Claims
- 1. The method of assembling a multisection perforating gun of the type wherein each section includes threadable connections at its top and bottom ends and a plurality of vertically and angularly spaced shaped charge containers having the primer ends of such containers disposed adjacent the vertical axis of the respective section to define an axial passage through the section, and a pulling means extending through the axial passage, comprising the steps of:
- (1) disposing a housing containing a reel of primer cord beneath the lowermost gun section, the free end of said primer cord having a detachable connector secured thereto for successive connection to the bottom ends of said pulling means;
- (2) connecting the bottom end of the pulling means of said lowermost gun section to said primer cord detachable connector;
- (3) threadably securing the lowermost gun section to said reel housing;
- (4) pulling a portion of the primer cord off the reel and through the axial passage of said lowermost gun section by said pulling means, thereby removing the pulling means from said lowermost section;
- (5) disposing the next gun section above the lowermost gun section;
- (6) connecting the bottom end of the pulling means of the next gun section to said primer cord detachable connector;
- (7) threadably securing said next gun section to the lower gun section;
- (8) pulling the primer cord through the axial passage of said next gun section, thereby removing the pulling means from said next section; and
- (9) repeating steps (5), (6), (7) and (8) for each additional gun section required to be assembled.
- 2. The method of claim 1 wherein a length of detonation conducting tubing is secured in side-by-side relation to the entire length of said primer cord.
- 3. The method of claim 1 wherein, prior to assembly, a fusible tube is inserted in the axial passage of each said gun section.
- 4. The method of claim 1 further comprising the step of operatively connecting an end of said primer cord to a detonatable primer charge.
- 5. The method of claim 2 further comprising the steps of igniting only the top end of the detonation conducting tubing and detonating the bottom end of said primer cord by detonation transmitted by said detonation conducting tubing.
- 6. The method of assembling a multi-section perforating gun for a subterranan well having a plurality of tubular carriers supporting a plurality of shaped charge containers with the primer ends of such containers disposed adjacent the axis of the tubular carrier, comprising the sequential steps of:
- (1) successively assembling and inserting the tubular carriers, devoid of booster charges, in the well so that all shaped charge containers are below the surface;
- (2) inserting a continuous length of primer cord along the axis of the tubular carriers to lie adjacent the primer ends of each shaped charge container; and
- (3) assembling a firing mechanism, including a primer charge, in operative relationship to the top end of said primer cord.
- 7. The method of claim 6 further comprising the step of securing a booster charge intermediate the top end of the primer cord and the primer charge.
- 8. The method of assembling a perforating gun for a subterranean well having a tubular carrier apertured to receive a plurality of shaped charge containers in the wall thereof, comprising the steps of:
- (1) inserting a small diameter fusible guide tube coaxially within the tubular carrier;
- (2) securing shaped charge containers respectively in the tubular carrier apertures with the primer ends thereof in close proximity to said fusible tube;
- (3) inserting the tubular carrier in the well so that all shaped charge containers are disposed below the surface;
- (4) inserting a continuous length of primer cord coaxially through the bore of the fusible tubing; and
- (5) assembling a firing mechanism, including a primer charge, to the top of the tubular carrier in operative relationship to one end of said primer cord.
- 9. The method of claim 8 further comprising the step of securing a booster charge intermediate the top end of the primer cord and the primer charge.
- 10. The method of assembling a multisection perforating gun for a subterranean well comprising the steps of:
- (1) assembling a plurality of tubular carriers in axially stacked relation by means including a plurality of hollow nipples, each said tubular carrier having a plurality of vertically and angularly spaced apertures in the wall thereof and a small diameter length of fusible material tubing coaxially mounted therein;
- (2) securing shaped charge containers respectively in the tubular carrier apertures with the primer ends thereof in close proximity to said fusible tube;
- (3) inserting the tubular carrier in the well so that all shaped charge containers are disposed below the surface;
- (4) inserting a continuous length of primer cord coaxially through the aligned bores of the fusible tubing lengths and the hollow nipples; and
- (5) assembling a firing mechanism, including a primer charge to one end of the continuous primer cord.
- 11. The method of claim 10 further comprising the step of securing a booster charge intermediate the end of the primer cord and the primer charge.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a Division of Ser. No. 743,578 filed on June 11, 1985, U.S. Pat. No. 4,635,734.
This application is related in subject matter to: U.S. patent application Ser. No. 743,580 now U.S. Pat. No. 4,657,089, entitled "Method and Apparatus for Initiating Subterranean Well Perforating Gun Firing from Bottom to Top"; U.S. patent application Ser. No. 743,429 now U.S. Pat. No. 4,640,370, entitled "Perforating Gun for Initiation of Shooting from Bottom to Top"; and U.S. patent application Ser. No. 743,579 now U.S. Pat. No. 4,598,776, entitled "Method and Apparatus for Firing Multisection Perforating Guns".
1. Field of the Invention
The invention relates to perforating production formation of a subterranean well, and to methods for assembling and arming such gun in a manner that minimizes the risk of injury to the persons doing the assembly.
2. History of the Prior Art
The utilization of a plurality of vertically and angularly spaced shaped charges to effect the perforation of a subterranean well represents the modern approach to achieving perforation of the casing and the adjoining production formation. Such shaped charges are substantially concurrently fired by the ignition of a primer cord which passes successively past the primer ends of each of the shaped charge containers. It is not uncommon for the zone to be perforated to extend from ten to one thousand feet in length, thus necessitating the fabrication of the perforating gun as a plurality of axially stacked, substantially identical gun sections. The transmission of the firing energy from the uppermost section to the lowermost section is commonly accomplished through the mounting of booster charges on each of the ends of a primer cord which is utilized only within an individual gun section. The booster charges are required to insure that sufficient energy is transmitted from one primer cord to the next to insure a successive ignition of all primer cords. There have been many instances of unsuccessful transfer of ignition energy from one gun section to the next, necessitating the removal of the apparatus from the well.
As is well known to those skilled in the art, the booster charges commonly employed contain lead azide, an explosive which is extremely sensitive and susceptible to detonation by a relatively low level impact or shock. It is sufficiently dangerous that the assembly of perforating guns containing lead azide boosters at the factory is prohibited, due to regulations preventing the transport of such guns containing lead azide boosters on the public highways or on maritime carriers. It thus becomes necessary to insert the lead azide boosters in the perforating gun at the well site and, in this environment, it is readily possible to prematurely detonate the lead azide booster charges with the consequent high risk of injury to personnel effecting the assembly and arming of the multisection perforating gun.
In contrast, the primer cord commonly employed in perforating guns to effect the ignition of the shaped charges is relatively insensitive to inadvertant shock detonation and requires a substantial degree of heat to effect its ignition. Thus, a perforating gun construction which permits the firing of all of the shaped charges, regardless of the number of gun sections, by a single continuous length of primer cord, would obviously represent a substantial advantage for the industry.
The invention contemplates mounting the required number of shaped charge containers in vertically and angularly spaced apertures provided in the wall of a tubular carrier. If the vertical extent of the zone to be perforated is in excess of about ten feet, then a plurality of axially stacked perforated gun sections are employed, with each section comprising an apertured tubular carrier which may be interconnected in axially stacked relationship by hollow nipples.
The shaped charge containers are assembled in wall apertures of the tubular carrier or housing with the inner or primer ends of such shaped charge containers disposed in close proximity to the axis of the carrier, yet providing sufficient space to permit a length of primer cord to be readily inserted between the juxtaposed ends of the shaped charge containers.
In accordance with a preferred modification of the invention, a continuous strand of primer cord having a length at least equal to the total length of the plurality of gun sections to be assembled at the well site, is wound on a hollow reel mounted in a housing which can be assembled to the bottom of the lowermost gun section with the axis of the hollow reel disposed in a vertical position so the primer cord can be prewound to freely unwind as it is pulled to the top. A detachable connector having a hook engaging eye or some similar form of detachable connection, is then crimped onto the upper free end of the primer cord for pulling by a suitable cable through the superimposed gun section. Preferably, each gun section is provided at the factory with a length of metal or plastic cord or cable, extending axially through the center of the gun section and having a hook or some similar form of detachable connection secured to each projecting end of the cable, one end being detachably connectable to the primer cord and the other end being connectable to a suitable hoist or pulling mechanism provided on the drilling rig.
The reel containing housing is vertically positioned on the floor of the drilling rig and the lowermost perforating gun section is then suspended above the reel housing. The bottom projecting end of the cable traversing the lowermost gun section is connected to the detachable connection on the end of the primer cord and the lowermost gun section is connected. Then the cable or cord is pulled upwardly to pull a length of the primer cord off the reel and upwardly through the lowermost gun section. The reel housing and the lowermost gun section may be partially lowered into the well opening. The cable removed from the lowermost gun section is disconnected from the primer cord and the free end of the primer cord is suitably secured.
The next gun section is then positioned in vertical alignment with the lowermost gun section and the bottom projecting end of the pull cable of such gun section is connected to the connector provided on the end of the primer cord and the guns are connected. Then the perforating cord is pulled by such cable through the next gun section to the lowermost gun section. The assembly operation proceeds in similar fashion until the required number of gun sections have been assembled and at that point, the top end of the primer cord is secured in conventional manner to a booster charge forming part of a detonating or firing mechanism.
The firing mechanism coontains a primer charge which is detonatable by impact or electric means in conventional fashion. Such a detonation of the primer charge, when the gun assembly is properly positioned within the well, will effect the detonation of the booster charge and the detonation of the top end of the primer cord. The detonating shock wave produced by the primer cord travels downwardly through all of the assembled gun sections in close proximity to the inner or primer ends of the shaped charge containers mounted in each gun section, and thus all such shaped charge containers are detonated.
If it is desired to fire the perforating gun from the bottom up in the manner described and claimed in co-pending application Ser. No. 743,580, filed concurrently herewith and assigned to the Assignee of this application, then the top end of the primer cord is not provided with a booster charge and is isolated from the detonation effects of the primer charge. Instead, a detonation or flame-transmitting tube is ignited by the detonation of the primer charge and this tube, which can be secured to the primer cord and pulled through the gun assemblies concurrently with the primer cord, transmits a flame downwardly to the lowermost end of the primer cord where it ignites a booster charge connected to the primer cord, thus detonating the primer cord at the bottom and such detonation travels upwardly to successively detonate the shaped charge containers of each of the gun sections disposed above the bottom of the gun.
In another embodiment of this invention, each tubular carrier is additionally provided with a relatively small diameter fusible guide tubing which is coaxially disposed within the carrier and has a bore sufficiently large to freely accommodate a primer cord therein.
The shaped charge containers are then assembled in the wall apertures of the tubular carrier or carriers with the inner or primer ends of such shaped charge containers disposed in close proximity to the exterior wall of the fusible guide tubing. This entire operation can be accomplished at the well site, and, as each horizontal array of shaped charge containers is assembled in the respective carrier, the carrier is then lowered into the well so as to dispose the assembled shaped charges below the well surface even prior to arming of the perforating gun. When all of the shaped charges are assembled in the perforating gun sections, the gun is lowered so that all such shaped charges are disposed below the well surface. A single continuous length of primer cord is then inserted coaxially through the axially stacked tubular carriers, passing through the bore of the aligned lengths of small diameter fusible guide tubing. A single booster charge is then connected to the top end of the continuous length of primer cord and this booster charge is in turn assembled in conventional fashion beneath a firing mechanism containing a primer charge.
The entire gun, together with any related equipment, such as screens, packer and/or gravel pack apparatus, is then lowered into the well so as to position the perforating gun adjacent the zone to be perforated. The actuation of the firing mechanism in any conventional manner, such as by dropping a detonating bar through the bore of the tubular string carrying the perforating gun into the well, will effect the ignition of the primer charge which in turn will ignite the booster charge and in turn ignite the primer cord. The heat and shock wave developed by the ignited continuous primer cord passes rapidly down the entire perforating gun assembly and is sufficiently intense as to melt and fragment the fusible guide tubing within which the primer cord is inserted. This permits the heat of the detonating primer cord to be applied directly to the primer ends of the shaped charge containers and effect their discharge in conventional fashion.
Thus, the assembly and firing of a perforating gun embodying this invention is accomplished in a more efficient manner, which also provides a much higher degree of safety for the well personnel than has heretofore been possible.
Further advantages of the invention will be readily apparent to those skilled in the art from the following detailed description, taken in conjunction with the annexed sheets of drawings, on which are shown two preferred embodiments of the invention.
US Referenced Citations (7)
Divisions (1)
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Number |
Date |
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743578 |
Jun 1985 |
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Patent Grant
4747201
