US2736260A

US2736260A - Schlumberger

Info

Publication number: US2736260A
Authority: US
Publication date: 1956-02-28
Anticipated expiration: 1973-02-28

Description

Feb. 28, 1956 M. SCHLUMBERGER 2,736,260

ELECTRI FIRING SYSTE OR X LOSIVELY ERATED BOREHO TO Filed Nov. 19, 1949 2 Sheets-Sheet 1 F'IGJ.

v l NTOR. IO MARCEL SC MBERGER H IS ATTORNEYS.

Feb. 28, 1956 M. SCHLUMBERGER 2,736,260

ELECTRICAL FIRING SYSTEM FOR EXPLOSIVELY OPERATED BOREHOLE TOOLS 2 Sheets-Sheet 2 Filed Nov. 19, 1949 l m H a l INVENTOR. MARCEL SCHLUMBERGEFi $122 f' mm HIS ATTORNEYS.

2,736,260 Patented Feb. 28, 1956 ELECTRICAL FIRING SYSTEM FOR EXPLOSIVELY OPERATED BOREHOLE TOOLS Marcel Schlumberger, Paris, France, assignor to Societe de Prospection Electrique Procedes, Schlumberger, Paris, France, a corporation of France Application November 19, 1949, Serial No. 128,386 Claims priority, application France February 19, 1949 9 Claims. (Cl. 102-20) The present invention relates to firing systems for exposive charges and more particularly to new and improved electrical systems for setting off a plurality of explosive charges either one by one or as a group in predetermined sequence.

In producing oil from wells, explosively propelled projectiles are widely used in sample taking and casing perforating operations, for example. The systems currently employed for setting off the explosive charges in the well from the surface of the earth are relatively complex and tend to be faulty in operation at the excessive temperatures encountered in the exceedingly deep holes now being drilled. Moreover, bore hole tools of recent design in which the explosive power has been increased, are subjected to greater shocks so that the frequency of occurrence of faulty operations has gone up.

It is an object of the invention, accordingly, to provide new and improved firing systems for explosive charges which are free from the above noted deficiencies of the prior art.

Another object of the invention is'to provide new and improved firing systems of the above character which are simple and rugged in construction yet highly effective in operation.

Still anotherobject of the invention is to provide new and improved firing systems of the above character in which the explosive charges may be fired one by one.

A further object of the invention is to provide new and improved firing systems of the above character by means of which a group of explosive charges may be set off substantially simultaneously in predetermined sequence.

These and other objects of the invention are attained by providing a plurality of igniters of equal resistance for the respective explosive charges and connecting them in an electrical network simulating a transmission line. More particularly, the igniters are shunted across the line and equal resistances are inserted in series with the line be tween adjacent igniters, the line being terminated in its characteristic impedance. For ignition of the entire group of igniters in sequence, constant current is supplied to the network and its intensity is adjusted to the value required just to ignite the first igniter. Under these conditions, the entire group of igniters will be ignited sequentially.

In another embodiment, constant current of the proper value just to ignite the first igniter is supplied to the network through hold-in switch means at the surface of the earth and normally closed concussion responsive switch means in the bore hole. When the hold-in switch means is closed, it is maintained closed so long as current is flowing to the network. Upon ignition of the first igniter, the shock of the explosion opens the concussion responsive switch means, stopping the flow of current and opening the hold-in switch means. The concussion responsive switch means again closes but the hold-in switch means must again be closed in order to ignite the next succeeding igniter. With this construction, therefore, the igniters may be ignited one by one, as desired.

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

Fig. 1 is a schematic diagram of an electrical firing circuit constructed according to the invention for firing a group of explosive charges in a bore hole tool substantially simultaneously in predetermined sequence;

Fig. 2 is a view in elevation of gun perforator apparatus embodying the novel firing circuit shown in Fig. 1;

Fig. 3 is a view in transverse section taken along line 3-3 of Fig. 2; and

Fig. 4 is a schematic diagram of a modified form of firing circuit designed to permit the explosive charges in a bore hole tool to be set oif one by one.

While the novel firing systems of the invention are of general utility for controlling the firing of a plurality of explosive charges from a relatively remote point, they will be described herein, by way of example, as applied to gun perforating apparatus of the type usually employed for perforating a bore hole casing.

- Referring first to Fig. 1, the box 10 designates a gun perforator adapted to be lowered into a bore hole 11 which usually contains a column of conducting liquid 12. As shown in Fig. 2, the perforator 10 may comprise, for example, a substantially cylindrical body 13, made of steel or other suitable strong material, for example, having a rounded cap 14 at the lower end thereof to facilitate the passage of the apparatus through a well. The upper end of the body 13 is joined by a conventional coupling member 15 to a cable head 16 in which is secured a supporting cable 17, in the usual manner.

Longitudinally spaced along the body 13 and angularly disposed about the longitudinal axis thereof are a plurality of laterally extending gun barrels 18. As shown in Fig. 3, each gun barrel 18 is adapted to be screwed into a threaded bore 19 in the body 13 and it has a flanged portion 20 adapted to be seated in a recess 21, suitable gasket means 22 being provided to insure a watertight joint. Recesses 23 or other suitable means may be formed in the barrel 18 to facilitate its insertion and removal by wrench means.

Each of the bores 19 has a substantially cylindrical rear portion 24, and a portion 25 which converges rearwardly to a circular depression 29 surrounding a fiat raised portion 27. The bore portions 24 and 25 cooperate with a rearwardly converging portion 28 formed on the gun barrel 18 to form a substantially annular powder chamber 30.

The powder chamber 30 is adapted to receive an explosive charge 31 in a container of similar shape which may be made of plastic material, for example, and which is provided with a flat base portion 32 which is adapted to lie just above the raised portion 27.

In each gun barrel 18 is formed a gun bore 26 which is adapted to receive a casing perforating projectile 33. The projectile 33 is preferably provided with a forward stopper member 34 made of flexible material such as rubber, for example, and a rear, burr eliminating member 35. Projectiles of this type are disclosed in the copending application Serial No. 120,084, filed October 7, 1949, by Pierre Dubost, for Fluid Scaling and Burr Elimination Projectile for Gun Perforators.

The explosive charge 31 may be ignited by an electrical igniter 36, one end of which is connected to the pointed end of a conducting tube 37 tightly fitted in an adapter 38 threaded into a bore 39 formed in the perforator body 13. igniters of this type are more fully described in the applicants copending application Serial No. 128,323; filed November 19, 1949, for Electrical Igniters. The other end of'the igniter 36 is connected to a conductor 40 which is insulated from the conducting tube 37 and which is connected to a conductor 41. Suitable gasket means 42' and packing means 43 maybe employed to prevent the entrance of bore hole fluid through the bore 39.

The conductor 4:1 is disposed in a spiral groove 42. formed in the outer wall of the perforator body 13 and it is connected at its upper and lower ends to the terminal blocks 43 and 4-4, respectively (Fig. 2). The

terminal blocks

43 and 44 and the groove 42 permit easy removal of the wire 41 yet prevent excessive wear of the wire 41 in passing through the bore hole. As a further precaution against wear, a steel strip 60 may be placed in the groove 42 over the wire 41.

As best shown in Fig. l, the igniters 36 for the several explosive charges 31 in the gun perforator 10 are connected between the conductor 41 and ground. Further, the system is so designed that the resistances of the pertions 45 of the conductor 41 lying between adjacent igniters 36 are equal. The electrical network comprising the shunt igniters 36 and the series sections of the conductor 41 simulates an electrical transmission line.

According to the invention, the network is terminated in a resistance 46 which is equal to the characteristic impedance of the line. In a typical system, the resistance values for igniters 36 and the conductor portions 45 might be 2 ohms and 1 ohm, respectively, in which case the resistor 46 would have a value of 2 ohms, for example.

It will be understood, therefore, that if the current supplied to the network is just enough to insure ignition of the topmost igniter 36, the currents flowing through the other igniters 36 will be less than that required for their ignition. Further, upon destruction of the topmost igniter 36 following ignition thereof, the impedance of the network measured at the next succeeding igniter 36 is substantially the same so that, if current of the same constant intensity is supplied, the current through the next succeeding igniter will be just sufficient for its ignition, while the currents through the remaining igniters will not be suflic'ient for their ignition.

The upper end of the conductor 41 (Fig. 2) is connected to a conductor 47 in the supporting cable 17 which may be connected to one terminal of a suitable source of constant current 43 (Fig. 1) located at the surface of the earth, the other terminal of which is grounded at 52. The source 48 may comprise, for example, a battery 49 connected in series with a resistance 50 which is relatively large as compared with the total resistance introduced by the conductor 41.. A conventional switch '51 may be interposed between the source 48 and the ground 52 and a conventional current indicating instrument 53 may be inserted in series with the conductor 47 so that the current flowing to the network may be observed.

In operation, the perforating apparatus is lowered into the well with the switch 51 open, as shown in Fig. 1. When the desired level for perforation has been reached,

the switch 51 is closed, thus supplying to the network current of constant intensity and causing ignition of only the first igniter 36. This sets oil the topmost explosive charge 31 and destroys the topmost igniter 36. The transient effect produced by the sudden opening of the circuit causes a slight deflection on the meter 53. The next igniter 36 now receives sufficient current for its ignition while the remaining igniters receive less current than the amount required for ignition so that the second explosive charge is set otf in the same manner. In similar fashion, the remaining explosive charges are exploded in sequence. It will be understood that the sequence of events described above takes place very rapidly so that the explosive charges in the perforating apparatus are set off substantially simultaneously. The constant reading of the meter 53 will indicate to the operator that the operation is complete so that he can open the switch 51 and withdraw the tool from the bore hole 10.

If it is desired to set ofif the explosive charges 31 one by one, as desired, the system shown in Fig. 4 may be employed. The firing network in this figure is essentially the same as shown in Fig. 1 but a concussion responsive switch 54 is disposed in the bore hole with the perforating apparatus 10, and a hold-in switch 55 is connected in series with the conductor 47 at the surface.

The switch 54 is so designed that it normally connects the conductor 41 to the cable conductor 47 but when an explosive charge is set off, the concussion developed operates the switch 54 and breaks the connection between the two conductors. To this end, the switch 54 may comprise, for example, a switch which is normally maintained closed by a steel ball resting on the switch actuator, the ball being so disposed as to be thrown otf the switch actuator by the concussion developed and to return to its rest position on the switch actuator after the forces of: concussion have been dissipated.

The switch 55 may be provided with a hold-in coil 56 which is energized when the switch is closed and which holds the switch closed until the circuit is subsequently opened.

In operation of the embodiment shown in Fig. 4, the perforating apparatus 10 is moved to the desired level in the bore hole whereupon the switch 55 is closed. It then remains closed by operation of the holding coil 56. This ignites the first igniter 36 and explodes the first explosive charge 31. The concussion developed by the explosion jars the switch 54 causing it to break the energizing circuit and to deenergize the hold-in coil 56 of the switch 55, permitting the latter to open. This operation takes place before the current supplied to the network has had an opportunity to rise to the value required for ignition of the next succeeding igniter 36. it will be understood, therefore, that the switch 55 must be actuated each time an igniter 35 is to be ignited. Hence, the several igniters 36 can be exploded one by one at different depths in the bore hole, if desired.

Where it is desired to set oif more explosive charges than can be accommodated in a single perforator body 13, it will be understood that the plug 14 may be removed so as to permit additional bodies to be attached to the body 13. In such case, the terminal block 43 of a lower perforator body 13 will be connected to the terminal block 44 of the next higher perforator body, and the resistance 46 (Fig. 1) will be connected from the terminal block 44 of the lowermost perforator body 13 to ground.

It will be understood from the foregoing description that the invention provides a novel and highly effective firing circuit for controlling the firing of a plurality of explosive charges from a relatively remote point. By connecting the igniters for the explosive charges in a network simulating a transmission line and terminating the network in the characteristic impedance of the line, a group of igniters may be fired in sequence and substantially simultaneously. Further, by incorporating in the circuit a hold-in switch at the surface together with percussionresponsive switch means in the bore hole, the igniters may be set off one by one, as desired.

It will be further understood that the specific embodiments disclosed herein are susceptible of considerable modification within the spirit of the invention. For example, an alternating current source may be employed instead of D. C., provided that an equivalent A. C. impedance network is substituted for the resistance network shown in the several forms of the invention described above. Also, headphones or a loudspeaker might be loosely coupled to the conductor 47 to obtain audible indications of the operation of the apparatus. The illustrative embodiments disclosed herein, therefore, are not to be regarded as limiting in any way the scope of the following claims.

I claim:

1. In a system for controlling the firing of a plurality of explosive charges, the combination of an electrical transmission channel having an input end and a terminus, a plurality of electrical igniters of equal impedance connected in shunt in said channel, a plurality of equal impedances connected in series in said channel between adjacent igniters, and an impedance connected to said channel at the terminus thereof and being substantially equal to the characteristic impedance of said channel.

2. In a system for controlling the firing of a plurality of explosive charges, the combination of an electrical transmission channel having an input end and a terminus, a plurality of electrical igniters of equal impedance connected in shunt in said channel, a plurality of equal impedances connected in series in said channel between adjacent igniters, a source of current connected to the input end of said channel, switching means interposed between said source and the channel, and an impedance connected to the terminus of said channel, the value of said last named impedance being substantially equal to the characteristic impedance of the channel.

3. In a system according to claim 2, the provision of means for maintaining the current from the source of current at a constant amplitude when said switching means connects said source to the transmission channel.

4. In a system for controlling the firing of a plurality of explosive charges, the combination of a plurality of electrical igniters, a plurality of impedances, means connecting said igniters in shunt and said impedances in series between adjacent igniters to form a simulated transmission line, a source of electrical energy connected to one end of said line, manually operable, switching means having current responsive hold-in means interposed between the source and said one end of the line, and normally closed concussion responsive switching means interposed between the source and said one end of the line for interrupting the connection therebetween.

5. In a system for controlling the firing of a plurality of explosive charges, the combination of a plurality of electrical igniters of equal impedance, a plurality of equal impedances, means connecting said igniters in shunt and said impedances in series between adjacent igniters to form a simulated transmission line having an input end and a terminus, a source of electrical energy connected to the input end of said line, hold-in switching means interposed between the source and said input end of the line, normally closed concussion responsive switching means interposed between the source and said input end of the line, and an impedance connected to said terminus of the line, said last-named impedance having a value substantially equal to the characteristic impedance of the line.

6. In a system for controlling the firing of a plurality of explosive charges in a bore hole tool adapted to be lowered into a bore hole, the combination of a plurality of electricaligniters of equal impedance associated with corresponding explosive charges in the tool, a plurality of equal electrical impedances, means connecting said igniters in shunt and said impedances in series between adjacent igniters to form a simulated electrical transmission line having an input end and a terminus, an impedance connected to the terminus of said line and equal to the characteristic impedance of said line, a source of electrical energy at the surface of the earth, electrical connections between said source and the input end of the line, and switching means interposed between the source and said input end of the line.

7. In a system for controlling the firing of a plurality of longitudinally spaced apart explosive charges in a bore hole tool adapted to be lowered into a bore hole, an electrical conductor carried by the tool and extending longitudinally thereof, a plurality of electrical igniters of equal impedance associated with the explosive charges in said tool, respectively, the opposite ends of each of said igniters being connected to ground and to a point on said conductor, respectively, such that the latter introduces equal amounts of impedance between adjacent igniters, a source of electrical energy at the surface of the earth having a terminal connected to one end of said conductor and another terminal connected to ground, switching means interposed between the sourceand said one end of the conductor, and an electrical impedance connected to the other end of said conductor and to ground and equal in value to the characteristic impedance of the simulated transmission line formed by said igniters and conductor.

8. In a system for controlling the firing of a plurality of explosive charges in a bore hole tool adapted to be lowered into a bore hole, the combination of a plurality of electrical igniters of equal impedance associated with corresponding explosive charges in the tool, a plurality of equal electrical impedances, means connecting said igniters in shunt and said impedances in series between adjacent igniters to form a simulated electrical transmission line having an input end and a terminus, an impedance connected to said terminus of said line and equal to the characteristic impedance of said line, a source of electrical energy at the surface of the earth, electrical connections between said source and the input end of the line, normally open switching means at the surface of the earth for controlling the connections between the source and said input end of the line, means responsive to current flowing to said line for maintaining said switching means closed, and normally closed concussion operated switching means operatively associated with said tool for breaking the connections between the source and said input end of the line to render said current responsive means inoperative.

9. In a system for controlling the firing of a plurality of longitudinally spaced apart explosive charges in a bore hole tool adapted to be lowered into a bore hole, an electrical conductor carried by the tool and extending longitudinally thereof, a plurality of electrical igniters of equal impedance associated with the explosive charges in said tool, respectively, the opposite ends of each of said igniters being connected to ground and to a point on said conductor, respectively, such that the latter introduces equal amounts of impedance between adjacent igniters, a source of electrical energy at the surface of the earth having a terminal connected to one end of said conductor and another terminal connected to ground, normally open switching means interposed between the source and said one end of the conductor, means responsive to the current flowing to said conductor for maintaining said switching means closed, concussion responsive switching means operatively associated with said bore hole tool for breaking the connections between the source and said one end of the conductor to render said current responsive means inoperative, and an electrical impedance connected to the other end of said conductor and to ground and equal in value to the characteristic impedance of the simulated transmission line formed by said igniters and conductor.

References Cited in the file of this patent UNITED STATES PATENTS 1,078,463 Rawson Nov. 11, 1913 1,448,976 Palmer Mar. 10, 1923 2,296,318 Thompson Sept. 22, 1942 2,363,234 Doll Nov. 2, 1944 2,369,238 Kaveler Feb. 13, 1945 2,381,081 Schlumberger Aug. 7, 1945 2,400,549 Glennon et al May 21, 1946 FOREIGN PATENTS 326,332 France May 23, 1903 757,734 France Dec. 30, 1933