Ignition system for shaped charge perforating gun

Abstract: A new shape charge includes an integrated circuit semiconductor bridge detonating device responsive to ordinary current for triggering a switch in the detonating device and igniting a pyrotechnic composition on a small integrated circuit semiconductor bridge in the detonation device in response to the current, thereby igniting an explosive material in the shape charge and firing the shape charge. Since the integrated circuit detonating device is utilized, responsive to ordinary current for detonation, prior art detonating cords are not needed. A plurality of shape charges in a perforating gun are fired substantially simultaneously using the new shape charge of the present invention.

Description: The subject invention pertains to a new shape charge for use in a perforating gun, and more particularly, to a new solid state detonator for use in each such shape charge. Perforating guns of the prior art generally include a plurality of shape charges, each charge containing an explosive material. A detonating cord is traditionally connected to each shape charge for detonating the explosive material in each charge when a heat source ignites the detonating cord. However, the detonating cord could be ignited when radio-frequency (RF) energy nearby induces a current in an input circuit high enough to ignite the cord. Therefore, elaborate steps must be taken to ensure that RF energy does not inadvertently detonate the charges in the perforating gun. Such steps have thus far concentrated on utilization of sophisticated input circuits designed to create large current surges that ultimately ignite the detonating cord. Use of detonating cords creates a safety risk; thus, such detonating cords must be handled carefully to avoid accidents. Of course, when detonating cords are used, shape charges in the perforating gun must be detonated sequentially, since the charges cannot be detonated simultaneously. All of these considerations reflect the need for a new type of shape charge, one which is immune to RF energy, one which does not use detonating cords to reduce the safety risk, and one which allows all shape charges in the perforating gun to be detonated substantially simultaneously. US-A-3,517,758 (Schuster) describes a control apparatus for detonating shape charges in a perforating gun. Electrically-responsive detonating means or initiators are arranged within detonating proximity of the rear of each shape charge. Each initiator is assembled with a shape charge into the rear portion of the shape charge. GB-A-2,190,730 (Detonix) describes a detonator having an integrated circuit firing element including a miniature energy dissipation device which initiates an explosive compound and is located on a substate which forms part of the integrated circuit. The device may be resistive, may be formed by a semi-conductor device or be a field effect device. This patent does not describe a shape charge for borehole applications. Accordingly, it is a primary object of the present invention to provide a new shape charge, adapted for use in a perforating gun, which does not require the use of a traditional detonating cord for purposes of detonating the charge. It is a further object of the present invention to provide a new shape charge, for use in a perforating gun, which contains an integrated circuit chip, which chip includes a solid state detonator for detonating the charge. It is a further object of the present invention to provide a new shape charge which utilizes a standard copper wire lead, called a contactor, for energizing the solid state detonator on the integrated circuit chip thereby firing the detonator and providing enough explosive potential to detonate the shape charge. These and other objects of the present invention are accomplished by: a method of detonating a shape charge as set forth in claim 1; a method of detonating a perforating gun as set forth in claim 2; a shape charge as set forth in claim 3; and a perforating gun as set forth in claim 4. As a result of the invention, no detonating cords, otherwise called prima cords, are used. The safety risk is reduced. Since a large current surge is needed to vaporize the bridge compound, the solid state detonator of the present invention is immune to RF energy, especially in view of the function of the bleeder resistor. Further scope of applicability of the present invention will become apparent from the detailed description presented hereinafter. It should be understood, however, that the detailed description and the specific examples, while representing a preferred embodiment of the present invention, are given by way of illustration only, since various changes and modifications within the scope of the invention will become obvious to one skilled in the art from a reading of the following detailed description. A full understanding of the present invention will be obtained from the detailed description of the preferred embodiment presented hereinbelow, and the accompanying drawings, which are given by way of illustration only and are not intended to be limitative of the present invention, and wherein figure 1 illustrates a perforating gun disposed in a borehole; figure 2 illustrates in more detail a typical perforating gun which may be used as the perforating gun of figure 1, the gun having a conventional detonating cord connected to each shape charge; figure 3 illustrates a new shape charge useful for incorporation into the perforating gun of figure 2; figures 4a-4b illustrate the semiconductor bridge incorporated into the new shape charge of figure 3; figure 5 illustrates an input circuit connected to the semiconductor bridge of figures 4a-4b which forms a part of the integrated circuit semiconductor bridge detonating device disposed in the shape charge of figure 3; and figure 6 illustrates another input circuit connected to the semiconductor bridge of figures 4a-4b which forms a part of the integrated circuit semiconductor bridge detonating device disposed in the shape charge of figure 3. Referring to figure 1, a perforating gun 12 disposed in a borehole 10 is illustrated. The perforating gun 12 comprises a plurality of charges 18. Each charge perforates the formation upon detonation. Referring to figure 2, a more detailed construction of a typical perforating gun, which may be used as the perforating gun of figure 1, is illustrated. The perforating gun of figure 2 is illustrated for purposes of example only, since it is necessary to illustrate in this specification a general environment in which a shape charge is located. Any perforating gun, which contains shape charges, may be used for purposes of this illustration. The perforating gun of figure 2 is fully described and set forth in U.S. Patent 3,659,658 to Brieger, the disclosure of which is incorporated by reference into this specification. In figure 2, a plurality of charges 18 are disposed in a typical perforating gun. A detonating cord 40 is connected to each charge 18. When the detonating cord 40 is ignited, via detonator 40a, each charge 18 in the gun is detonated sequentially. Referring to figure 3, a new shape charge 18, in accordance with the present invention, is illustrated. In figure 3, each charge 18 of figure 2 comprises a steel case 18a, an explosive material 18b disposed in the steel case 18a, a semiconductor bridge detonating device 18c, in accordance with the present invention, in contact with the explosive material 18b, a contactor 40 including electric current conductor 18f connected to one end of the semiconductor bridge detonating device 18c, and an electrical return path 18g connected to ground potential. The explosive material 18b may comprise any of the standard materials found in shape charges for perforating guns. For example, U.S. Patent 4,724,767 entitled "shape charge apparatus and method" or U.S. Patent 4,450,768 entitled "shaped charge and method of making it" disclose typical shape charges that contain standard explosive materials, the disclosures in these patents being incorporated by reference into this specification. Referring to figure 5, the semiconductor bridge detonating device (SCBDD) 18c of figure 3 is illustrated. The SCBDD 18c is an integrated circuit housed within the shape charge illustrated in figure 3. In figure 5, the SCBDD 18c includes a charging capacitor C connected in parallel with a bleeder resistor R. This parallel combination of charging capacitor C and bleeder resistor R is connected to a semiconductor bridge (SCB) 18c1 via a switch SW, which switch SW may be a standard silicon controlled rectifier (SCR). The SCB 18c1 is itself a portion of the Semiconductor Bridge Detonating Device (SCBDD) integrated circuit chip of figure 5. Referring to figure 6, another embodiment of the semiconductor bridge detonating device (SCBDD) 18c of figure 3 is illustrated. As mentioned hereinabove, the SCBDD 18c is an integrated circuit housed within the shape charge illustrated in figure 3. In figure 6, contactor 40 is connected to a charging capacitor C via lines 18f and 18g from figure 3. The charging capacitor C is connected to the anode of a silicon controlled rectifier SCR. The gate G of the SCR is connected to a zener diode (zener), the zener being further connected to the contactor 40. The cathode C of the SCR is connected to the semiconductor bridge 18c1 (as further described with reference to figures 4a and 4b below). The charging capacitor C charges to a voltage level between approximately 10 to 20 VDC. The zener diode breaks down at a voltage approximately equal to 25-30 VDC. The SCR fires when the gate voltage lies between 20-50 VDC. Referring to figures 4a-4b, a further more detailed construction of the SCB 18c1 of figure 5 is illustrated. In figure 4a and 4b, a doped silicon layer c1b is deposited onto a sapphire substrate c1a. An aluminum land c1c is deposited onto one side of the doped silicon layer c1b and a further aluminum land c1d is deposited onto the other side of the doped silicon layer c1b so as to define a gap or bridge c1e between each land c1c/c1d. As noted in figure 4b, an explosive/pyrotechnic composition c1f bridges the gap c1e between land c1c and land c1d. When a current of sufficient magnitude energizes land c1c or c1d, the explosive/pyrotechnic composition vaporizes, which, in turn, ignites the explosive material 18b of figure 3 and detonates the shape charge 18. As noted in U.S. Patent 4,708,060, the explosive/pyrotechnic composition c1f may comprise highly sensitive explosives as well as relatively insensitive ones, e.g., high energy explosives such as, but not limited to, PETN, HNAB, HMX, pyrotechnics, sensitive primaries, gun powders, etc. The semiconductor bridge (SCB) 18c1 is fully described and set forth in US Patent 4,708,060 entitled "Semiconductor Bridge (SCB) Igniter", filed February 19, 1985, issued November 24, 1987, the disclosure of which is incorporated by reference into the specification of this application. The sapphire substrate c1a is a non-electrically conducting substrate. The doped silicon layer c1b is comprised of an electrical material mounted on the non-electrically conducting sapphire substrate cla and has a negative temperature coefficient of electrical resistivity at an elevated temperature, the doped silicon layer c1b covering an area of the sapphire substrate and defining a pair of spaced pads c1b1 and c1b2 connected by a bridge c1b3. The area of each of the pads c1b1 and c1b2 is much larger than the area of the bridge c1b3. The resistance of the bridge c1b3 is less than about three ohms. A metallized layer covers each of the spaced lads c1b1 and c1b2. An electrical conductor c1c and c1d is connected to each of the metallized layers. The electrical resistance between the electrical conductors (aluminum lands) c1c and c1d is determined by the electrical resistance of the bridge c1b3. The explosive/pyrotechnic material c1f covers the electrical conductor aluminum lands c1c and c1d so as to connect land c1c to land c1d. The area of the bridge c1b3 in contact with the explosive/pyrotechnic material c1f is sufficient to ignite the explosive material c1f when the bridge c1b3 forms a plasma (vaporizes) in response to an electrical current passing therethrough. The above paragraphs describe a new shape charge 18 of figure 3 that is substituted for the charges 18 illustrated in figure 2 of the drawings. When each of the charges 18 in figures 2 are replaced by the charge 18 shown in figure 3, the detonating cord 40 of figures 2 must be replaced by contactor 40 of figure 3, the contactor 40 being a standard copper wire adapted for conducting an electrical current. As a result, since a new solid state detonating device is being used in each charge, the plurality of charges may be detonated substantially simultaneously by passing a current through the contactor 40 to each of the new charges illustrated in figure 3. Furthermore, the detonation takes place safely since a detonating cord is no longer needed. A functional description of the present invention will be set forth in the following paragraphs with reference to figures 1-5 of the drawings, and in particular, to figures 3-5 of the drawings. Referring to figure 2, a new perforating gun, in accordance with the present invention, includes a plurality of new shape charges 18, each charge of the gun being the charge 18 shown in figure 3 of the drawings. Item 40, attached to each new charge 18 in figure 2, is an ordinary copper wire, called a "contactor", identical to the contactor 40 shown in figure 3. Detonating cords, also known as primer cords, are not utilized with the new shape charges 18 of the new perforating gun of the present invention. When the new charges 18 are positioned in a desired location in a borehole and are ready for detonation, a current surge is transmitted down contactor wire 40 to each new charge 18, and along wire conductor 18f in figure 5. The current conducted along wire conductor 18f is a large current surge provided by, for example, any typical voltage multiplier circuit. The large current conducted along wire conductor 18f is high enough to charge the charging capacitor C in figure 5, even though bleeder resistor R continues to bleed some of the charge on capacitor C to ground. Switch "SW" may, for example, be a silicon controlled rectifier (SCR). When it is desired to detonate the new charges in the new perforating gun of the present invention, containing the charges shown in figure 3, when the charging capacitor C of figure 5 is fully charged, the user at the surface of a well transmits a further current down a separate wire connected to the SCRs of each SCBDD 18c of each charge 18, thereby firing the SCRs substantially simultaneously. When this occurs, the charge on capacitor C in each SCBDD 18c of each charge 18 conducts along land c1c of the SCB 18c1 to the explosive/pyrotechnic material c1f of the SCB 18c1. Since the current is a large current surge provided, for example, by a voltage multiplier circuit, the current is large enough to vaporize the explosive/pyrotechnic material c1f in each SCB of each SCBDD 18c of each charge 18 in the new perforating gun of the present invention. The vaporization of each pyrotechnic material c1f in the SCBs of each SCBDD 18c ignites the explosive material 18b in each charge 18 in the new perforating gun. The charges 18 detonate substantially simultaneously. No detonating cords or primer cords are utilized. Therefore, a safer perforating gun is the result. A further functional description of the present invention will be set forth in the following paragraph with reference to figures 3, 4, and 6 of the drawings. When the charges 18 are located in the desired position within the borehole, a current is conducted down contactor wire 40 to all shape charges in the perforating gun. The current is further conducted along wire conductor 18f in figure 6. The charging capacitor C is charged to approximately 10-20 VDC. When the voltage on wire conductor 18f and across charging capacitor C reaches 25-30 VDC, the zener diode (Zener) breaks down, at which time, the 25-30 VDC appears on the gate G of the SCR. The SCR will fire when the voltage on gate G reaches a predetermined level, typically a voltage somewhere between 20-50VDC. Assuming the SCR will fire when the gate G voltage reaches 35 VDC, after the Zener diode (zener) breaks down, and when the gate G voltage of SCR reaches 35 VDC, the SCR will fire, thereby allowing the 10-20 VDC charge on the charging capacitor C to flow to the SCB 18cl. This charge will flow through land clc of the SCB, as shown in figure 4b, igniting the explosive/pyrotechnic composition c1f. When the composition c1f ignites, the explosive material 18b in the shape charge ignites, thereby firing the shape charge of figure 3. The shape charge was fired using ordinary current to trigger a switch in an integrated circuit in the shape charge, thereby firing a small integrated circuit semiconductor bridge, rather than using the obsolete prior art method of using detonating cords to fire the shape charge.

Claims: A method of detonating a shape charge adapted to be disposed in a perforating gun for perforating a formation traversed by a borehole, said shape charge including an explosive material, an integrated circuit detonator disposed adjacent said explosive material and a conductor wire connected to the detonator, the detonator including a charge storage means connected to said conductor wire, a bridge means including a composition bridging a first land and a second land, and a switch means for changing from a first state to a second state thereby connecting said charge storage means to said bridge means in response to a firing current, said method comprising the steps of: conducting an input current along said conductor wire to said shape charge; receiving said input current in said charge storage means and storing a charge therein; generating said firing current in response to said input current but only when a voltage associated with said input current is greater than or equal to a predetermined level; changing the state of said switch means from said first state to said second state in response to said firing current thereby conducting a further current from said charge storage means to said composition in said bridge means; detonating said composition in said bridge means in response to said further current; and detonating said explosive in said shape charge in response to detonation of said composition of said bridge means. A method of detonating a perforating gun for perforating a formation traversed by a borehole, said perforating gun including at least one shape charge and a conductor wire connected to the shape charge, said shape charge including an explosive material and an integrated circuit detonator disposed adjacent said explosive material, the detonator including a charge storage means connected to said conductor wire, a bridge means including a composition bridging a first land and a second land, and a switch means for changing from a first state to a second state thereby connecting said charge storage means to said bridge means in response to a firing current, said method comprising the steps of: conducting an input current along said conductor wire to said shape charge; receiving said input current in said charge storage means and storing a charge therein; generating said firing current in response to said input current but only when a voltage associated with said input current is greater than or equal to a predetermined level; changing the state of said switch means from said first state to said second state in response to said firing current thereby conducting a further current from said charge storage means to said composition in said bridge means; detonating said composition in said bridge means in response to said further current; and detonating said explosive in said shape charge in response to detonation of said composition of said bridge means. A shape charge adapted to be disposed in a perforating gun and comprising an explosive material (18b) and a conductor wire (18f,18g) adapted for conducting an input current characterized by: an integrated circuit detonator (18c) disposed adjacent said explosive material and connected to said conductor wire, the detonator including: a charge storage means (C) connected to said conductor wire for storing a charge therein in response to an input current conducted through said conducting wire; a bridge means (18c1) including a composition (c1f) bridging a first land (c1c) and a second land (c1d); a switch means (SCR) for changing from a first state to a second state thereby connecting said charge storage means (C) to said bridge means (18c1) in response to a firing current; and means (zener) for generating said firing current in response to said input current but only when a voltage associated with said input current is greater than or equal to a predetermined level thereby changing said switch means (SCR) from said first state to said second state, whereby a further current is received through said switch means (SCR) from said charge storage means (C) to said composition (clf) in said bridge means in response to said firing current to detonate said composition (c1f) in said bridge means in response to said further current, said explosive material (18b) in said shape charge detonating in response to detonation of said composition of said bridge means. A perforating gun adapted to be disposed in a borehole comprising: a conductor wire adapted for conducting an input current and; at least one shape charge (18) including an explosive material (18b) and connected to the conductor wire; characterized in that said shape charge includes an integrated circuit detonator (18c) disposed adjacent said explosive material and connected to said conductor wire, the detonator including: a charge storage means (C) connected to said conductor wire for storing a charge therein in response to an input current conducted through said conductor wire; a bridge means (18c1) including a composition (c1f) bridging a first land (c1c) and a second land (c1d); a switch means (SCR) for changing from a first state to a second state thereby connecting said charge storage means (C) to said bridge means (18c1) in response to a firing current; and means for generating said firing current in response to said input current but only when a voltage associated with said input current is greater than or equal to a predetermined level thereby changing said switch means (SCR) from said first state to said second state, whereby a further current is received through said switch means from said charge storage means (C) to said composition in said bridge means in response to said firing current to detonate said composition (c1f) in said bridge means in response to said further current, said explosive material (18b) in said shape charge detonating in response to detonation of said composition of said bridge means. The perforating gun of claim 4, wherein the means for generating the firing current includes a zener diode.

Inventors: HENDLEY EDWARD, HENDLEY, EDWARD
Applicants: SCHLUMBERGER HOLDINGS, SCHLUMBERGER LTD, SCHLUMBERGER TECHNOLOGY BV, SOC D PROSPECTION ELECTR SCHLU, SCHLUMBERGER HOLDINGS LIMITED, SCHLUMBERGER LIMITED, SCHLUMBERGER TECHNOLOGY B.V., SOCIETE DE PROSPECTION ELECTRIQUE SCHLUMBERGER
Application year: 1990
Main classification: E21B43
IPC codes: E21B43, F42B3