US2684030A

US2684030A - Apparatus for slotting and cutting pipe

Info

Publication number: US2684030A
Application number: US129252A
Authority: US
Inventors: Muskat Morris; Floyd W Parker; William L Kehl
Original assignee: Gulf Research and Development Co
Current assignee: Gulf Research and Development Co
Priority date: 1945-09-11
Filing date: 1949-11-25
Publication date: 1954-07-20
Anticipated expiration: 1971-07-20

Description

y 9 M. MUSKAT ET AL 2,684,030

APPARATUS FOR SLOTTING AND CUTTING PIPE Original Filed Sept. 11, 1945 INVENTORS MORRIS MUSKTYI FLOYD w. PARK/RR lLLIfiM L- KEHL MATTORNEY Patented July 20, 1954 APPARATUS-EOR SLOTTING AND'T-CUT-TING PIPE Morris Muskat, .Oakmont, Pa, Floyd W. .Parker, Harrogate,,,.Tenn.,.and William L. Kehl, Penn Township, Allegheny County, Pa;, assignorsto- Gulf Research &- Development -Gompany,- Pittsburgh, Pa., a corporation of Delaware Original application:- September: 11, 1945, Serialv No..615,568... Divided amllthis applicationcNovember 25, 1949; Serial No. 129,252

4 Claims:- 1?

This-invention concerns atnew-and useful appara-tus for cutting pipe; Which-apparatus is particularlyadvantageous for use in limited confines such-as Well bores. Inparticularitconcerns'ap: paratusfor employing specially shaped and spee V cially disposed explosive charges .for cutting well casing.

This application a division'oi ourcopending application Ser; No. 615,568, filed September 11,

entitled Apparatus, for Perforating and resultant effect of shaping the, high explosive.

charge so that its end provides a concave surface facing theobject to be penetrated, and in which, moreover; this concave surface'is linedwith an inert-material such as a metal, ceramic or plastic.

Such shaped and lined charges. are very eifective increating holes in solid .objects including steel;

rock, cement; etc. The holes created areoi considerable depth and diameter, although these may bevaried over an appreciable range by varying the calibre of the explosive charge, its dis-v tribution and composition, the geometry of the. concave shaped'surface, the materialand thick-v ness of the liner, and the standmftdistance be-V- tween the forward end ofthe. charge. and the target. We have utilized this eifect in the ap paratus of this invention useful for pipe-cutting operations in boreholes.

This invention is useful in cutting off well case ing. if it is'desired to recover such casings aboveacemented portion. Heretofore expensive mechanical devices have been inserted into the Well on'a rotatable drill stem to out the casing around its, circumference. Ino-ld wells, having no. drill ing equipment available, it has been common to use explosives to break off the casing. Shootingj' the casing by meanspf ordinary explosives often results in spreadingof the broken end so that it is sometimes :diflicult or impossible to pull thepipe out of the hole. By theuser-offourxinvention employing properly-shaped explosive charges; a clean circumferential cut is easily and quickly made. Itmay likewise be used for cut ting olf collars. between-strings of casings. The apparatus is also applicable to cutting off drill pipewhich has become stuck. t may further be used for-cutting off any pipe; whether in the groundor above the ground,- when conditions permit access only-to their-aside thereof I It: iseccording-ly an object of this -invention 'to provide an improved apparatus: for cutting: thecasing ofaborehole:

Another-obj ect ofthis invention is t0"13I-.OVldel apparatus for cuttingthe casing-of a borehole by.

' the useof a shaped high explosive-charge.

Another object of thisinventionis. to provide apparatus-Which achieves a highly efiicient cuteting action through steel "or metal pipe.

Anothero-bj set of this invention I is to 1 provide amps-cutting means employing the-cuttin effect? of an explosive jet;

It is'also an object of thisinvention to provide a method of cutting well casing WhlCll-iS sub-'- stantiallyfree from the disadvantage of forming burrs onthe inside of-the casing around'the cut orslotma-de therein.

A still further object of this invention is to" provideapparatus for severi-ng pipe -by the use =-of aspecially-shaped high explosive charge Anotherobject of this invention-is to provide a means for severing pipe employing the cuttingefiectofan explosive jet.

These and-otheruseful objects may be accom plished b ytheapparatus of our invention clescrib'edin this specification, of which'the accompanyingydrawings form a part; and inwhi-ch:

Figure 1' shows atop-plan'view, partly 'in section ofa form-ofthe explosive-cartridge useful forsevering pipe or casing;

Figure 2 shows-aside view of the form of explosive-cartrldge of Figure 1 Figure '3 shows a longitudinal section of an ap paratus for cutting pipe by-means of-ashaped explosive charge; and

Figure shows a section of'the apparatus-taken along line AA'of Figure 3.

In'the apparatus of our invent-ionthe explosive is placed a certain distance from the target, namely, the wall of the pipe; Theeifect of the explosive is to createa cut or slot in the target by virtue of a specially shapedand lined cavity in the surface of the explosive facing" the target. The target is notshattered; Virtually the whole penetrating power of I the explosiveused arises from-theeiiect of the cavity plusliner formed in the surface-of the explosive facing the material to be out; This fact is-apparently closely related to what-has been previouslyknown'in the explosive artasthe' Munroe efi'ect. While there are theories for this-effect; it basically represents purely an empirical discovery. The theory sug gests the-possibility'that anexplosive'jet of very high velocity-is 'formed opposite the-cavity; and this j et "has a strong penetrating or cutting effect: The nature'oithe'jet-maybecontrolled and its eihciency augmented by placing inert non-explosive material in the cavity as a liner.

The dimensions of the cut produced by a shaped explosive charge depend on the shape and the dimensions of the cavity; the kind, amount and distribution of high explosive in the charge; the nature of the confinement of the charge; the material, dimensions, and physical properties of the cavity liner; the distance between the base of the cavity and the surface of the target material; and the nature of the target material. By making proper selections of the above variables, the jet effect can be made to penetrate large distances into the target material.

The jet may be controlled by suitably varying other important parameters of the cavity liner, such as the included angle, liner material, liner weight, and stand-off from the target. It is true that an unlined cavity will give approximately the same target hole volume as the lined cavity, but the depth of the penetration is very much greater with the lined charge. The reason for this appears to be that the high explosive forms, from the liner material, a fine spray or jet which :has very high penetrating power. The material of the cavity liner may be metallic, for example, steel, aluminum, brass, lead, copper; or it may be ceramic; or glass; or of plastic composition. The cavity need not of necessity have a straightsided cross-section, but may be circular, parabolic, or may have other equivalent shapes.

Material of appreciable density within the cavity greatly diminishes the penetrating action of the charge merely because it prevents formation of the jet. When any dense material is some distance from the base of the cavity it is equivalent to a corresponding amount of the target in the path of the penetrating jet. In either case the residual penetration is greatly reduced. Therefore, material of appreciable density, for example water, must be excluded from the cavity, since the presence of such matter within the cavity greatly diminishes the penetrating action of the cavity charge. Thus, for work in liquids, the base of the cavity is provided with a suitable cover to prevent any liquid entering the cavity. The nature of the material surrounding the charge also influences the hole-formation performance considerably. An otherwise unconfined charge in a well would effectively be confined by Y any fluid present in the well. Thus, if unconfined shots are to be made in a fluid-filled well, the charges may be placed in a suitably-designed container which prevents the fiuid from surrounding the charges.

The high explosive may be of any type such as pentolite, tetryl, TNT, etc, and may be augmented by any suitable chosen booster explosive. For example, tetryl could be used as a booster for pentolite, since the former is more sensitive to shock than the latter. The choice of high explosive material must be governed by the conditions under which it is to be used as is generally the case in any explosive application.

The apparatus encompassed by this invention makes use of linear wedge-shaped lined cavities to make linear cuts in the casing. In particular, to cut the casing around its circumference so as to permit pulling of the upper section, this apparatus uses a wedge-shaped lined cavity encircling a cylindrical stem of high explosive which may be solid or filled with a central inert core. On detonation of the high explosive along its inner boundary a uniform cut will be produced in the casing opposite the lined cavity. The

4. .wedge angle, the nature of the liner, and standoif of the cavity from the casing wall are chosen to fit the particular condition of the application.

Figures 1 and 2 show a lined cavity charge in which the cavity 50 ext-ends circumferentially around the explosive charge 5!. The cavity 50 is lined with lining material 52 and is closed by a cover 53. Detonation of the explosive is initiated at the center point 54 where there may be a small axial hole for inserting the fuse. Such a shaped charge may be employed in an apparatus for cutting casing, such as shown in Figures 3 and 4.

Figure 3 shows a longitudinal sectional view of a casing cutter in a well bore and Figure 4 is a transverse sectional view taken on the line A-A of Figure 3. A ring-shaped explosive charge 30! containing a peripheral trough or cavity 302 is lined by a liner 303. Well fluids are prevented from entering the cavity 302 by the cylindrical cover 304 which forms pressure-tight seals with upper plate 305 and lower plate 305 by means of .

gaskets

301 and 308. An axially-located metal .piece 309 also makes pressure-tight seals with

plates

305 and 306 by means of gaskets 310 and 3! I. The section of the piece 300 lying between

plates

305 and 306 is enlarged and serves to prevent the collapse of these plates when the cutter is subjected to high external pressure. The piece 309 is attached to the lower plate 306 by means of the threads 3l2. The lock ring 3&3 serves to secure the top 305 on piece 309. A plurality of radial holes 3| 4 in the piece 300 communicate between the charge 301 and an axial hole 3l5. The radial holes 314 and the portion of the hole 315 near the radial holes 3| 4 are filled with explosive. An end plug 3H5 is attached to the lower end of piece 309 by means of the threads 3| 1, and forms a pressure-tight seal with piece 309 by virtue of gasket 3|8. An electrically-actuated .detonator 310 is in contact with the explosive contained in the hole 3l5. The lead wires 320 pass through the hole 315 to the fuze-chamber .32! which is attached to piece 309 by means of threads 322 and forms a pressure-tight seal with piece 309 by virtue of gasket 323. A cable 32 attached to the chamber 32I is the means of 2i5sing and lowering the cutter within the casing The assembly of the casing cutter is accomplished in the following way: The plug 316 is threaded into piece 309 and the latter into bottom plate 300. The explosive within piece 309 may be introduced at this time or previously. The ring-shaped charge 30L together with the liner 303, is then placed in position around the enlarged portion of piece 309 as is the cylinder 304. The top plate 305 and the lock-ring 3E3 are then placed in position and secured. The electric detonator 3l9 is then inserted into the bore 3l5 so as to be in contact with the explosive, and the leads 320 are connected to the fuzechamber 32I after which the latter is threaded onto the upper end of piece 300.

The fuze-chamber 3 may contain mechanisms which arm and disarm the device under appropriate conditions, and a mechanism for locating the ends of easing segments if it is desired to cut away the casing at any fixed distance relative to a collar.

The operation of the device is as follows: When the cutter has been lowered to the proper position in a well and when all arming devices in the fuze-chamber have functioned, an operator on the surface sends an electrical impulse to the detonator 3I9 by means of the cable 324 and a battery or other source of voltage at the surface. The detonation wave initiated on the axis by the detonator is propagated through the channels 3| 4 to the charge 31' which, on detonation, severs the casing 325 along the plane AA.

The explosive may be any suitable high-explosive such as 50-50 pentolite, and may be formed in any convenient manner such as casting or pressing. The annular region bounded by the cylinder 394, the liner 303 and the

plates

305 and 306 must be kept free of any dense matter of any kind. The cutting ability of the device depends on the shape, thickness, and material of the liner 303, the stand-01f distance measured from the outermost position of the liner to the target, and the material of the target itself. We have discovered that the width of the charge 3!, i. e., the separation between

plates

305 and 306 should be approximately 1 to 3 times the combined thickness of the cylinder 304 and casing 325.

We have discovered that steel liners 303, Figure 3, having a cavity angle in the range of 80 to 140 and with thicknesses ranging from 0.02 to 0.04 charge width are most satisfactory. The corresponding stand-off range is preferably from 0 to 2 charge widths.

Liner 303, Figure 3, may alternatively be made of aluminum. In this case the desirable cavity angle is in the range of 70 to 140 with thickness ranging from 0.04 to 0.10 times the charge width. The stand-01f may range from 0.5 to 4.0 times the charge width for best results, the larger stand-offs being associated with the larger cavity angles.

We have shown the cutting charge liner to have a strictly angular cavity shape as drawn in Figures 1 to 4, but it may alternatively be parabolic, circular, or have other shapes. Furthermore, liners may be made of materials besides steel or aluminum, these being cited merely by way of example. The liner of the cutting charge cavity may be any of the inert materials previously mentioned.

What we claim is:

1. Apparatus for cutting pipe comprising an explosive charge in the shape of anannular ring having an outwardly-directed cavity, an explosion-confining annular lower plate in contact with the lower side of said ring, an explosionconfining annular upper plate in contact with the upper side of said ring, support means passing through the central openings of said ring and said plates supporting said plates in spaced relationship, said support means having an axial channel and a plurality of radial channels from said axial channel to the inner surface of said ring, an explosive in said axial channel and in said radial channels, and means for initiating detonation of said explosive in said axial channel.

2. Apparatus for cutting pipe comprising an explosive charge in the shape of an annular ring having an outwardly-directed cavity, an explosion-confining annular lower plate in contact with the lower side of said explosive ring, an explosion-confining annular upper plate in contact with the upper side of said explosive ring, support means passing through the central openings of said explosive ring and said plates supporting said plates in spaced relationship, detonating means in said support means, and an explosivefilled channel leading from said detonating means to the inner surface of said explosive ring.

3. Apparatus for cutting pipe comprising an explosive charge in the shape of an annular ring having an outwardly-directed cavity, an explosion-confining annular lower plate in contact with the lower side of said explosive ring, an explosion-confining annular upper plate in contact with the upper side of said explosive ring, support means passing through the central openings of said explosive ring and said plates supporting said plates in spaced relationship, a cover over the cavity of said explosive ring sealed against said upper and lower plates, detonating means in said support means and an explosive-filled channel leading from said detonating means to the inner surface of said explosive ring.

4. Apparatus for cutting pipe comprising an explosive charge in the shape of an annular ring having an outwardly-directed cavity, an explosion-confining annular lower plate in contact with the lower side of said explosive ring, an explosion-confining annular upper plate in contact with the upper side of said explosive ring, support means passing through the central openings of said explosive ring and said plates supporting said plates in spaced relationship, a liner contiguous to the cavity of said explosive ring, a cover over the cavity of said explosive ring sealed against said upper and lower plates, detonating means in said support means, and an explosivefilled channel leading from said detonating means to the inner surface of said explosive ring.

References Cited in the file of this patent- UNITED STATES PATENTS Number Name Date Re. 23,211 Mohaupt Mar. 21, 1950 2,399,211 Davis Apr. 30, 1946 2,415,814 Davis Feb. 18, 1947 OTHER REFERENCES An article by Sukharersky in a Russian publication, Voina i Tekhnika, volume 253 of 1926, pages 18-24 and 6 sheets of drawings. (Copy in Div. 70.) An unoficial translation of this article comprising 24 sheets of material drawings included is in Division 70.

A Scientific Approach to the Industrial Application of Shaped Charges, by Lawrence, in the Explosive Engineer, November-December, 1947, pages 171-183. (Copy in Div. 70.)