US3316970A - Apparatus for cutting a notch in a subsurface formation - Google Patents

Description

y 1967 J. L. HUITT ETAL APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION Original Filed Oct. 8, 1964 6 Fig. 3

INVENTORS J/MM/E L. A/U/TTI' JOSEP/l L PE/fA/PE/f United States Patent Office 3,315,970 Patented May 2, 1967 3,316,970 APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION Jimmie L. Huitt, Glensllaw, and Joseph L. Pekarek, Penn Hills, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Original application Oct. 8, 1964, Ser. No. 402,601, now Patent No. 3,254,720, dated June 7, 1966. Divided and this application Sept. 23, 1965, Ser. No. 489,635 9 Claims. (Cl. 166-555) This application is a division of, and contains only material divided from, United States application for Letters Patent Ser. No. 402,601, filed Oct. 8, 1964, now Patent No. 3,254,720. Application Ser. No. 402,601 is a continuation-in-part of, and contains material divided from, United States application for Letters Patent Ser. No. 113,432, filed May 29, 1961, which issued on July 6, 1965, as United States Patent No. 3,193,012. The invention described herein relates to the fracturing of subsurface formations penetrated by a well, and more particularly to apparatus for cutting a notch in such formations for the initiation of a fracture.

It has become common practice to create fractures extending from the borehole of a well into a subsurface formation to increase the productive capacity of the well regardless of whether the well is used in the primary production of fluids from the subsurface formation or is an injection or production well used in a secondary recovery process. The fractures are created by pumping a liquid down the well and applying a pressure, usually called the breakdown pressure, adequate to overcome the tensile strength of the subsurface formation and the weight of the overburden.

It is important, if the maximum improvement in the capacity of the well is to be obtained by fracturing, that the fracture be properly located and oriented. In the Dismukes Patent No. 2,699,212 a process is described for the accurate location and orientation of the fracture. In that process, a notch is cut in the borehole wall to create a plane of weakness and increase the surface subjected to the pressure applied to the fracturing fluid to cause the fracture to form as an extension of the notch. The notch also lowers the breakdown pressure required to fracture the formation.

It is advantageous to fracture wells that have been cased through the zone to be fractured. The pressure of the fracturing fluid is then applied to the formation only at an opening that has been cut in the casing at the desired location; hence, accurate control of the location of the point of initiation of the fracture is assured. Notches cut in the subsurface formation to be fractured are advantageous in fracturing a formation from a well in which casing has been set because of the reduced pressure that is necessary to create the desired fracture. Frequently, the breakdown pressure exceeds the pressure that may be applied to the casing if a notch has not been cut in the borehole wall. It is then necessary to set a packer in the casing isolating the opening through which the fracture is to .be made from the remainder of the casing and run tubing through the packer for delivery of the fracturing fluid into the isolated portion of the casing.

One of the methods that has been widely used for cutting a notch in a subsurface formation for initiation of a fracture employs a fluid which is directed at a high velocity from a nozzle against the borehole wall. The fluid may be a liquid, which may be a corrosive liquid such as an acid, or a suspension of abrasive particles in a liquid or gas. This method, usually referred to as hydraulic cutting, is faster than the cutting of a notch with a mechanically operated tool. Moreover, the hydraulic cutting of the desired notch does not require a rotary rig, as do mechanical tools adapted to cut a horizontal notch, thereby allowing a substantial saving in the cost of the undercutting operation. However, in some instances the marked reduction in breakdown pressure and accurate location of the fracture that is obtained when a notch is cut by hydraulic means in an open hole have not been realized when an abrasive slurry is used to cut the desired notch in a cased well.

This invention relates to apparatus for hydraulically cutting a notch in a formation penetrated by a cased well for the initiation of a fracture in which on opening of substantial width is cut through the casing, and thereafter a hydraulic cutting fluid is discharged from a nozzle through the opening in the casing to cut the desired notch in the subsurface formation. The width of the opening cut in the casing is at least four times the diameter of the nozzle opening.

In the drawings:

FIGURE 1 is a diagrammatic illustration, partially in vertical section, of apparatus in which a mechanical tool is used to cut an opening in the casing;

FIGURE 2 is a vertical sectional view of the cutting tool and nozzle used in the embodiment of the invention illustrated in FIGURE 1;

FIGURE 3 is a vertical sectional view along the section line 3-3 in FIGURE 2 of the apparatus for cutting the opening in the casing.

We have discovered that the removal of a section of the casing substantially larger than the diameter of the stream discharged from the nozzle used to cut the notch in the formation prior to cutting the notch in the formation allows the creation of a notch extending a greater distance radially from the casing into the formation. The nozzles ordinarily used for the cutting of casing or the cutting of notches in subsurface formations by hydraulic means have a diameter not exceeding 4 inchv A preferred nozzle has an opening with a diameter of inch. In the process of this invention, the opening cut in the casing has a width at least four times the diameter of the opening in the nozzle used to cut the notch in the formation. The maximum width of the opening in the casing in governed by considerations other than those important to this invention. Ordinarily, there is no improvement in the depth or shape of the notch cut in the formation if the opening in the casing is more than about ten times the diameter of the nozzle used to cut the notch in the formation. The removal of a section of the casing greater than approximately ten times the diameter of the nozzle used to cut the notch in the formation may be objectionable because of the exposure of a larger area of the formation to the fracturing liquid with a resultant diminishing accuracy of location of the fracture.

Although the reason for the increased depth of cut into the formation made possible by the process of this invention is not known with certainty, it is believed that when the opening in the casing is the result only of discharging a stream of cutting fluid from the nozzle used to cut the notch in the formation, the opening in the casing does not have sufiicient area to allow cutting fluid to flow back into the borehole of the well after striking the outer portion of the cut without interfering with the flow of cutting fluid outwardly from the nozzle. Apparently, the backflow of hydraulic fluid from the outer portion of the notch cut into the borehole of the well is not at a high enough velocity to cut the casing and increase the opening in the casing to a width which will eliminate the interference with the outwardly flowing stream discharged from the nozzle.

A series of tests was run to determine the elfect of increasing the width of the opening in the casing through VhlCl'l a high velocity stream of water and sand is diected to cut a notch in the subsurface formation. A arget was prepared from a 24-inch section of 20-nch ).D. seamless steel casing having a wall thickness of ).438 inch. The ends of the casing were closed with 20- nch extra strong seamless steel welding caps. An openng was cut in one of the welding caps to receive /2- nch CD. 17 lb./ft. casing which was extended down into he target to a depth about 4 inches from the bottom of Lhe target and welded in place at the opening. The lower end of the 5 /2-inch O.D. casing was closed with a 5-inch :xtra strong seamless steel welding cap. Two openings were cut in the end of the target near the opening for the S /z-inch O.D. casing to receive 1-inch couplings. The annular space between the 5 /2-inch casing and the 20- inch casing was filled with a lb./gal. neat Portland cement. The cement was set under 700 p.s.i. pressure for a period of at least 14 days. An opening outside of the target in the 5 /2-inch casing was fitted with a 2-inch coupling to which suitable valves were connected for control of the back pressure during the cutting of the notch in the casing in the cement surrounding the casing.

A 2-inch pipe having a hydraulic nozzle head mounted at its lower end to direct an abrasive slurry laterally against the 5 /2-inch O.D. casing was extended down through the 5' /2-incl1 O.D. casing. Suitable connections were provided for supplying the hydraulic slurry under pressure into the 2-inch pipe, to allow rotation of the 2- inch pipe within the 5 /2-inch O.D. casing, and to control the flow from the 5 /2-inch O.D casing whereby the desired pressure could be maintained in the annulus between the 2-inch pipe and the 5 /2-inch O.D. casing. An abrasive slurry of water containing sand in a concentration of 1 /2 lb./gal. was pumped down through the 2-inch pipe and discharged from the nozzle against the 5 /2-inch O.D. casing while a back pressure of 700 p.s.i. was maintained inside the 5 /2-inch O.D. casing. The 2- inch pipe was rotated at a rate of 6 rpm. The cutting action was discontinued periodically and the depth of the notch cut in the formation measured.

Several different nozzle heads were used to cut the opening in the casing and the notch in the cement surrounding the 5 /2-inch O.D. casing. In Tests Nos. 1, 2, and 3 all of the nozzles were in the same horizontal plane and the same nozzles were used for cutting the opening in the casing and the notch. In Test No. 4 the nozzle head used for cutting the opening in the casing had three nozzles arranged in a spiral around the nozzle head. In Test No. 5 the nozzle head had four nozzles arranged in a spiral similar to the lower nozzle body illustrated in FIGURE 3. Nozzle heads with the individual nozzles arranged in the same horizontal plane were used in every test to cut the notch in the cement. The results of the tests are set forth in Table I. In all of the tests the nozzles used to cut the notch in the cement had a diameter of inch.

TABLE I f Depth of Notch Beyond It will be noted from Test No. 1 in which a section /2 inch wide was removed from the casing by means of the nozzles used to cut the notch in the target that the maximum diameter of the notch was 14 inches after a minute cutting period. Because there was no increase in the notch diameter after a 20-minute cutting period over the notch diameter after a 15-minute cutting period,

the maximum notch diameter apparently had been obtained. By increasing the width of the section removed from the 5 /2-inch casing to 1 /8 inch, the diameter of the notch was increased to 17 inches in a 17-minute cutting period. Moreover, the diameter of the notch was increased 2 inches by increasing the cutting period from 12 to 17 minutes. Hence, a further increase in the notch diameter may have been obtained if a longer cutting eriod had been used.

An even greater increase in the diameter of the notch was obtained with a cutting tool having four nozzles, as is shown by comparison of Tests Nos. 2 and 5. In Run No. 5 in which the width of the section removed from the casing was 1 /2 inches, a notch diameter of 19 inches was obtained. That notch diameter was equal to the inside diameter of the 20-inch casing used in construction of the target. Moreover, there was an approximately 3-inch increase in diameter during the last 5 minutes of the cutting period. The area of the formation exposed by the notch in Test No. 5 was approximately twice the area of the formation exposed by the 14-inch notch of Test No. 2.

When the apparatus of this invention is used to cut a notch through casing and into a formation, the notch so obtained is of substantially greater length, with substantially no change in width, as compared to notches cut by conventional means. The longer, narrower shape of the notch obtained using the apparatus of this invention provides a greater concentration of forces at the apex of the notch and more accurately fixes the plane of the fracture. Moreover, formation notches formed through narrow openings in the casing, such as the casing notches formed by conventional means, tend to approach the wall of the casing at an acute angle, as a result of which upon application of pressure during a fracturing operation, substantial forces are created which tend to separate the casing from the formation. The notches formed through wide openings in the casing, by using the apparatus of this invention, approach the outer surface of the casing at an obtuse angle which minimizes forces tending to separate the casing from the formation during a subsequent fracturing operation.

One embodiment of the invention is illustrated in FIG- URES 1 to 3 for the mechanical removal of a section of the casing to form the desired wide opening. Referring to FIGURE 1, a well indicated generally by reference numeral It) is illustrated with a borehole extending through the pay zone 12. Casing 14 is set completely through the pay zone. The well is illustrated with its upper end closed at the surface by a casing head 16 on which a blowout preventer 18 is mounted. A T 20 on the upper end of the blowout preventer 18 has a lateral outlet for connection to a line 22 for discharge of a circulating fluid.

Within the casing near the lower portion of the pay zone 12 is the tool, indicated generally by reference numeral 24, for cutting the opening in the casing and the notch in the pay zone 12. The tool 24 is connected at its upper end to drill pipe 26 connected to the lower end of a kelly 28 which is illustrated extending upwardly from the T 26 through a rotary table 30 mounted on a rotary rig 32.

Referring to FIGURE 2, tool 24, which is illustrated in vertical section, is made up of a tubular housing 34 connected at its upper end to a hydraulic nozzle head 36 which is suitably threaded at its upper end for connection to the lower end of the drill pipe 26. Housing 34 has a central passage 38 extending through it in which a piston 40 is adapted to slide. Piston 40 is urged upwardly by a helical spring 42 which engages the lower surface of the piston 40 and a shoulder 44 extending from the inner surface of passage 38. Extending downwardly from piston 40 are spaced connecting rods 46 be tween which an arbor 48 extends. A pair of pivot arms 50 adapted to rotate on the arbor 48 are connected by means of pivot pins 54 to a pair of cutters 56 which are rotatably mounted on an axle 58 extending between opposite faces of the housing 34. One of the pivot arms 50 is connected to the cutter 56 on one side and the other pivot arms 50 to the cutter 56 on the opposite side of the center line between arbor 43 and axle 58 to cause the cutting elements to move in opposite directions as the piston 40 is forced downwardly. A tubular neck 60 in the piston 40 has an orifice insert 62 which permits a limited flow through the piston 40.

Hydraulic nozzle head 36 has a central passage 64 extending lengthwise through it in which a sleeve 66 is slidably mounted. During the period when a section is cut from the casing, sleeve 66 is held in the upper position illustrated in FIGURE 2 by a shear pin 68. A plurality of nozzle ports 70 adapted to receive nozzle inserts 72 are provided in the wall of the hydraulic nozzle head 36 for the discharge of a cutting fluid during the cutting of a notch in the formation. Openings 74 in the wall of sleeve 66 are located for alignment with the nozzle port 70 upon shearing of shear pin 63 and movement of the sleeve 66 to its lower position.

In the operation of the apparatus illustrated in FIG- URES 1 through 3, the tool 24 is suspended with the cutters 56 at the desired elevation by means of drill pipe 26. A circulating liquid is pumped down through the kelly 28 and the drill pipe 26 and through the hydraulic nozzle head 36 into the housing 34 while the tool is rotated by means of the kelly 28 on rotary table 36. The pressure drop through orifice 62 causes downward movement of the piston 40 which in turn causes the cutters 56 to rotate to an extended position at which they engage the casing. The cutters 56 are shaped to cut an opening of the desired width in the casing. Rotation of the tool 24 and circulation of the circulating liquid is continued until the piston 40 descends to a level below relief ports 76 at which position the cutters 56 are fully extended and the desired opening has been cut completely through the casing 14. The pressure on the circulating liquid drops to indicate when the casing cutting operation is completed. Thereafter, the flow of the circulating liquid is stopped and the spring 4-2 returns the piston 40 to the position illustrated in FIGURE 2 of the drawings.

The tool is then lowered on the drill pipe 26 a distance adapted to bring the orifice ports 70 in alignment with the opening cut in the casing by the cutters 56. A ball 78 is dropped down the drill pipe to come to rest on a valve seat 80 at the bottom of sleeve 66. Liquid is then pumped into the upper end of the drill pipe under pressure sufficient to shear shear pin 68 and cause sleeve 66 to move downwardly and bring openings 74 into alignment with the nozzle ports 70. Then, while the tool is rotated by means of the kelly 28 in rotary table 36, a hydraulic cutting fluid such as an abrasive slurry of sand suspended in water is pumped down the drill pipe 26 and through the nozzle 72 for a period adequate to cut the desired notch.

This invention has been described for apparatus adapted to cut a continuous ring from the casing and a continuous horizontal notch in the surrounding formation. The apparatus described herein is constructed and arranged to cut in the casing an opening having a Width equal to at least four times the diameter of the opening in the nozzles that are used to cut hydraulically a notch in the formation, and it has been demonstrated that such an apparatus provides a formation notch having advantages that are not obtainable using the means for casing and formation notching that hitherto were available.

We claim:

1. Apparatus adapted to be run into a eased well on the lower end of pipe for cutting a notch in a subsurface formation penetrated by the well comprising means adapted to be attached to the lower end of the pipe for cutting hydraulically a notch in the formation, said hydraulic cutting means having therein a plurality of openings for the discharge of hydraulic cutting fluid pumped down the drill pipe, said hydraulic cutting means comprising means to close said openings to said hydraulic cutting fluid pumped down the drill pipe and means to selectively open said closing means to permit the discharge of said hydraulic cutting fluid through said openings, and means secured to the lower end of said hydraulic cutting means for cutting mechanically a notch in the casing, said mechanical cutting means constructed and arranged to cut in the casing an opening having a width equal to at least four times the diameter of the openings in the hydraulic cutting means.

2. Apparatus adapted to be run into a cased well on the lower end of pipe for cutting a notch in a subsurface formation penetrated by the Well comprising a tubular nozzle head adapted to be attached to the lower end of the pipe, nozzles mounted in the nozzle head for the discharge of hydraulic cutting fluid pumped down the pipe, a sleeve slidable within the nozzle head having a central opening therethrough and pasages therein positioned for alignment with said nozzles, shearable means holding the sleeve in a position with the passages out of alignment with the nozzles, a valve seat in the central opening through the sleeve 'below the passages therethrough adapted to receive valve means to close said central opening for movement of the sleeve to a position at which the passages therethrough are in alignment with the nozzles, and mechanical casing cutting means mounted on the lower end of the nozzle head, said casing cutting means constructed and arranged to cut in the casing an opening having a width equal to at least four times the diameter of the opening in the nozzles.

3. Apparatus adapted to be run into a cased well on the lower end of pipe for cutting a notch in a subsurface formation penetrated by the well comprising a nozzle head attached to the lower end of the pipe, nozzles mounted in the nozzle head for the discharge of hydraulic cutting fluid pumped down the pipe, a sleeve slidable Within the nozzle head and having a central opening therethrough and passages therein positioned for alignment with said nozzles, shearable means holding the sleeve in a position with the passages out of alignment with the nozzles, a valve seat in the central opening through the sleeve below the passages therethrough adapted to receive valve means to close said central opening for movement of the sleeve to a position at which the passages therethrough are in alignment with the nozzles, a housing mounted on the lower end of the nozzle head, a plurality of cutting blades secured and substantially contained within the lower end of the housing, hydraulically actuated means within the housing connected to the blades constructed and arranged to extend the blades laterally outwardly from the housing whereby the blades cut in the casing an opening having a width equal to at least four times the diameter of the openings in the nozzles.

4. Apparatus adapted to be run into a cased well on the lower end of pipe for cutting a notch in a sub-surface formation penetrated by the well comprising a nozzle head adapted to be attached to the lower end of the pipe, nozzles mounted in the nozzle head for the discharge of hydraulic cutting fluid pumped down the pipe, a sleeve s'idable within the nozzle head having a central opening therethrough and passages therein positioned for alignment with said nozzles, shearable means holding the sleeve in a position with the passage out of alignment with the nozzles, a valve seat in the central opening through the sleeve below the passages therethrough adapted to receive valve means to close said central opening for movement of the sleeve to a position at which the passages therethrough are in alignment with the nozzles, a housing connected to the lower end of the nozzle head, said housing having a central opening therethrough, a piston slidable in the central opening of the housing, -a plurality of cutting blades connected to the lower end of the piston andcontained within the lower end of the housing, said blades onstructed and arranged to extend laterally upwardly 70111 the housing on downward movement of the piston cut in the casing an opening having a width equal to t least four times the diameter of the openings in the ozzles.

5. Apparatus adapted to be run into a cased well on he lower end of pipe for cutting a notch in a sub-surface ormation penetrated by the well comprising a tubular tozzle head adapted to be attached to the lower end of he pipe, nozzles mounted in the nozzle head for the disharge of hydraulic cutting fluid pumped down the drill )ipe, a sleeve slidable within the nozzle head having a :entral opening therethrough and passages therein posiioned for alignment with said nozzles, shearable means iolding the sleeve in a position with the passages out of tlignment with the nozzles, a valve seat in the central )pening through the sleeve below the passages therehrough adapted to receive valve means to close said cenral opening for movement of the sleeve to a position at which the passages therethrough are in alignment with ;he nozzles, a housing mounted on the lower end of the nozzle head, said housing having a central opening therethrough, a piston slidable in the central opening of the housing, connecting means engaging the bottom of the piston and slidably enclosed in the central opening of the housing, a plurality of cutting blades pivotally attached to the lower end of the connecting means within the housing, said blades constructed and arranged to extend laterally outwardly from the housing on downward movement of the piston and connecting means to cut in the casing an opening having a width. equal to at least four times the diameter of the opening in the nozzles.

6. Apparatus adapted to be run into a cased well on the lower end of pipe for cutting a notch in a sub-surface formation penetrated by the well comprising a tubular nozzle head adapted to be attached to the lower end of the pipe, nozzles mounted in the nozzle head for the discharge of hydraulic fluid pumped down the drill pipe, a sleeve slidable within the nozzle head having a central opening therethrough and passages therein positioned for alignment with said nozzles, shearable means holding the sleeve in a position with the passages out of alignment with the nozzles, a valve seat in the central opening through the sleeve below the passages therethrough adapted to receive valve means to close said central opening for movement of the sleeve to a position at which the passages therethrough are in alignment with the nozzles, a housing mounted on the lower end of the nozzle head, said housing having a central opening therethrough, a piston slidable in the central opening of the housing, yieldable means enclosed in the housing and engaging the bottom of said piston to urge the piston normally upward in the housing, connecting means slidable within the central opening of the housing and engaging the bottom of the piston, a plurality of cutting blades pivotally attached to the connecting means within the lower end of the housing, said blades constructed and arranged to extend laterally outwardly from the housing on downward movement of the piston against the action of the yieldable means to cut in the casing an opening having a width equal to at least four times the diameter of the opening in the nozzles.

7. Apparatus adapted to be run into a cased well on the lower end of pipe for hydraulically cutting a notch in a subsurface formation penetrated by the well comprising a tubular nozzle head adapted to be attached to the lower end of the pipe, nozzles mounted in the nozzle head for the discharge of hydraulic cutting fluid pumped down the drill pipe, a sleeve slidable within the nozzle head and having a central opening therethrough and passages therein positioned for alignment with said nozzles, shearable means holding the sleeve in a position with the passages out of alignment with the nozzles, a valve seat in the central opening through the sleeve below the passages therethrough adapted to receive valve means to close said central opening for movement of the sleeve to a position at which the passages therethrough are in alignment with the nozzles, a housing mounted on the lower end of the nozzle head, said housing having a central opening therethrough, a piston slidable in the central opening of the housing, a pair of connecting rods extending downwardly from the lower end of the piston, pivot arms pivotally connected to the lower end of the connecting rods and extending downwardly therefrom, and a pair of cutters rotatably mounted within the housing below the pivot arms and pivotally connected to said pivot arms, said cutters constructed and arranged to extend laterally on downward movement of the piston to cut in the casing an opening having a width equal to at least four times the diameter of the opening in the nozzles.

8. Apparatus adapted to be run into a cased well on the lower end of pipe for hydraulically cutting a notch in a subsurface formation penetrated by the well comprising a tubular nozzle head adapted to be attached to the lower end of the pipe, nozzles mounted in the nozzle head for the discharge of hydraulic cutting fluid pumped down the drill pipe, a sleeve slidable Within the nozzle head having a central opening therethrough and passages therein positioned for alignment with said nozzles, shearable means holding the sleeve in a position with the passages out of alignment with the nozzles, a valve seat in the central opening through the sleeve below the passages therethrough adapted to receive valve means to close said central opening for movement of the sleeve to a position at which the passages therethrough are in alignment with the nozzles, a housing mounted on the lower end of the nozzle head, said housing having a central opening therethrough, a piston slidable in the central opening of the housing, a pair of connecting rods extending downwardly from the lower end of the piston within the central opening of the housing, a helical spring surrounding the upper end of the connecting rods within the central opening of the housing and engaging the bottom of the piston, pivot arms pivotal'ay connected to the connecting rods and extending downwardly therefrom, a plurality of cutting blades rotatably mounted within the housing below the pivot arms and pivotally connected to said pivot arms, said blades constructed and arranged to extend laterally outwardly on downward movement of the piston to cut in the casing an opening having a width equal to at least four times the diameter of the opening in the nozzles.

9. Apparatus as described in claim 8 wherein the housing has a plurality of pressure relief ports extending through the wall thereof, said ports being located in the housing wall at a position such that the ports are closed by the piston until the piston is displaced to substantially its lowermost position within the housing whereupon the ports are opened and fluid is permitted to flow from the interior of the housing outwardly through the ports into the well.

References Qited by the Examiner UNlTED STATES PATENTS 1,780,100 4/1928 Ventresca 166-55.8 1,993,182 3/1935 Santiago -269 2,218,766 10/1940 Parker 166--55.8 2,501,411 3/1950 Ryan 175--422 3,224,507 12/1965 Cordary et al. 166-55.8

CHARLES E. OCONNELL, Primary Examiner,

IAMES A. LEPPINK, Examiner.

Claims (1)

1. APPARATUS ADAPTED TO BE RUN INTO A CASED WELL ON THE LOWER END OF PIPE FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION PENETRATED BY THE WELL COMPRISING MEANS ADAPTED TO BE ATTACHED TO THE LOWER END OF THE PIPE FOR CUTTING HYDRAULICALLY A NOTCH IN THE FORMATION, SAID HYDRAULIC CUTTING MEANS HAVING THEREIN A PLURALITY OF OPENINGS FOR THE DISCHARGE OF HYDRAULIC CUTTING FLUID PUMPED DOWN THE DRILL PIPE, SAID HYDRAULIC CUTTING MEANS COMPRISING MEANS TO CLOSE SAID OPENINGS TO SAID HYDRAULIC CUTTING FLUID PUMPED DOWN THE DRILL PIPE AND MEANS TO SELECTIVELY OPEN SAID CLOSING MEANS TO PERMIT THE DISCHARGE OF SAID HYDRAULIC CUTTING FLUID THROUGH SAID OPENINGS, AND MEANS SECURED TO THE LOWER END OF SAID HYDRAULIC CUTTING MEANS FOR CUTTING MECHANICALLY A NOTCH IN THE CASING, SAID MECHANICAL CUTTING MEANS CONSTRUCTED AND

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