US3046886A - Seismic explosive anchor - Google Patents

Description

July 31, 1962 c. M. JOSLIN SEISMIC EXPLOSIVE ANCHOR Filed April 6, 1959 CHARLES M. JOSLIN INVENTOR.

United. States Patent "ice 3,046,886 SEISMIC EXPLOSIVE ANCHOR Charles M. Joslin, Quitman, Miss, assignor, by mesne assignments, to Socony Mobil Oil Company, Inc., New York, N.Y., a corporation of New York Filed Apr. 6, 1959, Ser. No. 804,322 2 Claims. (Cl. 102--21.8)

This invention relates to seismic exploration and more particularly to anchoring explosive charges at selected depths in a shot hole for generating seismic waves.

In seismic exploration elongated, tubular containers of explosives are placed in shot holes and detonated at selected depths for the generation of seismic waves. It is often desirable to utilize a plurality of seismic charges at different depths in the borehole and to detonate them at predetermined intervals or sequences for enhancing the utility of the resultant seismic waves. Difficulty has been encountered in maintaining charges at predetermined depths.

It is an object of the present invention to provide a charge anchor which is relatively inexpensive and yet which is positive in its action in maintaining a seismic charge at a given depth as to permit the loading of charges without fouling the electrical circuit leading from an associated detonator or cap to the earths surface.

In accordance with the present invention, there is provided an anchor for explosive charges, the latter being characterized by a plurality of containers threadedly coupled in an end-to-end array and in which an elongated metallic strap provided with a central aperture receives one of the mating threaded elements and thus is fitted between adjacent charge containers. Wings extending from the container in a direction opposite the direction of movement of the charge in a borehole are provided with tips which resiliently engage the borehole wall and oppose movement of the charge out of the borehole.

In a more specific aspect of the invention, there is provided a seismic charge array in which a plurality of elongated explosive containers are joined together in an end-to-end relationship with at least one elongated strap pierced at the mid-point thereof and secured between abutting portions of two adjacent containers and forming arms extending in diametrically opposed directions and at acute angles relative to the axis of said array and adapted to engage the walls of a borehole into which said array is to be placed and to oppose movement of said array out of said borehole.

For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a view of a shot anchor blank;

FIG. 2 is a side view of a shot anchor formed from the blank of FIG. 1;

FIG. 3 is a view partially in section showing the shot anchor in position to be secured to a pair of explosive elements; and

FIG. 4 illustrates a shot anchor in place in a borehole.

Referring now to FIG. 1, there is illustrated a shot anchor comprising an elongated sheet metal strap which is provided with pointed extremities 11 and 12 and having a central circular aperture 13. The anchor blank 10 of FIG. 1 is shaped into the form illustrated in FIG. 2. The arms 16 and 17 of the anchor are bent abruptly from a plane of the aperture 13 at an angle of approximately 75 The tips 11 and 12 are bent as along lines 14 and 15, FIG. 1, at an angle which is about 30 from the plane of the arms 16 and 17, respectively.

As illustrated in FIG. 3, the anchor is to be secured between adjacent containers of explosives 19 and 20. The

3,046,886 Patented July 31, 1962 arms 16 and 17 extend outwardly from the axis of containers 19 and 20. The lower container 19 is provided with a threaded endmember 21 which is adapted to be threadedly secured internally of the threaded lower end of the container 20. Such interlocking features are provided on commercially available geophysical explosives. The apertur 13 is adapted to receive the threaded end member 21. When the nut portion of the container 20 is served tightly onto member 21, the anchor 10 is rigidly secured to and made an integral part of the explosive charge assembly.

An assembly of charges such as illustrated in FIG. 4 includes four containers of explosive 30, 31, 32 and 33 which are interlocked to provide an elongated charge. Three charge anchors 34, 35 and 36 are incorporated in the assembly rigidly to secure the charge assembly at a selected depth in the borehole. The anchors extend upward and angularly away from the axis of the charge assembly as to engage the walls of the borehole 37. Thus the charge unit may be lowered to a preselected depth in the borehole. The loading mechanisms may then be removed without fear of raising the charge unit from the preselected depth.

In operation, a plurality of units such as illustrated in FIG. 4 may be employed in a single borehole and may be lowered to desired depths and there anchored.

In accordance with a preferred embodiment of the invention, the charge anchors were formed of a strip of 14 gauge sheet steel 22" in length and 2 A in width. The width of the charge anchor was made equal to the diameter of the charge container for minimum spatial requirements. Charge anchors of 22" in total length were found to be satisfactory for use in shot holes of the order of four to five inches in diameter.

Having described the invention, it will now be understood that further modifications may be made therein without departing from the scope of the appended claims. While it has been indicated that metal may be used, it will be understood that other materials of suitable rigidity and compliance may be employed. Furthermore, the unit may be utilized in connection with other types of conplings between charge containers. The aperture 13, receiving one of a pair of telescopically mating elements which form the charge coupling structure, permits the anchor to be a unitary element, thus simple in construction but positive in operation.

What is claimed is:

1. In a seismic charge array wherein a plurality of tubular explosive charge containers are to be connected together in an end-to-end array with threadedly mating male and female elements prior to introduction into a borehole, the combination which comprises an elongated strap including a central portion having an aperture adapted to receive one of said male elements, and to be fitted and directly secured between said tubular containers by the male and female coupling elements with arms extending in diametrically opposed direction from said central portion at an angle of the order of 15 with respect to the walls of said containers, and extending in direction opposite the direction of movement of said array into the borehole, each of said arms including an end portion directed outward at an angle of the order of 30 with respect to the plane of its associated arm.

2. A seismic charge array for introduction into a borehole comprising a plurality of elongated explosive containers joined together in an end-to-end relationship, at least one elongated strap pierced at the mid-point thereof by said containers and directly secured between adjacent containers by end portions of said containers, and forming arms extending in diametrically opposite directions at an angle of the order of 15 with respect to the axis of said array in directions opposite the direction of movement 3 of said array in the borehole, and each having an end portion directed outward at an angle of the order of 30 with respect to the plane of its associated arm, and adapted to engage the walls .of the borehole into which said array is to be placed to oppose movement of said 5 array out of the borehole.

References Cited in the file of this patent UNITED STATES PATENTS 1,218,140 Weber Mar. 6, 1917 10

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