US3050122A - Formation notching apparatus - Google Patents

Description

Aug. 1962 J. L. HUITT ETAL 3,050,122

FORMATION NOTCHING APPARATUS Filed April 4, 1960 5 Sheets-Sheet 2 INVENTORS J/MM/E LhU/TT aosspy 1.. PEKAAEK 1% 342 y 500x440 TOPANEL/AN, JR. 23

Aug. 21, 1962 J. HUlTT ETAL FORMATION NOTCHING APPARATUS 5 Sheets-Sheet 3 Filed April 4, 1960 IINVENTORE I J/MM/E L HU/TT J0 JOSEPH 4. PE/(AREK EDWARD 7'0PA/VE4/AMJR.

1962 J. L. HUlTT ETAL 3,050,122

FORMATION NOTCHING APPARATUS ATTORNEY Patented Aug. 21, 1962 free 3,050,122 FORMATION NOTCI-IING APPARATUS Jimmie L. Huitt, Glenshaw, Joseph L. Pekarek, Penn Hills, and Edward Topaneiian, Jr Pittsburgh, Pa, assignors to Gulf Research & Development Company,

Pittsburgh, Pa., a corporation of Delaware Filed Apr. 4, 1966, Ser. No. 19,792

Claims. (Cl. 16655.8)

This invention relates to apparatus for use in treating wells and more particularly to apparatus which is adapted to cut a continuous notch in the borehole walls which when subjected to: hydraulic pressure serves to position and orient artificial fractures subsequently made in the earth formation.

The apparatus of our invention is particularly adapted for cutting notches in the borehole wall in accordance with the method for completing wells which is disclosed and claimed in the patent application of Jimmie L. Huitt, Serial No. 19,791 filed April 4, 1960, in the United States Patent Office, now abandoned in favor of a continuationin-part application. In the Huitt method, a continuous V-shaped notch oriented in the plane of the desired fracture is mechanically cut in the borehole wall at a predetermined depth. A cutting element which is substantially greater in length than width and which tapers to a relatively sharp point at its forward edge is employed to operate on the borehole wall so as to form in the borehole wall a continuous circumferential V-shaped notch having a diameter at least twice as great as that of the borehole and a depth of penetration from the borehole surface at least 1.3 times greater than its width at the face of the borehole. Thereafter, hydraulic pressure is applied to the notch to fracture the formation. By forming a V-shaped notch of the desired dimensions in the borehole wall large stress concentrations are produced at the apex of the notch resulting in the development of a surface or plane of weaknes in the formation. The plane of weakness extends into the formation from the apex of the notch in substantially the same plane thereof. Application of hydraulic pressure to the notch causes the formation to fracture along the plane of weakness which has been developed in the formation. The Huitt method provides a method for accurately positioning and orienting substantially horizontal fractures in earth formations. The present invention provides an apparatus which is particularly advantageous for use in cutting notches in the walls of the borehole in accordance with the Huitt method of completing wells.

When the Well treating method described in the Huitt application is carried out in cased wells a section of the casing must be removed to permit a suitable cutting memher to contact the formation in the proper plane so as to form the desired notch therein. The same cutting mem ber cannot be employed satisfactorily to sever the casing and to form the desired notch in the borehole walls. In order to form the desired notch in the walls of the borehole, the cutting element employed must taper to a relatively sharp point at its forward edge and be comparatively long so as to extend through the casing and into the formation the desired distance. On the other hand, the casing severing elements need not have the same shape nor length as the formation notching elements, but should be of heavier construction so as to withstand the high shearing strains encountered in severing the casing. Thus, it is desirable to provide an apparatus which can be employed in a well to remove a sec tion of the well casing and to form the desired V-shaped notch in the borehole walls.

The apparatus provided by the present invention is adapted for use in a borehole to remove a section of the well casing and to form the desired notch or cavity in the walls of the borehole prior to hydraulically fracturing the earth formation. The apparatus of the invention enables a section of the casing to be removed and a continuous V-shaped notch to be made in the borehole wall at a predetermined depth without removing the apparatus from the well bore between the two operations.

The herein disclosed apparatus is provided with separate means for removing a section of casing and for forming the V-sha-ped cavity in the borehole. The provision of separate elements which are designed specifically for performing these particular operations results in wear and breakage of parts being maintained at a minimum.

The apparatus of our invention is illustrated in the accompanying drawings wherein:

FIGURE la is a longitudinal section taken through the upper portion of one embodiment of the apparatus of the invention showing the casing severing means in position for lowering and raising in the well bore.

FIGURE lb is a longitudinal section taken through the lower end of the apparatus of FIGURE 1a showing the formation notching means in position for lowering and raising in the well bore.

FIGURE 2 is a longitudinal section though the upper portion of the apparatus of FIGURE 1a showing the casing severing means actuated.

FIGURES 3a and 3b are views similar to FIGURE 1a and FIGURE 1b respectively, showing the position of the various part of the apparatus when the formation notching elements are actuated.

FIGURE 4 is a plan view taken on line IVIV of FIGURE 1a.

FIGURE 5 is a longitudinal sectional view of a modified form of the apparatus of the invention having separate casing severing means and formation notching means and showing the Various parts in position for lowering and raising in the well bore.

FIGURE 6 is a view similar to FIGURE 5 showing the casing severing means actuated.

FIGURE 7 is a View similar to FIGURE 5 showing the formation notching means actuated.

FIGURE 8 is a side view in elevation of the lower end of the apparatus of FIGURE 5.

FIGURE 9 is a view of the apparatus of FIGURE 5 taken on the line IX-IX of FIGURE 8.

FIGURE 10 i a cross-sectional view of the apparatus of FIGURE 5 taken generally on the line X-X of FIG- URE 9 and with the casing severing blades and formation notching blades shown in elevation.

FIGURES 11a, 11b, 11c and 11d are views in elevation taken on the respective lines of FIGURE 9 showing the individual casing severing blades and formation notching blades of the apparatus.

FIGURE 12 is a perspective view showing the structure of the fluid-pressure actuated piston members to which the casing severing blades and formation notching blades are operatively attached.

Reference is made to the drawings in which like numerals indicate the same elements in the various views (letters are employed with the numerals to designate corresponding elements) In FIGURE 1a adapter 1 serves to connect the formation notching apparatus of the invention designated generally by the numeral 2 with a drill pipe (not shown), the drill pipe having a central passage as is conventional for supplying drilling fluid.

Adapter 1 is screwed into housing 3 by means of threads 4. Adapter 1 is provided with a central passage 5 for the purpose of supplying fluid under pressure to piston chamber 6 which is located within liner 7. A hollow check ring 8 having an inverted frusto-conical inner surface is attached to the upper end of the liner 7. Liner 7 is maintained in the upper position by means of shear pin 9 and is prevented from rotating within housing 3 by means of spline 10. Stop member 11 is pivotally disposed within spline and is adapted for inward movement by the action of spring 12.

Slidably fitted within piston chamber 6 is piston 13 which is provided with a longitudinal central passage 14 which permits hydraulic fluid to circulate through the piston to contact the casing severing blades '15. The hydraulic fluid thus serves to lubricate these casing severing elements and to flush cuttings and chips therefrom during the casing severing operation. To prevent leakage, sealing material 16 is attached to shoulder portion 17 on piston 13 by means of screws 18. The neck portion 19 of piston 13 is smaller than interior passage 14 so that it functions as a constriction in the fluid stream whereby the velocity is changed causing a pressure ditferential across piston 13. In this way, a substantial downward pressure diiierential is caused to act on piston 13 whenever fluid discharges through it. A spring 20 is placed around piston 13 abutting against shoulder 17 on the piston and the inwardly projecting lower end of liner 7. The spring 20 asserts an upward force against piston 13 to support the piston in its upper position when no fluid pressure is applied thereto. Arms 21 which are pivotally connected by means of pivot pin 22 to the lower end of piston 13 connect with casing severing elements 15. The casing severing elements 15 are attached to arms 21 by means of pivot pins 23. Pin 24 is rigidly attached to liner 7 and extends transversely through the casing severing elements 15 to form a pivot point for these severing elements. Thus, as piston 13 moves downwardly under the hydraulic pressure, the cutting elements 15 by means of the linkage shown, pivot on pins 23 and 24 and project outwardly from opposite sides of the tool through slots 25 which are provided in the housing 3. The fluid pressure is continuously applied to force the casing severing elements 15 into cutting engagement with the casing while at the same time the tool is rotated until the desired window or slot is cut in the casing. At the completion of the casing severing operation, casing severing elements 15 are fully extended as shown in FIGURE 2. This condition is indicated to the operator at the surface by a discernible drop in pump pressure due to pressure fluid escaping to the annulus through bypass ports 26 which extend through liner 7 and housing 3. The bypass ports 26 are uncovered when piston 13 is in its lowermost position and the casing severing elements 15 fully actuated.

After the slot or window is made in the well casing, the fluid pressure acting on piston 13 is released. Spring 20 then moves piston 13 upwardly thereby retracting the casing severing blades 15.

In FIGURE 1b, the lower portion of the formation notching apparatus of the invention is shown. Situated in the lower portion of the tool is lower piston chamber 27 in which piston 28 is slidably fitted. Piston 28 is provided with a longitudinal central passage 29 which permits hydraulic fluid to circulate through the piston to contact the formation notching blades 30. Piston 28 is provided also with an enlarged shoulder 31 which forms a sliding seal with housing 3. Sealing material 32 is attached by means of screw 33 to shoulder 31 to prevent fluid leakage. The neck portion 34 of piston 28 is of reduced diameter in order to set up a pressure difierential across the piston to assist in providing a downward impetus to the piston 28. Spring 35 supports piston 28 in its upper position when no fluid pressure is applied to the piston. Arms 36 are pivotally attached by pin 37 to the lower end of piston 28. The formation notching blades 30 are pivotally attached to the lower ends of arm 36 by pins 38. Pin 39 is rigidly attached to housing 3 and extends transversely through the formation notching blades 30 to form a pivot point for these blades. Slots 40 are provided in the lower end of housing 3 to permit the formation notching blades to project outwardly into cutting engagement with the earth formation. Bypass ports 41 extend through housing 3 and provide fluid communication between the interior of the tool and the well annulus when the lower piston 28 is in its lowermost position.

The blades 30 which are employed to notch the formation have an elongated V-shape and taper to a relatively sharp point at the forward working edge 42. The blades are relatively narrow in width and sufliciently long so as to extend through the casing into the formation a sufficient distance to form the desired notch. Thus, for example, for use in a 6% inch diameter well cased with 5 /2 inch casing, notching blades having a width of 3 /2 inches and a length of about 8 inches are eminently satisfactory to form the desired notch in the formation.

In operation, the formation notching apparatus of the invention illustrated in FIGURES 1 through 4 is attached to the lower end of a drill pipe and lowered into a well until the casing severing blades -15 are opposite the location where the notch is to be made in the formation. During the introduction of the apparatus into the well the parts thereof are in the positions shown in- FIGURES la and 1b. When the apparatus is at the desired depth fluid is introduced through the drill string and circulated down through passage 5 in adapter 1 into piston chamber 6. The pressure fluid flows through the longitudinal central passage 14 in piston 13 to flush the casing severing elements 15 both before and during the time that these elements are in cutting engagement with the casing. The smaller neck portion 19 of piston 13 functions as a constriction in the fluid stream causing a pressure differential across the piston 13. This pressure differential causes the piston 13 to move downwardly against the resisting force of spring 20. As the piston 13 moves downwardly, the casing severing elements 15 by means of the linkages shown, pivot on pins 23 and 24 and project outwardly from opposite sides of the tool through slots 25 into cutting engagement With the casing. The tool is rotated at suitable speed while the hydraulic pressure is applied to cut a continuous slot or window in the casing. The tool is lowered slightly during the cutting operation in order to maintain at a minimum the width of the window in the casing. However, the Window which is cut in the casing must be sufliciently large to permit the formation notching blades to extend therethrough and contact the formation. The casing severing operation is substantially complete when piston 13 is in its lowermost position and the casing severing elements 15 are fully extended as shown in FIGURE 2. Completion of the casing severing operation is indicated at the surface by the discernible drop in pump pressure which occurs when the shoulder 17 on piston 13 moves below bypass ports 26. When the bypass ports 26 are uncovered the pressure fluid escapes through the bypass ports to the annulus thereby relieving the downward pressure acting upon piston 13. At this time, introduction of the pressure fluid is discontinued and the tool is raised slightly to permit spring 20 to move piston 13 upwardly to its upper position and thereby retract the casing severing elements 15.

After the window or slot is formed in the casing, the V-shaped notch is formed in the walls of the borehole. To accomplish this, the tool is raised within the Well a sufiicient distance so that the formation notching blades 3t? are opposite the slot which has been cut in the casing. A tripping ball or the like is then dropped down the drill pipe to form a seal with the check ring 8 and to prevent circulation of fluid through the tool. As introduction of the pressure fluid continues, a substantial pressure is developed above the tripping ball or sealing means and eventually causes pin 9 to shear. The liner 7 then moves downwardly to its lowermost position as shown in FIGURE 3a. When line 7 is in its lowermost position, stop member 11 is pivoted inwardly by the action of spring 12 to maintain liner 7 in the lower position. The tripping ball is then removed from the apparatus by reversing the fluid flow through the apparatus. In carrying out this operation, fluid is pumped down the annulus between the tool housing and the casing and enters the tool through the slots 48 which are provided in housing 3. The flow of fluid up through the tool will carry the tripping ball to the surface. After the tripping ball has been retrieved, fluid pressure is again introduced through the drill pipe and into the interior of the tool. At this time, the position of the various parts of the tool is such that the casing notching elements are below the slots and therefore cannot be projected into cutting engagement with the casing even though there is a downward force being exerted on piston 13 as a result of the pressure differential existing across the piston. Continned introduction of the pressure fluid creates a pressure diflerential across the lower piston 28 thereby causing piston 28 to move downwardly. The downward movement of piston 28 causes the formation notching blades 30 by means of the linkages shown to pivot and to project outwardly through slots 44) in housing 3 and through the window or slot previously cut in the easing into cutting engagement with the formation. While the formation notching blades are being forced into a projected or fully actuated position, the tool is lowered slightly and rotated at a suitable speed to cut the desired continuous V-shaped notch in the earth formation. Fluid pressure is applied to the tool and the tool is rotated at least until there is a drop in pump pressure which results from exposure of bypass ports 41 by the downward move ment of piston 28. At this time, the formation notching blades are substantially fully actuated as in FIGURE 3b.

FIGURES 5 to 11 illustrate a modified form of the apparatus of the invention in which the casing severing blades and the formation notching blades are located within the tool on substantially the same horizontal plane. This form of apparatus enables the casing severing operation and the formation notching operation to be conducted without the necessity of moving the tool between the two operations.

In FIGURE 5, the modified form of the formation notching apparatus of the invention designated generally by the numeral 52 is shown positioned within the casing 53 opposite a producing formation 54 in which a substantially horizontal fracture is desired. In operation, the device is lowered into the well bore on a drill spring or other suitable tubular member. The body or housing 55 of the formation notching apparatus is threadably secured to an operating drill string by means of an adapter 56. Liner or bushing 57 fits snugly within housing 55. Disposed in close sliding fit within space 58 within the liner 57 is fluid-transfer valving element 59. The valving element 59 is provided with a central passage 60 through which fluid under pressure is supplied for actuation of the casing severing means. Located below the space 58 is piston chamber 61 in which piston 62 is fitted and works therein. A shoulder portion 63 on piston 62 forms a sliding seal with liner 57. Packing rings 64 are provided on shoulder 63 to prevent leakage. Passage 65 in liner 57 provides fluid communication between the space 58 and piston chamber 61. Piston 62 is provided with a vertical central passage 66 and openings 67 which permit the hydraulic fluid to circulate through the piston 62 to contact the casing severing elements 68. Shear pin 69 maintains fluid transfer valve 59 in its uppermost position. When in this position pressure fluid which is introduced through the drill string passes through central passage 69 in valve element 59 and then through fluid passage 65 to act upon piston 62. The neck portion 70 of piston 62 has a smaller inside diameter than that of interior central passage 66 in piston 62 so that it functions as a constriction in the fluid stream whereby the velocity is changed causing a pressure differential across piston 62. In this way a substantial downward pressure differential is caused to act on the piston 62 whenever fluid discharges through it. A spring 71 is placed around piston 62 abutting against shoulder 63 on piston 62 and a shoe 72 which is carried on liner 57. The spring 71 exerts an upper force against piston 62 to support the 6 piston in its upper position when no fluid pressure is applied thereto.

Piston 62 is provided at its lower end with a base plate 73 to which are rigidly secured connecting rods 74. Connecting rods 74- extend through bushing 75 and have their lower ends 76 projecting inwardly for pivotal connection with arm members 77 which serve to actuate casing severing blades 68. Pins 78 pivotally connect rods '74 and arm members 77. Blades 68 are employed to produce a slot or window in the casing at the depth where the notch and eventually the fracture is to be made in the formation. The cutting blades 68 have a suflicient mass and contain a suitably hard material such as tungsten carbide or the like to enable the blades to sever the metal casing with a minimum of wear. Casing severing blades 68 are illustrated as being generally rectangular in shape with a curved inner end. However, these blades can be of any other equivalent shape which will permit the cutting-away of the desired section of casing.

The casing severing blades 68 are attached to arms 77 by means of pivot pins 79. Pins 80 which extend inwardly from opposite sides of housing 55 are attached to the inner ends of cutting blades 68 and form a pivot point for the cutting blades 68. Thus, as piston 62 moves downwardly under the hydraulic pressure the cutting blades 68 by means of the linkage shown, pivot on pins 78, 79 and 88 and project outwardly from opposite sides of the tool through slots 81 which are provided in the lower portion of housing 55. The fluid pressure is continuously applied to force blades 68 into cutting engagement with the casing while at the same time the tool is rotated until the desired window or slot is cut in the casing. At completion of the casing severing operation, blades 68 are fully extended as shown in FIGURE 6. This condition is indicated to the operator at the surface by a discernible drop in pump pressure due to pressure fluid escaping to the annulus through bypass ports 82 which extend through bushing 57 and housing 55. The bypass ports 82 are uncovered when piston 62 is in its lowermost position and casing severing blades 68 fully actuated. Passageway 110 is provided in bushing 75 to permit circulation of hydraulic fluid to the blades 68. The hydraulic fluid thus serves to lubricate these blades and to flush cuttings and chips therefrom during the casing severing operation.

After the slot or window is made in the well casing the fluid pressure acting on piston 62 is released. Spring 71 then moves piston 62 upwardly thereby retracting the casing severing elements 68.

In order to actuate the formation notching blades 83 the fluid pressure is diverted from upper piston 62 to lower piston 84. This is done by sealing the upper end of passage 60 in the valve element 59 by such means as a tripping ball as shown in FIGURE 7. Due to the fact that there is no immediate outlet for the fluid being supplied under pressure from the surface of the ground, the pressure will build up within space 85 above valve element 59 and ultimately cause pin 69 to shear. This causes valve element 59 to move downward under its own weight augmented by the weight of the fluid pressure until it abuts spider or shoe 86 carried by liner 57. When valve element 59 is in this lowermost position, slot 87 in Valve element 5? comes into alignment with fluid passages 88 and 89 which are located within liner 57. The passage 89 extends through liner 57 and the upper portion of bushing 75 to communicate with the upper end of lower chamber 96. 'Thus, fluid communication is established between passages 88 and 89 permitting circulation of pressure fluid to piston chamber 90 to act on piston 84 while completely bypassing the upper piston 62.

The lower piston 84 which works within chamber 80 is provided with an enlarged shoulder 91 which forms a sliding seal with bushing 75. Packing rings 92 are provided on shoulder 91 to prevent fluid leakage. Central passage 93 and openings 94 in piston 84 permit the hydraulic fluid to circulate through the piston and to contact the formation notching blades 83 during the formation notching operation. The neck portion 95 of piston 84 is of reduced intennal diameter in order to set up a pressure differential across the piston to assist in providing downward impetus to the piston. Spring 6 supports piston 84 in its normal upper position when no fluid pressure is applied to the piston. Arm members 97 are received in recess 98- in the lower end of piston 84 and are pivotally attached thereto by pin 99. The formation notching blades 83 are pivotally attached to the lower ends of arms 97 by pins 100. The downward movement of lower piston 84 under the action of fluid pressure causes the formation notching blades 83 to pivot and project outwardly in opposite directions from the tool through slots 101 which are provided on opposite sides of the housing 55.

The relative positions of the casing cutting elements 68 and the formation notching blades 83 within the tool are shown most clearly in FIGURES 8 through 11. In these views, the casing severing elements 68 and formation notching blades 83 are in their retracted positions within the body of the tool. Referring particularly to these figures, it is seen that the casing severing elements 68 are spaced so as to project from opposite sides of the tool through the outer slots 81 which are provided in the lower portion of the tool. Likewise, the formation notching blades 83 are disposed relatively close together within the center of the tool so as to project from opposite sides of the tool through the inner slots 1631. Ribs 102 and 163 which are extensions of housing 55 extend upwardly in the lower end of the casing to provide lateral support to the casing severing blades 68 and formation notching blades 83 during the respective cutting operations.

In operation, the formation notching apparatus illustrated in FIGURES 5 through 11 is attached to the lower end of a drill pipe and lowered into a well to the desired depth in the formation. During the introduction of the apparatus into the well the parts thereof are in the position shown in FIGURE 5. When the apparatus is at the desired depth, fiuid is introduced into the drill string and circulated down through adapter 56, passages 60 and 65 and into piston chamber 61. The pressure fluid flows through piston 62 by virtue of the central passage 66 and openings 67 therein. The pressure fluid then flows through passage 11% in bushing 75 to flush the casing severing elements 68 before and during the time these elements are in cutting engagement with the casing. The reduced neck portion 70 of piston 62 functions as a constriction in the fluid stream causing a pressure differential across the piston 62. The pressure differential across piston 62 causes the piston to move downwardly against the resisting action of spring 71. As the piston 62 moves downwardly the casing severing elements 68 by means of the linkage shown pivot on pins 73, 79 and 80 and are forced into cutting engagement with the casing. The casing severing blades 63 project outwardly from opposite sides of the tool through slots 81 which are provided in the lower portion of the housing 55 and are supported against lateral or side movement by the upwardly extending rib members 162 and 103. The tool is continuously rotated while the hydraulic pressure is applied to cut a continuous slot or window in the casing which will permit the formation notching blades to contact the formation. This operation is substantially complete when piston 62 is in its lowermost position and the casing severing blades 68 are fully extended as shown in FIGURE 6. Completion of the casing severing operation is indicated at the surface by a considerable drop in pump pressure which occurs when the upper end of the piston 62 moves past bypass ports 82. When the bypass ports 82 are uncovered, the pressure fluid escapes through these ports to the annulus between the casing and the tool thereby relieving the downward pressure acting upon piston 62. At this point introduction of the fluid pressure is discontinued. Spring 71 exerting an upward force thereon returns piston 62 to its uppermost position thereby retracting the casing severing blades 68. After the window or slot is formed in the casing, the desired V-shaped notch is formed in the walls of the borehole. This is accomplished by means of the V-shaped formation notching blades 83. The formation notching blades 83 are urged into the formation by applying fluid pressure on lower piston 84. To this end, a tripping ball or other suitable sealing element is dropped down the drill pipe so as to seal the upper end of passage 60 in valve element 59 as shown in FIGURE 7. As introduction of the pressure fluid continues, a substantial pressure is developed in space 8-5 above valve element 59 which eventually causes pin 69 to shear. The valve element 59 then moves downwardly to its lowermost position abutting the shoe or spider 36 which is carried on liner 57. When valve element 59 is in its lowermost position slot 87 which is located therein comes into alignment with fluid passages 88 and 89 in liner 5-7 and permits circulation of the pressure fluid to piston chamber 90 to act on the lower piston 84- while bypassing upper piston 62. The pressure fluid passes through passage 93 and openings 94 in the piston 84 and flushes the formation notching blades 83 before and during the notching operation. The neck portion 95 of the piston 84 being of reduced diameter causes a pressure differential across the piston which forces the piston to move downwardly. The downward movement of piston 34 by means of the linkages shown causes the formation notching blades 83 to project outwardly through slots 101 in housing 55 and through the window previously cut in the easing into cutting engagement with the formation. Continued rotation of the tool causes the desired continuous circumferential notch to be cut in the formation. Notice is given to the operator at the surface that the formation notching blades 83 are fully extended by the drop in pump pressure which occurs as the upper end of the piston 84 moves below bypass ports 10'4 thereby permitting the pressure fluid to escape to the annulus between the tool and the casing. Introduction of the pressure fluid is then discontinued. Upon release of the fluid pressure, spring 96 returns piston 84 to its uppermost position thereby retracting the formation notching blades 83. The formation notching apparatus is then withdrawn from the well.

The apparatus of the invention provides separate and independent means for conveniently removing a section of the casing and forming a continuous circumferential V-shaped notch in the borehole wall at a predetermined depth in the earth formation. With the apparatus of the invention a section of the casing is removed and the desired notch made in the formation without removing the apparatus fro-m the well bore. The provision of separate and independent means designed for severing the casing and notching the formation maintains breakage and wear of parts to a minimum. The design of the apparatus, which is rugged and simple, is such that fractures can be made at any desired depth in the borehole with minimum amount of stand-off at the bottom of the hole.

Obviously the apparatus of the invention is susceptible to modifications and variations in its construction. Therefore, those modifications and variations which fall within the spirit of the invention and the scope of the appended claims are to be considered part of the invention.

We claim:

1. Apparatus for use Within a well bore to form a notch in the walls of the well bore comprising: a generally tubular housing adapted to be lowered into and rotated with the well bore, means for introducing fluid under pressure within the upper end of said housing, casing severing means disposed within said housing adapted for movement into a projected operative position in cutting engagement with the well casing, formation notching means disposed within said housing adapted for movement into a projected operative position in cutting engagement with the walls of the well bore, the said formation notching means comprising a pair of oppositely disposed cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge thereof and a longitudinal dimension substantially greater than the transverse dimension thereof so as to permit substantial penetration into the earth formation, fluid pressure operated means within said housing for moving said casing severing means and formation notching means to projected operative position, slots in said housing through which said casing severing means and said formation notching means project into operative position, and means for retracting said casing severing means and said formation notching means to a non-projected inoperative position.

2. Apparatus for use within a well bore to form a continuous circumferential notch in the walls of the well bore comprising: a generally tubular housing adapted to be lowered into and rotated within the well bore, means for introducing fluid under pressure within the upper end of said housing, casing severing means disposed within said housing adapted for movement into a projected operative position in cutting engagement with the well casing, formation notching means disposed within said housing adapted for movement into a projected operative position in cutting engagement with the walls of the well bore, said formation notching means comprising cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge and a longitudinal dimension which is substantially greater than the transverse dimension thereof so as to perm-it substantial penetration into the earth formation, fluid pressure operated means within said housing for moving said casing severing means and formation notching means to projected operative position, slots in said housing through which said casing severing means and formation notching means project outwardly into operative position, means for retracting said casing severing means and formation notching means to a non-projected inoperative position.

3. Apparatus for use within a well 'bore to form a continuous circumferential notch in the walls of the well bore comprising: a generally tubular housing adapted to be lowered into and rotated within the wall bore, means for introducing fluid under pressure within the upper end of said housing, casing severing means disposed within said housing adapted for movement into a projected operative position in cutting engagement with the well casing, said casing severing means comprising a pair of oppositely disposed cutting elements adapted for projection from opposite sides of said housing into cutting engagement with the well casing, formation notching means disposed within said housing, said formation notching means comprising a pair of oppositely disposed cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge and a longitudinal dimension which is substantial-1y greater than the transverse dimension thereof so as to permit substantial penetration into the earth formation, slots in said housing through which said casing severing means and formation notching means project outwardly into operative position, fluid pressure operated means within said housing for moving said casing severing means and formation notching means to projected operative position, means for retracting said casing severing means and formation notching means into non-projected inoperative position.

4. Apparatus for use within a well bore for forming a continuous circumferential notch in the walls of the well bore comprising a generally tubular housing adapted to be lowered into and rotated within the well bore, a piston chamber located within said housing having a piston slidably fitted therein, casing severing means pivotally connected to said piston and adapted for movement into a projected operative position in cutting engagement with the well casing, a second piston chamber located within said housing having a second piston slidably fitted therein, formation notching means pivotally connected to said last-mentioned piston and adapted for movement into a projected operative position in cutting engagement with the walls of the well bore, said formation notching means comprising a pair of oppositely disposed cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge and a longitudinal dimension substantially greater than the transverse dimension thereof so as to permit substantial penetration into the earth formation, slots in said housing through which said casing severing means and formation notching means project outwardly into operative position, means for supplying fluid under pressure to said housing, means for circulating pressure fluid to each of said piston members to thereby independently move the said casing severing means and formation notching means into projected operative position, means for retracting said casing severing means and formation notching means to a non-projected inoperative position.

5. Apparatus for use within a well bore for forming a continuous circumferential notch in the walls of the well bore comprising: a generally tubular housing adapted to be lowered into and rotated within the well bore, a piston chamber located within the upper end of said housing having a piston slidably fitted therein, casing severing means pivotally connected to said piston and adapted for pivoting about a fixed point and to project outwardly from the said housing into cutting engagement within the well casing, openings located within said housing so as to perm-it the escape of fluid from the tool when the said piston is in a lower position, a second piston chamber located within said housing having a second piston slidably fitted therein, formation notching means pivotally connected to said last-mentioned piston and adapted for pivoting about a fixed point and to project outwardly from said housing into cutting engagement with the walls of the well bore, openings located within said housing so as to permit the escape of fluid from the tool when the said last-mentioned piston member is in a lower position, means for supplying fluid under pressure to said housing and means for circulating the pressure fluid to each of said piston members to thereby independently move the said casing severing means and formation notching means into projected operative position, means for retracting said casing severing means and formation notching means to non-projected inoperative position.

6. Apparatus for use within a well bore for forming a continuous circumferential notch in the walls of the well bore comp-rising: a generally tubular housing adapted to be lowered into and rotated within the well bore, means for introducing fluid under pressure within the upper end of said housing, a hollow elongated annular liner adapted for longitudinal movement snugly fitted within the upper end of said housing, a shear pin supporting said liner in its uppermost position, a piston chamber located within said liner, a piston having a longitudinal central passage therein slidably fitted within said piston chamber, openings extending through said liner and housing and so located as .to permit escape of fluid from the apparatus when said piston is in a lower position, casing severing means pivotally connected to said piston and adapted for pivoting about a fixed point and to project outwardly from said housing, two oppositely disposed longitudinal slots in said housing through which said casing severing means project into cutting engagement with the well casing, a second piston chamber located within said housing below said upper piston chamber, a piston having a longitudinal central passage therein slidably fitted within said last-mentioned piston chamber, openings located in the lower end of said housing so as to permit escape of fluid from the interior of said housing when said last-mentioned piston is in a lower position, formation notching means pivotally connected to said lower piston and adapted for pivoting about a fixed point and to project outwardly from said housing, said format-ion notching means comprising a pair 75 of oppositely disposed cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge, slots located in the lower end of said housing through which said formation notching means project into cutting engagement with the walls of the well bore, and means for retracting said casing severing means and formation notching means to a non projected inoperative position.

7. Apparatus for use within a well bore for forming a continuous circumferential notch in the walls of the well bore comprising: a generally tubular housing adapted to be lowered into and rotated within the well bore, means for introducing fluid under pressure within the upper end of said housing, a hollow elongated annular liner adapted for longitudinal movement snugly fitted within the upper end of said housing, a shear pin supporting said liner in its uppermost position, a piston chamber located within said liner, a piston having a longitudinal central passage therein slidably fitted within said piston chamber, linkage pivotally connecting said piston member to casing severing means which are adapted for movement into cutting engagement with the well casing, openings extending through said liner and housing and so located as to permit escape of fluid from the apparatus when said piston is in a lower position, two oppositely disposed longitudinal slots in said housing through which said casing severing means project into cutting engagement with the well casing, a second piston chamber located within said housing below said upper piston chamber, a piston having a longitudinal cen tral passage therein slidably fitted with said last-mentioned piston chamber, openings located in the lower end of said housing so as to permit escape of fluid from the interior of said housing when said last-mentioned piston is in a lower position, linkage pivotally connecting said lastmentioned piston member to formation notching means which are adapted for movement into a projected operative position in cutting engagement with the Walls of the well here, said formation notching means comprising a pair of oppositely disposed cut-ting elements having a generally elongated V-shape and a relatively sharp point at the forward edge, slots located in the lower end of said housing through which said formation notching means project into cutting engagement with the walls of the well bore, and spring members positioned about each of said piston members adapted to exert an upward force on said piston members when no fluid pressure is applied thereto thereby maintaining said casing severing means and formation notching means in a non-projected inoperative position.

8. Apparatus for use within a well bore for donning a continuous circumferential notch in the walls of the well bore, said apparatus comprising a generally tubular housing adapted to be lowered into and rotated within the well bore, a piston chamber located within the upper end of said housing, a piston having a longitudinal central passage therein slida-bly fitted within and adapted for longitudinal movement within said piston chamber, casing severing means pivotally connected to said piston and adapted -for movement into a projected operative position in cutting engagement with the well casing, a second piston chamber located within said housing below said upper piston chamber, a piston having a longitudinal central passage slidably fitted within and adapted for longitudinal movement Within said lastmentioned piston chamber, formation notching means pivotally connected to said lower piston and adapted for movement into projected operative position in cutting engagement with the walls of the well bore, said formation notching means comprising cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge, means for in- .troducing fluid under pressure within the upper end of said housing, a fluid transfer valve element disposed within the upper end of said housing adapted for movement between an upper and lower position to thereby control the circulation of hydraulic fluid to each of said piston members, and means for retracting said casing severing means and said formation notching means to a non'projected in operative position.

9. Apparatus for use Within a well bore for forming a continuous circumferential V-shaped notch in the walls of the borehole, said apparatus comprising: a generally tubular housing having fluid passages therein and adapted to -be lowered into and rotated within the Well bore, a piston chamber located within the upper end of said housing, a piston having a longitudinal central passage slidably fitted within and adapted for longitudinal move ment within said piston chamber, linkage pivotally connecting said piston member to casing severing means which are adapted for movement into cutting engagement 'With the well casing, a second piston chamber located within said housing below said upper piston chamber, a second piston having a longitudinal central passage slidably fitted within and adapted for longitudinal movement within said last-mentioned piston chamber, linkage pivotally connecting said last-mentioned piston member to formation notching means which are adapted for movement into a projected operative position in cutting engagement with the walls of the well bore, said formation notching means comprising a pair of oppositely disposed cutting elements having a generally elongated V-shape and a relatively sharp point at their forward edge, means for introducing fluid under pressure within the upper end of said housing, a fluid transfer valve element disposed within the upper end of said housing adapted for movement between an upper and lower position to thereby control the circulation of hydraulic fluid to each of said piston members, and spring means for retracting said casing severing means and formation notching means to a non-projected inoperative position.

10. Apparatus for use within a well bore for forming a continuous circumferential notch in the walls of the well bore, said apparatus comprising a generally tubular housing adapted to be lowered into and rotated within the well bore, a piston chamber located within the upper end of said housing, a piston having a longitudinal central passage therein slidably fitted within and adapted for longitudinal movement within said piston chamber, openings extending through said housing and so located as to permit escape of fluid from said piston chamber when said piston is in a lower position, casing severing means pivotally connected to said piston and adapted for movement into a projected operative position in cutting engagement with the well casing, a second piston chamber lo cated within said housing below said upper piston chamher, a piston having a longitudinal central passage slidably fitted within and adapted for longitudinal movement within said last-mentioned piston chamber, openings located in the lower end of said housing so as to permit escape of fluid from said last-mentioned piston chamber when the last-mentioned piston is in the lower position, formation notching means pivotally connected to said lower piston and adapted for movement into projected operative position in cutting engagement with the walls of the well bore, said formation notching means comprising cutting elements having a generally elongated V-shape and a relatively sharp point at the forward edge, means for introducing fluid under pressure within the upper end of said housing, a fluid transfer valve element disposed within the upper end of said housing adapted for movement between an upper and lower position to thereby control the circulation of hydraulic fluid to each of said piston members, and means for retracting said casing severing means and said formation notching means to a non-projected inoperative position.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 O5O l22 August. 21. 1962 Jimmie L Huitt et aln It is hereby certified that error appears in the above numbered pat ent requiring correction and that the said Letters Patent should read as corrected below.

Column l line 69, for "line" read liner column 5, line 42, for "spring" read string --3 column 8 line 68 for "with" read within column 9 line 42 for "wall" read well Signed and sealed this 11th day of December 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD flfing Officer Commissioner of Patents

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