US2934147A - Apparatus for severing subsurface well devices - Google Patents

Description

April 26, 1960 R. c. BAKER APPARATUS FOR SEVERING SUBSURFACE WELL DEVICES Filed April 20. 1956.

2 Sheets-Sheet 1 INVENTOR.

flames/v 6'. 4 056 April 26, 1960 APPARATUS FOR SEVERING SUBSURFACE WELL DEVICES FilQd April 20. 1956' R. C. BAKER 2 Sheets-Sheet 2 IN V EN TOR.

.8503! CL 3455a UnitedSrates Patent APPARATUS FOR SEVERING SUBSURFACE WELL DEVICES Reuben C. Baker,'Coalinga, Calif., assignor to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California The present invention relates to subsurface apparatus, and moreparticularly to apparatus for severing or rup- {Qurmg another device or equipment disposed in a well ore.

Certain devices or equipment may be located or anchored in a well bore, which are to be removed therefrom. As an example, a well packer may be anchored in packed-01f condition in a well casing, providing a barrier in the latter which is to be eliminated. Heretofore, removal or elimination of the device, such as the well packer, has been accomplished by employing a rotary drill bit, which drilled or cut away the device, the cuttings. or particles being removed from the well bore by the drilling mud ordinarily used in a drilling operation. Although eifective in removing the device, the drill bit method is usually time consuming and costly.

Accordingly, it is an object of the present invention to provide an apparatus for expediting the removal of well packers, or other obstructions, in a well bore.

Another object of the invention is to provide a severing or rupturing apparatus capable of cutting or breaking :away a large portion of a subsurface device, such as a well packer, in a well bore, and withdrawing it in sub .stantially an intact condition to the top of the well bore.

A further object of the invention is to provide subsurface apparatus capable of exerting a large force on :a device in a well bore, in order to sever or break the device and permit withdrawal of a substantial portion thereof from the well bore, the source of the large disrupting'force being located at the subsurface apparatus Iitself.

An additional object of the invention is to provide .an apparatus adapted to be lowered in a well bore and to be coupled to a well packer therein, the apparatus being capable of severing the main body of the packer and withdrawing it to the top of the well bore.

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. This form is shown in the drawings :accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of :the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section, partly shown in side elevation, of an apparatus embodying the invention disposed in a well casing for operation upon a well packer :anchored to the latter; 7

Fig. 2 is an enlarged combined side elevation and longitudinal section of the severing or cutting portion of .the apparatus shown in Fig. 1 prior to its actuation;

Fig. 3 .is a view similar to Fig. 2, disclosing the appa- :ratus as having severed the body portion of the anchored well packer;

Fig. 4 is a fragmentary longitudinal section of the Patented Apr. 26, 1960 severing apparatus, with the parts in the position they occupy during withdrawal of a portion of the well packer from the well casing;

Fig. 5 is a cross-section taken along the line 5-5 on Fig. 2.

As disclosed in the drawings, 'a well packer A has been anchored in packed-0E condition in a well casing B against longitudinal movement in both directions. Such well packer is to be removed from the well casing, so that the latter will have an unobstructed bore therewithin at the location of the packer. The removal of the well packer is assisted by a cutting or severing tool C, which can be lowered in the well casing on a runningin string D, such as a string of tubing extending to the top of the hole, to be placed in appropriate relation to the well packer to sever a major portion of the latter and permit its Withdrawal from the well bore.

The well packer A is of a known type, including a main body 10 having a set of lower slips 11held in anchoring engagement with the well casing by a lower expander 12, to prevent downward movement of the well packer in the casing. An upper set of segmental slips 13 engages the well casing B, being held and an chored thereagainst by an upper expander 14 disposed around the main body of the packer. Between the two expanders is a rubber packing sleeve 15, which is sealed oil against the wall of the well casing as well as the exterior of the body.

The packer disclosed is described in US. Patent No. 2,703,623, and is set through the agency of an outer sleeve or cylinder 16 slidable downwardly along the body head 17, the cylinder head 18 engaging the upper end of the upper slips 13. The cylinder head 18 may have a split ratchet ring 19 therein engaging ratchet teeth 20 on the periphery of the body 10 of the tool, to permit relative upward movement of the body within the sleeve 16, 'but precluding relative downward movement between these parts.

The body head 17 is constituted as a threaded box 21 having a left-hand internal thread. Such threaded box is availed of in the present instance to anchor the severing or rupturing tool C to the body, to appropriately locate the cutting portions of the tool within the well packer, as described hereinbelow.

The severing or rupturing tool includes a plunger or mandrel 22 having a lower guide portion 23 and a downwardly tapering wedge or cam 24. Surrounding the mandrel is a severing sleeve 25 having an upper flange portion 26 received within an internal groove 27 in a supporting sleeve 28 threadedly secured within a sub 29, which is, in turn, threadedly attached to the lower head portion 30 of a power cylinder 31 forming part of the actuating mechanism for shifting the plunger 22 in a downward direction. The lower portion of the severing sleeve 25 is constituted as a plurality of depending inherently contractible spring-like legs 32 which extend along the cam surface 24 of the mandrel and terminate in outwardly directedchisels or teeth 33 having relatively sharp outer edges 34. The edges 34 of the teeth lie in substantially the same plane normal to the aixs of the mandrel 22, so that the forcing of the chisels outwardly against the inner wall of the packer body 10 tends to rupture or break the same. Such outward forcing occurs when the plunger or mandrel 22 is shifted downwardly with respect to the chisel elements 33, as hereinafter described, causing the wedge 24 to expand the chisels into the wall of the packer body.

The supporting sleeve 28 is adapted to be latched into the threaded box portion 21 of the body 10, and, when so latched into the body, the chisel elements 33 will be located within the body at its lower portion, and immediately above the lower guide part 10a of the body,

which engages the lower set of segmental slips 11. The latch device includes a latch sleeve 35 encompassing the supporting sleeve 28, the upper end of the latch sleeve being received within an annular recess 36 defined between a depending skirt 37 of the sub 29 and the periphery of the supporting sleeve. Circumferentially spaced spring-like legs 38 depend from the upper portion of the latch sleeve 35, these legs together having an external left-hand thread 39 formed thereon which are companion to and adapted to mesh with the internal thread 21 in the body box. The lower sides 39a of the threads 39 are tapered in a downward and inward direction, to permit the legs 38 to ratchet in a downward direction past the internal threads 21, inward springing of the legs being permitted by affording relief 40 in the supporting sleeve 28 behind the legs 38. However, once the legs have ratcheted into position within the threaded box 21, a slight upward movement of the sub 29 and the'sleeve 28 will shift a tapered or frusto-conical retainer surface 41 on the supporting sleeve behind lower companion tapered surfaces 42 on the threaded legs, to urge and hold the latter outwardly into full threaded engagement with the internal threads 21 of the packer body 10.

' As stated above, the sub 29 is threadedly attached to the lower head 30 of a power cylinder 31. This head is threadedly secured within a cylinder sleeve 43, which is, in turn, threadedly attached to an upper head 44 having a pressure chamber 45 therewithin. Slidably mounted within the cylinder 31 is a piston 46 attached to a piston rod 47 slidable through the lower head 30, the lower end of the rod 47 resting upon and engaging the upper end 48 of the actuating mandrel 22 of the severing tool.

The upper end of the mandrel 22 has a retainer ring 49 fixed thereon having a lower downward and inwardly tapering surface 50 engaging a companion surface 51 on the upper end of a split snap ring 52 which tends to.

contract inherently, to remain under the tapered surface or shoulder 50 of the retainer ring. This snap ring 52 rests upon the upper end of the sub 29 and tends to prevent downward movement of the plunger or mandrel 22 with respect to the supporting sleeve 28 and the severing sleeve 25 depending therefrom. However, when suflicient downward force is imposed on the plunger 22, the tapered surface 50 of the retainer ring 49 will cam the snap ring 52 outwardly, the retainer ring 49 then sliding within the snap ring free from substantial restraint from the latter, to permit downward movement of the plunger 22 with respect to the severing sleeve 25 and its chisel elements 33.

A fluid or gas under pressure is developed within the pressure chamber 45 of the cylinder, such gas under pressure acting downwardly on the piston 46, urging it and the piston rod 47 downwardly within the cylinder, the downward force being transmitted to the plunger or mandrel 22. The cylinder 31 is maintained in a fluidtight condition by seal rings 53 on the piston engaging the cylinder wall, by rod seal rings 54 on the lower head 30 engaging the rod 47, and by thread seal rings 55 on both heads 30, 44 engaging the cylinder sleeve 43.

In the present instance, the gas under pressure is developed in the cylinder as a result of the relatively slow combustion of a power charge possessing its own source of oxygen and contained within a suitable tube or holder 56 resting upon the piston 46 and disposed in the pressure chamber 45. This power charge may be of the type specifically disclosed in United States Patent No. 2,640,- 547, to which attention is directed. The power charge itself is ignited by firing a cartridge 57 disposed within a gun barrel 58 secured in the upper end of the upper head 44, the cartridge being clamped between the upper iend of the gun barrel 58 and a cap 59 threaded on the atter.

The cartridge 57 is fired when struck by the lower end 60 of a firing pin 61 slidably mounted within a latch body 62, the lower end of which is threadedly secured to the upper cylinder head 44 and the upper end of which is secured to a tubular trip; body 63, the latter being threadedly attached tothe tubular string D extending to the top of the hole. The pin 61 is urged in a downward direction by a helical compression spring 64 encircling the upper portion of the firing pin and engaging a spring seat 65 in the latch body 62, the lower end of the spring engaging the firing pin flange 66. The spring 64 is prevented from propelling the firing pin 61 downwardly into engagement with the cartridge 57, to fire the latter, by a pair of latches 67 disposed within a slot 68 extending through the latch body and pivotally mounted on fulcrum pins 69 secured to the latch body 62 and extending across its slot. The latches 67 have upwardly extending arms 70 from which fingers 71 project inwardly for engagement under the firing pin flange 66, the arms being urged toward each other by a tension spring 72 interconnecting their upper ends. The fingers 71 are removable from the firing pin flange 66 by shifting the depending leg portions 73 of the latch elements in an inward direction, which will swing the arms 70 and the fingers 71 outwardly, until the latter are disengaged from the flange 66, which then permits the spring 64 to propel the firing pin 61 downwardly against the cartn'dge'57 to fire the latter.

As disclosed in the drawings, the latches 67 are released hydraulically from the firing pin 61 by a trip sleeve 75 that is slidably mounted on the exterior of the trip body 63. This sleeve is initially held in an upward position on the trip body by one or more shear screws 76 threaded into the sleeve and extending into a groove 77 in the body. When in this position, the lower end 78 0f the trip sleeve 75 is disposed immediately above the latch legs 73, the upper end 79 of the sleeve engaging a downwardly facing shoulder 80 on the trip body. The upper portion 81 of the trip body below the shoulder 80 has a larger external diameter than the lower portion 82 of the trip body, and the internal diameter of the upper portion 83 of the trip sleeve is correspondingly greater than the intermediate portion 84 of the trip sleeve, to conform thereto. In efiect, the difference in diameters between the upper and intermediate portions 83, 84 of the trip sleeve forms a shoulder or head 85 adapted to be acted upon by fluid under pressure within the trip body 63, and passing through the body ports 86 into a cylinder space 87 between the body 63 and the sleeve 75. This fluid under pressure acts in a downward direction on the head 85 to urge the sleeve 75 in a downward direction.

Leakage of fluid in a downward direction between the sleeve 75 and trip body 63 is prevented by a suitable side seal ring 88, such as a rubber O ring, disposed in an internal groove 89 in the intermediate portion 84 of the sleeve and slidably and sealingly engaging the periphery of the trip body. Similarly, fluid is prevented from leaking in an upward direction out of the cylinder space 87 between the sleeve and the trip body by an annular seal ring 90, such as the rubber 0 ring, disposed in an internal groove 91 in the upper portion of the sleeve and slidably and sealingly engaging the periphery of the trip body.

When the sleeve 75 is to be shifted downwardly to release the latches 67 from the firing pin 61, a suitable tripping element 92, such as a trip ball, is allowed to move downwardly into engagement with a companion seat 93 in the tubular trip body 63 below the ports 86, to prevent downward passage of fluid through the trip body. Accordingly, the pressure of the fluid in the tubular string D and the trip body 63 can be increased sufliciently to overcome the shear strength of the screws 76 by acting on the sleeve head 85, shearing of the screws allowing the sleeve to be shifted downwardly hydraulically until its lower end 77 engages the latch legs 73, shifting such latch legs inwardly and the arms 70 outwardly until the fingers 71 move out of engagement from the flange 66,

releasing the firing pin 61 and permitting it to strikethe cartridge 57 to ignite the same.

In the actual use of the apparatus, the well packer A is disposed in anchored and packed-off condition within the well casing B and the severing mechanism C, power mechanism attached thereto, firing mechanism, and trip mechanism are out of the well casing. The well packer then has a bore or passage 90 therein opening outwardly through the upper end of the body 10.

The severing apparatus C is then assembled, with the retainer ring 49 disposed above the split snap ring 52-, which assures the disposition of the wedge or cam 24 in its uppermost position with respect to the chisels 33 that surround it. The severing apparatus is then run in the Well casing B on the tubular string D until the location of the well packer A is reached, the plunger 22 and severing sleeve 25 moving into the body passage 90a, followed by the latch sleeve 35, the tapered thread surfaces 39 of which will engage the box threads 21 and cam the latch legs-38 inwardly so that they ratchet freely over the box threads, until the lower end 37 of the sub engages the upper end of the body head 17, which will preclude further downward movement of the severaing apparatus C with respect to the packer body 10. An upward pull taken on the tubular string D will then shift the supporting sleeve retainer surface 41 against the lower ends 42 of the latch legs 38, shifting and holding them outwardly into full threaded engagement with the box threads 21, and thereby coupling the sub 29 and the cylinder 31 to the packer body lit). With the parts in this position, the lower chisel teeth 33 are disposed within the body of the tool A at the lower end of the latter, and immediately above the body guide 10a, as disclosed'in Fig. 1.

The trip ball 9a is dropped down through the tubing string D, if it has not been previously placed within the trip body 63, and will gravitate through the fluid in the latter into engagement with its companion seat 93, which will prevent downward passage of fluid through the tubul-ar trip body. The fluid pressure can now be built up in the tubular string D and the trip body 63, this fluid under pressure passing through the body ports 86 into the cylinder space 87, and acting in a downward direction on the sleeve head 85. When the pressure reaches a sufficient value to overcome the strength of the shear screws '76, the latter are disrupted and the sleeve 75 moved downwardly hydraulically into engagement with the inclined latch legs 73, shifting the latter inwardly and the arms 70 outwardly to remove the fingers 71 from holding engagement under the firing pin flange 66. t

The spring 64 can now expand and propel the firing pin 61 downwardly, striking it against the cartridge 57 and firing the latter. The flame emanating from the cartridge ignites the upper end of the power charge 55, causing the combustion of the latter and producing a gas under pressure within the pressure chamber 45 and the cylinder 31. This gas under pressure is acting downwardly on a piston 45 and the rod- 47, which bears against the upper end of the mandrel 22. At first the pressure is of an insuflicient value to overcome the force of the holding ring 52, which is engaging the retainer ring 4-9 on the plunger 22. However, when suflicient pressure develops in the pressure chamber 45, as a result of the continuing combustion of the power charge 56, the split snap ring 52 is expanded, which will allow the retainer ring 4% to slide there-through, the piston 46 and the piston rod 47 then forcing the plunger 22 downwardly along the sub 29, supporting sleeve 28 and the severing sleeve 2'5. The wedge or cam 24 is then shifted downwardly along the chisel elements 33, forcing them outwardly against the body 10. As the pressure in the cylinder 31 continues to increase, the chisel elements 33 press more strongly against the body 10. Eventually the pressure will have reached a value as to overcome the strength of the body 10, causing the chisel elements to rupture the latter. The

body will break, inasmuch as it is usually made of cast iron or the like, the body being completely severedto a further extent, limited by engagement of the retainer ring 4-9 with an inwardly directed stop shoulder 100 provided on the supporting sleeve 28 immediately above the upper end of the severing sleeve 25. When the retainer ring 49 engages the sleeve shoulder 104), the chisel elements 33 are then disposed opposite a circumferential recess Till on the mandrel above its cam or wedge portion 24, which will allow the chisel elements to retract, so that their edges 34 do not extend outwardly beyond the inner wall of the body 10. The tubular string D, and the apparatus depending therefrom, can now be elevated and such elevating action will carry the body 10 and the cylinder sleeve 16 surrounding it in an upward direction, permitting them to be withdrawn completely from the well casing B, and allowing only the lowermost portion of the body 10, its guide portion 10a, the slips ll, 13, expanders 12, 14 and packing 15 to remain in the well casing. These parts can easily be removed from their anchoring location, as by subsequently lowering another tool in the well casing and striking it against the parts to drive them to the bottom of the well bore, Where they are out of the way of properly producing the well.

Instead of merely driving the parts remaining in the well casing to the bottom of the hole, they may be removed by a drilling bit very readily, inasmuch as a substantial quantity of the metallic portion of the well packer, namely, its body and cylinder sleeve, has been removed by the parting or severing apparatus C.

If, for some reason, the body It) cannot be removed following the severing action, since the body portion It! may be immovably stuck in the well casing, the severing apparatus C can be disconnected from the body and withdrawn from the hole. Such disconnection can occur by rotating the tubular string D to the right, which will correspondingly rotate the trip body 63, latch body 62, cylinder 31, sub 29 and supporting sleeve 28 to the right. The supporting sleeve 25 has a plurality of keys 195' secured thereto extending within the slots 106 between the threaded latch legs 38, so that the right-hand rotation is transferred to the latter. In view of the fact that the legs 38 have a left-hand threaded connection with the body ltd, their right-hand rotation will enable them to be unscrewed from the packer body. chisel elements 33 do not interfere with the upward unscrewing and disconnection of the apparatus from the body 10, since they are disposed opposite the recessed portion 1M of the plunger 22., and have retracted inherently to an effective diameter that is less than the internal diameter of the packer body 10.

The severing apparatus C can now be withdrawn from the well casing B. It will then become necessary to employ other means, such as a rotary drill bit, to remove the Well packer A from the well casing. However, in the usual case, the body 1%) and cylinder sleeve 16 will I body it? of apacker.

body at its lower portion by the chisel members 33.

it is, accordingly, apparent that a severing or cutting apparatus has been provided which is effective in cutting through a relatively heavy tubular member, such as the A very great severing force is available, inasmuch as a very high pressure can be developed in the cylinder 31, which, for example, may be 7,500 to 10,000 p.s.i. This pressure acts over a rather large piston area and the total force on the piston is further multiplied by the relatively steep taper of the cam 24, which aifords a very considerable mechanical advantage acting on the chisels 33. The sharp edges 34 of the latter, penetrating into the body, afford a further increase in the force available for rupturing or severing the body of the well packer. feet the cutting action and the removal of the body 10,

The a The time required to efas well as the cylinder sleeve 16, is very much less than the time that would be required to disintegrate these parts under the action of a drillingbit, as has heretofore been done. Although the entire packer apparatus is not withdrawn from the well casing through use of the severing apparatus, a considerable part is still withdrawn, allowing the remainder of the apparatus to be removed from the anchoring location of the packer in the well casing, either by subsequently driving it to the bottom of the well casing, or by disintegrating it under the action of a rotary drill bit, or the like.

The invention claims:

1. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; cutter elements carried by said member; wedge means adjacent said cutter. elements in a position in which said cutter elements are retracted, said wedge means being adapted to force said elements against the device with a force sufiicient to sever the same; means on said supporting member adaptedto secure said supporting member to the device to elevate the device and to positively locate said elements in a predetermined position adjacent the device; and means for moving said wedge means longitudinally along and against said cutter elements to force said elements against the device and sever the same.

2. In the apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said member adapted to secure said member to the device whereby said member can elevate the device following severing of the device; cutter elements carried by said member; wedge means adjacent said cutter elements in a position in which said cutter elements are retracted, said wedge means being adapted to force said elements against the device with a force sufiicient to sever the same; and means for moving said wedge means longitudinally of said supporting member and cutter elements to force said elements against the device and sever the same.

3. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said member adapted to secure said member to the device to prevent upward movement of said member; cutter elements carried by said member; wedge means adjacent said cutter elements in a position in which said cutter elements are retracted; and means for moving said wedge means downwardly along said supporting member and cutter elements to force said elements against the device and sever the same.

4. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; cutter elements carried by said member; wedge means adjacent said cutter elements; cylinder and piston means connected to said supporting member and operatively connected to said wedge means; and means for generating a gas underpressure in said cylinder and piston means to move said wedge means longitudinally along said cutter elements to force said elements against the device and sever the same.

5. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said member adapted to secure said member to the device to prevent upward movement of said member; cutter elements carried by said member; wedge means adjacent said cutter elements; cylinder and piston means connected to said supporting member and operatively connected to said wedge means; and means for generating a gas under pressure in said cylinder and piston means to move said wedge means downwardly along said cutter elements to force said elements against the device and sever the same.

6. In apparatus for severing a tubular member disposed in a Well bore: a supporting member adapted to be lowered in the well bore; latch means on said supporting member adapted to secure said supporting means to the tubular member, whereby said supporting member can elevate the tubular member following severing of said tubular, member; cutter elements carried by said supporting member and adapted to move longitudinally within the tubular member; wedge means disposed be hind said cutter elements in a position in which said cutter elements are retracted and adapted to be located in the tubular member; and means for moving said wedge means longitudinally of said supporting member and (utter elements to force said elements outwardly against the tubular member and sever the same.

7. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said member adapted to secure said member to the device to prevent upward movement of said member; cutter elements carried by said member; wedge means adjacent said cutter elements; cylinder means connected to said supporting member; piston means slidable in said cylinder means and operatively connected to said wedge means; and means for generating a gas under pressure in said cylinder means to move said piston means downwardly in said cylinder means to correspondingly shift said wedge means downwardly along said cutter elements to force said elements against the device and sever the same.

8. In apparatus for severing a tubular member disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said supporting member adapted to secure said supporting member to the tubular member against upward movement; cutter elements carried by said supporting member and adapted to move downwardly within the tubular member; Wedge means disposed behind said cutter elements and adapted to be located within the tubular member; cylinder means secured to said supporting member; piston means slidable in said cylinder means and operatively connected to said wedge means; and means for generating a gas under pressure in said cylinder means to move said piston means downwardly and said wedge means downwardly along said cutter elements to force said cutter elements outwardly against the tubular member and sever the same.

9. In apparatus for severing a device disposed in a a Well here: a supporting member adapted to be lowered in the well bore; cutter elements carried by said member; wedge means adjacent said cutter elements for forcing said elements against the device with a force sulficient to sever the same; means releasably connecting said wedge means to said supporting member to prevent longitudinal movement of said wedge means against said cutter means; and means acting upon said wedge means to release said releasable means and move said wedge means longitudinally along and against said cutter elements to force said elements against the device and sever the same.

10. In apparatus for severing a tubular member disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said supporting member adapted to secure said supporting member to the tubular member against upward movement; cutter elements carried by said supporting member and adapted to move downwardly within the tubular member; wedge means disposed behind said cutter elements and adapted to be located within the tubular member; means releasably connecting said wedge means to said supporting member; cylinder means connected to said supporting member; piston means movable downwardly in said cylinder means and operatively connected to said wedge means; and means for generating gas under pressure to said cylinder means to move said piston means and wedge means downwardly to release said releasable means and shifit said wedge means downwardly along said cutter elements to force said cutter elements outwardly against the tubular member and sever the same.

11. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; inherently retractable cutter elements carried by said member; wedge means adjacent said cutter elements; and means for moving said wedge means longitudinally along and against said cutter elements to force said elements against the device and sever the same, said wedge means having a recessed portion into which said elements can withdraw inherently from engagement with the device after the device has been severed.

12. In apparatus for severing a device disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said member adapted to secure said member to the device to prevent upward movement of said member; cutter elements carried by said member; wedge means adjacent said cutter elements in a position in which said cutter elements are retracted; cylinder means connected to said supporting member; piston means slidable in said cylinder means and operatively connected to said wedge means; and means for generating a gas under pressure in said cylinder means to move said piston means downwardly in said cylinder means to correspondingly shift said wedge means downwardly along said cutter elements to force said elements against the device and sever the same, said wedge means having a recessed portion into which said elements can be withdrawn from engagement with the device after the device has been severed.

13. In apparatus for severing a tubular member disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said supporting member adapted to secure said supporting member to the tubular member against upward movement; cutter elements carried by said supporting member and adapted to move downwardly within the tubular member; wedge means disposed behind said cutter elements and adapted to be located within the tubular member; means releasably connecting said wedge means to said supporting member; cylinder means connected to said supporting member; piston means movable downwardly in said cylinder means and operatively connected to said wedge means; and means for generating gas under pressure in said cylinder means to move said piston means and wedge means downwardly to release said releasable means and shift said wedge means downwardly along said cutter elements to force said cutter elements outwardly against the tubular member and sever the same, said wedge means having a recessedportion into which said elements can retract from engagement with the tubular member after the tubular member has been severed.

14. In apparatus for severing a device disposed in a well bore and adapted to be lowered in the well bore on a tubular string; a supporting member adapted to be lowered in the well bore; cutter elements carried by said member; wedge means adjacent said cutter elements; cylinder and piston means connected to said supporting member and operatively connected to said wedge means; means for generating a gas under pressure in said cylinder and piston means to move said wedge means longitudinally along said cutter elements to force said elements against the device and sever the same; and means for initiating generation of said gas, comprising tubular means connectible to the tubular string, and hydraulically operable means slidable along said tubular means by fluid pressure in said tubular means and tubular string. 7

15. In apparatus for operating a device in a well bore: cylinder and piston means adapted to be operatively connected to the device; a combustible charge in said cylinder and piston means adapted to generate a gas under pressure; igniter means for initiating combustion of said charge; tubular means connectible to a tubular runningin string and secured to said cylinder and piston means; hydraulically operable means movable along said tubu- 10 lar means; and means for feeding fiuid under pressure from within said tubular means and the running-in string to said hydraulically operable means to move said hydraulically operable means along said tubular means to actuate said igniter means.

16. In apparatus for severing a hollow device disposed in a well core, said device having a threaded box: a supporting member adapted to be lowered in the well bore; cutter elements carried by said member in a position in which said cutter elements are retracted; means on said supporting member adapted to enter and be secured to the threaded box to locate said elements in a predetermined position adjacent the device; means engageable with said elements to force said elements against the device and sever the same; and means for moving said means engageable with said elements against said elements to force said elements against the device and sever the same.

17. In apparatus for severing a hollow device disposed in a well bore, said device having a threaded box: a supporting member adapted to be lowered in the well bore; cutter elements carried by said member in a position in which said cutter elements are retracted; means on said supporting member adapted to enter and be secured to the threaded box to locate said elements in a predetermined position adjacent the device; wedge means engageable with said cutter elements to force said elements against the device. to sever the same; and means for moving said wedge means longitudinally along and against said cutter elements to force said elements against the device and sever the same.

18. In apparatus for severing a hollow device disposed in a well bore: a supporting member adapted to be lowered in the well bore; latch means on said member adapted to secure said member to the device to prevent upward movement of said member; cutter elements carried by said member; wedge means adjacent said cutter elements in a position in which said cutter elements are retracted; cylinder means connected to said supporting member; piston means slidable in said cylinder means and operatively connected to said wedge means; and means providing a fluid under pressure in said cylinder means to move said piston means downwardly in said cylinder means to correspondingly shift said wedge means downwardly along said cutter elements to force said elements against the device and sever the same.

19. In apparatus for severing a hollow device disposed in a well bore, said device having a threaded box: a. supporting member adapted to be lowered in the well bore; cutter elements carried by said member; means on said supporting member adapted to enter and be secured to the threaded box to locate said elements in a predetermined position adjacent the device and to prevent upward movement of said supporting member relative to the device; Wedge means adjacent said cutter elements in a position in which said cutter elements are retracted; cylinder means connected to said supporting member; piston means slidable in said cylinder means and operatively connected to said wedge means; and means providing a fluid under pressure in said cylinder means to move said piston means downwardly in said cylinder means to correspondingly shift said wedge means downwardly along said cutter elements to force said elements against the device and sever the same.

References Cited in the file of this patent UNITED STATES PATENTS 598,805 Munn Feb. 8, 1898 2,116,465 Patterson May 3, 1938 2,243,099 Johnson May 27, 1941 2,481,637 Yancey Sept. 13, 1949 2,640,547 Baker et al. June 2, 1953 2,671,510 Slick et al. Mar. 9, 1954 2,751,019 Baker June 19, 1956

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