US2994269A - Liquid-responsive explosive charge firing system disabler - Google Patents

Description

Aug. 1, 1961 M. SCHLUMBERGER LIQUID-RESPONSIVE EXPLCSIVE CHARGE FIRING SYSTEM DISABLER 2 Sheets-Sheet 1 .Filed March 30, 1950 INVENTOR.

MARCEL SCHLUMBERGER I 91% Zia/.0 HI ATTORNEYS.

1951 M. SCHLUMBERGER 2,994,269

LIQUIDRESPONSIVE EXPLOSIVE CHARGE FIRING SYSTEM DISABLER Filed March 30, 1950 2 Shets-Sheet 2 FIG. 4. FiG.5.

INVENTOR. MARCEL SCHLUM BERGER HIS ATTORNEYS.

United States Patent 2,994,269 LIQUID-RESPONSIVE EXPLOSIVE CHARGE FIRING SYSTEM DISABLER Marcel Schlumberger, Paris, France, assignor, by mesne assignments, to Borg-Warner Corporation, Chicago,

Ill., a corporation of Illinois Filed Mar. 30, 1950, Ser. No. 152,823 Claims priority, application France Apr. '5, 1949 4 Claims. .(Cl. 102-20) The present invention relates to firing systems for setting off, from a relatively remote point, one or more explosive charges submerged in a body of liquid. More specifically, it has to do with novel and highly effective apparatus for disabling firing systems of this character if and when conditions unsuitable for proper operation obtain.

In the present practice, devices employing so-called shaped or hollow charges are being used for perforating the metal casings with which oil wells and the like are usually lined. Such apparatus may comprise, for example, a water-tight, pressure-resistant housing carrying one or more explosive charges therein. Each charge is provided with a cavity which faces a port formed in the side wall of the housing and the port is closed by a sealed cover in such fashion as to provide a predetermined air space or standoff in front of the charge cavity. It is also customary to provide air cushion means within the housing and outside of the charges for absorbing a sulficient amount of the concussion produced when the charges are set off to prevent possible damage to the well casing.

If the ports in the housing are not entirely water-tight, the drilling mud or other liquid which is usually present in a well may leak into the air spaces in front of the cavities in the charges and into the air cushion means, thereby rendering them partly or wholly incapable of performing their intended functions. This is a particularly serious problem in deep wells where the hydrostatic pressure of the mud or other liquid in the well may be enormous and the likelihood of leakage is correspondingly great.

It is an object of the invention, accordingly, to provide, in apparatus comprising an enclosed housing adapted to be submerged in a liquid, means responsive to leakage of the liquid into the housing.

Another object is to provide, in apparatus of the character described above, means for indicating at a relatively remote position that leakage of liquid into the submerged housing has occurred.

A further object is to provide, in well casing perforating apparatus or the like including a water-tight pressureresistant body housing a plurality of explosive charges adapted to be lowered into a well containing a column of liquid an having closed ports therein, means responsive to the leakage of liquid into said body for disabling the means for setting off said explosive charges.

These and other objects of the invention are attained by providing a chamber in the body to be submerged which is so located and formed that any liquid leaking into the body will pass to the chamber. Within the chamber is mounted means responsive to the presence of liquid therein. When the body houses one or more explosive charges together with firing means therefor, the liquid-responsive means may be designed to disable the firing means for the charges if suflicient liquid has leaked into the chamber.

In one embodiment, float means is disposed in the chamber in the body which is adapted to rise when liquid passes to the chamber. Upon reaching a predetermined level, the float means engages contact means and may short-circuit electric igniting means for setting ofi one or 2,994,269 Patented Aug. 1, 1961 ice more explosive charges in the body, for example, thereby disabling the same.

Alternatively, the electric igniting means may be disabled by utilizing weak insulation such as thin textile material, for example, between short-circuiting connections to the terminals of the igniting means. If conducting liquid such as'drilling mud in a well leaks into the chamber it wets the insulation and produces a shortcircuit across the terminals of the igniting means.

Instead of short-circuiting the electrical igniting means, means may be provided, according to the invention, for breaking the energizing circuit to the igniting means when liquid leaks into the housing.

According to another embodiment, the igniting explosive material may be disposed in a container that is pervious to liquid. The container is so placed in the housing that it will be wetted by liquid leaking into the chamber, thereby wetting the explosive material and rendering it incapable of ignition.

The invention may be better understood from the following detailed description of several representative embodiments taken in conjunction with the accompanying drawings in which:

FIG. 1 is a partial view in longitudinal section of shaped charge well casing perforating apparatus constructed according to the invention;

FIG. 2 is a view in longitudinal section illustrating another form of the invention;

FIG. 3 is a partial view in longitudinal section of a further modification;

FIGS. 4 and 5 illustrate schematically a further embodiment in which the circuit to electrical igniting means is normally maintained closed by securing means which is rendered ineffective by the presence of liquid, FIGS. 4 and 5 showing the apparatus in the closed circuit and open circuit positions, respectively; and

FIGS. 6 and 7 illustrate further modifications of the invention in which the igniting means for the charges is adapted to be disabled by the wetting of the explosive material contained therein.

In the form of the invention shown in FIG. 1, electrical igniting means for setting off one or more shaped explosive charges is adapted to be short-circuited whenever a predetermined quantity of liquid leaks into the housing of well casing perforating apparatus. This figure shows the lower portion of well casing perforating apparatus 10 having a plurality of longitudinally spaced apart, radially directed bores 11 formed therein within which so-called shaped explosive charges 12 are adapted to be mounted.

Each of the charges 12 may be disposed in a container 13 of suitable shape which may be provided with an outwardly extending flange 14 at the forward end thereof to provide a forward support for the charge. The rear end of the charge 13 may be supported in any suitable manner as by a support 15 mounted within the bore 11 and extending axially of the perforator apparatus 10. The bores 11 are adapted to be sealed by suitable closure members 16 which are shaped so as to provide a desired air space or standoff 17 in front of the charge 13, according to the usual practice. The closure members 16 may be held tightly in position by suitable retaining means 18, gaskets 19 or the like being provided to insure watertightness.

The explosive charges 13 may be ignited in any suitable manner as by means of a primacord fuse 20, for example, which extends along the perforator 10 through the passages 71 therein and through slots 21 and 22 formed in the supports 15, and which rests against the rear end of each charge 13, as shown. The primacord 20 may be detonated in any desired manner as, for example, by means of a suitable electric detonator 23 mounted at the lower 3 end thereof, as shown in FIG. 1. The detonator 23 may be disposed in a smaller chamber 24 lying beneath the lowermost bore 11 and communicating therewith through a passage 72. The chamber 24 may be closed by a suitable plug 25, gasket means 26 or the like being provided to insure water-tightness.

In accordance with the invention, means is provided for short-circuiting the electric detonator 23 if and when a predetermined quantity of liquid leaks into the well casing perforating apparatus. To this end, a chamber 27 is formed in the perforator beneath the chamber 24 and communicating therewith through a longitudinal passage 28. The chamber 27 may be closed at its lower end by means of a plug 29, suitable gasket means 30 being provided to insure a water-tight joint. It will be understood that if any liquid, such as the drilling mud in a well into which the perforating apparatus 10 may be lowered, leaks into the perforating apparatus, such liquid will flow downwardly and will collect in the lowermost chamber 27.

Within the chamber 27 is mounted conducting float means 31 which is adapted to rise as liquid collects in the chamber 27 and to engage two contacts 32 and 33 mounted at opposite sides of an insulating support 34. The contact 32 is connected by a conductor 35 to one terminal of the detonator 23 and by a conductor 36 in the cable (not shown), on which the perforating apparatus 10 is supported in a well, and through a switch 39 to one terminal of a source of electrical energy 73 located at the surface of the earth. The contact 33 is connected by a conductor 37 to the other terminal of the detonator 23 and by the conductor 38 in the supporting cable (not shown) to the other terminal of the electrical energy source 73.

In operation, the perforating apparatus 10 is lowered to the desired depth in a bore hole where a perforating operation is to be made. If all of the closure members 16, 25 and 29 are water-tight, no bore hole liquid will leak into the apparatus and the float 31 will remain in the position shown in FIG. 1. Under these conditions, the closing of the switch 39 at the surface of the earth will result in detonation of the primacord 20 and substantially simultaneous detonation of the charges 13. On the other hand, if any of the closure means 16, 25 and 29 are not entirely water-tight so that some of the bore hole liquid leaks into the perforating apparatus 10, the accumulation of this liquid in the lowermost chamber 27 will lift the float 31 and eventually move it into engagement with the contacts 32 and 33, thus short-circuiting the electric detonator 23 and rendering it impossible to set off the charges 13 by closing the switch 39.

In the embodiment shown in FIG. 2,. the leads 36 and 38 are provided with weak insulation at their lower ends and are wound as a pair on a metal support 40 mounted in the chamber 27 and are eventually connected to the terminals of the electric detonator 23. In this embodiment, the detonator 23 can be set off by closing the switch 39 (FIG. 1) at the surface so long as there is no accumulation of liquid in the chamber 27. However, if any liquid collects in the chamber 27 it will dampen the weak insulation on the conductors 36 and 38 causing a shortcircuit and rendering it impossible to set off the detonator 23 by closing the switch 39.

A similar detonator short-circuiting means is shown in FIG. 3. In this modification, one terminal of the electric detonator 23 is connected by a conductor 41 to the body of the perforating apparatus 10 at 42 and the other terminal is connected by a conductor 43 in series with a resistor 44 to a point 45 on a metallic member 46 which is supported within the chamber 27 and insulated therefrom by weak insulation 47 such as textile material, for example. The conductor 38 in the supporting cable is also connected to the metallic member 46 at the point 45 and the source of electrical energy 73 is grounded at the surface of the earth, the energizing circuit for the dt tonator 23 being completed through ground.

So long as no liquid is present within the chamber 27, the insulating material 47 maintains a very high resistance between the metallic member 46 and the body of the perforating apparatus 10 so that the electric detonator 23 can be set off by closing the switch 39 at the surface of the earth in the usual manner. However, as soon as the liquid collects in the chamber 27 the insulating material 47 becomes damp so that the resistance between the metallic member 46 and the body of the perforating apparatus 10 is much reduced. The value of the resistance 44 in series with the detonator 23 is suitably chosen that,

under these conditions, the major part of the current from the source 36 when the switch 39 is closed will pass to ground and not through the detonator 23, thus disabling the latter.

Instead of short-circuiting the electric detonator, the energizing circuit to the detonator may be broken by means responsive to the presence of liquid within the perforating apparatus 10, as shown in FIGS. 4 and S. In this form of the invention, one terminal of the electric detonator 23 is grounded to the body of the perforating apparatus 10 by a conductor 48 and its other terminal is connected to a contact 49 carried by one arm 50 of a spring element 51, the other arm 52 of which carries a cooperating contact 53. The contact 53 may be connected to the conductor 38 in the supporting cable (not shown).

The cooperating contacts 49 and 53 on the spring 51 are normally maintained in engagement by suitable means such as a strip of a textile material 54 to which an adhesive coating has been applied. This spring element 51 with its contacts 49 and 53 may be mounted in the chamber 27 of the perforating apparatus shown in FIG. 1, such that the contacts 53 and 49 are insulated therefrom. So long as the chamber 27 contains no liquid, the contacts 49 and 53 will remain in engagement and the detonator 23 can be set off by closing the switch 39 at the surface.

If, however, suflicient liquid collects in the chamber 27, it will wet the strip 54 of textile material, rendering the adhesive coating thereon ineffective and permitting the arms 50 and S2 of the spring to move apart and disengage the contacts 53 and 49. At the same time, the contact 49 will engage a contact 70 which is connected to ground, thus short-circuiting the detonator 23. Under these conditions, it will be impossible to set off the detonator 23 by manipulation of the switch 39 at the surface of the earth.

It is also possible to disable the igniting means by so disposing it that the explosive material therein will be wetted by any liquid which may leak into the apparatus, as shown in FIG 6 and 7. In FIG. 6, one end of the primacord fuse 20 is shown inserted in a sleeve member 55, the end of which may be closed by a suitable plug 57. The plug 57 carries electric igniting means 23 which may comprise, for example, an igniting filament 59 connected to conductors 60 and embedded in a body of explosive material 61 in a suitable container 58. Both the plug 57 and the container 58 are preferably made of material such as unvarnished cardboard which is pervious to liquid, instead of the varnished cardboard ordinarily used. The plug 57 and the electric detonator 23 are preferably disposed within the lowermost chamber 27 in the gun perforating apparatus 10 of FIG. 1.

So long as the chamber 27 remains dry, the electric detonator 23 will operate in the usual manner. If, however, sutficient liquid accumulates in the chamber 27, it will penetrate the sleeve member 55 and the container 58 and wet the explosive material 61, thereby rendering the latter incapable of ignition.

In the modification shown in FIG. 7, the sleeve member 55 is provided with a plurality of small holes 62 in the side wall thereof. Normally, the holes 62 are covered by a sleeve 63 of suitable material such as cellophaue which is removed just prior to the insertion of the sleeve member 55 in the perforating apparatus 10. In this form of the apparatus, any liquid collecting in the lowermost chamber 27 of the perforating apparatus will enter the holes 62 and penetrate the wall of the container 58, thereby wetting the explosive material 61 and rendering it incapable of ignition.

The invention thus provides new and improved means responsive to the leakage of liquid into a housing of the type employed in well casing perforating operations in wells containing a column of liquid such as drilling mud, for example, for disabling the firing means for the exposive charges in such apparatus. It is of particular utility in apparatus such as shaped charge well casing perforators in which the leakage of liquid into the apparatus is likely to impair the effectiveness of the air spaces both in front of the apparatus and around the charges, which are essential for effective operation.

The several embodiments described above and illustrated in the drawings are obviously susceptible of modification without departing from the invention, as will be well understood to those skilled in the art. Further, it will be understood that a suitable signalling device such as a neon tube 80, for example, may be provided at the surface of the earth in the detonator energizing circuit which will flash if the switch 39 is closed at a time when the electric detonator 23 in FIGS. 1-3, inclusive, is short-circuited, thereby providing a clear indication of the leakage of liquid into the well casing perforating apparatus 10. Such a signalling device could be used alone, although it is preferable to use it in conjunction with means for disabling the firing system for the charges, according to the invention. The specific embodiments disclosed, therefore, are not to be regarded as restricting in any way the scope of the accompanying claims.

I claim:

1. In combination, a hollow body adapted to be lowered into a liquid and having at least one explosive charge chamber therein and a port providing communication between said chamber and the exterior of the body, normally water-tight closure means for said port, an explosive charge in said chamber and having a cavity facing said port, there being air spaces in front of said cavity and around said charge, a liquid collection chamber in said body beneath said charge communicating with said explosive charge chamber, explosive fuse means for deto nating said charge, a container disposed in proximity to one end of said fuse means and in said liquid collecting chamber, a fuse initiating charge in said container, and electrical means for igniting said charge, said container being made of liquid-pervious material so as to render said initiating charge ineffective when liquid is present in said chamber.

2. In combination, a hollow body adapted to be lowered into a liquid and having at least one explosive charge chamber therein and a portproviding communication between said chamber and the exterior of the body, normally water-tight closure means for said port, an explosive charge in said chamber and having a cavity facing said port, there being air spaces in front of said cavity and around said charge, a liquid collection chamber in said body beneath said charge communicating with said explosive charge chamber, explosive fuse means for detonating said charge, a sleeve member mounted at one end of said fuse means and in said liquid collecting chamber, said sleeve member having perforations therein permitting the flow of liquid therethrough, a cap member for said sleeve member, a liquid-pervious container secured to said cap, an initiating charge in said container, and electric igniting means for said charge.

3. In a perforating gun of the character described, wherein shaped charges of explosive are supported within a hermetically-sealed barrel with the spaces between said charges occupied by gas and the charges are arranged to be initiated by an electric blasting cap within the barrel, the improvement comprising, said electric blasting cap being disposed below said shaped charges and having an igniter element spaced from a base charge therein, said cap being vented at a plurality of circumferentially spaced positions at a section axially between the igniter and the base charge to admit liquid to the space between said charges on the interior of the cap.

4. In a perforating gun of the character described, wherein spaced, shaped charges of explosive are initiated by an electric blasting cap, the improvement comprising, said electric blasting cap having a case, an explosive train in the case, and a closure plug for the case, said explosive train being composed of a plurality of explosively-active ingredients arranged to constitute an ignition charge and at least one other charge, said other charge being explosively sensitive to firing of said ignition charge and arranged to be directly detonated thereby, but spaced therefrom at a distance less than suflicient to inhibit detonation thereof directly by said ignition charge, and said case having vents extending from the exterior to the interior thereof adjacent the space between said ignition charge and said other charge.

References Cited in the file of this patent UNITED STATES PATENTS 1,901,469 Piccard Mar. 14, 1933 2,305,229 Alexander Dec. 15, 1942 2,432,367 Andresen Dec. 9, 1947 2,494,256 Muskat Jan. 10, 1950 2,759,417 ONeill Aug. 21, 1956 OTHER REFERENCES Book entitled Elements of Ammunition, by Major Theodore C. OHart, published by John Wiley & Sons, New York, March 21, 1946, page 59. (Copy in Div. 10.)

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