Device for cutting a pipe inside of a well

Sept. 4, 1956 _w. _G. sweetman 2,761,384

DEVICE FOR CUTTING A PIPE INSIDE OF A WELL

Filed Feb. 26, 195] 2 Sheets-Sheet 1

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, ^INVENTOR.

William q.pu/eetman

BY

ATTORNEY

Sept. 4, 1956 w. g. sweetman 2,761,384

DEVICE FOR CUTTING A PIPE INSIDE OF A WELT.

Filed Feb. 26, 1951 2 Sheets-Sheet 2

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BY

ATTORNEY

United States Patent Office

2,761,384

Patented Sept. 4, 1956

2,761,384

DEVICE FOR CUTTING A PIPE INSIDE OF A WELL

William G. Sweetman, Houston, Tex.

Application February 26,1951, Serial No. 212,788

Claims. (CI. 102—21.8)

This invention relates to a device for severing a pipe in a well, and particularly to a well pipe severing device employing a hollowed high explosive charge to produce a pipe-severing jet of gases.

In my co-pending application Serial No. 703,655, filed October 16, 1946, now Patent No. 2,587,243, and Serial No. 709,246, filed November 12, 1946, now Patent No. 2,587,244, I have described method and apparatus employing hollowed high explosive charges for cutting and perforating various objects, including pipes inside a well by means of circular explosive charges.

The present invention has for its principal objects the provision of an improved form of cutting tool or device which is especially useful for severing a pipe inside of a well; which is relatively simple in design and inexpensive to construct; which may be lowered and positioned inside a well pipe without difficulty in the presence of fluid in the well bore; and which is highly efficient in operation.

Another object is the provision of a pipe severing device including an annular casing enclosing an annular hollowed high explosive charge for generating the desired cutting jet.

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

In the drawing:

Fig. 1 is a longitudinal cross-sectional view of a com- _4gplete severing device in accordance with this invention;

Fig. 2 is an elevational view, partly in section, of the upper member of the casing which encloses the cutting charge;

Fig. 3 is a top plan view of the upper member illus- ₅₀trated in Fig. 2;

Fig. 4 is an elevational view, partly in section, of the lower member of the casing;

Fig. 5 is a top plan view of the lower member;

Fig. 6 is an elevational view, partly in section, of the 55 explosive cutting element of the device;

Fig. 7 is a top plan view, having a part thereof broken away, of the explosive cutting element;

Fig. 8 is a view showing the device in position in a pipe preparatory to severing the pipe;

Fig. 9 is an enlarged cross-sectional view of another embodiment of the liner element for the explosive cutting element; and

Fig. 10 is a view illustrating a modification of the carrier structure of the device.

Referring to the drawings, the cutting device comprises a casing, designated generally by the numeral 10, which may be constructed of any suitable metal, such as aluminum, steel, cast iron, or the like, or may be constructed of any suitable plastic, glass, or ceramic material, having suitable structural strength and rigidity to meet the conditions encountered in a well bore, par2 ticularly where fluid is present. Casing 10 is of generally annular or ring-like shape having an external diameter as near as possible to that of the pipe into which it is to be inserted while still permitting the device to descend 5 freely through the pipe, and having an internal diameter to provide an axial bore 11 of maximum dimensions commensurate with the amount of annular space required in the body of casing 10 to house the cutting elements of the device.

¹θ Casing 10 is composed of complementary annular upper and lower members 12 and 13, respectively, adapted to be joined along a plane extending transversely of the longitudinal axis of the casing. Upper member 12 is provided with an internal annular chamber 14, generally ® rectangular in cross-section, which opens to the lower end of member 12 and is defined at the sides by annular inner and outer walls 15 and 16, respectively. Outer wall 16 is provided with an internal annular recess 17 ₂θ located intermediate the upper and lower ends of chamber 14 and extending radially outwardly therefrom toward, but spaced from, the outer face of wall 16. Lower member 13 is generally complementary in shape and in external and internal diameters to those of the lower end ₂g of member 12 and is provided with an upwardly extending annular boss 18 of somewhat lesser width than members 12 and 13 but dimensioned to form a close sliding fit between walls 15 and 16, and having a height such as to extend only a short distance into the lower end of chamber 14 when the members of the casing are assembled, thereby forming a bottom wall for chamber 14. The reduced width of boss 18 provides flanges 19—19 on opposite sides of boss 18 which are adapted to abut against the lower ends of walls 15 and 16 when members 12 and 13 are joined. A passageway 20 extends longitudinally entirely through wall 15 and the contiguous flange 19, for purposes to be described hereinafter. Members 12 and 13 may be joined together in any suitable and known manner but are preferably united by means of one of the well-known commercial adhesive materials or cements, indicated at 21, adapted to form a strong bond between the members and to effectively seal the joint therebetween against intrusion of any extraneous fluid. As an example of such a material, adhesive sealing mixture No. 801, manufactured by Minnesota Mining &amp; Manufacturing Co. of Minneapolis, Minnesota, is very effective for this purpose.

A high-explosive charge 22 is annularly shaped and dimensioned to fit snugly in chamber 14 and is provided throughout its outer periphery with a hollow 23 of reentrant form, which, in cross-section, may be angular as shown, or may be arcuate or other similar shape. An annular liner element 24, conforming in shape to hollow 23, is fitted snugly within hollow 23 and is provided with spacer elements 25—25, which extend radially outwardly from the opposite sides of the outer end of liner element 24 parallel to the axis of the hollow and are adapted to abut against the inner face of wall 16 on opposite sides of recess 17 which thereby forms an extension of the holθθ lowed end of the charge. The spacer elements 25, together with the depth of recess 17 provide the appropriate stand-off distance for the charge to permit proper generation and convergence of the gases resulting from detonation of the charge to form a thin annular jet which performs the desired cutting action. Recess 17 forms a sealed space for the zone of convergence of the gases to protect development of the jet against interference by extraneous materials.

γθ A cylindrical pellet 26 or similar small body of a suitable booster explosive is embedded in the inner end of charge 22 at a point adjacent passageway 20. The end

2,761, 3 of pellet 26 will be disposed contiguous to the portion of the inner face of wall· 15 opposite passageway - 20. _:

Charge 22 and booster pellet 26 may be one of the numerous well-known high-brisance chemical materials such as pentaerythritol tetranitrate (“PETN”), trinitro- ' 5 toluene (“TNT”), “Pentolite” (50% “PETN” and 50% “TNT”),, “Tetryl,” “Amatol,” “Cyclonite,” and the, Eke, or mixtures thereof . The charge may be cast, - molded -: or otherwise suitably formed to provide the desired shape.

Liner element 24 is made of thin material, which may 10 be metal, such as copper, steel, aluminum, or the like,:: or may be made of thin plastic, glass, or ceramic material. The angle of: the liner hollow, and of the charge may be : : between about 30° and about: 90° depending upon the dimensions of the charge and the depth of penetration ¹⁵desired. The: thickness of . the liner will be such as will : . permit the liner to disintegrate completely upon detonation of the charge without the formation of a solid body or - ^;projectile. : These characteristics of the: charge and. liner and the principles of operation are all described in the aforementioned: applications Serial Nos. 703,655 and 709,246.

Liner element 24 may be made of uniform wall· thickness, if desired. However, Fig. 9. illustrates a modified form: of: liner ' element: in: which the wall thickness is reduced or tapered gradually from the outer end of the^; liner: element toward the apex thereof, as illustrated, in^; somewhat exaggerated form, the tapering walls of the_:liner element being'indicated by the numeral 24a. I have found that'by: tapering or reducing the wall thickness of the liner: element: toward its apex,: disintegration of: the liner' element' is made more complete with a resultant substantial increase in_: the: penetration efficiency of the resulting jet. . That is, greater penetration may be obtained with the same weight of explosive than can be obtained when employing a liner element of uniform wall thick-: iiess, or conversely the same degree of penetration may be obtained with a lesser weight of explosive. 4 ' ^ : As will be obvious, spacer elements 25 may be formed integrally with the body of liner element 24 or may be made as separate elements and interposed in chamber 14 between the inner face of wall 16 and the ends of liner element 24, during assembly of the device.

In order to detonate booster 26 and charge 22, a short length of a flexible cord-type detonating element 27, such as the well-known “Prima Cord,” is inserted through passageway 20 and extended therethrough. With this arrangement, upon detonation of the detonating cord, in a manner to be described hereinafter, the detonating shock will be transmitted through the thin metal wall provided between passageway 20 and the inner face of wall 15 into the end of peilet 26 which will be set-off thereby and will, in turn, set-off the main explosive charge 22.

To run the cutting device inside a well pipe, the device is suspended from a suitable carrier. In accordance with an embodiment of the present invention, the carrier comprises a generally cylindrical head 28, which may be constructed of metal to provide some degree of weight to the structure, and provided with an internally threaded socket 29 at its upper end from which an axial passageway 30 extends to the lower end of the head. A plurality of angularly spaced brackets 31, have their upper ends extending into slots 32 provided in the outer surface of head 28 and are attached to the head 28 by means of cap screws 33. The lower ends of brackets 31 are connected in any suitable manner to casing 10 in order to support the cutting device from the carrier. In the embodiment illustrated, upper member 12 is provided with a plurality of angularly spaced up-standing lugs 34. The lower end of each of tbe brackets 31 may then be connected to one of the lugs 34 by means of a bolt 35 which extends transversely through the end of the bracket and the lug. Head 28 may be provided with a plurality of flexible metallic fingers 36 which are angularly spaced about the head and extend upwardly and outwardly there384 ' ' ' ' ' from to engage a projection or groove in the pipe for suitably positioning: the cutting device inside the, pipe.

Head 28 is adapted to be connected to .a lowering cable _: 37 (Fig. 8) by means of a threaded connector 38 which is screwed into socket 29. An electrical conductor wire 39 is, threaded through cable 37; and connector 38 and is led through passageway 30 and into the upper end of a sleeve 40 where it is connected to an electrically fired blasting . cap 41,. of _: generally conventional, and wellknown form.,: The upper end of detonating cord 27 is : inserted into the lower end of sleeve 40 into end-abutting contact, with the lower end of blasting cap 41, The inserted ends of conductor 39. and detonating cord 27 are . taped or otherwise fastened to: hold them: in place in sleeve 40 and the latter may, in turn, be taped or other: wise fastened to one of the brackets 31 as shown iff'Figs, l and :8. , The, lower end of detonating cord 27 may be suitably sealed and : taped as at: 42 (Fig, 1), and: then swung up and tied in any convenient manner to casing Hi®: (Fig.,8). ,-, , Operation of the device is as, follows: The cutting device assembled in the manner shown in Figs. 1 and 8 ' is connected, to: lowering cable 37: and, lowered inside a well pipe ,43 which is to be isevered: thereby., : When the device has attained approximately the depth at which the cut is to be made, the device will; be pulled upward . sufficiently to allow, fingers 36 to lodge in the groove 44 formed by the joint between adjacent pipe sections nearest the point of the cut.: The fingers,: being of flexible construction, will· be compressed, sufficiently to pass the , pipe joints; as the device is lowered, but when the device , is raised, the fingers will expand sufficiently to enter the : groove between: the: pipe, ends and, lodge against the, end of the upper one of the pipe sections to thereby fix the 3° position of cutting device.. The: resulting resistance to : further upward movement will be transmitted through cable 37, to the, operator at the surface as an indication , that the cutting: device has become positioned at the desired point. , Thereupon, electric, current, supplied at 40 the surface from any conventional type of electrical initiator, will be transmitted through conductor 39 to cap 41 which will be fired thereby and will set-off in quick succession detonator cord 27, booster pellet 26 and the main explosive charge 22. ,The latter, by reason of its 45 hollowed construction and the liner form and arrangement, will produce a thin, high velocity, annular jet of gases which will cut annularly through the metal forming wall 16 and the adjacent portion of the wall of pipe 43, severing the latter cleanly throughout its circum50 ference. The carrier will normally not be damaged and may then be withdrawn from the pipe for re-use by attachment thereto of a new explosive cutting element.

It will be seen that the described construction provides a very compact and simple arrangement for the cutting 55 elements which may be very cheaply constructed. The compact annular construction permits the bore 11 to be made very large, so that the device may be lowered easily through a body of liquid or other fluid which is usually present in well pipes. Also, by means of the 00 described construction the hollowed end of the charge may be disposed very close to the inner wall of the pipe so that the maximum penetrating efficiency of the charge may he utilized. Moreover, the cutting elements may be made for use in various sized pipes, including particu05 larly very large diameter pipes and the same carrier may be used for various sized cutting element.

Fig. 10 illustrates a modification of the carrier structure by which the cutting device may be more effectively centered during the operation of lowering it through pipe 70 43, particularly to reduce any tendency of casing 10 to tilt or swing sideways as it passes downwardly through liquid which may be present in the pipe, which might otherwise tend to cause casing 10 to bind or stick on the walls of the pipe.

In this modification, one or more elongated tubular

2,761,384 metal bars or rods 45 are interposed at a suitable point in the lowering string, as, for example, between head 28 and connector 38, the lower end of bars 45 being screwed into socket 29 and the upper end screwed to connector 38. Bars 45 will thus, in effect, become an upward extension of head 28 for all practical purposes. A centering guide, indicated generally by the numeral 46, is mounted on bars 45, and may be of any suitable and generally conventional form adapted to center the cutting device in the bore of pipe 43. As shown, by way of illustration, guide 46 may comprise a collar 47 mounted on bar 45 and having connected thereto a plurality of angularly spaced, outwardly bowed spring elements 48 which are adapted to resiliently slide on the inner wall of pipe 43. Guide 46 will normally be spaced above head 28, so that spring elements 48 and fingers 36 will provide longitudinally spaced points of contact between the carrier and the wall of pipe 43 which will assure effective centering of the cutting device in its passage downwardly through pipe 43. The added weight provided by bars 45 will further aid in effecting rapid lowering of the cutting device.

It will be understood that various alterations and modifications may be made in the illustrative embodiment within the scope of the appended claims but without departing from the spirit of this invention.