US3048102A

US3048102A - Perforating apparatus

Info

Publication number: US3048102A
Application number: US790215A
Authority: US
Inventors: Maurice P Lebourg
Original assignee: Schlumberger Well Surveying Corp
Current assignee: Schlumberger Well Surveying Corp
Priority date: 1959-01-30
Filing date: 1959-01-30
Publication date: 1962-08-07
Anticipated expiration: 1979-08-07
Also published as: FR1247099A

Description

Aug. 7, 1962 M. P. LEBOURG 3,048,102

PERFORATING APPARATUS Filed Jan. 30, 1959 MOO/V66 F? lebour INVENTOR.

ATTORNEY The present invention relates to perforating apparatus,

and, more particularly, to shaped charge perforating apparatus which is retrievable after firing through a string of tubing in a well and which leaves little or no debris in the well. I So-called expendable type, shaped charge perforating apparatus has been developed which will pass through tubing and is adapted to disintegrate upon detonation of the charges thus leaving an amount of debris in the well. In one arrangement of this type, the shaped charges are disposed in individual, fluid-tight, thin-walled containers (commonly cal-led capsule charges) suitably linked to one another to form a chain of charges. Another arrangement has shaped charges disposed within a fluidtight, frangible, thin-walled housing. While these arrangements enjoy a certain degree of success, there is always a certain amount of debris from the containers or housmg which must be left in the well. Ordinarily, the debris is of little consequence, but in some applications it is desirable to reduce the debris left in the well.

One proposed solution to reduce the amount of debris left in the well has been to eliminate the linkages or frangible housing by placing capsule charges in a retrievable frame or carrier member. However, the reduction of debris has not been significant since most of the debris results from the break-up of the capsule container itself. Additionally, after the carrier member has been exposed to one or more operations, it is distorted beyond use by the explosive pressures generated when the charges are detonated. Therefore it will be appreciated that there is a need for an inexpensive perforating apparatus which will reduce the amount of debris left in the well.

It is, accordingly, an object of the present invention to provide a new and improved shaped charge perforating apparatus for use in wells having a string of tubing arranged so that the debris from detonated shaped charges may be retrieved through the string of tubing.

It is a further object of the present invention to provide a new and improved housing for shaped charge perforating apparatus for use in wells having a string of tubing wherein the housing and shaped charges therein are so arranged that the explosive pressures generated upon detonation of the shaped charges do not unduly distort the housing thereby permitting the housing to be retrieved through the tubing.

Another object of the present invention is to provide new and improved housing for shaped charge perforating apparatus for use in wells having a string of tubing wherein the housing is provided with a wall portion of reduced thickness adjacent a shaped charge to improve the performance of the charge and control the outward protrusion of the burr caused by an explosive jet penetrating the wall portion upon detonation of a shaped charge.

A still further object of the present invention is to provide a new and improved housing, for shaped charge perforating apparatus for use in wells having a string of tubing wherein the housing is both retn'evable and expendable and of simple and economic construction.

These and other objects of the present invention are accomplished by perforating apparatus having explosive shaped charges disposed within an elongated thin-Walled tubular housing which is adapted to retain the debris upon detonation of the charges. The outer wall surface of the housing is provided with a concavity or indentation adjacent to the forward end of a shaped charge so as 3,048,102 ?atented Aug. 7, 1962 to be penetrated readily by the perforating jet of the charge and minimize the outward protrusion of the burr caused by the jet thereby permitting the housing to be retrieved through thestring of tubing.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings in which:

FIG. 1 is an elevatioual view of perforating apparatus which embodies the present invention disposed below the lower end of a tubing string in a section of a cased borehole;

FIG. 2 is a view in longitudinal cross section illustrating a portion of the perforating apparatus shown in FIG. 1 before detonation of the shaped charge;

FIG. 3 is a transverse cross-sectional View taken along lines 33 of FIG. 2;

And FIG. 4 is a longitudinal cross-sectional view of the portion of the housing shown in FIG. 2 after detonation of the shaped charge.

Referring now to FIG. 1, a portion of a cased borehole 10 is shown traversing earth formations 11 and 12, the formation 12 being assumed to be the formation of interest. A tubing string 14 extends downwardly from the ground surface to some point above the formation 12 while the annulus between the lower end of the tubing string 14 and the cased borehole 10 is suitably packed off by conventional packing means 15. Perforating apparatus 16 embodying the present invention is shown in position adjacent earth formation 12 and generally includes a cable head 17, a conventional casing collar locator 18, a tubular housing 19 and a bottom nose piece 20 which fully closes the bottom end of the housing. Collar locator 18 and bottom nose piece 20 are coupled to the housing 19 by suitable fluid-tight connections so that the housing is sealed with respect to well fluids, although its interior remains at some appropriate pressure, as, for example, atmospheric pressure. Housing 19 may be constructed of steel or any appropriate material having a sufficient strength to resist well pressures and tc avoid disintegration or undue distortion when the perforating apparatus is operated.

Apparatus 16 is adapted to be lowered through the borehole into a position adjacent earth formation 12 and retrieved therefrom through tubing 14 by means of a winch (not shown) at the ground surface and an armored electrical cable 21 connected between the winch and the cable head 17. While it is not shown, it is apparent that various means may be employed to position the apparatus centrally in the borehole, for example, conventional centralizing means. Likewise, eccentering means, sucl as the magnetic orienting device disclosed in the copending application Serial No. 719,255, filed March 5, 1958 by Maurice P. Lebourg may be employed to eccentricall position the apparatus.

Spaced vertically from one another within housing 1! are a plurality of conventional shaped charge explosive: 22 which are interconnected for detonation by an igniting means 23 as, for example, a conventional primacord A detonator or blasting cap 24 for the primacord is con nected through the electrical cable 21 to a control switcl (not shown) at the surface so that the firing of th charges 22 may be initiated electrically in a well-know] manner.

As shown in detail in FIG. 2, housing 19 is a thin walled tubing member which receives an elongated shapet charge 22 having a longitudinal axis 28 which is dis posed transversely to the longitudinal axis 28a of th housing. While only a portion of the housing and on shaped charge is shown, it should be understood tha other portions of the housing and charges are similarly arranged, the charges being distributed along the housing so as to face one of several directions in a customary fashion.

Shaped charge 22 includes an elongated hollow container 25 having a forward, tubular portion 26 and a rearward, frustoconical, thin-walled portion 27 which tapers inwardly from the tubular portion 26 towards longitudinal axis 28 of the charge 22. The forward extremity 29 of the tubular portion 26 (FIG. 3) is suitably curved so as to conform to the curvature of the inner wall 33 of the housing. At the rearward extremity of the container 25 is a semi-cylindrical recess 30 extending transversely to the longitudinal axis 28 of the charge which receives the primacord 23. With the primacord 23 in recess 30 the assembled primacord and container may be slidably positioned within the housing 19.

Container 25 is firmly secured and located within the housing by means of a fixture 31 provided with an annular collar 32a which receives and is suitably fixed, as for example, by welding, to the forward tubular portion 26. An extension 3211 projects from the lower extremity of collar toward a wall portion of housing 19 adjacent to and below the forward extremity 29 of tubular portion 26 and joins a downwardly extending tang 320 which conforms to and is in contact with the inner wall 33 of the housing. A threaded bore 34 in the lower end of the tang 320 is adapted to be aligned with a lateral opening 35 in the wall of the housing so that a fastener 36, for example, a screw, may secure the container 25 in a fixed position Within the housing with extremity 29 engaging surface 33. It will be appreciated that so long as fastener 36 engages threaded bore 34, the charge 22 is accurately positioned and fixed within the housing at all times.

The hollow container 25 is substantially filled with a high explosive 37 and a small, conventional booster explosive material 38 is disposed adjacent to the primacord 23 at the rearmost end of the primary explosive 37. The explosive materials are composed of suitable materials well known to those skilled in the art, for example, the booster explosive may be 98% cyclonite and 2% wax and the primary explosive, pure cyclonite. For a given size of container 25, the amount of primary explosive 37 may be decreased by the provision of an open-end, comically-shaped liner 40 or spacer fitted within the rearward portion 27 of the container. It will, of course, be apparent that the size and shape of the liner 40, or of the container 25, may be varied to accommodate any desired amount of explosive. The forward end of the primary explosive material 37 is provided with a conicallyshaped cavity and fitted with a metal liner 41, for example, of copper, in a well-known manner.

In accordance with the present invention, a portion of the housing 19 adjacent to the forward end of the lined cavity is cut away as best seen in FIG. 2 to form an indentation or concavity 42 disposed directly in the path of the perforating jet which, of course, is generated upon the detonation of the shaped charge. More specifically, the indentation 42 is defined by an arc of an imaginary cylinder with the axis 44 of the cylinder transverse to the longitudinal axis 28 of the shaped charge and with the axes 28, 44 lying in a common plane. The precise form of the indentation may be varied so long as the portion of the indentation which is to be penetrated is spaced between the inner and outer walls of the housing a sufficient distance. Moreover, the shape and size of the indentation and the thickness of the housing wall in the indented portion should be arranged to resist deformation due to Well pressures to be encountered. With proper spacing, the indentation, when penetrated by the explosive jet of the charge, contains the major portion of the burr within the cylindrical confines of the outer wall of the housing.

In operation, the perforating apparatus 16 is lowered through the tubing 14 until it is disposed adjacent the formation to be penetrated. Thereafter the charges 22 are detonated in a well-known manner. The detonation of each of the charges 22 produces a perforating jet which pierces a central portion of the indentation 42. A burr 45 (FIG. 4) is formed about the penetration hole '46 which extends outwardly from the periphery of the hole and has a major portion remaining within the confines of the cylinder defined by outer wall 43 of the housing. Small tips of the burr 45 which may extend beyond the outer wall of the housing are easily broken 01f upon contact with the tubing '14 or casing when the apparatus is raised. Fragments of the container 25 are retained with the housing 19 so that the debris may be retrieved with the housing.

The explosive pressures generated by the detonated charges have a high order of magnitude for a short period of time tending to expand the Walls of the housing particularly in a zone intersected by the plane defined by line 33 (FIG. 2) so that some bulging of the housing will occur (FIG. 4). However, it will be appreciated that since the indented portion of the housing adjacent the forward end of a shaped charge retains the burr within the confines of the outer Wall of the housing, the bulging of the housing is the only factor remaining to hinder passage of the housing through a small diameter tubing. It is, of course, necessary to control the swelling of the housing so that the housing is not split by the explosive forces.

The swelling of the housing may be controlled by adjusting the ratio of the explosive weight relative to the spacing of the shaped charge from the inner walls of the housing. For example, if the tubing 14 has a nominal internal diameter of 2 /2 inches and the diameter of the housing is 2 inches then the swelling may be slightly less than a half-inch. In actual practice, for a measure of safety the swelling is held to a low value.

The following practical embodiments of the present invention serve to illustrate more clearly its applications, but are illustrative only and should not be considered as limiting the scope of the invention in any sense.

Examples Housing CD. (in) 1% 1% 1% 2 2 s 2 2% Housing 1.1). (in)- 1% 1% 1 1 ,4 1% 1 1% Material (U Wall Thickness (in.) A6 its V1 710 40 Weight of Explosive (gr. 4 4 8. 8 6 7. 0 7. 2 8. 8 Open Area A (sq. m.) 15 15 15 15 15 15 15 Ratio of Weight of Explosive (grams) to Open Area (sq. in.) 26.7 26.7 58.6 33.3 46.7 48 58.6 Housing O.D. After Firing (lines 33). 1 962 1 %2 296.2 2%; 2%2 2 2 ghotls per foot of Housing 2 4 2 4 2 2 2 we mg 34x2 2 9 2 External Fluid Pressure on Housing at A 362 M52 A2 A2 time of firing p.s.i. (internal pressureatmosphnc) 500 500 2 1, 000 500 500 600 500 1 Cold rolled mild steel.

1 Increased to prevent splitting of housing.

In the foregoing examples, the open area A is calculated by subtracting the cross-sectional area of the container in the plane defined by lines 33 from the area defined within the inner wall of the housing. It will be noted that if the Weight of explosive for a given area A is increased the swelling will increase. Similarly, if the area is decreased for a given weight of explosive the swelling increases. It has been found that when the area A is decreased to a Zero value, the housing invariably splits. Although the precise mathematical relationship between the various factors which control the swelling has not been found, the above examples serve amply to illustrate the invention.

The indentation in the housing for the foregoing examples was an arc of a cylinder having 2 /2 inches diameter with the thinnest portion of the wall measuring A of an inch. It has been found that with a minimum thickness of of an inch for the wall that the perforating apparatus can withstand borehole pressures of at least 10,000 p.s.i.

It will be appreciated from the foregoing that the present invention provides a perforating apparatus adapted to be retrieved through tubing after firing. This is accomplished by providing a wall portion of reduced thickness adjacent the forward end of a shaped charge which improves the performance of the charge and controls the outward protrusion of the burr. The housing and shaped charge are also arranged so that the bulging effect of the housing is controlled. It will be further apparent that the debris from the charges is retained within the housing. Since the housing may be made of ordinary stock material and little machining is required, the housing is simple and inexpensive to fabricate for perforating operations. Thus, although the housing is expended upon one trip into a well, it is entirely within the economics of perforating service.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made Without departing from this invention in its broader aspects, and therefore the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A shaped charge perforating apparatus sized to be lowered and raised through a string of small-diametered tubing between the ground surface and a level desired to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: an elongated, functionally integral tubular housing including inner and outer cylindrical wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one indentation therein which extends inwardly from said outer wall surface towards said inner wall surface thereby forming a wall portion of reduced thickness, said wall portion of reduced thickness having sufiicient strength to resist the effects of borehole pressures encountered, and being spaced inwardly from said outer wall surface a sufficient distance to contain the major portion of a burr formed within the cylindrical confines of said outer wall surface when the Wall portion is penetrated, and perforating means disposed within said housing and sized to extend across substantially the diameter of said bore, said perforating means including an explosive material having a forward, hollowed-out end portion positioned adjacent to said wall portion of reduced thickness.

2. A shaped charge perforating apparatus sized to be lowered and raised through a string of small-diametered tubing between the ground surface and a level desired to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: an elongated, functionally integral tubular housing having a longitudinal axis and including inner and outer cylindrical wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one concavity therein which extends inwardly from said outer wall surface towards said inner wall surface thereby forming a wall portion of reduced thickness, said wall portion of reduced thickness having sufficient strength to resist the efiects of borehole pressures encountered and being spaced inwardly from said outer wall surface a sufficient distance to contain the major portion of a burr formed within the cylindrical confines of said outer wall surface when the wall portion is penetrated, and perforating means disposed within said housing and sized to extend across substantially the diameter of said bore, said perforating means including an explosive material having a forward hollowedout end portion positioned adjacent to said wall portion of reduced thickness, the cross-sectional area of said perforating means transverse to said longitudinal axis being less than the cross-sectional area defined within said inner wall surface to provide an air space thereby minimizing the bulging effect caused by detonation of said explosive.

3. A shaped charge perforating apparatus sized to be lowered and raised through a string of tubing between the ground surface and a level desired to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: an elongated, functionally integral tubular housing having a longitudinal axis and including inner and outer cylindrical wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one concavity extending inwardly from said outer Wall surface towards said inner wall surface thereby forming a wall portion of reduced thickness, said wall portion of reduced thickness having suificient strength to resist the effects of borehole pressures encountered and being spaced inwardly from said outer wall surface a sufficient distance to contain the major portion of a burr formed Within the cylindrical confines of said outer wall surface when the wall portion is penetrated, and perforating means disposed within said housing and sized to extend across substantially the diameter of said bore, said perforating means including an explosive material having a forward, hollowed-out end portion positioned adjacent said wall portion of reduced thickness, the cross-sectional area of said perforating means transverse to said longitudinal axis being less than the cross-sectional area defined with. in said inner wall surface to provide an air space thereby minimizing the bulging effect caused by detonation of said explosive, said concavity having an outer periphery on said outer surface which is greater than the periphery of a hole through said wall portion of reduced thickness caused by detonation of said explosive material.

4. A shaped charge perforating apparatus sized to be lowered and raised through a string of small-diametered tubing between the ground surface and a level desired to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: anelongated, functionally integral tubular housing constructed of ductile material throughout its length and having a relatively thin wall, said housing further having a longitudinal axis and having inner and outer cylindrical wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one indentation in the outer surface thereby forming a wall portion of reduced thickness, perforating means disposed within said housing and sized to extend across substantially the diameter of said bore, said perforating means including an explosive material having a forward hollowed-out end portion positioned adjacent said wall portion of reduced thickness, said indentation being spaced between said inner and outer surfaces so that upon penetration by an explosive jet, the major portior of a burr formed will lie within the cylindrical confines of said outer surface.

5. A shaped charge perforating apparatus sized to be lowered and raised through a string of small-diametered tubing between the ground surface and a level to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: an elongated, functionally integral tubular housing having a longitudinal axis and including inner and outer cylindrical wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one indentation in the outer surface thereby forming a wall portion of reduced thickness, said indentation being defined by the arc of an imaginary cylinder having an axis transversely positioned relative to said longitudinal axis, perforating means disposed within said housing and sized to extend across substantially the diameter of said bore, said perforating means including an explosive material having a forward hollowed-out end portion positioned adjacent said wall portion of reduced thickness, said indentation being spaced between said inner and outer surfaces so that upon penetration by an explosive jet, the major portion of a burr formed will lie within the cylindrical confines of said outer surface.

6. A Shaped charge perforating apparatus sized to be lowered and raised through a string of small-diametered tubing between the ground surface and a level to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: an elongated, functionally integral tubular housing having a longitudinal axis and including inner and outer cylindrical Wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one indentation in the outer surface thereby forming a wall portion of reduced thickness, said indentation being defined by the arc of an imaginary cylinder having an axis transversely positioned relative to said longitudinal axis, said housing further having at least one location opening for each indentation spaced longitudinally from an indentation, perforating means sized to be slidably received through one of the ends of said housing and extend across substantially the diameter of said bore, said perforating means including a hollow container having a preselected fastening location disposed longitudinally from said hollow container a distance comparable to the longitudinal spacing between said location opening and said indentation, an xplosive material having a forward hollowed-out end portion in said container positioned adjacent said wall portion of reduced thickness, said for- Ward end portion thereby being disposed in a preselected position relative to said fastening location, said indentation being spaced between said inner and outer surfaces so that upon penetration by an explosive jet, the major portion of a burr formed will lie within the cylindrical confines of said outer surface, and fastening means adapted to extend through said location opening into said preselected fastening location to secure said container to said housing and thereby provide an indication of the location of the forward end portion of said explosive material.

7. A shaped charge perforating apparatus sized to be lowered and raised through a string of small-diametered tubing between the ground surface and a level to be perforated and adapted to retrieve the debris from the shaped charges therein comprising: an elongated, functionally integral tubular housing having a longitudinal axis and including inner and outer cylindrical wall surfaces, a portion of said housing having a bore of uniform diameter defined by said inner wall surface and having at least one indentation in the outer surface thereby forming a wall portion of reduced thickness, said indentation being defined by the arc of an imaginary cylinder having an axis transversely positioned relative to said longitudinal axis, said housing further having at least one location opening for each indentation spaced longitudinally from an indentation, perforating means sized to lie disposed within said housing through one of the ends of said housing, said perforating means extending across substantially the diameter of said bore and including a hollow container having a portion with a threaded bore, an explosive material having a forward hollowed-out end portion in said container positioned adjacent said wall portion of reduced thickness, said forward end portion thereby being disposed in a preselected position relative to said threaded bore, said indentation being spaced between said inner and outer surfaces so that upon penetration by an explosive jet the major portion of a burr formed will lie within the cylindrical confines of said outer surface, and screw means adapted to extend through said location opening into said threaded bore to secure said container to said housing and thereby provide an indication of the location of the forward end portion of said explosive material.

8. A shaped charge perforating apparatus comprised of: an elongated, functionally integral tubular housing having selected areas along its length, said housing having location openings respectively displaced from said selected areas of the housing so as to avoid coincidence therewith, a plurality of hollow containers sized to be disposed within said housing through one of the ends of said housing and sized to extend across substantially the diameter in said housing, said containers respectively having a preselected fastening portion displaced from the hollow portion of said containers so that when said fastening portions are aligned with said location openings the hollow portions are adjacent said selected areas; explosive material having a forward hollowed out end portion for developing a perforating jet disposed in the hollow portion of each of said containers so that said explosive material when detonated will develop a perforating jet through a selected area; and fastening means arranged to extend through said location openings for securing said fastening portions to said housing to insure alignment of the perforation jets with said selected areas and to provide an indication of such alignment.

9. A shaped charge perforating apparatus comprised of: an elongated, functionally integral tubular housing member having selected areas along its length, said housing having location openings respectively displaced from said selected areas of the housing so as to avoid coincidence therewith, a plurality of hollow containers sized to be disposed within said housing through one of the ends of the said housing and sized to extend across substantially the diameter in said housing, said containers respectively having a threaded bore portion displaced from the hollow portion of said containers so that when said threaded bore portions are aligned with said location openings the hollow portions are adjacent said selected areas; explosive material having a forward hollowed out end portion for developing a perforating jet disposed in the hollow portion of each of said containers so that said explosive material when detonated will develop a perforating jet through a selected area; and screw means arranged to extend through said location openings for securing said threaded bore portions to said housing to insure alignment of the perforating jets with said selected areas and to provide an indication of such alignment.

10. Perforating apparatus comprising: a thin-walled, tubular, ductile, metallic, functionally integral housing sized for passage through a small-diametered well string with minimum safe clearance, said housing in its normal condition having cylindrical inner and outer surfaces free of protuberances, said housing having a series of cylindrically curved concavities spaced longitudinally of said housing along its outer surface, the axes of said housing and said concavities being transverse, a plurality of shaped charges sized for slidable positioning within said housing in a transverse position with their front end conforming to said inner surface, means extending longitudinally of said shaped charges within said housing for positioning said charges having front end portions aligned with respect to each of said concavities, and means for closing the ends of said housing against entry of fluid and escape of debris, the front end of each shaped charge being substantially co-extensive with the corresponding concavity to form a perforation burr centrally of such concavity substantially Within the cylindrical profile of said outer surface.

11. Perforating apparatus comprising: a thin Walled, tubular, ductile, metallic, functionally integral housing having cylindrical inner and outer surf-aces, said housing having a bore of uniform diameter defined by said inner wall surface and having a series of cylindrically curved concavities in said outer surface which are spaced longitudinally from one another, a plurality of shaped charges positioned Within said housing arranged to produce perforating jets along perforating axes transverse to the axis of said housing, said shaped charges extending across substantially the diameter of said bore, means for se- 10 curing said shaped charges relative to said housing so that their front end portions respectively are centrally aligned with a concavity, so that a perforation burr formed \by a perforating jet penetrating a concavity lies substantially within the cylindrical profile of said outer surface.

References Cited in the file of this patent UNITED STATES PATENTS