US3254720A

US3254720A - Apparatus for cutting a notch in a subsurface formation

Info

Publication number: US3254720A
Application number: US402601A
Authority: US
Inventors: Jimmie L Huitt; Joseph L Pekarek
Original assignee: Gulf Research and Development Co
Current assignee: Gulf Research and Development Co
Priority date: 1964-10-08
Filing date: 1964-10-08
Publication date: 1966-06-07
Anticipated expiration: 1983-06-07

Description

June 7, 1966 J. L. HUlTT ET AL 3,254,720

APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION Filed Oct. 8, 1964 5 Sheets-Sheet 1 INVENTORS. J/MM/f 1. flu/rr JOSEPH A PE/(AREK June 7, 1966 J. L. HUlTT ET AL APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION Filed Oct. 8. 1964 5 Sheets-Sheet 2 INVENTORS. J/MM/E L. HU/TT' JOSEPH L. PE/OLQEK June 7, 1966 .1. HUlTT ETAL APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION 5 Sheets-Sheet 5 Filed Oct. 8, 1964 INVENTORS J/MM/E L. f/U/TT JOSEPH L. PE/(APEK United States Patent 3,254,720 APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION Jimmie L. Huitt, Glenshaw, and Joseph L. Pekarek, Penn Hills, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed Oct. 8, 1964, Ser. No. 402,601 6 Claims. (Cl. 16655) This application is a continuation-in-part of United States Patent No. 3,193,012 entitled Method of Cutting a Notch in an Underground Formation Penetrated by a Well, issued July 6, 1965 on application Serial No. 113,432, filed May 29, 1961. This application contains material divided from said patent and said application, and 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 ad- "vantageous in fracturing a formation from a well in which casing has been set because of the reduced pressure that 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 hori zontal notch, thereby allowing a substantial saving in the cost of the undercutting operation. However, in some instances the marked reduction in breakdown pres- 3,254,720 Patented June 7, 1966 sure 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 an opening of substantial width is cut through the casing, and there after a hydraulic cutting fluid is discharged from a nozzle through the opening in the casing to cut thedesired notch in the subsurface formation.

ameter of the nozzle opening. In a preferred embodiment of this invention, the opening in the casing is cut by a high velocity stream discharged from one set of nozzles and thereafter second stage nozzles located at the midpoint of the opening are made operative and a notch is cut in the formation by a high velocity stream discharged through the second set of nozzles.

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; 1

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 33 in FIGURE 2 of the apparatus for cutting the opening in the casing;

FIGURE 4 is a sectional view of an embodiment of this invention in which the opening of substantial width in the casing is .cut hydraulically;

FIGURE 5 shows a comparison of the configuration of a notch cut in the subsurface formation by the apparatus of this invention with notches cut when the same nozzles used to cut the notch in the formation are used to cut the opening in the casing;

FIGURE 6 is a longitudinal sectional view taken along the section line 6--6 in FIGURE 7 of a preferred em bodiment of this invention shown in condition for cutting the opening in the casing, in which the opening in the casing and the notch of the formation are out without moving the tool vertically in the hole during the change from one operation to the other;

FIGURE 7 is a sectional view taken along the section line 7-.7 in FIGURE 6 showing the orientation of the nozzles for cutting the opening in the casing;

FIGURE 8 is a horizontal sectional view of the preferred embodiment of this invention with the second stage nozzles in operating condition; and

FIGURE 9 is a fragmentary vertical sectional view of the preferred embodiment of this invention taken along section line 9-9 in FIGURE 7.

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 A inch. 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 is 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 The width of the opening cut in the casing is at least four times the di-.

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 OD. casing while a back pressure of 700 p.s.i. was maintained inside the %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 of the formation to the fracturing liquid with a resultant 5 Cut in the formation measured. diminishing accuracy of location of the fracture. Several diiferent nozzle heads were used to cut the Although the reason for the increased depth of cut Opening in the casing and the notch in the cement 511T- into the formation made possible by the process of this rounding the Sue-inch h I11 Tests invention is not known with certainty, it is believed that and 3 an of the nozzles were m the Same heFlzonml when the opening in the casing is the result only of dis- Plane, e the m nozzles were used for cuttmg the charging a stream of cutting fluid from the nozzle used Openmg m the casmg and notch 4 t nozzle head used for cutting the opening III the casing to cut the notch in the formatlon, the opening in the h d h 1 d l d h l in does not have sufficient area to allow cutting fluid a t tee es arrange m a Splra aroun t e nozz 6 cas g head. In Test No. 5 the nozzle head had four nozzles to flow back into the borehole of the well after striking arranged in a Spiral Similar to the lower nozzle body the outer portlon of the cut without interfering with the illustrated in FIGURE Nozzle heads with the flow of euttmg field outwardly f nozzle dividual nozzles arranged in the same horizontal plane patently, the baekflow of hydrauhe fiuld from the Outer were used in every test to cut the notch in the cement. portion of the notch cut into the borehole of the well is h results f the tests are set f th in Table 1 In all not at a high enough velocity to cut the casing and of the tests the nozzles used to cut the notch in the increase the opening in the casing to a width which will cement had a diameter of 7 inch.

TABLE I Depth of Notch Beyond Casing After Test Width of N0. of Cutting for No. Casing Nozzles for Opening, in. Cutting Notch 7min 12 min 15 min. 17 min. 20 min.

eliminate the interference with the outwardly flowing It will be noted from tetst No. 1 in which a section /2 stream discharged from the nozzle. inch wide was removed from the casing by means of the A series of tests was run to determine the effect of nozzles used to cut the notch in the target that the maxiincreasing the width of the opening in the casing through mum diameter of the notch was 14 inches after a ZO-minute which a high velocity stream of water and sand is directed cutting period. Because there was no increase in the notch to cut a notch in the subsurface formation. A target diameter after a 20-minute cutting period over the notch was prepared from a 24-inch section of 20-inch O.D. diameter after a 15-minute cutting period, the maximum seamless steel casing having a wall thickness of 0.438 notch diameter apparently had been obtained. By ininch. The ends of the casing were closed with 20-inch creasing the width of the section removed from the 5 /2- extra strong seamless steel welding caps. An opening was inch casing to 1 /8 inch, the diameter of the notch was cut in one of the welding caps to receive 5 /2-inch O.D. increased to 17 inches in a 17-minute cutting period. 17 lb./ft. casing which was extended down into the target Moreover, the diameter of the notch was increased 2 to a depth about 4 inches from the bottom of the target inches by increasing the cutting period from 12 to 17 and welded in place at the opening. The lower end of minutes. Hence, a further increase in the notch diameter the 5 /2-inch O.D. casing was closed with a 5-inch extra may have been obtained if a larger cutting period had strong seamless steel welding cap. Two openings were been used. cut in the end of the target near the opening for the 5 /2- An even greater increase in the diameter of the notch inch O.D. casing to receive 1 inch couplings. The anwas obtained with a cutting tool having four nozzles, as nular space between the 5 /2-inch casing and the 20-inch is shown by comparison of Tests Nos. 2 and 5. In Run casing was filled with a 15 lb./ gal. neat Portland cement. No. 5 in which the width of the section removed from The cement was set under 700 p.s.i. pressure for a period the casing was 1 /2 inches, a notch diameter of 19 inches of at least 14 days. An opening outside of the target was obtained. That notch diameter was equal to the inin the 5 /2-inch casing was fitted with a 2-inch coupling side diameter of the 20-inch casing used in construction to which suitable valves were connected for control of the of the target. Moreover, there was an approximately 3- back pressure during the cutting of the notch in the casing in h increase in am t r during the last 5 minutes of in the cement surroundin the casing, the cutting period. The area of the formation exposed A 2-inch pipe having a hydraulic nozzle head mounted y the notch in T st N 5 Was approximately twice the at its lower end to direct an abrasive slurry laterally area of the formation exposed y the 1 n notch of against the 5 /z-inch O.D. casing was extended down Test N n through the 5 /2-inch O.D. casing. Suitable connections Referring to FIGURE 5 in Which the eehfigllratioh of were provided for supplying the hydraulic slurry under the notch 1 cut during Test No. 2 is compared with that pressure into the 2-in ch pipe, to allow rotation of the 0f the notch 2 Cut in Test it ll be ticed that z-i h pipe i hi h 5 -i h 0 D i d to the increased length of the notch is obtained with subtrol the flow from the .5 /2-inch O.D. casing whereby the stalltiany change in Width- The longer, IlaITOWeI desired pressure could be maintained in the annulus be- Shape of the notch Obtained in Test 5 Provides a t n the 24 b pipe d h 5 4 1 0 D i An greater concentration of forces at the apex of the notch abrasive slurry of water containing sand in a concentraand more r ely fiXeS t plane f th fracture. tion of 1 /2 lb./ gal. was pumped down through the 2-inch Moreover, notches formed through narrower openings pipe and discharged from the nozzle against the 5 /2-inch in the casing tend to approach the wall of the casing at an acute angle, as a result of which upon application of pressure during the fracturing operation, substantial forces tending to separate the formation from the casing are created. The notches formed through wide openings in the casing approach the outer surface of the casing at an obtuse angle which minimizes forces tending to separate the casing from the formation during the subsequent fracturing. The notches formed actually are more irregular than indicated in FIGURE 5 which indicates an average of the shape of cross sections taken along different radii, and permits a more accurate comparison of the two notches.

One embodiment of the invention is illustrated in FIGURES 1 to 4 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 18 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 20 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 between 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 arm 50 to the cutter 56 on the opposite side of the center line between arbor 48 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 68 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 30. 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 poston 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 throughthe 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 42 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 30, 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.

A tool for use in this invention in which both the opening in the casing and the notch are cut hydraulically is illustrated in FIGURE 4. Referring to that figure, the tool, indicated generally by reference numeral 82, illustrated suspended on the-lower end of a string of tubing 84, consists of an upper nozzle head 86 having a plurality of nozzle ports 88 positioned in a single horizontal plane. Nozzle inserts 90 of a suitable hard metal such as tungsten carbide are mounted in the ports 88 by any suitable means such as the screw threads illustrated in FIGURE 4. Fitting slidably within the upper body 86 is a sleeve 92 having an upper section of large diameter connected to a lower section of smaller diameter by a sloping surface 96 which serves as a valveseat. Above the level of surface 96 are openings 98 extending through the Wall of sleeve 92 in position for alignment with the nozzle ports 88. The sleeve 92 is held in the upper position illustrated in FIGURE 4 with the openings 98 out of alignment with the nozzle ports 88 by a shear pin 100 during the period the opening is cut in the casing.

Connected to the lower end of sleeve 92 is a lower nozzle body 102 having noozle ports 104 extending through it. The number and location of the nozzle ports 104 is designed to cause the stream discharged from the nozzle to overlap and thereby remove a continuous section without intervening strips of metal. The number of nozzle ports 104 will be determined by the width of opening that is desired in the casing. In the apparatus illustrated in FIGURE 4, the lower nozzle body 102 is provided with four nozzle ports 104 pointing in directions separated by 90 from one another. A nozzle insert 106 of suitable hard material is mounted in each of the nozzle ports 104. The size of the central opening 108 in the lower body 102 is decreased at the lower end of the lower body to provide a valve seat 110.

In the operation of the apparatus illustrated in FIG-. URE 4, the hydraulic tool 82 is run into the well on tubing 84 to the desired depth. A ball 112 of proper size to engage the valve seat M0 and close the lower end of the tool 82 is dropped down the tubing. Thereafter, an abrasive slurry is pumped down the tubing and discharged from the nozzles 104 while the tubing is rotated. Rotation of the lower nozzle body 102 with the tubing 84 is accomplished by means of a slot 114 in the lower end of upper nozzle body 86 which is engaged by a key 116 extending from the outer surface of the sleeve 92. The rotation of the tool and the pumping of the cutting fluids through the nozzles of the lower nozzle body is continued for a period adequate to cut on opening in the casing. The tool 82 is then lowered a distance adequate to bring the nozzle ports 88 into alignment with the center of the opening cut in the casing Wall. A ball 1-18 is then dropped down the tubing to engage surface 96 to close the lower end of sleeve 92. Liquid pressure is applied to break the shear pin 100 and move the sleeve 92 to a lower position at which passages 98 are in alignment with the nozzle ports 88. Downward movement of the sleeve 92 is limited by a retaining ring 120 at the lower end of the upper nozzle body. The tool is then rotated as before while a cutting fluid is pumped down the tubing and through the nozzles 91 to cut the desired notch in the subsurface formation.

Referring to FIGURE 6 in which the preferred embodiment of this invention is illustrated, a cylindrical nozzle head 122 is threaded, as indicated at 124, for connection to the lower end of drill string 26 or other tubing for running into the well. The nozzle head 122 is threaded at its lower end to receive a bushing 12 6 having a central opening through which fluids may flow. The diameter of the central opening through the bushing is smaller than the inner diameter of the nozzle head to form a shoulder 127. Slidable within the nozzle head 122 is a sleeve 128 having a base plate 130 secured to its lower end. Base plate 130 has a central opening 131 extending therethrough and a valve seat 133 surrounding the upper end of opening 131. The sleeve 128 is shorter than the nozzle head 122; hence, the sleeve can slide within the nozzle head from an upper position illustrated in FIGURE 6 to a lower position in which the base plate 13%) engages the shoulder 127. During the cutting of an opening in the casing and running of the tool into the well, the sleeve is held in its upper position by a shear pin 132 engaging the nozzle head and the base plate 130. A key 134 extending from the side of the base plate rides in a slot 135 L pirevent rotation of the sleeve relative to the nozzle Nozzle head 122 is drilled and tapped in a spiral arr angement to receive a plurality of first stage nozzles 136 as shown in FIGURE 7. In the apparatus illustrated in the drawings, four first stage nozzles 136 are oriented at 90 intervals. As in the case of nozzle inserts 106 illustrated in FIGURE 4, the first stage nozzles 136 are vertically spaced from one another whereby the streams of abrasive fluid discharged from the nozzles overlap to cut an opening in the casing substantially wider than the diameter of the orifice of the second stage nozzles. In a typical arrangement, the nozzles 136 have inch diameter throats vertically spaced inch from one another. The widening pattern of the streams discharged from the nozzle throats causes the streams to overlap and cut a continuous opening free of debris from the casing.

Nozzle head 122 is drilled at 138 to receive a plurality of second stage nozzles 140' positioned in a single horizontal plane midway between the center lines of the highest and lowest first stage nozzles 136. The second stage nozzles 140 are oriented at 90 intervals from one another at an angle of 45 from the first stage nozzles 136. Second stage nozzles 140 have a diameter less than A the width of the opening to be cut in the casing. With the arrangement of first stage nozzles described in the preceding paragraph, nozzles 140 have a diameter of inch or less.

Ports 142 extending through sleeve 128 are in alignment with the nozzles 136 when the sleeve is in the upper position illustrated in FIGURE 6. Openings 144 angularly displaced 45 from the ports 142 extend through the sleeve 128 at a position above ports 1 42 to be in alignment with the nozzles 140 when the sleeve is in the lower position with the base plate 130 bearing against the bushing 126. A horizontal shoulder 146 extends inwardly around the inner surface of the sleeve 128 to provide a valve seat between the ports 142 and openings 144. The

8 opening through the sleeve 128 defined by shoulder 146 is larger than the opening 131 through base plate 130.

In the operation of the apparatus illustrated in FIG- URES 6 through 9, the nozzle head 122 is lowered into the Well to the desired depth on the lower end of a string of drill pipe or tubing. A ball 148 of smaller diameter than the opening defined by shoulder 146 is dropped down the drill string and engages .the valve seat 133 at the top of the base plate 130. An abrasive slurry is pumped down the drill string and discharged through ports 142 and first stage nozzles 136 in a high velocity stream to cut an opening in the casing. The nozzle head is anchored at the desired depth by a hydraulic hold-down in the drill pipe string immediately above the nozzle head 122. The drill string and tool are rotated during the cutting operation. After a circumferential opening has been cut in the casing, a ball 150 of a size adapted to seat on shoulder 146 is dropped down the drill string while maintaining pressure on the drill string to keep the holddown operation. The ball prevents flow of liquids through openings 142 and causes the pressure to build up within the drill string to a level which breaks shear pin 132. The sleeve 128 moves to the lower position with the openings 14-4 in alignment with second stage nozzles which are centered in the circumferential opening cut in the casing by the first stage nozzles. The abrasive slurry is discharged through second stage nozzles 14-0 against the formation to cut the desired notch in the formation.

It will be noticed that the second stage nozzles 140 are positioned nearer the face of the formation than the nozzles 136; thus, the two stage nozzle arrangement illustrated in FIGURES 6 through 9 positions the nozzles at the desired stand-off for more efficient cutting as well as for cutting the wide opening in the casing necessary for cutting a formation notch of substantial depth. The preferred embodiment of the invention illustrated in FIGURES 6 through 9 has the advantage that no vertical movement of the nozzle head is necessary between the first stage cutting of the opening in the casing and the second stage cutting of the notch in the formation. Because the lower end of the drill string can be locked securely in place and maintained in that position throughout the operation, the position of the second stage nozzles is fixed and the stream discharging from them can be centered accurately within the opening cut in the casing.

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 invention can also be used for cutting other types of holes in the formation for facilitating fracturing. For example, it may be desirable to make a series of holes instead of a slot, in the formation hydraulically by not rotating the nozzle during the cutting operation. The advantages of this invention can then be realized by cutting a hole in the casing having a substantially larger diameter than the diameter of the nozzle used to cut the hole in the formation.

We claim:

1. Apparatus adapted to be run into a well on the lower end of pipe for hydraulically cutting an opening in casing of the well and in the formation surrounding the well comprising a tubular nozzle head, a sleeve slidable vertically within the nozzle head from an upper position to a lower position, laterally directed first stage nozzles in the nozzle head vertically spaced from one another a distance to cause overlapping streams from the nozzles to impinge against the casing, a laterally directed second stage nozzle in the nozzle head positioned substantially at the midpoint vertically of the first stage nozzles, said first stage nozzles being constructed and spaced at distances one from another such that the streams from said nozzles abrade a strip of easing having a width equal to at least four times the diameter of said second stage nozzle, said second stage nozzle being angularly displaced from the first stage nozzles, ports in the sleeve positioned for alignment with the first stage nozzles when the sleeve is in the upper position, an opening in the sleeve angularly displaced from the ports and located above the ports whereby the opening is in alignment with the second stage nozzle when the sleeve is in the lower position, releasable means for holding the sleeve in the upper position, means for moving the sleeve from the upper to the lower position, and means to prevent rotation of the sleeve relative to the nozzle head.

2. Apparatus adapted to be run into a well on the lower end of pipe for hydraulically cutting an opening in casing of a well and the surrounding formation comprising a tubular nozzle head, a plurality of first stage nozzles opening laterally from the nozzle head, said first stage nozzles being vertically displaced from one another a distance adapted to discharge overlapping streams from the nozzles against the casing, laterally opening second stage nozzles in the casing substantially at the midpoint vertically of the first stage nozzles, said second stage nozzles being displaced angularly from the first stage nozzles and having a throat diameter less than one-fourth of the vertical extent of the impingement of the overlapping streams against the casing, a sleeve slidable within the casing from an upper position to a lower position, ports in the sleeve positioned for alignment with the sleeve when the sleeve is in its upper position, openings in the sleeve positioned for alignment with the second stage nozzles and positioned above the ports a distance whereby a movement on the sleeve to the lower position the opening is in alignment with the second stage nozzles, releasable means for holding the sleeve at its upper position, means for moving the sleeve from the upper position to the lower position, a vertical slot in the inner wall of the lower portion of the nozzle head, and means extending from the sleeve into the slot to prevent rotation of the sleeve relative to the nozzle head.

3. Apparatus as set forth in claim 2 in which the second stage nozzles are positioned radially outward from the first stage nozzles.

4. Apparatus adapted to be run into a well on the lower end of pipe for hydraulically cutting a circumferential opening in the casing of a well and the formation surrounding the well comprising a tubular nozzle head adapted to be run into the well on tubing string, said nozzle head having a shoulder extending inwardly near its lower end, a sleeve slidable within the nozzle head from an upper position to a.lower position at which the sleeve rests on the shoulder, releasable means engaging the nozzle head and the sleeve to hold the sleeve in the upper position, a vertical slot in the inner surface of the nozzle head, a key extending outwardly from the lower end of the sleeve into the slot to prevent rotation of the sleeve relative to the notch, a plurality of laterally directed first stage nozzles in the nozzle head vertically displaced one from another a distance adapted to direct overlapping streams outwardly from said nozzles, each of said first stage nozzles being angularly displaced from the others, a plurality of laterally directed second stage nozzles in the nozzle head, said second stage nozzles being located in a single horizontal plane substantially at the midpoint vertically of the first stage nozzles, said second stage nozzles having a diameter not more than one fourth the ventical sweep of the streams directed from the first stage nozzles, ports in the sleeve positioned for alignment with the first stage nozzles when the sleeve is in the upper .position, openings in the sleeve located above the ports a 1% distance whereby said openings are in alignment with the second stage nozzles when the sleeve is in the lower position, releasable means for holding the sleeve in the upper position, and means for moving the sleeve from the upper position to the lower position.

5. Apparatus as set forth in claim 4 including a base plate'secured to the lower end of the sleeve, a passage having a diameter less than the inner diameter of the sleeve extending longitudinally through the base plate, a valve seat at the upper end of the passage, and a shoulder around the inner surface of the sleeve between the ports and the openings therein to form an upper valve seat, said upper valve seat having a diameter larger than the diameter of the passage in the base plate.

6. Apparatus adapted to be run into a well on the lower end of pipe for hydraulically cutting an opening in casing of the well and in the formation surrounding the well comprising a tubular nozzle head, a sleeve slidable within the nozzle head from an upper position to a lower position, a shear pin holding the sleeve in the upper position, stop means extending inwardly from the inner surface of the nozzle head to limit downward movement of the sleeve within the nozzle head, a base plate secured to the lower end of the sleeve, a vertical passage having a diameter smaller than the inner diameter of the sleeve extending through the base plate, a valve seat at the upper end of the passage, a plurality of first stage nozzles opening outwardly through the nozzle head, said first stage nozzles being angularly displaced approximately one from another and vertically displaced one from another a distance whereby the stream discharged from one first stage nozzle overlaps the stream discharged from the vertically adjacent first stage nozzle, second stage nozzles opening outwardly through the nozzle head, said second stage nozzles being located in a single vertical plane substantially at the midpoint vertically of the first stage nozzles and being angularly displaced approximately 90 one from another and 45 from the first stage nozzles, said second stage nozzles having a diameter not greater than one-fourth the vertical sweep of the streams from the first stage nozzles impinging on the casing, ports in the sleeve positioned for alignment with the first stage nozzles when the sleeve is in the upper position, openings in the sleeve positioned above the ports for alignment with the second stage nozzles when the sleeve is in the lower position, a vertical slot in the lower part of the inner wall of the nozzle head, means extending from the base plate into the slot to prevent rotation of the sleeve relative to the nozzle head, and a shoulder extending inwardly from the inner surface of the sleeve between the ports and the openings to form a valve seat having a central opening therethrough of larger diameter than the vertical passage in the base plate.

References Cited by the Examiner UNITED STATES PATENTS 2,155,609 4/1925 McClendon et a1. 166154 2,236,761 4/1941 Nichols --268 3,066,735 12/1962 Zingg 166222 JACOB L. NACKENOFF, Primary Examiner.

BENJAMIN HERSI-I, CHARLES E. OCONNELL,

Examiners.

J. A. LEPPINK, Assistant Examiner.

Claims

1. APPARATUS ADAPTED TO BE RUN INTO A WELL ON THE LOWER END OF PIPE FOR HYDRAYLICALLY CUTTING AN OPENING IN CASING OF THE WELL AND IN THE FORMATION SURROUNDING THE WELL COMPRISING A TUBULAR NOZZLE HEAD, A SLEEVE SLIDABLE VERTICALLY WITHIN THE NOZZLE HEAD FROM AN UPPER POSITION TO A LOWER POSITION, LATERALLY DIRECTED FIRST STAGE NOZZLES IN THE NOZZLE HEAD VERTICALLY SPACED FROM ONE ANOTHER A DISTANCE TO CAUSE OVERLAPPING STREAMS FROM THE NOZZLES TO IMPINGE AGAINST THE CASING, A LATERALLY DIRECTED SECOND STAGE NOZZLE IN THE NOZZLE HEAD POSITIONED SUBSTANTIALLY AT THE MIDPOINT VERTICALLY OF THE FIRST STAGE NOZZLES, SAID FIRST STAGE NOZZLES BEING CONSTRUCTED AND SPACED AT DISTANCES ONE FROM ANOTHER SUCH THAT THE STREAMS FROM SAID NOZZLES ABRADE A STRIP OF CASING HAVING A WIDTH EQUAL TO AT LEAST FOUR TIMES THE DIAMETER OF SAID SECOND STAGE NOZZLE, SAID SECOND STAGE NOZZLES BEING ANGULARLY DISPLACED FROM THE FIRST STAGE NOZZLES, PORTS IN THE SLEEVE POSITIONED FOR ALIGNMENT WITH THE FIRST STAGE NOZZLES WHEN THE SLEEVE IS IN THE UPPER POSITION, AN OPENING IN THE SLEEVE ANGULARLY DISPLACED FROM THE PORTS AND LOCATED ABOVE THE PORTS WHEREBY THE OPENING IS IN ALIGNMENT WITH THE SECOND STAGE NOZZLE WHEN THE SLEEVE IS IN THE LOWER POSITION, RELEASABLE MEANS FOR HOLDING THE SLEEVE IN THE UPPER POSITION, MEANS FOR MOVING THE SLEEVE FROM THE UPPER TO THE LOWER POSITION, AND MEASN TO PREVENT ROTATION OF THE SLEEVE RELATIVE TO THE NOZZLE HEAD.