BACKGROUND OF THE INVENTION
Heretofore many explosive devices and methods have been proposed for fracturing a geological formation thereby increasing the effective permeability thereof. For example, attempts to detonate trinitrotoluene (TNT) and other high explosives in a borehole have generally proven ineffective in that the forces created by the blast often escape up the borehole.
Secondly, bullets and shaped charges used for such purposes provide only limited penetration into the formation with very little additional fracturing of said formation.
SUMMARY OF THE INVENTION
The present invention utilizes the forces created by opposing pancake charges upon a noncompressible liquid, namely, water, acid or other composition which liquifies at the relatively high borehole temperatures, to provide high velocity jets or streams of said liquid which are introduced into the perforations, radiating cracks and fissures initiated by one or more laterally directed shaped charges or bullets, fracturing the formation and increasing the permeability thereof.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a longitudinal, vertical sectional view of one embodiment of the invention.
FIG. 2 is a longitudinal, vertical sectional view of a modification of the embodiment of FIG. 1.
FIG. 3 is a longitudinal, vertical sectional view of another embodiment of the invention.
FIG. 4 is a longitudinal, vertical sectional view of still another embodiment of the invention.
Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a controlled directional charge assembly 10 consisting, in general, of first and second vertically spaced, inwardly directed, pancake charges 11-12, and at least one laterally directed shaped charge 13 intermediate said pancake charges 11,12.
More specifically, assembly 10 includes a generally cylindrical casing 14 composed of a suitable metal, ceramic or plastic provided interiorly with female threads 15-16 in proximity to each end thereof. Base plate 17, preferably of the same composition as casing 14, includes threads 18 adapted to engage female threads 15 in said casing. The first explosive charge 11 is conventionally secured in said casing adjacent base plate 17. Top plate 19 includes an upwardly extending eye 20 to which one end of cable 21 is connected, an axial bore 22, and threads 23 adapted to engage female threads 16 in said casing. The second explosive charge 12 is conventionally secured in casing adjacent top plate 19. Charges 11-12, generally of cylindrical shape and having substantially flat planar opposing surfaces transverse to the longitudinal axis of casing 14, may be of the well known explosives such as compressed pentaerythritol tertanitrate, blends of this compound with trinitrotoluene, or compressed trimethylene trinitramine, sold under the trade name RDX.
Although detonator 24 is illustrated adjacent charge 12, it is understood that said detonator or a plurality of detonators may be provided in any desired location either within said casing or exteriorly thereof. Furthermore, such detonator or detonators may be of the type which are remotely activated either electrically, by Primacord, or by a radio signal.
Laterally directed shaped charge 13, such as is well known in the art, includes body 25 with cavity 26 therein accommodating explosive charge 27 of the type heretofore mentioned with booster charge 28 in direct contact therewith rearwardly; outwardly opening cone 29 is secured in said cavity forwardly of explosive charge 27. Body 25 is conventionally secured to cap 30; the outer surface of cap 30 may either be convex or concave. Threads 31 on said cap are adapted to engage female threads 32 in said casing. Upon detonation, shaped charge 13 penetrates the adjacent formation in a relatively small diameter, pencil-shaped perforation with cracks and fissures radiating outwardly thereof.
First and second chargses 11,12 and booster charge 28 of laterally directed shaped charge 13 are connected by means of detonating cord 33 to detonator 24; conductor 34 passes downwardly through bore 22 in top plate 19 and one end connects to said detonator.
Liquid 35, such as water, acid or other composition which liquifies at the relatively high borehole temperatures, is introduced through port 36 into space 37 within said casing; plug 38 is conventionally secured in port 36.
Assembly 10 is lowered into a borehole to a predetermined depth by means of cable 21. It is to be understood that charges 11-13 are detonated in such a manner that laterally directed charge 13 at least partially penetrates the adjacent formation; at such time, the inwardly directed charges 11,12 simultaneously apply opposing forces upon liquid 35 creating a very high velocity jet or stream of said liquid which enters the perforation, cracks and fissures started by said laterally directed charge and additionally fractures the entire formation. In those instances where an acid such as hydrochloric or nitric is used as the liquid, said acid dissolves plugging debris and unconsolidated materials which impede the flow of liquids and/or gases into a borehole.
There is shown in FIG. 2 a controlled directional charge assembly 39 constructed in accordance with the principles heretofore described wherein at least one laterally directed projectile or bullet 40 is utilized intermediate pancake charges 11,12. More particularly, gun barrel 41 includes threads 42 which engage female threads 43 in casing 14. High explosive 44 is placed in barrel 41 rearwardly of bullet 40; booster charge 45 in direct contact therewith is activated by detonating cord 33 or the like. Desirably a disc 46 is secured in the foremost end of barrel 41 to prevent the entry of debris.
Referring now to FIG. 3 of the drawings, controlled directional charge assembly 47 comprises cylindrical casing 48 with bottom plate 49 and top plate 50 detachably secured thereto. First and second transversely extending, vertically spaced and inwardly directed pancake charges 51-52 are secured in said casing in proximity to the respective lower and upper ends thereof. A pair 53 of diametrically opposed and laterally directed shaped charges 54-55 are detachably secured in said casing downwardly of charge 52 in the manner heretofore described. A second pair 56 of opposing and laterally directed shaped charges are spaced vertically below pair 53 and desirably rotated 90° relative thereto. It is understood that any desired number of pairs of vertically spaced and laterally directed shaped charges may be utilized intermediate charges 51,52; detonating cord 57 connects to charges 51-52, said pairs of laterally directed shaped charges, and to detonator 58, respectively. Liquid 59 of the type heretofore mentioned is introduced through port 60 into space 61 within casing 48; plug 62 is conventionally secured in port 60.
In such embodiment, the charges are detonated in such a manner that the opposing pairs of laterally directed shaped charges at least partially penetrate the adjacent formation; at such time the inwardly directed pancake charges 51,52 simultaneously apply opposing forces on liquid 59 whereby high velocity streams of said liquid enter the perforations initially created by said laterally directed shaped charges thereby additionally fracturing the formation.
The controlled directional charge assembly 63 of FIG. 4 comprises at least first and second subassemblies 64-65 which are detachably connected. For purposes of convenience only, subassembly 65 will be described in detail; it is understood that subassembly 64 is essentially similar in construction thereto.
Subassembly 65 includes cylindrical casing 66 provided interiorly with female threads 67-68 in proximity to each end thereof. Bottom plate 69 includes threads 70 adapted to engage female threads 67 in said casing. Top plate 71 includes threads 72 adapted to engage female threads 68 in the upper end of said casing. First and second transversely extending, vertically spaced and inwardly directed pancake charges 73-74 of the type heretofore mentioned are conventionally secured in the lower and upper portions of said casing, respectively. Detonator 75 may be positioned adjacent top plate 71, elsewhere in said casing, or exteriorly thereof; one end of conductor 76 connects to said detonator.
Preferably four vertically spaced and laterally directed shaped charges 77-80 are detachably secured in casing 66 intermediate charges 73-74. Each of said laterally directed charges 77-80 is rotated 90° relative to the charge vertically thereabove with charges 77,79 and 78,80 extending in opposite directions. Detonating cord 81 or the like connects to detonator 75, pancake charges 73-74, laterally directed shaped charges 77-80, and thence to the corresponding charges in subassembly 64. Liquid 82 of the type heretofore mentioned is introduced into space 83 within casing 66 through port 84 with plug 85 conventionally secured therein.
Subassembly 64 includes casing 86 with bottom plate 87 and top plate 88 detachably secured therein; first and second transversely extending, vertically spaced and inwardly directed pancake charges 89-90 are conventionally secured adjacent bottom plate 87 and top plate 88, respectively; laterally directed shaped charges 91-94 (shaped charge 93 not shown); and liquid 95 of the type heretofore mentioned is provided in space 96 within casing 86. An externally threaded coupling 97 engages female threads 67 in casing 66 downwardly of bottom plate 69 and female threads 98 in the uppermost portion of casing 86 of subassembly 64. Detonating cord 81 heretofore mentioned connects to pancake charges 89,90 and shaped charges 91-94, respectively.
In such embodiment, the charges are detonated in such a manner that the laterally directed shaped charges, namely, charges 77-80 and 91-94 at least partially penetrate the adjacent formation at which time pancake charges 73,74 and 89,90 simultaneously apply opposite forces upon liquids 22 and 95, respectively, whereby high velocity jets or streams of said liquids are forced into the perforations previously initiated by said laterally directed charges.
It is understood that shaped charges 13, 77-80, 91-94, pairs 53,56 of such shaped charges, and barrel 41 for bullet 40 in each of the several embodiments of the invention may be inclined at any desired angle relative to the horizontal plane whereby the perforations created thereby are either up-dip or down-dip with respect to the adjacent formation. Furthermore, as an additioanl step in increasing the permeability of a geological formation, an explosive slurry, such as is well known in the art, may be introduced into said formation previously fractured in the manner heretofore described whereby previously displaced chips and fragments act as projectiles thereby additionally penetrating the formation.
It is understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.