US3620314A

US3620314A - Combination bullet-perforating gun and shaped charge perforator apparatus and method

Info

Publication number: US3620314A
Application number: US866834A
Authority: US
Inventors: Floyd O Bohn
Original assignee: Dresser Industries Inc
Current assignee: Western Atlas International Inc
Priority date: 1969-10-16
Filing date: 1969-10-16
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16
Also published as: FR2064369B3; FR2064369A7

Abstract

A bullet-perforating gun and a shaped charged perforator are aligned in a common plane within a tool suitable for passage through an earth borehole. One or both of the perforators have their axes, respectively, inclined such that the resulting two perforations intersect before either reaches its normal depth of penetration. The perforators are arranged to fire simultaneously. Because of the time difference in speed of action, the shaped charge perforates first. At a time later, the bullet makes a perforation which breaks into the shaped charge perforation. In escaping through the shaped charge hole, the gases flush out the pulverized material from the bullet perforation, the shaped charge perforation and any enlargement of the common portions of the two holes.

Description

United States Patent [72] Inventor Floyd 0. Bohn Houston. Tea.

[21] Appl. No. 866,834

[22] Filed Oct. 16, 1969 (45] Patented Nov. 16, 1971 [73] Assignee Dresser lndustrles, Inc.

Dallas, Tex.

[ 54] COMBINATION BULLET-PERFORATING GUN AND SHAPED CHARGE PERFORATOR APPARATUS AND METHOD 5 Claims, 6 Drawing Figs.

[51] lnt.Cl E2111 43/117 [50] Field of Search l75/4.57-4.6;

[56] References Clted UNITED STATES PATENTS 2,928,658 3/1960 Miner 17514.6 x 3,080,005 3/1963 Porter l75/4.6 x

3,089,416 5/1963 Gilbert 175/411 3,101,051 8/1963 Gilbert..... 175/41: 3,348,621 10/1967 Schuster 175/41; X

ABSTRACT: A bullet-perforating gun and a shaped charged perforator are aligned in a common plane within a tool suitable for passage through an earth borehole. One or both of the perforators have their axes, respectively, inclined such that the resulting two perforations intersect before either reaches its normal depth of penetration. The perforutors are arranged to fire simultaneously. Because of the time difference in speed of action, the shaped charge perforates first. At a time later, the bullet makes a perforation which breaks into the shaped charge perforation. ln escaping through the shaped charge hole, the gases flush out the pulverized material from the bullet perforation, the shaped charge perforation and any enlargement of the common portions of the two holes.

IFIIA PAIENTEnunv 1s m: 620 3 1 4 sum 1 or 2 INVENTOR FLOYD O. BOHN wm ggm q ATTORNEY PAIENTEnunv 16 Ian SHEET 2 BF 2 FIG. 4A

FIG-4B FIG.4C

INVENTOI? FLOYD O. BOHN yn;

FIG. 3

A T TOR/V5 Y COMBINATION BULLET-PERFORA'I'ING GUN AND SHAPED CHARGE PERFORATOR APPARATUS AND METHOD BACKGROUND OF THE. INVENTION This invention relates generally to improved method and apparatus useful in perforation of oil and gas wells and the like. More particularly, but not by way of limitation, the invention relates to improved methods and apparatus for completion of a well in earth formations.

Generally, in the completion of oil and gas wells and the like, an elongated metal casing is positioned in the well bore. Due to the irregularity of the well bore and due to the difference in diameter between the well bore and the metal casing, a cementitious material is usually pumped into the annular space, The cement serves to pennanently fix the metal casing in the well bore and to prevent migration of well fluids through the annular space. It is obvious that the metal casing and the cement disposed adjacent a productive formation will prevent the flow of fluids from the formations into the interior of the casing. Therefore, the practice has been to perforate the metal casing, the cement and the adjacent formation by the use of either shaped charge or bullet perforators. The perforators are lowered into the casing to a position adjacent the formation of interest and then fired from the earth's surface through an appropriate electrical circuit.

No matter which type of perforator has been used by those in the art, both the bullet and the shaped charged perforators break down the formation while making a hole. The pulverized matrix and formation elements are compacted in some portions of the hole. This debris is detrimental to both the productivity and fluid injectivity ofa perforation.

It is therefore the primary object of the present invention to provide improved methods and apparatus for perforating earth formations surrounding an earth borehole; and it is another object of the invention to provide methods and apparatus useful in perforating earth formations surrounding an earth borehole wherein portions of the debris incident to the perforation are removed coincidentally with the formation of debris within the hole.

The objects of the invention are achieved, generally, by method and apparatus within the preferred embodiment wherein a shaped charge perforation intersects with a bullet perforation and the gases formed therefrom are used to clear out the debris from the holes. These and other objects, fealures, and advantages of the present invention will become more apparent from a reading of the following detailed description and accompanying drawing, in which:

FIG. I is a cross-sectional view of a shaped charge constructed in accordance with the invention;

FIG. 2 is a cross-sectional view of a bullet gun perforator constructed in accordance with the invention;

FIG. 3 is a vertical cross section illustrating the combined perforating apparatus constructed in accordance with the invention disposed in a cased well bore; and

FIGS. 4A. B and C are a series of vector diagrams illustrating alternative angular relationships between the perforators according to the invention. Referring now to the drawing in detail, and especially to FIG. I, there is illustrated therein a shaped charge constructed in accordance with the invention. The shaped charge 10 includes a hollow body l2, an explosive material I4 partly filling the interior of the hollow body I2. and a cap I6 closing one end of the hollow body 12.

The explosive material I4 has a conical cavity 18 in the end thereof adjacent the cap l6. A liner 20, which is also of conical configuration. is located in the hollow body I2 in jLlX' taposition with the surface of the explosive material 14 forming the cavity 18. The liner 20 may be constructed from relatively thin sheet metal. but is preferably constructed from a granular metal as disclosed in US. Pat. No. 3,255,659 issued on June 14, I966 to Alexis A. Venghiattis.

A plurality of particles 2l are located between the surface of the explosive material l4 and the liner 20. The particles 2l are preferably formed from an inert material and preferably have at least one dimension that is not less than one-half the diameter of the perforation that is formed upon detonation of the shaped charge 10.

As will be understood by those skilled in the art of shaped charges, the conical cavity ID in the charge 10 produces the so-called Monroe effect upon detonation that results in a high energy, high-speed jet of sufficient energy magnitude to form perforations. The rate of detonation of such a shaped charge and the subsequent jet stream is in the order of 25,000 lt/sec.

Referring now to FIG. 2, there is illustrated a bullet perforation gun a'esembly 30 comprised of a generally cylindrical tubular gun body 31. The gun body 3] may be formed of a generally elongated solid steel cylinder of sumcient strength and solidity to withstand the pressures generated by the firing of the gun. The gun body 31 is provided with the laterally extending

coaxial bores

26 and 28. The smaller diameter bore 26 extends innermost and forms the charge chamber. Positioned in the charge chamber 26 is a combined propellant charge and bullet unit 34. A bore 36 having an initial tapered position 38 extends from the rear wall of the charge chamber 26 to a cylindrical cavity 40 in the peripheral wall of the gun body 31. The tapered portion 38 of the bore 36 accommodates the tapered head 42 of a firing pin 44 which extends through the bore 36 into the cavity 40 where the electrical connection to the firing pin 44 is made to conductor 46. The tapered head 42 and the firing pin 44 are insulated from the gun body. A seal 48 is engaged with the wall of the cavity to form a seal for the cavity 40 and to prevent the entrance of well fluid into the gun.

The cylindrical wall of the outer bore 28 is formed into female threads to engage with the male threads of a generally tubular barrel member 50 which has a central core 51 forming a barrel for the gun and the bullet 80. Additional details for building such a gun, along with the power charge considerations, can be found in US. Pat. No. 3,376,375 issued Apr. 2, I968 to Forrest V. Porter.

A bullet from such a gun travels in the order of 3.000 ItJsec. However, this velocity is not attained until a measurable length of time is used in combustion of the propellant powder. initial pressure buildup and finally acceleration of the bullet and flight through the barrel of the gun.

Thus, it should be appreciated that when a bullet gun and a shaped charge gun are fired simultaneously, the perforating by the shaped charge is completed before that of the bullet perforator due to the differences in velocity of the two perforators.

Although the preferred embodiment of the invention is directed to specific forms of the shaped charge and bullet gun perforators, it should especially be appreciated that such forms are merely illustrative of types of perforators and are not meant to be a limitation upon the invention. Other examples of shaped charge perforators are found in U.S. Pat. No. 3,358,780 issued Dec. 19, I967 to Alexis A. Venghiattis and US. Pat. No. 3,415,321 issued Dec. l0, I968 to Alex A. Venghiattis. Likewise, additional examples of bullet gun perforators are found in US. Pat. No. 2,953,971 issued Sept. 27, 1960.

Referring now to FIG. 3 of the drawing. there is illustrated a borehole instrument 6!) adapted to traverse a cased borehole 6l having a casing 62. Between the metal casing 62 and the earth formation 64 is the cement 63 as is well known in the art. The cable 65 is used to raise and lower the instrument 60 in the borehole and also contains the necessary conductors for causing the perforators to be activated. The instrument 60 is centered within the cased borehole by the conventional centralizer means 77. If desired, the instrument side having the perforators adjacent thereto can be urged into contact with the casing as is known in the art.

Located within the instrument 60 is a bullet perforator 30 and a shaped charge perforator I0. The shaped charge perforator I0 is connected to a Primacord 70, a booster 7i and a detonator 72. The detonator 72 is connected to an electrical wire 73 through the adapter 74 to one of the conductors in the cable which leads to an electrical source (not shown) at the earth s surface (not shown). As is well known, electric current passing through the conductor 73 ignites the detonator 72, the booster 7! and the Primacord 70. Due to the high-explosive nature of Primacord, an electrical signal appearing at the conductor 73 detonates the shaped charge essentially simultaneously.

The bullet gun perforator 30, as explained previously with respect to FIG. 2, has connected thereto an electrical conductor 46 which passes through the cable 65 to the earths surface.

Although the preferred embodiment contemplates the electrical signals for the two types of perforators coming down separate conductors in the cable 65, the signal can be transmitted down a common conductor, one voltage signal being used to detonate both perforators.

By having the shaped charge in a common plane with the bullet gun 30, while at the same time having their axes inclined, respectively, with respect to the longitudinal axis '75 of the instrument 60 such that the axes of the two perforators intersect. the perforations also intersect at a point in the earth formation 64. As explained previously, the gas flow (indicated by the arrows 76) passes through the shaped charge perforation back into the borehole, carrying debris within the gas.

FIGS. 4A, B and C illustrate the angular relationship between the perforators for achieving the desired results. FlG. 4A illustrates the longitudinal axis 85 of the bullet gun 30 as being substantially perpendicular to the longitudinal axis 75 of the instrument 60, whereas the longitudinal axis 86 of the shaped charge 10 is inclined at an angle l with respect to axis FIG. 48 illustrates an alternative embodiment wherein axis 86 is inclined at an angle l whereas axis 85 is inclined at an angle 0, which can be the same as angle 41' ifdesired.

FIG. 4C illustrates an alternative embodiment wherein axis 85 is inclined at an angle lb while maintaining axis 86 substantially perpendicular to axis 75.

Thus it should be appreciated that by having one or both of the

axes

85 and 86 inclined with respect to axis 75, the

axes

85 and 86 are aligned to intersect since they are positioned in a common plane. The angle between the

axes

85 and 86 is preferably chosen such that the intersection within the formation occurs before either perforation would reach its normal depth of penetration.

Although only one bullet gun and one shaped charge are illustrated and described with respect to the instrument 60, additional pairs of shaped charges and bullet guns can be provided within the instrument 60 in a similar manner as described for the single pair.

In addition to utilizing the difference in speed of perforation, a second difference is used to advantage. Although there are gases involved in the detonation of the high explosives used in shaped charges, it is primarily the wave of detonation or jet that makes a hole in the target. Even in soft rock targets, there is little or no evidence of hole erosion by high-velocity gases. In contrast, the bullet obtains its energy from the pressure of the gases resulting from the combustion of the propellant powder. Particularly in very short barrel guns, such as the casing perforator, there is a large volume of high-pressure gas available for use after the bullet has left the gun barrel. This residual gas leaves evidence of its ability to do work in some rock targets. Softer rocks are eroded and the hole is quite often cleansed of pulverized debris.

Thus, there has been described herein the preferred embodiments of a new and improved perforation method and apparatus. However, the details are presented by way of example only and it is contemplated that many changes and modifications can be made thereto without departing from the spirit of the invention. For example, instead of using a shaped charge in combination with a bullet gun. it is contemplated that one can use any two perforators, regardless of type, wherein one perforator penetrates faster than the other. Thus, a highvelocity shaped charge can be used in combination with a lowvelocity shaped charge. Likewise, a high-velocity bullet gun can be used with a low-velocity bullet.

As an alternative embodiment. it should be appreciated that instead of using the illustrated apparatus for ignition of the pair of perforators, satisfactory results have also been obtained from using a flame train hole to create a substantially simultaneous ignition. By having the flame train hole start in the shaped charge section and extend into the combustion chamber of the bullet perforator, ignition of the primacord and shaped charge creates a flame, through the flame train hole, which ignites the bullet gun. Although this approach can be used with separate sections, it is quite readily adaptable to having the two perforators in a common steel bar.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

I. Perforating apparatus for use in perforating earth formations surrounding an earth borehole, comprising:

instrument means adapted to traverse on earth borehole;

a first perforator in said instrument means having a first perforating velocity and aligned in a given plane;

a second perforator in said instrument means having a second perforating velocity different from said first perforating velocity and being aligned in said given plane,

said first perforator and said second perforator being aligned to provide intersecting paths of perforation before either of said perforators reaches its normal depth of penetration within said earth formations; and

means to substantially simultaneously fire said perforators.

2. The apparatus according to claim I wherein said first perforator is a shaped charge and said second perforator is a bullet gun.

3. The apparatus according to claim I wherein the longitudinal axis of one of said perforators is perpendicular to the longitudinal axis of said instrument and the longitudinal axis of the other of said perforators is inclined to the longitudinal axis of said instrument.

4. The apparatus according to claim I wherein the longitudinal axis of each of said perforators is inclined to the longitu dinal axis of said instrument.

5. A method of perforating the formation surrounding an earth borehole, comprising:

positioning a first perforator in said borehole wherein said first perforator has a given rate of penetration;

positioning a second perforator in said borehole wherein said second perforator has a rate of penetration difi'erent from said given rate, said first perforator and said second perforator being aligned in a common plane and having their longitudinal axes arranged, respectively, to provide intersecting paths of perforation before either of said perforators reaches its normal depth of penetration within the earth formation; and

simultaneously firing said perforators.

I 1 l 0 i

Claims

1. Perforating apparatus for use in perforating earth formations surrounding an earth borehole, comprising: instrument means adapted to traverse on earth borehole; a first perforator in said instrument means having a first perforating velocity and aligned in a given plane; a second perforator in said instrument means having a second perforating velocity different from said first perforating velocity and being aligned in said given plane, said first perforator and said second perforator being aligned to provide intersecting paths of perforation before either of said perforators reaches its normal depth of penetration within said earth formations; and means to substantially simultaneously fire said perforators.

2. The apparatus according to claim 1 wherein said first perforator is a shaped charge and said second perforator is a bullet gun.

3. The apparatus according to claim 1 wherein the longitudinal axis of one of said perforators is perpendicular to the longitudinal axis of said instrument and the longitudinal axis of the other of said perforators is inclined to the longitudinal axis of said instrument.

4. The apparatus according to claim 1 wherein the longitudinal axis of each of said perforators is inclined to the longitudinal axis of said instrument.

5. A method of perforating the formation surrounding an earth borehole, comprising: positioning a first perforator in said borehole wherein said first perforator has a given rate of penetration; positioning a second perforator in said borehole wherein said second perforator has a rate of penetration different from said given rate, said first perforator and said second perforator being aligned in a common plane and having their longitudinal axes arranged, respectively, to provide intersecting paths of perforation before either of said perforators reaches its normal depth of penetration within the earth formation; and simultaneously firing said perforators.