US3468386A - Formation perforator - Google Patents

Description

p 3, 1969 E. JOHNSON FORMATION PERFORATOR 2 Sheets-Sheet 1 Filed Sept. 5, 1967 WA//////////// //u INVENTOR. HARO'LD E, JOHNSON ATTORNEYS p 3, 1969 E. JOHNSON FORMATION PERFORATOR 2 sheets-Sleet 2 Filed Sept. 5, 1967 (a fa- INVENTOR. HAROLD E JOHNSON ATTORNEYS United States Patent O 3,468,386 FORMATION PERFORATOR Harold E. Johnson, 4318 Harvard, Midland, Tex. 79701 Filed Sept. 5, 1967, Ser. No. 665,640 Int. Cl. E21b 43/117, 33/12 U.S. Cl. 175-4.6 9 Claims ABSTRACT OF THE DISCLOSURE A formation perforating apparatus is secured sealingly in an opening of a casng sub in a manner that the face of the perforator is unobstructed by the casing shell so that a shaped charge or perforating bullet contained within the perforator does not have to penetrate the casmg upon detonation. The perforator is detonated by Primacord or detonating wire from the surface. The perforator This invention relates to the production of hydrocarbons and more particularly to the perforation of subterranean formations capable of producing oil or gas. Still more particularly, this invention relates to an apparatus for perforating a producng formation, such as an oil producing formaton, to stimulate the production of fluid therefrom.

After a productive formaton, one capable of producing oil or gas, has been drilled to the chosen depth, a casing is inserted down the length of the borehole and the space between the exterior surface of the casing and the interier surface of the borehole is filled with cement. Then, in order to produce fluid from the well, explosive charges or bullet perforators are lowered down the well to a position opposite the productive formation and the explosives are set ofl. The explosive charges or bullets make puneture holes through the casing and cement liner and penetrate into the formation permitting the well fluid to flow into the casing and be produced. 'Ihs process is referred to as completing the well. The greatest disadvantage of this process is that the explosive charge or bullet must penetrate the casing and the total thickness of the cement liner before the productive formation is reached.

The primary object of this invention is to provide a more effective means for perforating a productive formation. Another object of this invention is to provide a means for the perforaton of a productive formation in a manner that the perforating means does not have to first penetrate the casing.

Still another object of this invention is to provide a means for selectively closing open portions of the well casing after the perforation operation has been carried out.

Further objects and advantages of the nvention will become apparent from the following description and claims, and from the accompanying drawings, wheren:

FIGURE 1 is a sectional view of a borehole illustratng one manner in which an apparatus of this invention may be used.

FIGURE 2 is an enlarged sectional view of a shaped charge apparatus used according to this invention.

FIGURE 3 is a sectional View of another embodiment of a shaped charge apparatus according to this invention.

3,468,386 Patented Sept. 23, 1969 FIGURE 4 is a longitudinal sectional view of still another embodiment of a shaped charge according to this invention.

FIGURE 5 is a sectional view of still another embodiment of a shaped charge according to this invention.

FIGURE 6 is a view along the lines 6--6 of FIG- URE 5.

FIGURE 7 is an elevational view of a shifting tool for positioning a sleeve valve of this invention.

This invention comprises the placing of explosive devices, such as shaped charges or perforating guns sealingly in openings in the casing of a well in a manner that when the casing is put in place and the well is cemented, only a thin portion of cement is present between the explosive device and the face of the productive formation. Thus, the shaped charge or bullet need penetrate only a small thickness of cement in order to reach the productive formation. The explosive nnits are preferably ignited by Primacord or detonating wire in a remote manner from the surface. When shaped charges are used, the housing for the charge disintegrates after exploding, and if desired, a sliding sleeve valve may be selectively positioned over 'any of the openings resulting from the shot.

Referring now to the drawings in detail, a borehole 10 is shown drilled through a productive formation 12. Conventionally, after the well is drilled, casing is set in place and the interval between the casing and the face of the borehole is filled with cement. In the figures, a section of casing 14 is shown in position down the' borehole 10 and is surrounded by cement 16 which is used to seal oli formation fluids from the well. Through openings 18 in casng 14 are positioned perforators 20 which are shown in the drawings to be of the type employing a shaped charge, but could also be of the type incorporating perforating bullets. It is preferred to use the shaped charge perforator since the perforator housing is designed to disintegrate upon explosion. 'Ihe perforator 20 slips into an O-ring seal adapter 22 which is external of the casing, and preferably the perforator 20 and O-ring seal adapter 22 abut against a retaining shoulder 24 for increased stability. O-rng seal adapter 22 may be held in place removably as by threads, but preferably, it is generally more convenient to weld the O-ring seal adapter 22 into position on the casing. Perforator 20 is designed to fit closely into O-ring seal adapter 22, and for holding the perforator in a sealable position a recess 26 is formed in O-ring seal adapter 22 and a compressible O-ring 28 of a material such as Neoprene fits into recess 26 and is compressed slightly by surface 30 of perforator 20. O-ring seal adapter 22 includes a recess 32 into which a clip ring 34 is inserted after perforator 20 is in position by means of which clip ring 34 holds perforator 20 in place. Protruding through casing 14 is a conical portion 36 of perforator 20 which is of substantially thicker wall section than a front wall 38 of perforator 20. Front wall 38 is formed purposely thin so that it will be easily frangible. Comical section 36 is given its conformation in order to provide the proper geometry for a shaped charge 40 formed within perforator 20. shaped charge 40 is held in position by a thin Copper liner 41. 'Ihe explosive material forming the shaped charge may be any of the conventional explosives generally used in such shaped charges. At the apex of the conically shaped charge is positioned a booster charge 42 of explosive which is employed to detonate the main body of explosive. An axial passageway 44 provides communication between booster charge 42 and a transverse passageway 46 through which passageway 46 passes a detonating means such as Primacord 48 which is ignitable from the interior of the casing 14 and remotely ignitable from the surface of the ground. That is, an ignition means may be positioned within the casing &468386 close to the perforator and may be controlled from the surface of the ground for safety. Primacord is shown as a preferred ignition means, but other ignition means such as detonating `wire may be used to set off the booster charge and shaped charge.

In using the perforator of this invention the location of the productive formation should be accurately determined in order that the casing sub containing the' desired number of perforating units may be properly located. Well logging and other related conventional measurements may be employed in selecting the most desirable location of the perforating units as well as the number and type of units to be employed. One manner of positioning the formation perforator casing sub is to attach a casing float collar or casing cementing adapter to the bottom of a section of casing of slightly less total length than the distance from the bottom of the hole up to the position chosen to be the lower end of the casing sub. Primacord or detonating wire is attached to each of the perforating units employed and the perforating casing sub is lowered into the hole preferably before the detonating unit 50 is attached. The detonating unit 50 may be of any conventional type usable' with the explosive chosen for the perforators, that is, a mechanical, electrical, or timing device type detonator, and may also be retrievable. After proper positioning of the formation perforating casing sub a locating device such as a gamma ray logging tool having a collar locator may be run down the borehole to check the positioning of the perforating units before completing the operation. If the position of the perforating units is correct, the casing may be cemented in place and after the cement cures, the explosive perforator may be detonated.

It is preferred that the perforator 20 be made of a material which will disintegrate upon explosion of the shaped charge so that the opening 18 in the casing wall will be clean and free of debris. Such a material would be diecast aluminum or an easily frangible ceramic. After detonation, a closure device, such as a sliding O-ring sleeve valve 52 comprisng a tubular section 54 having a close fit against the interior wall of the casing 14, may be moved into position over opening 18 in which a perforator 20 has just been exploded. O-ring sleeve valve 52 includes a circumferential recess 56 near each end of the cylindrical valve into which is placed an O-ring 58 to provide sealing engagement with the interior wall of casing 14. O-rirg sleeve valve 52 is slid into position over opening 18 and in its closed position abuts a stop 60 adjacent opening 18. In the drawing stop 60 is shown in FIGURES 1 and 2 of rectangular crdss-sectional configuration for the sake of clarity. In most installations stop 60 is more suitably formed with an angular or rounded cross-sectional conformation which will facilitate the operation of a sleeve shifting tool and also cause the stops to be less subject to damage from well bore equipment. Sliding O-ring sleeve valve 52 may be operated from the surface by means of a sleeve shifting tool similar to that shown in FIGURE 7. Such a shifting tool is run on a -wireline, rod string, or tubing string. Sleeve valve 52 may be operated selectively so that a chosen number of openings 18 may be covered or uncovered as desired. FIGURE 1 shows, for the purpose of illustration, how a sleeve valve 52 may be brought into a closed position over opening 18 in order to prevent communication between a perforation 64 and the interior of casing 14. Of course, sleeve valve 52 is shown in a simplified form for the sake of illustration and suitable variations in the valve structure are within the scope of this invention. FIGURES 3, 4, 5 and 6 show additional embodiments of shaped charge apparatus prepared according to this invention. In the embodiment shown in FIGURE 3 the shaped charge device is positioned substantially eXteriorly of the casing to which it is attached. A bore 66 is formed in the wall of casing 14 and a threaded mounting boss 68 is inserted through the bore 66 from the exterior of the casing and is held in place by cooperation of a retaining nut 70 threadably engaging the mounting boss. On the eXterior of casing 14 the perforated device includes a thick-walled housing portion 72 preferably made integral with mounting boss 68. Housing 72 has a concave rear surface 74 which permits abutment of the housing with the exterior wall of the casing. inside the housing 72 is positioned a shaped charge 76 which is held in place by a thin frangible wall. 78. Mounting boss 68 has a hollowed-out portion which is occupied by a booster charge 80 so arranged to detonate shaped charge 76. A passageway 82 is provided to communicate with a bore portion 84. Booster charge 80 communcates through passageway 82 with a length of Primacord which is positioned through bore 84. Thus, in operation the shaped charge described in FIGURE 3 is ignited in the same manner as described in the embodiment of FIGURE 2.

In FIGURE 4 is shown an elongated perforating apparatus in which the shaped charge is positioned longitudinally along the casing.

An elongated perforator 86 is positioned exteriorly on the casing 14 and is supported at an upper and lower extremity by a conventional clamping band 88 which can be positioned around the casing and perforator by conventional means, such as a machine nut and bolt, and arranged to hold the perforator in position by cooperation with an extension 90 of the perforator housing. In cross-section elongated perforator 86 is similar to the cross-section of the perforator shown of FIGURE 3.

FIGURES 5 and 6 show still another variaton of exteriorly positioned perforators according to this invention. In this embodiment the formation perforator is positioned around the external periphery of the casing 14. Although a series of arcuate perforators could be positioned around the exterior periphery of the casing, the most convenient and preferred Construction is to use perforators which are essentially semi-circular in shape as shown in FIGURE 5. The semi-circular perforators 92 are held in position abutting the casing 14 in the same manner as the perforators shown in FIGURE 3. That is, a mounting boss 94 is inserted through a bore 96 in casing 14 and is held in position by the cooperation of a retaining nut 98 with threads 100 on mounting boss 94. FIGURE 6 is a longitudinal section view of the semi-circular perforators of FIGURE S and in cross-sectional view shows these perforators to be constructed essentially like the perforators of FIGURE 3.

FIGURE 7 shows a shifting tool 102 usable with the Sliding valve 52 of this invention in positioning valve 52 after formation perforation has been aceomplished. Shifting tool 102 includes a body portion 104 to which is attached a shifting dog 106 and a one-way release trigger 108. shifting dog 106 has protruding therefrom a cocking cam 110, a releasing cam 112, and a shoulder 114. Oneway release trigger 108 is spring-loaded and ratchet controlled so that the trigger is biased to rotate counterclockwise. The shifting tool is run into the casing with shifting dog 106 in a retracted cocked position. When the one-way released trigger 108 contacts upper valve stop 116 the release trigger is rotated counterclockwise to release the lease dog. The tool is then lowered until shoulder 114 approaches lower valve stop 116. Then the direction of movement is reversed so that shoulder 114 is brought into abutment with the lower portion of sleeve valve 52 and the shifting tool raises the sleeve valve to its closed position. At this time the shifting dog is automatically released when releasing cam 112 is forced over upper valve stop 116. Shoulder 114 then slides through sleeve valve 52 and the tool can be extracted. If, instead of raising the shifting tool when the sleeve valve is closed, the shifting tool is again moved downward, cocking cam will contact upper valve stop 116 and the shifting dog can be returned to the retracted position by the rotation of release trigger 108 to its initial cocked position.

&468386 Since many different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the specific embodiments described in detail herein are not to be taken in a limiting sense, since the scope of the invention is best de fined by the appended claims.

What is claimed:

1. A formation perforator comprising:

a casing section positionable in a borehole adjacent a productive formation, said casing having an opening in the wall thereof opposite said productive formation,

perforator means sealingly positonable in said opening of said casing adjacent said productive formation,

means operable from within said casing for actuating said perforator means, and

a sliding sleeve valve interiorly of said casing and positionable adjacent said opening in said casing Wall, said valve operable from within said casing by means controllable from the surface of the ground to position said valve to sealngly cover said opening.

2. A formaton perforator as described in claim 1 in which:

said perforator means includes a housing containing a shaped explosive cha'ge.

3. A formation perforator as described in claim 1 wherein said housing containing said shaped explosive charge is positioned substantally exteriorly of said casing.

4. A formation perforator as described in claim 3 wherein said housing containing said shaped explosve charge comprises an elongated housing positioned parallel to the longitudinal axis of said casing.

5. A formation perforzlor as described in claim 3 wherein said housing containing said shaped explosive churge comprises an elongted housing positioned 'adially around said casing substantially normal to the longtudnal axis of said casing.

6. A formation perforator as described in claim 1 wherein said housing containing said shaped explosive charge is positioned in said opening substantially interiorly of said casng.

7. A formation perforator as described in claim 6 wherein said housing containing said shaped charge includes a thin-walled front portion facing exteriorly of said casing and a thick-walled conical fear portion facing interiorly of said casing, a booster explosive charge positioned adjacent said shaped explosive charge, a transverse passageway adjacent the apex of said conical portion, and ignition means passing through said transverse passage- Way to set off said booster charge, said ignition means ignitable from within said casing.

8. A formation perforator as described in claim 7 in which said housing is removably positiona-ble in said casing, said casing includes a retaining shoulder refining said opening and against which said housing abuts, an O-ring seal adapter adjacent said opening exteriorly of said casing for holding said housing in sealable alignment, and a clip-ring retainer to hold said housing in tight engagement against said retaining shoulder.

9. A formation perforator as described in claim 8 in which said ignition means includes a wire-line ignitor assembly.

References Cited UNITED STATES PATENTS 2,201,290 5/1940 Greene 166-35 X 2,500,754 3/1950 Huber 175-4.52 X

2,587,244 2/1952 Sweetman 175-4.6

2,725,942 12/1955 McCullough 166-37 X 2,775,304 12/1956 Zandmer 166--100 2,873,676 2/1959 Caldwell 175-4.6

2,939,532 6/1960 Morriss 166-63 3,270,8l4 9/1966 Richardson et ai. 166-100 X 3,336,759 8/[967 Copper 166-35 X 3,357,504 12/1967 Calhoun 175-4.52

DAVID H. BROWN, Primary Examiner U.S. Cl. X.R. 166-63,

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