US2297006A - Gun perforator firing system - Google Patents

Description

Sept. 1942- R. w. LOHMAN 2,297,006

GUN PERFORATOR FIRING SYSTEM Filed March 7, 1941 INVENTOR 441 WL OHMA/Y ATTORNEY Patented Sept. 29, 1942 GUN PERFORATOB FIRING SYSTEM Ralph W. Lohman, South Pasadena, Calif., as-

signor to-Lane-Wclia Company, Los Angeles, Calm, a corporation of Delaware Application March 1, 1941, Serial No. 382,209 9 Claims. (01. lea-0.5)

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 01' 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 01' a given voltage to the input end of the cable or whereby the gun units may be fired at diflerent 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 tire each of the cartridges contained in the gun unit 01 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, toprovide 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 toaccomplish 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 whichithe wiring diagram shows my firing system in association withthe gun units of a gun perforator.

Each gun unit for the gun perforator com-- prises a cartridge I containing an explosive and a fuse or ignition wire 2. The ignition wire is preferably grounded to the bullet 3 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 5 and resistor 6 to a current supply line I. A condenser I is connected in a circuit parallel 'I'heseveral cartridges l and their corresponding spark gaps 5, resistors 6 and condensers 8 from a suitable source 9 so that each of the condensers 0 are caused to charge. By graduating the value of the resistors 6 the rates at which the diflerent condensers charged difier. The several spark gaps function as switches and are designed to break down or pass current at a predetermined potential so that as eachcondenser reaches a predetermined potential the associated spark gap breaks down, causing a sudden current surge directly to ground through the cartridge suflicient 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 which will be predetermined by the values of the resistors.

It should, of course, be noted that the resistors B may be equal in value and the capacity of the condensers or capacitors 8 may be varied, or the 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 predetermined timed sequence.

Ifit 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 endof the cable after the discharge of a given cartridge and again close the circuit when the desired time has arrived.

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 conwith each cartridge. and its spark gap, so that the cartridge and spark gap form a discharge circuit for the condenser.

ductor I may be relatively small and the conductor I may be of correspondingly small diameter. This is particularly advantageous in gunperiorating 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 or capacitors become- 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 I so that the possible range of resistance variation in the cable has no appreciable effect. v

It should be observed further that, due to the resistors 8, no current or voltage surges take place inthe 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 v 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 a the prior art permits.

I claim:

1. A firing system for gun perforators having -a cartridge provided with an electrically respon-.

sive ignition fuse, comprising: a capacitor;

- means for charging said capacitor; and means for discharging said capacitor through said car-- energy from said reservoir through said ignition fuse when the quantity of said electrical energy in said reservoir reaches a predetermined value. 3. A firing system for gun perforators having a plurality of cartridges, each provided with an electrically responsive ignition fuse, comprising: a plurality of capacitors corresponding to said ignition fuses; means for charging said capacitors; and means for discharging said capacitors through their respective ignition fuses in timed sequence. 1

4. A firing system for gun perforators having a plurality of cartridges, each provided with an electrically responsive ignition fuse, comprising: reservoirs of electrical energy located in the immediate vicinity of and corresponding to said cartridges; means for supplying said reservoirs with electrical energy; and means for discharg-' handicap in the operation of my present system.

ing the electrical energy from said reservoirs through their corresponding cartridges and ignition fuses at time spaced intervals.

5. A firing system for gun perforators having a plurality of cartridges, each provided with an electrically responsive ignition fuse, comprising: a capacitor for each ignition fuse; means charging said capacitors at various predetermined rates; and means for discharging said capacitors through their respectiveignition fuses as each capacitor reaches a predetermined charged condition, whereby said cartridges are fired at time spaced intervals corresponding to the predetermined rates at which they are charged.

a plurality of cartridges, each provided with an electrically responsive ignition fuse, comprising: a plurality of capacitors in close proximity to and electrically associated individually with said ignition fuses; means for charging said capacitors with current insufllcient to ignite said fuses directly; and means for discharging the accumulated energy in said capacitors through said ignition fuses in timed sequence.

' 7. A firing system for gun perforators havin a cartridge provided with an electrically responsive ignition fuse, comprising: a capacitor in close proximity to and electrically associated with said ignition fuse; means for charging said capacitor with current insufiicient to ignite said fuse; and means for discharging the accumulated energy in said capacitor through said fuse;

8. A method of firing the electrically responsive cartridges of a gun perforator, characterized by: charging at a slow and predetermined rate a. plurality of reservoirs of electrical energy electrically'associated with said cartridges; and discharging the electrical energy from said reset RALPH W. LOHMAN.

6. A firing system for gun perforators having cartridges at time spacediin-"

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