Gun perforator firing system

Sept. 29, 1942.

R. W. LOHMAN

2,297,006

GUN PERFORATOR FIRING SYSTEM

Filed March 7, 1941

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Patented Sept 29, 1942

2,297,006

UNITED STATES PATENT OFFICE

2,297,006

GUN PERFORATOR FIRING SYSTEM

Ralph W. Lohman, South Pasadena, Calif., assignor to Lane-Wells Company, Los Angeles, Calif., a corporation of Delaware

Application March 7,

Claims.

My invention relates to gun perforator firing systems; that is, systems whereby a multiple unit gun perforator suspended in a well casing from a conductor cable may be caused to fire its gun units in consecutive order by electrical control to the single conductor cable. Among the objects of my invention are:

First, to provide a gun perforator firing system wherein only a nominal amount of current needs to be supplied through the conductor cable, thus causing only a small voltage drop thereover and thereby permitting the use of a small conductor even though the cable length may be several thousand feet;

Second, to provide a gun perforator firing system wherein a predetermined time interval is obtained between the discharge of each gun unit, merely by the steady application of a given voltage to the input end of the cable or whereby the gun units may be fired at different time intervals by controlling or interrupting the supply of current, all from a remote station;

Third, to provide a system of this character which insures an adequate amount of energy to fire each of the cartridges contained in the gun unit of the gun perforator, even though the fuses or resistances in the cartridges may vary in their resistance value or be comparatively low in value and require a substantial current;

Fourth, to provide a system of this character wherein high voltage surges in the conductor cable are eliminated, so that the possibility of damaging the cable due to voltage surges is eliminated; and

Fifth, to provide a gun perforator firing system which eliminates stepping switches or other moving parts in order to accomplish sequential firing of the gun units.

With the above and other objects in view, as may appear hereinafter, reference is directed to the accompanying drawing, in which the wiring diagram shows my firing system in association with the gun units of a gun perforator.

Each gun unit for the gun perforator comprises a cartridge I containing an explosive and a fuse or ignition wire 2. The ignition wife is preferably grounded to the bullet S of the gun units which, in turn, is grounded to the body of the gun perforator (not shown). The other end of each cartridge is connected through a spark gap 8 and resistor 6 to a current supply line 7. A condenser 8 is connected in a circuit parallel with each cartridge and its spark gap, so that the cartridge and spark gap form a discharge circuit for the condenser.

1941, Serial No. 382,209 (CL 164—0.5)

The several cartridges ( and their corresponding spark gaps 5, resistors 6 and condensers 8 are in parallel circuits between the supply line 7 and the ground 4. Direct Current is supplied 5 . from a suitable source 9 so that each of the condensers 8 are caused to charge. By graduating the value of the resistors 6 the rates at which the different condensers or capacitors become charged differ. The several spark gaps function 10 as switches and are designed to break down or pass current at a predetermined potential so that as each condenser reaches a predetermined potential the associated spark gap breaks down, causing a sudden current surge directly to ground 15 through the cartridge sufficient to raise the fuse 2 to incandescence and thereby ignite the explosive. If voltage is supplied at a constant value from the source 9, the condensers will charge and then discharge in timed sequence 20 which will be predetermined by the values of the resistors.

It should, of course, be noted that the resistors 6 may be equal in value and the capacity of the condensers or capacitors 8 may be varied, or the 25 condensers and resistors may be constant and the spacing of the spark gap 5 may be varied. In other words, by graduating either the spark gaps, the condensers or the resistors, the condensers may be caused to discharge in a prede30 termined timed sequence.

If it is desired to increase the time interval above that which is predetermined by the resistors, it is merely necessary to interrupt the flow of current at the input end . of the cable 35 after the discharge of a given cartridge and again close the circuit when the desired time has arrived.

It will be observed that the amount of current supplied through the conductor 7 may be ex40 tremely low; in fact, may be below the value necessary to ignite the fuses 2 collectively, or even one of the fuses individually. Consequently, the conductor cable which contains the conductor 7 may be relatively small and the conductor 7 may be of correspondingly small diameter. This is particularly advantageous in gunperforating deep wells, wherein the conductor cable may be as long as 15,000 feet; necessarily, the diameter of the conductor is limited and, consequently, its resistance is comparatively great. The permissible voltage is also limited; consequently the amount of energy that can be transmitted over such a line is relatively small. While this is a serious disadvantage in the operation of conventional gun perforators, it offers no

3,397,006 handicap in the operation of my present system.

The only possible effect of a high resistance cable is to increase the time required to charge the condenser. Actually, the cable resistance is materially lower than the resistors · so that the possible range of resistance variation in the cable has no appreciable effect.

It should be observed further that, due to the resistors 6, no current or voltage surges take place in the cable itself when the cartridges are fired, even though, the cable may have inductive characteristics and even though a large amount of current is discharged through the spark gaps and their cartridges.

Various changes and alternate arrangements may be made within the scope of the appended claims, in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.