enclosed within a tube 140 which.

than the wall thickness of theneck 158. Theball detent 161 is normally held from inward movement by thehead 153 and the inner wall of the releasing collar. The outer, underfacev of theball detent 161 is supported on an annular upwardly facingshoulder 162 on the inner wall of the releasingcollar 154. When thehead 153 moves upwardly with respect to the neck 15d, under the influence of high pressure gas, as previously explained, .thehead 153 moves above theball 161, allowing the ball to fall inwardly, inside the neck 15S, thus releasing thecollar 154 from theneck 158. Theline 112 is a relatively weak line and will be broken as indicated at 163 by the upward pull of thecollar 154 after the bridging plug has been set. Thecollar 154 may be provided withO ring seal 168 to prevent fluid lentering the inside chamber ofcollar 154.

The upper portion of the releasingcollar 154 is provided with means for attaching it securely to thehoisting line 112. lt is customary to provide electric conductor lines such as 112 with several wraps ofinsulation 164 and an outer sheath of strandedsteel wire 165 which carries the load. Theouter sheath 165 is passed through astuffing box 166 intoaline socket 167 and the outer wires of thesheath 165 are turned back and/ or imbedded inra body of babbitt or lead` as indicated at 169. Such a construction permits the hoisting line to support a considerable load, on the order cf 6G() lbs., but permits the line toV be pulled out of thesocket 167 if the releasingcollar 154 should become stuck in the well, thus saving the line and avoiding a fishing job. I

The methods of igniting the propellant and releasing the cable as outlined in the description of FIGURE 4 and FIGURE 5, also provide for a time interval between the igniting of the propellant and the releasing of the hoisting cable. This time interval is provided so that the packer and its slips may be set into holding contact with the casing Wall before the packer is released from the cable. Premature release could allow the packer assembly to fall downwardly in the well bore or casing before the slips have engaged the well casing. In FIGURE 5, this time interval is provided in the following manner.

Thepropellant 23a, when ignited by means ofigniter 139, burns and produces gas withincreasing pressure within thechamber 119 and in thechamber 128 provided between theseals 124 and 125, thus, shearing pins 129, 110 and A111, releasing theslips 16S and 109 and theshoes 114 and 131 between the shoulders 136-and 13S. In-

- creasing pressure within the chamber12S forces piston 122 upward in relation tocylinder 123 and moves shoulder 11S upward in' relation toshoulder 136. This upward movement compresses thepacker sleeves 106 and 107 and expands them outwardly into contact with the well casing (not shown). Further upward movement of theshoulder 138 forces theslips 168 and 109 outward into contact with the casing due to the' tapers 132 and 115 ofshoes 131 and 114. The pressure developed within thepropellant chamber 119 may increase during the packer setting time interval described above and will increase to higher pressures when thepacker sleeves 106 and 107 and theslips 168 and 169 are forced into full contact with the casing, resulting in the release of thecollar 154. The collar releasing means, as described in the operation of FIGURE 5, provides pressure responsive means for releasing the collar. A compression spring143 may be provided to prevent the collar from being released from the l@ Y ber in said cylinder, and a fluid passageway connecting 2. In a bridging plug as set forth in claim 1, further said combustion chamber with said expansion chamber; including means associated with said plunger for releasing ignitable propellant means in said combustion chamber; said hoisting lineA from said plug after said plug has been an igniter in said tubular piston and associated with said l set in a Well.

l propellant, spring-pressed percussion means for initiating 5 said igniter; a latch for said percussion means normally References Cited m the me of thls patent holding the percussion means in its retracted position; UNITED STATES PATENTS plunger means for releasing said latch; and means aSSo- 2,807,325 Webb Sept. 24, 1957 ciated With said hoisting line for actuating said plunger.

Claims (1)

1. IN A BRIDGING PLUG ADAPTED TO BE RUN ON A HOISTING LINE AND HAVING A TUBULAR PISTON AND TUBULAR CYLINDER MOUNTED ON AND IN TELESCOPIC RELATION TO EACH OTHER, A COMBUSTION CHAMBER IN SAID PISTON, AN EXPANSION CHAMBER IN SAID CYLINDER, AND A FLUID PASSAGEWAY CONNECTING SAID COMBUSTION CHAMBER WITH SAID EXPANSION CHAMBER; IGNITABLE PROPELLANT MEANS IN SAID COMBUSTION CHAMBER; AN IGNITER IN SAID TUBULAR PISTON AND ASSOCIATED WITH SAID PROPELLANT, SPRING-PRESSED PERCUSSION MEANS FOR INITIATING SAID INGNITER; A LATCH FOR SAID PERCUSSION MEANS NORMALLY HOLDING THE PERCUSSION MEANS IN ITS RETRACTED POSITION; PLUNGER MEANS FOR RELEASING SAID LATCH; AND MEANS ASSOCIATED WITH SAID HOISTING LINE FOR ACTUATING SAID PLUNGER.

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