US3190219A - Perforating device - Google Patents

Description

June 1965 A. VENGHIATTIS PERFORATING DEVICE Filed Feb. 2; 1960 IN V EN TOR.

/e 'eei WM w Arm/m5) United States Patent ice 3,190,219 PERFGR'ATING DEVICE Alexis Vengliiattis, Houston, Tex., assignor to Dresser Industries, Inc, Dallas, Tex., a corporation of Delaware Filed Feb. 2, 1960, Ser. No. 6,317 7 Claims. (Cl. 102-20) This invention relates to pressure wave forming and directing devices and more particularly to explosive devices adapted for theperforating of well casing in oil, gas and water wells and the like earth boreholes for obtaining production from fluid-bearing formations traversed by such earth boreholes.

In the past, perforating has been carried out principally either by means of bullet guns or by shaped charges utilizing the so-called Monroe Effect. In a shaped charge,

an explosive body is provided with a hollowed-out portion, usually in the form a cone-shaped concavity in its forward surface, and detonation thereof causes the formation of a high velocity jet of gases to issue forwardly from such hollowed-out portion or concavity which has very substantially penetrating power.

In well perforating by either bullets or shaped charge jets, an opening in the surrounding earth formation is produced by the displacement and resulting compaction of the formation material. This compaction produces a region of compressed material of reduced permeability around the perforation which is known in the art as the damaged zone and which has the effect of impeding the flow of fluids from the formation through the perforation and into the well borehole or casing. It has been found to be advantageous to introduce a quantity of corrosive substance, such as nitric or hydrochloric acid, into such perforations as they are formed, in sufficient quantity to partially dissolve or loosen the compacted particles of the damaged zone and'thus restore or increase'the effective permeability of the perforated formation. Although many methods have been proposed to incorporate corrosive substances into the perforations simultaneously with their formation, no means has heretofore been provided for introducing the corrosive substance in as great a quantity as is made possible by the present invention.

It is an object of the present invention to provide an explosive device for perforating earth formations through casing without utilizing either bullets or shaped charges.

It is a further object of the invention to provide a device effective to introduce a substantial quantity of acid or other corrosive substance into a perforation as it is formed in an earth formation.

It is another object of the invention to provide an explosive device for use in perforating through the casing of an oil well, which device is highly effective, relatively inexpensive and simple to manufacture.

These objects are attained by providing an explosive device which includes a pressure-wave refracting and directing member which has a forwardly opening concave surface with pressure-wave-producing means, such as a body of explosive, adjacent this surface, rearwardly thereof and spaced therefrom by a body of inert, that is, non-explosive, pressure-wave transmission material. This transmission medium is preferably a liquid and in some embodiments of the invention is water, while in others it is a corrosive substance such as hydrochloric acid. The

3,190,219 Patented June 22, 1965 explosive body, unlike that used in the shaped charge devices, need not have a concave or hollowed out forward surface portion since the present invention does not depend for its operation upon the Monroe Effect as that phenomenon is generally understood by those skilled in the art. Because the Monroe Effect is not utilized in the invention, the means for producing the pressure-wave may assume a variety of forms and shapes and can be put to uses for which conventional shaped charges are unsuitable or impractical.

In the accompanying drawings:

FIG. 1 is a view in longitudinal section taken through an explosive device in accordance with one form of the invention; and

FIG. 2 is a View partially in longitudinal section taken through a portion of the body of a perforating gun embodying another form of the invention.

Turning first to FIG. 1, there is illustrated an individual explosive device or capsule 10 a plurality of which may be assembled into a perforating gun just as individual shaped charge capsules are so assembled. Capsule 10 includes a generally cylindrical outer case 11 made of a suitable metal or plastic closed at the front with a cap 12 (which is fluid-tight) and enclosing in its rear portion a body 13 of high explosive material. The explosive body 13 may be any of the well known explosives such as compressed pentaerythritol tetranitrate, blends of this compound with trinitrotoluene, or compressed trimethylene trinitramine, sold under the trade name of RDX. The explosive body 13 is of generally cylindrical shape and has a substantially flat planar front or forward surface 14.

Located behind the explosive body 13 is a booster charge 16, a smaller body of explosive which is indirect contact with body 13. The booster charge is detonated in conventional manner by an elongated detonating cord (not shown) which passes through the opening 17 and is separated from booster charge 16 by thin wall 1111. Such detonating cord is known as Primacord and is widely used for detonating shaped charges.

A cone 18 is located forwardly of the explosive body 13 with its edges retained by or attached to the side of the case 11 as by solder or a suitable adhesive and with its concave outer surface 19 facing outwardly toward the cap 12. The cone 18 is preferably fabricated by powder metallurgy techniques from a material such as copper powder or, alternatively, it may be cut from sheet metal. Cone 18 is usually provided with a rounded apex. In a typicalernbodiment of the invention employing a 20 gram explosive body, cone 18 was formed from sheet copper to a thickness of 0.020 inch; had an included angle of 45 and was rounded to a radius of 7 of an inch at its apex.

The inner surface of the case 11, the convex inner surface 21 of the cone 18 and the forward surface 14 of the explosive body 13 define a dishshaped space 2.2 which in FIG. 1 is shown as filled with a body of liquid indicated by the reference character 23. In assembling the device the liquid is introduced into the space 23 by any convenient means such as through a port 24 in the side of case 12 which is shown as closed by theplng26. The

A plurality of indvidual capsules lltl may be assembled into a gun for making a plurality of perforations simultaneously as is well known to the art. The capsules may be assembled according to the teachings of, for example, US. Patent 2,756,677 to I. J. McCullough or U.S. Patent 2,764,938 to R. P. Harcus.

Upon detonation of the explosive body 13, the pressure-wave produced thereby is transmitted through the body of liquid 23 and is focused by the liquid body 26 and cone 18 into a relatively small diameter, high velocity forwardly moving stream composed of minute metal particles followed by the liquid 23 with the result that the well casing, cement, and adjacent earth formation in its path are penetrated in the form of a generally pencilshaped perforation similar to the one formed by shaped charges. The effect of the following liquid stream is to increase depth of penetration and to clean the opening of extraneous particles.

In some instances, such as the fracturing of earth formations to increase fluid flow or for cutting metal bodies and the like, it is desirable to form elongated cuts having shapes other than round in cross section. It will be evident that this result may be attained by altering the shape of the device it) to provide the case 11 and the explosive body 13 in the form of rectangular prisms rather than cylinders and altering the shape of the cone 18 to the form of a dihedral. A number of such units may be joined in a closed or annular assembly so that pressurewave is thereby directed radially outward or radially inward. Such a device is useful in the severing of stuck drill pipe or the like tubular members.

FIG. 2 illustrates, partly in longitudinal section, a portion of a cylindrical gun body adapted to be lowered into a borehole for perforation through casing, The generally cylindrical gun body 60 is hollow and is shown as being substantially filled by water or other suit-able liquid indicated by the reference character 61. The gun body has a plurality of apertures located in its sides, two of which are illustrated. Each opening is closed by a metallic screw port 63 which cooperates with gasket 62 to exclude borehole fluid from the gun body. A metallic cone 64 of the same type used as a focusing means in the previously described embodiment is secured fluid-tight at its outer edges to the screw port 63 by the solder connection indicated at 65 and extends into the interior of the gun body 60. The space 55 between the cone 6% and the screw port 63 is maintained free of liquid by reason of its fluid-tight sealed connection with the screw port.

The pressure-wave-producing means in this embodiment of the invention is an elongated cylindrical body of explosive 66 shown in elevation in FIG. 2. The explosive body is composed of a high explosive such as the RDX compound mentioned hereinbefore which is capable of being extruded or otherwise shaped into an elongated cylindrical body. Alternately, the explosive body 66 may consist of a tubular container filled with high explosive in granular or other suitable form. A suitable detonating device (not shown) is located at the top or bottom or both ends of the gun for electrical actuation from a remote point as is well known in the prior art.

In designing a gun of the type illustrated in FIG. 2, it is desirable to provide a sufficient number of pressure- Wave-directing devices (made up of cones and screw ports such as shown at 64 and 63 respectively) per unit length of body 60 so as to permit sufiicient release of the energy produced by the explosive to prevent or minimize damage to the gun body.

In either of the embodiments described, the liquid pressure-wave transmission medium may be either a chemically inert liquid, such as water, or a chemically reactive corrosive substance, such as an acid. The function of such acid is, in addition to serving as a pressure-wave transmission and refracting medium, to react with the damaged zone hereinbefore discussed and partially dissolve the same so as to increase the permeability of the inside walls of the perforations formed and to encourage the drainage of hydrocarbon fluids into them from the penetrated formation. Acids suitable for this purpose include hydrochloric acid and nitric acid, the particular acid chosen depending, of course, upon the chemical constitution of the particular formation being perforated.

In embodiments of the invention used within an earth borehole, the pressure-wave transmission medium may be a normally solid substance which liquifies at the high temperatures encountered within typical earth well boreholes. An example of such substances is orthophosphoric acid which, because of its chemical reactivity, is particularly useful in acidizing certain types of earth formations.

The present invention, then, provides a new and efficient means of perforating well casings and adjacent earth formations and of simultaneously injecting corrosive substances such as acid into the perforations to improve fluid flow into them. It will be apparent to those skilled in the art that certain modifications of the invention such as that illustrated in FIG. 1 may easily be adapted for such purposes as the internal severing of drill pipe, such as, for example, to facilitate its removal froma well wherein it is stuck. Such a cutting device is, of course, not limited to use within a Well but may find application in the metal severing art generally. 1

While certain specific embodiments of the invention have been described herein in detail it is to be understood that such is illustrative only, and that the invention is not limited thereby but includes all modifications thereof within the scope of definition of the appended claims.

I claim:

1. A device adapted to be lowered into an earth well borehole to produce perforations in the wall thereof comprising: a hollow, elongated case; means forming a plurality of openings in the side of said case; closure means covering each of said openings; a cone around each of said openings and extending with its apex pointed toward the interior of said hollow case; an elongated body of high explosive within said case extending longitudinally thereof, said explosive body being formed with a convex exterior surface; a non-explosive liquid pressure-wave transmission medium substantially filling the interior of said hollow body between said cones and said explosive body; and means for detonating said explosive body.

2. A device according to claim 1 wherein said pressure-wave transmission medium is water.

3. A device according to claim 1 wherein said pressure-wave transmission medium is an acid.

4. A device according to claim 1 wherein said pressure-wave transmission medium is hydrochloric acid.

5. A device adapted to be lowered into an earth well borehole for producing perforations in the wall thereof, comprising: an elongated, hollow generally cylindrical case; means forming a plurality of openings in the side of said case; closure means covering each of said openings; a cone around each of said openings and extending with its apex pointed toward the interior of said hollow case; an elongated body of a high explosive within said hollow case and extending longitudinally thereof, said explosive body formed with a convex surface; a nonexplosive liquid pressure-wave transmission medium substantially filling the interior of said hollow case between said cones and said convex surface of said explosive body; and means for detonating said explosive body.

6. A device according to claim 5 wherein said explosive body is a cylinder extending coaxially of said case.

7. A device adapted to be lowered into an earth well borehole for producing perforations in the wall thereof, comprising: an elongated hollow generally cylindrical case; means forming a plurality of openings in the side of said case; closure means covering each of said openings; a cone around each of said openings and extending with its apex pointed toward the interior of said hollow case; an elongated body of high explosive within said 5 6 hollow case and extending longitudinally thereof; a non 2,630,182 3/53 Klotz 102-21 explosive liquid pressure-wave transmission medium sub- 2,833,215 5/58 Spencer 102-21 stz ntially filling the interior of said hollow case between FOREIGN PATENTS said cones and said explosive body; :and means or detonating said explosive body. 5 1,161,445 3/58 France- Refel-ences Cited by the Examiner BENJAMIN A. BORCHELT, Primary Examiner.

UNITED STATES PATENTS ARTHUR M. HORTON, SAMUEL BOYD, Examiners.

Rs. 21,356 2/40 P itzer 102=21 I 1,913,015 6/33 Vodoz 102 24

Claims (1)

1. A DEVICE ADAPTED TO BE LOWERED INTO AN EARTH WELL BOREHOLE TO PRODUCE PERFORATIONS IN THE WALL THEREOF COMPRISING: A HOLLOW, ELONGATED CASE; MEANS FORMING A PLURALITY OF OPENINGS IN THE SIDE OF SAID CASE; CLOSURE MEANS COVERING EACH OF SAID OPENINGS; A CONE AROUND EACH OF SAID OPENINGS AND EXTENDING WITH ITS APEX POINTED TOWARD THE INTERIOR OF SAID HOLLOW CASE; AN ELONGATED BODY OF HIGH EXPLOSIVE WITHIN SAID CASE EXTENDING LONGITUDINALLY THEREOF, SAID EXPLOSIVE BODY BEING FORMED WITH A CONVEX EXTERIOR SURFACE; A NON-EXPLOSIVE LIQUID PRESSURE-WAVE TRANSMISSION MEDIUM SUBSTANTIALLY FILLING THE INTERIOR OF SAID HOLLOW BODY BETWEEN SAID CONES AND SAID EXPLOSIVE BODY; AND MEANS FOR DETONATING SAID EXPLOSIVE BODY.

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