US2697399A - Oil well blasting - Google Patents

Description

1954 E. P. MCADAMS OIL WELL BLASTING Filed July 11. 1950 EUGENE P,

A TTORNE Y5 United States Patent Ofiice 2,697,399 Patented Dec. 21, 1954 OIL WELL BLASTING Eugene P. McAdams, Woodbury, N. J., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application July 11, 1950, Serial No. 173,128

1 Claim. (Cl. 102-21.6)

This invention relates to a method of blasting oil wells and more particularly to such a method which is convenient and which does not leave undesired metallic debris in the well.

In blasting oil wells, it has been necessary heretofore to enclose the explosive used in a heavy metal container, or so-called torpedo shell, or to use a complicated system of metal wires or straps around explosive cartridges in order to lower the explosive into the well. When it was desired to use an amount of explosive for any one shot necessitating a series of containers, means had to be used for joining the containers together such as tongue and groove construction of the torpedoes or a system of hooks and bails. Such methods have been cumbersome, and have required space in the well, and when the explosive charges were detonated, these heavy metal containers or the wire arrangements were broken up in the well to form large metal fragments which remained in the well to interfere with subsequent operations.

An object of the present invention is a method of oil well blasting wherein the use of heavy metal containers or supports and the consequent formation therefrom of metallic debris in the well are avoided. A further object is a method of blasting wherein the explosive charges are introduced with facility into the well. A still further object is a method of oil well blasting wherein the explosive charges are inserted in such a way as to afford a maximum weight of explosive in that part of the oil well where blasting is desired. Additional objects will be disclosed as the invention is described more fully hereinafter.

I have found that the foregoing objects are accomplished by disposing a plurality of explosive charges on a flexible line, preferably by threading the line through a longitudinal channel in the charges. In detail this can be done by providing explosive charges, in containers of light material such as paper, cardboard, or plastic, with central longitudinal channels lined with a rigid material, threading said explosive charges by means of said channels on a flexible line having a stop at its base of greater diameter than the diameter of the channels in the explosive charges, lowering the resulting string of explosive charges into the oil well, and detonating them there by any desired means. A plurality of strings may be lowered in turn, if desired.

The method of operation of my invention will be seen more clearly by reference to the attached drawings, which are not to be taken as limiting in any way.

Figure 1 shows one of the explosive charges in accordance with my invention. Figure 2 shows a string of said explosive charges on a flexible line. Figure 3 illustrates a smaller charge than that of Figure 1, in this case containing a more sensitive explosive, and Figure 4 shows a string of the explosive charges of Figure 1 having interspersed therebetween explosive charges of the type illustrated in Figure 3.

In Figure l, 1 represents a cylindrical charge of a cast explosive such as amatol in a paper container 2 provided with caps 3 and 3 of paper at each end. Extending through the center of cylindrical charge 1 is a tube 4 of aluminum which is flanged outwardly over caps 3 and 3.

Figure 2 shows a series of the explosive charges of Figure l threaded on a wire rope 5 which passes through the aluminum tubes 4 in the centers of the explosive charges 1. Wire rope 5 is fastened at its lower end to a cap 6 which fits around the base of the lowest of the explosive charges 1 and at its upper end to a bail 7 of any desired form, by means of which the string of explosives may readily be lowered into the oil well.

In Figure 3, a smaller explosive charge 1, in this case of a more sensitive explosive such as pentolite is enclosed in a paper container 2 provided with caps 3 and 3, and an aluminum tube 4 as in the explosive charge of Figure 1.

Figure 4 shows a series of the explosive charges 1 of Figure l strung on a wire rope as in Figure 2, and, interspersed at intervals therebetween, charges 1' of Figure 3.

The explosive charges 1 and 1' illustrated in these drawings are formed by casting the explosive around the aluminum tube 4 flanged at the base and inserted through perforated paper cap 3 in which is placed a paper cylinder to form container 2. After the melt of explosive has cooled, perforated paper cap 3 is placed on the charge, and the upper end of tube 4 is flanged down over it. In assembling the explosive charges, the wire rope 5 is attached at its lower end to cap 6, and the explosive charges 1 and 1, the latter if desired, are strung on it by passing wire rope 5 through the aluminum tube 4 of each explosive charge until the desired number of explosive charges have been added. Bail 7 is then attached to wire rope 5, if desired, and the resulting string of explosive charges is lowered into the well and detonated by any desired means (not shown).

While I have shown cast explosive charges in iriy drawings, it is also possible to use compressed charges of explosives, for example, a series of compressed pellets, or even loose, granular, or gelatinous explosives. With loose, granular, or gelatinous explosives, however, it would be necessary for the containers to be of suflicient strength and rigidity to maintain the weight of the series of charges. Cast and compressed explosive charges are ordinarily strong enough in themselves to maintain a weight of a large number of charges in air or during lowering in oil wells.

While I find aluminum a particularly suitable material for the lining of the center channel of the explosive charge because it is dimensionally stable and resistant to heat, I may also use other rigid materials such as other metals or plastic. When metal or other rigid material is used only on the inside of the central longitudinal channel in the explosive charge, I have found that the metal or other rigid material is wholly disintegrated because the force of the explosion acts from all sides at once on the tubular lining. The metal liner thus does not leave behind metal fragments to interfere with well cleaning after the shot.

Any appropriate light material may be used as a covering for the external surfaces of the explosive charges, provided, as discussed previously, that with gelatinous or loose, granular explosives it is of suflicient rigidity to maintain the weight of the number of explosive charges put on the string. When paper or cardboard are used as covering materials, it is frequently desirable that they be made moistureproof by suitable treatment. A moistureproof plastic material, for example, is also suitable, as are other lightweight materials such as metal foil, for example. If metal is used, it must be of sufliciently light gage to disintegrate completely in the explosion.

While various types of lines such as rope or chains may be used for the threading of the explosive charges of my 7 invention, we prefer to use braided wire rope. This material is preferred because it has been found that it is disintegrated by the force of the explosion because of its texture, which comprises air spaces throughout the metal strands.

Any appropriate base member such as a cap, a plate, or a bar may be used as a stop for the lower end of the threading line, provided, obviously, that the diameter of the base member is greater than the diameter of the longitudinal channels in the explosive charge.

While it is ordinarily suflicient to use only a relatively insensitive explosive charge, it may also be desirable to introduce smaller charges of a more sensitive explosive as priming means at intervals where desired to aid in the propagation of the explosion.

3, It will be seen from the foregoing description of my invention thatthere is provided aconvenient and inexpensive means tor loading explosive charges in oil wells and that the use of heavy metal containers or wire or t p, a ra ements; a hu dr chte ner of 7 th r yp s is void d, h eby e im n ting, e-p nce, of; e rae m nt in e o zwellj tery he plosive ha ge isfired. he mqre i e. pace, betwe he expl sive harge is not require d for joining, series of; containers by, means Q v h ok. length; of; borehole cankbeloadedwinthe well; A, more u ifn n nr di t bmie -v f; explosive s b i Al explosive charges of greater diameter,may -be,used,' since the; space. formerly, occupied by, the torpedo tubes, or strap or wire,devices, may -n0w,he usedwforexplosive.

whilcgthe inventionlias been,describd ad quately, in the foregoing, it'will be understood that other variations inmaterials, construction, and arrangements may ,be made without departing fromflhe scopel-ofs'the invention. I intend,- therefore, to, be, lirnite d;,o nly,by the following claim.

Lclaim; A wholly disintegrablerblasting assembly forgoil well blastingconsisting of aseriesoi unitary, apertured ex,- plo'sive charges, mounted in} end-to-end relation on a flexible braided-wire. line, andzastop member fixedto theelld Qf, said lineio holdithe charges in position along the length, thereof; said charges each 1 comprising, a solid cast explosiye. composition dispose in a, tubular; con-v figurationabout a thin metal .tnbye withprotruding, flared nd, hail great rweightqf. xpl v per 1 ends, and having a pair of inwardly-facing, non-metallic, cup-like capsconcentric-withsaid tube and held inposition about the ends of said cast explosive by the flared ends of said tube and mating with opposite extremities of an open-ended, non-metallic, tubular container peripherally encompassing said cast explosive whereby said explosive composition incompletely encased by said nonmetallic container and caps,

Refietsn s- Cit tlih hefil .Q h sp m UNITED; STATES PATENTS:-

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