US3405769A - Well perforating apparatus - Google Patents

Description

Oct. 15, 1968 J. B. SHQRE ET AL 3,405,769

WELL PERFORATING APPARATUS Filed Feb. 28, 1967 J5me: .5. Jfiore INVENTURJ ATTORNE Y United States Patent 3,405,769 WELL PERFORATING APPARATUS James B. Shore, Friendswood, and William T. Bell,

Houston, Tex., assignors to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed Feb. 28, 1967, Ser. No. 619,393 6 Claims. (Cl. 175-453) ABSTRACT OF THE DISCLOSURE A perforating gun is provided for through the flow line operations wherein bends in the flow line require tools that are flexible in all planes. The perforating gun includes a wire shaped charge carrier which has a low cross sectional moment of inertia in the planes of its major and minor axis to provide such flexibility. The shaped charges are made of wear resistant material and are arranged within the carrier to prevent their inadvertent 1085 within the flow line.

Background of the invention This invention relates to 'a Well perforating apparatus and, more particularly, to a perforating apparatus having a flexible wire carrier for shaped charge explosive devices.

An important step in completing an oil well having a casing cemented in place is to create perforations through the casing and cement around it, which perforations extend into the surrounding earth formations. One widely used method for perforating a well is to lower a plurality of shaped explosive charge devices to levels in the well where oil bearing strata have been found. The shaped charges, which are supported at predetermined longitudinal spacings on a suitable carrier and are oriented in predetermined angular positions, are then detonated to produce the perforations which extend through the metal well casing and the surrounding cement into the oil bearing formation.

An important part of a shaped charge well perforating apparatus is the carrier. The carrier must be strong enough and rigid enough to support the charge devices and maintain them in their proper alignment. It should be constructed so as to be readily assembled and should preferably employ standardized, interchangeable parts which can be assembled in various configurations depending upon the number and spacing of the charge devices. A carrier meeting these characteristics is set forth in a US. patent to W. T. Bell et al. No. 3,282,213.

Recent developments in underwater oil well completions require that well tools for use therein be more flexible than tools normaly used with conventional completions. These developments concern the completion of off shore wells by placing the well head assembly on the ocean floor. A system has been developed which utilizes a central gathering station having several wells spaced therefrom and flow lines connecting the central gathering station with the well head assembly located on the floor of a body of water. These flow lines, which may be of considerable length, run horizontally along the ocean floor to the well head assembly at which point a radius is formed in the flow line to permit the passage of flexible tools through the flow line around the radius and into the well tubing string. Therefore, instead of using conventional floating rigs for servicing such wells, a method is performed whereby well service tools are pumped through the flow line from the central gathering platform. This movement of tools through the flow line is accomplished by applying fluid pressure behind the tools to pump them into position in the well. Well tools 3,405,769 Patented Oct. 15, 1968 utilized in such a system must be of such flexibility as to be capable of being pumped through the flow line around the radius in the flow line and into the tubing string. It is also readily seen that the loss of a portion of a tool within a flow line might cause jamming of the tools therein. Sticking of tools within a flow line is critical since pumping is the only means of recovery.

It is, therefore, an object of the present invention to provide a new and improved flexible perforating apparatus for pumping through the flow line of a Well.

Summary 0 the invention The present invention contemplates a perforating apparatus comprising a pair of elongated wire members each having alternate portions offset from and parallel to the longitudinal axis of the Wire members. When assembled as a carrier, the members are brought together along a central axis with the longitudinal axis of the members and the central axis of the assembly lying in a longitudinally extending plane. When assembled, the wire members have parallel spaced apart fiat portions adapted to receive encapsulated shaped explosive charge devices. The flat portions of the wire members are adapted for reception within circumferential grooves on the shaped charges. Alternate portions of the wire members, between the shaped charges, are placed together in a sliding relationship. Means are provided for maintaining the alternate portions of the wire members relative to one another in such a sliding relationship, such means preferably being a sleeve arranged about both of the wire members when the wire members are assembled.

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 other 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.

Brief description of the drawings FIGURE 1 shows a well head assembly and flow line with a string of perforating tools positioned in the flow line;

FIGURE 2 is a perspective view of a portion of the carrier which shows the wire members arranged for holding the shaped charges;

FIGURE 3 is a partial end view of a shaped charge and one of the wire members; and

FIGURE 4 is a plan view of a shaped charge positioned within the carrier.

Description of the preferred embodiments Referring first to FIGURE 1, a string of tools is shown positioned in a Well bore 12 for perforating a well by use of through the flow line techniques. A pair of parallel flow lines 13, 14 are shown entering a well head 16 and extending downwardly into the well bore. A packer device 17 isolates a portion of the well bore. A landing seat 18 is provided in the lower end of the flow line 14 to arrest downward travel of the well tools therein. Such through the flow line apparatus and techniques are described in greater detail in copending application Ser. No. 389,389.

The string of tools shown in FIGURE 1 includes a transport head 19 having seal means thereon to provide a seal between the interior of the flow line and the tool to facilitate pumping of the tool string through the flow line. A connecting link 20 connects the transport head with housing section 23 which carries a power source or batteries. A seating shoulder 24 is formed on the housing 23 and provides a means for locating the tool in the lower end of the flow tube, the seating shoulder being engageable with the inwardly extending landing seat 18 at the lower end of the flow tube to impede further travel of the tool string therethrough. Housing 23 is connected by means of another connecting link 24 to a switch section 26. The switch section has fiow tube engaging arms 27 for following the interior wall of the flow tube. At a selected position relative to the end of the flow tube, the arms are eifective upon their extension a preselected amount to close an electrical circuit (not shown) within the string of tools. More than one switch section can be included in the string of tools with a typical arrangement being shown in a copending patent application by James B. Shore filed Jan. 13, 1967.

A section of flexible tubing 28 is provided between the switch section 26 and an eccentralizer housing 29 with the length of the flexible tubing being suflicient to provide proper positioning of the perforating apparatus relative to the landing seat 18 in the fiow line. The eccentralizer section 29 has a wall-engaging member 31 extending therefrom to push outwardly against the wall of the casing. The eccentralizer maintains the perforating gun eccentered in the casing to provide an optimum clearance between the shaped charges and the casing wall. A perforating gun 32 is connected to the lower end of the eccentralizer section 29 by any convenient means such as screws or the like. The perforating gun includes a wire carrier 41 with shaped charges 40 positioned therein and a detonating cord 42 connecting the charges with an electrical circuit (not shown) in the string of tools. A blasting cap 43 is crimped or otherwise connected to the detonating cord and the electrical firing circuit to provide a detonating means. Strings or wires 44 are used to secure the detonating cord relative to the carrier 41.

FIGURE 2 shows the shaped charge carrier 41 in greater detail. The carrier is comprised of a pair of rectangularly shaped wire members 46, with each member having a plurality of alternating flat segments 47, 48 parallel to the longitudinal axis of the member. Alternate ones of the segments are offset to opposite sides of the longitudinal axis of the member and are connected at their ends by angular connecting segments 49. To form the wire carrier, a pair of the wire members are arranged in a mirror image relationship with alternate flat segments 48 being placed together to leave the other alternate fiat segments 47 spaced apart. The spaced apart segments form openings 51 into which shaped charge capsules 40 are cooperatively received.

As shown in FIGURE 2, the wire members 46 are held against the opposite sides of the shaped charge capsule 40 by metal sleeves 52 which are slidably received about the Wire members along contacting segments 48. The sleeve 52 is sized to maintain the wire segments 48 in contacting relationship with one another. However, at the same time, the sleeve 52 fits loosely enough to permit relative sliding between the wire members 46 when bending forces are applied to the wire members. Such relative sliding prevents the bending forces from producing a permanent set in the wire members. The closeness of the adjacent segments 48 is important in that the smaller the cross sectional area presented by the mating segments 98, the less the cross sectional moment of inertia, thereby providing greater flexibility of the carrier in the plane of greatest cross sectional dimension of the wire members. As shown in FIGURE 3, the plane of greatest cross sectional dimension or major axis of the wire members is normal to the side of the shaped charge and also normal to the longitudinal axis of the wire members.

It has been found that the wire members must be made of a metal which, when subjected to the severe dynamic shock of the exploding shaped charge devices, has sufiicient strength and tenacity to withstand such dynamic shocks as well as possessing a low rate of crack propagation. Therefore, a strong material which is also relatively j 4 ductile and malleable is suitable. Such a material is produced by heat treating 1065 steel to provide a Rockwell hardness of around 40. It is readily seen that the relative strength of the material to be used is dictated by the magnitude of explosive power produced by the shaped charge. Therefore, in certain situations, a lighter weight metal such as aluminum may be appropriate.

Accordingly, because the wire members are made of a relatively strong ductile and malleable material and because of their geometric shape and cross section, the wire members of the present invention are capable of sustaining the detonation of the charges they carry without fracture, and the carrier can be recovered in tact from the well after use. As a result of charge detonation, a significant amount of erosion or pitting as well as compression occurs in the portion of the members where the shaped charge devices are supported. However, in as much as the material is relatively ductile and has a correspondingly high toughness, the explosive energy impinging upon the members is absorbed without producing fracture and subsequent bending is possible without causing breakage despite the erosion and pitting.

As shown in FIGURE 3, the case of the shaped charge device 40 has oppositely disposed, outwardly extending, circumferential bosses 54, 56 and a circumferential flange 58. Only one side of the charge device is shown in FIG- URE 3, but it will be understood that the opposite side is shaped in the same manner. The bosses define a first circumferential groove 60 for receiving one side of the wire member segment 47. A second circumferential groove 62, which is defined between the boss 56 and the flange 58, may alternatively receive the segment 47 of the wire member. Thus, the shaped charge devices can bemounted on the carrier ineither of two positions, and the distance at which the shaped charge devices are mounted from the wall of the well can be varied accordingly. The preferred type of shaped charge devices are those having frangible cases which disintegrate upon detonation of the explosive charges therein. Thus, no large pieces of the cases are left to block the well. In addition, because of the close dimensions of the flow tube through which the perforating device must be pumped, the shaped charge devices must be designed to withstand the wear imposed by such treatment. Therefore, a cartridge made of a ceramic material which has such wear properties would suitably be used in such an application.

As shown in FIGURES 1 and 2, a plurality of shaped charge devices are mounted between the wire members in the manner shown in FIGURE 2 and are coupled to the detonating cord 42. The cord, leading from the detonator, is positioned behind the carrier and held in place by a notched boss 64 at the rear of each of the shaped charge devices which, in the embodiment illustrated in the drawings, are installed to point in the same direction. Alternatively, of course, the shaped charges may be oriented in alternatively opposite directions with the cord 42 passing from one side of the plane of the wire members to the other.

To assemble the perforating device, the shaped charge device is placed between the wire members, the Wire members are positioned in the grooves of the shaped charges and a suitable hand tool is used to bend the sleeves around the abutting segments 48 of the wire members. The detonating cord 42 is then inserted into the notched bosses 64 on the charge devices and tied to the carrier by means of wire or string 44. It is noted, particularly in viewing FIGURE 4, that the angular connecting segments 49 are spaced from one another a sufiicient distance to provide a longitudinally enlarged opening 51 for receiving the shaped charges. The enlarged opening provides sufiicient clearance at each end of the opening to permit movement between the wire members and the shaped charges. In addition, the circumferential grooves encircling the shaped charges permit the shaped charges 40 to rotate as the Wire members move relative to one another and relative to the shaped charges. Thus, the groove insures that the shaped charge will remain captured by the wire members in the event of such rotative movement to prevent their inadvertent loss in the flow line. In addition, the elongated opening 51 which provides for such relative movement between the parts of the assembly, also prevents forces from being applied to the shaped charges which might result from bending stresses on the wire members.

In the operation of this apparatus, when the perforating apparatus has been assembled and placed in the flow tube for pumping into the well, pressure is applied to the flow tube behind the string of tools to pump the tool string through the flow line into the well bore. By necessity, loops are provided in the flow lines to facilitate entry of the flow line into the well head. Such loops generate small radiuses in a flow line around which the string of tools must be moved. The construction of the shaped charge carrier and shaped charges described herein permits flexibility in more than one plane to thereby facilitate such movement through a flow line. Upon reaching a predetermined position in the well, the shaped charges are fired. Thereafter, pressure is applied to the bottom side of the transport head 19 via fiow line 13 and the string of tools is returned to the surface.

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. In a carrier apparatus for holding explosive charges for perforating a well, a pair of wire members each having alternate first and second straight portions parallel to the longitudinal axis of each of said members, said first and second straight portions being offset from one another one opposite sides of said longitudinal axis of said member, said members being arranged so that alternate first straight portions are arranged parallel to one another and slidably held together to form a section having a minimum cross sectional moment of inertia and alternate second straight portions are arranged parallel to one another and spaced apart to form a space for cooperatively accommodating a shaped charge device.

2. The apparatus of claim 1 wherein said wire members have fiat opposing surfaces.

3. The apparatus of claim 1 wherein said wire members have a rectangular cross section.

4. The apparatus of claim 1 and further including a sleeve slidably received about said first straight portions.

5. A perforating gun for use in a well bore including: a wire carrier having a pair of wire members arranged to provide flexibility in the planes of its major and minor axis; and means for holding said wire members together at portions along their length and at the same time permitting relative sliding movement between said wire members; said wire members having spaced apart portions providing an opening, when assembled, for receiving a shaped charge; said spaced apart portions having opposed straight surfaces for contacting and holding the shaped charge within the opening.

6. The apparatus of claim 5 and further including a shaped charge positioned within said opening, said shaped charge having a circumferential groove encircling said shaped charge for receiving the opposed straight surfaces of said wire members.

References Cited UNITED STATES PATENTS 2,799,224 7/1957 Long -4.6 X 2,981,185 4/1961 Caldwell 1754.6 X 3,036,521 5/1962 Owen 1754.6 3,100,443 8/1963 Pohoriles 175-4.6 X 3,282,213 11/1966 Bell et al. 175-46 X DAVID H. BROWN, Primary Examiner.

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