Impulse generator and method for perforating a cased wellbore

Abstract

An impulse generator ( 76 ) and method for using an impulse generator ( 76 ) to initiate a detonation in a shaped charge perforating apparatus ( 60 ) is disclosed. The shaped charge perforating apparatus ( 60 ) is adapted for use in a wellbore ( 62 ) and includes a plurality of shaped charges ( 86 ). A detonation cord ( 98 ) is operably coupled to each of the shaped charges ( 86 ). An initiator ( 78 ) is operable to detonate the detonation cord ( 98 ) upon receiving a triggering impulse. A Marx generator within the impulse generator ( 76 ) provides the triggering impulse to the initiator ( 78 ).

What is claimed is:  
     
         1 . A shaped charge perforating apparatus adapted for use in a wellbore, comprising: 
 a plurality of shaped charges;    a detonation cord operably coupled to the shaped charges;    an initiator operable to initiate a detonation within the detonation cord upon receiving a triggering impulse; and    a Marx generator operably associated with the initiator that is operable to generate the triggering impulse.    
     
     
         2 . The shaped charge perforating apparatus as recited in  claim 1  wherein the Marx generator further comprises an input terminal, an output terminal coupled to the initiator, a plurality of capacitors connected in series between the input terminal and the output terminal, a plurality of first surge arrester components connected between each of the capacitors in series, and a second surge arrester component positioned between the last one of the capacitors and the output terminal.  
     
     
         3 . The shaped charge perforating apparatus as recited in  claim 2  wherein the plurality of first surge arrester components and the second surge arrester component comprise gas surge arrester tubes.  
     
     
         4 . The shaped charge perforating apparatus as recited in  claim 2  wherein the plurality of capacitors comprise a ceramic material having a dielectric coefficient that increases with temperature.  
     
     
         5 . The shaped charge perforating apparatus as recited in  claim 2  wherein the triggering impulse is a discharge voltage impulse.  
     
     
         6 . The shaped charge perforating apparatus as recited in  claim 5  wherein the plurality of capacitors, the plurality of first surge arrester components and the second surge arrester component of the Marx generator comprises a plurality of stages whereby the discharge voltage impulse is proportional to the number of stages times a charging voltage applied to the Marx generator.  
     
     
         7 . The shaped charge perforating apparatus as recited in  claim 6  wherein each stage comprises one of the capacitors and one of the first or second surge arrester components.  
     
     
         8 . The shaped charge perforating apparatus as recited in  claim 6  wherein the Marx generator is operable to enter regenerative latch up upon receiving the charging voltage.  
     
     
         9 . The shaped charge perforating apparatus as recited in  claim 1  wherein the initiator is selected from the group consisting of bridge wire initiators, exploding bridge wire initiators, exploding foil initiators, percussion type initiators and pressure actuated initiators.  
     
     
         10 . The shaped charge perforating apparatus as recited in  claim 1  wherein the Marx generator is housed in a tubular housing that provides a circuit ground.  
     
     
         11 . An impulse generator for delivering a discharge voltage impulse to an initiator that initiates a detonation within a detonation cord connected to a plurality of shaped charges positionable in a wellbore, the impulse generator comprising: 
 an input terminal that is operable to receive a charging voltage;    an output terminal coupled to the initiator, the output terminal operable to deliver the discharge voltage impulse;    a plurality of capacitors connected in series between the input terminal and the output terminal;    a plurality of charging resistors connected in parallel with the capacitors;    a plurality of first surge arrester components connected between each of the capacitors in series; and    a second surge arrester component positioned between the last one of the capacitors and the output terminal, whereby the plurality of capacitors are operable to be charged in parallel through the charging resistors and discharged in series.    
     
     
         12 . The impulse generator for delivering a discharge voltage as recited in  claim 11  wherein the plurality of first surge arrester components and the second surge arrester component comprise gas surge arrester tubes.  
     
     
         13 . The impulse generator for delivering a discharge voltage as recited in  claim 11  wherein the plurality of capacitors comprise a ceramic material having a dielectric coefficient that increases with temperature.  
     
     
         14 . The impulse generator for delivering a discharge voltage as recited in  claim 11  wherein the charging voltage is supplied from a surface location via an electric line.  
     
     
         15 . The impulse generator for delivering a discharge voltage as recited in  claim 11  wherein the plurality of capacitors, the plurality of first surge arrester components and the second surge arrester component define a plurality of stages such that the discharge voltage impulse is proportional to the number of stages times the charging voltage applied to the input terminal.  
     
     
         16 . The impulse generator for delivering a discharge voltage as recited in  claim 15  wherein each stage comprises one of the capacitors and one of the first or second surge arrester components.  
     
     
         17 . The impulse generator for delivering a discharge voltage as recited in  claim 11  wherein the initiator is selected from the group consisting of bridgewire initiators, exploding bridgewire initiators, exploding foil initiators, percussion type initiators and pressure actuated initiators.  
     
     
         18 . The impulse generator for delivering a discharge voltage as recited in  claim 11  further comprising a housing that provides protection to the plurality of capacitors, the plurality of first surge arrester components and the second surge arrester component and provides a circuit ground.  
     
     
         19 . An impulse generator for generating a discharge voltage impulse, comprising: 
 an input terminal that is operable to receive a charging voltage;    an output terminal operable to deliver the discharge voltage impulse;    a plurality of capacitors connected in series between the input terminal and the output terminal;    a plurality of charging resistors connected in parallel with the capacitors;    a plurality of first surge arrester components connected between each of the capacitors in series; and    a second surge arrester component positioned between the last one of the capacitors and the output terminal, whereby the plurality of capacitors are operable to be charged in parallel through the charging resistors and discharged in series.    
     
     
         20 . The impulse generator for generating a discharge voltage impulse as recited in  claim 19  wherein the plurality of first surge arrester components and the second surge arrester component comprise gas surge arrester tubes.  
     
     
         21 . The impulse generator for generating a discharge voltage impulse as recited in  claim 19  wherein the plurality of capacitors comprise a ceramic material having a dielectric coefficient that increases with temperature.  
     
     
         22 . The impulse generator for generating a discharge voltage impulse as recited in  claim 19  wherein the plurality of capacitors, the plurality of first surge arrester components and the second surge arrester component define a plurality of stages such that the discharge voltage impulse is proportional to the number of stages times the charging voltage applied to the input terminal.  
     
     
         23 . The impulse generator for generating a discharge voltage impulse as recited in  claim 22  wherein each stage comprises one of the capacitors and one of the first or second surge arrester components.  
     
     
         24 . The impulse generator for generating a discharge voltage impulse as recited in  claim 19  further comprising a tubular housing that provides a circuit ground.  
     
     
         25 . A method for perforating a well casing that lines a subterranean well, the method comprising the steps of: 
 running downhole a shaped charge perforating apparatus including a plurality of shaped charges, a detonation cord operably coupled to the shaped charge, an initiator operable to detonate the detonation cord and a Marx generator operably associated with the initiator;    supplying a charging voltage to the Marx generator to generate a discharge voltage impulse;    transmitting the discharge voltage impulse to the initiator;    initiating a detonation within the detonation cord; and    detonating the shaped charges, thereby perforating the well casing that lines the subterranean well.    
     
     
         26 . The method as recited in  claim 25  wherein the step of supplying a charging voltage to the Marx generator to generate a discharge voltage impulse further comprises the step of triggering the Marx generator to enter regenerative latch up.  
     
     
         27 . The method as recited in  claim 25  wherein the step of supplying a charging voltage to the Marx generator to generate a discharge voltage impulse further comprises the step of executing a voltage multiplication on the charging voltage to generate the discharge voltage impulse.  
     
     
         28 . The method as recited in  claim 25  wherein the step of supplying a charging voltage to the Marx generator to generate a discharge voltage impulse further comprises supplying the charging voltage to an input terminal, charging a plurality of capacitors connected in series between the input terminal and an output terminal, overvolting a plurality of first surge arrester components connected between each of the capacitors in series and a second surge arrester component positioned between the last one of the capacitors and the output terminal and generating the discharge voltage impulse at the output terminal.  
     
     
         29 . The method as recited in  claim 28  wherein the plurality of first surge arrester components and the second surge arrester component comprise gas surge arrester tubes.  
     
     
         30 . The method as recited in  claim 28  wherein the plurality of capacitors comprise a ceramic material having a dielectric coefficient that increases with temperature.  
     
     
         31 . The method as recited in  claim 28  wherein the step of charging the plurality of capacitors connected in series between the input terminal and the output terminal further comprises the step of charging the plurality of capacitors in parallel via charging resistors.  
     
     
         32 . The method as recited in  claim 28  wherein the step of generating the discharge voltage impulse at the output terminal further comprises the step of discharging the plurality of capacitors in series.  
     
     
         33 . The method as recited in  claim 32  wherein the step of discharging the plurality of capacitors in series further comprises discharging the capacitors in series by the simultaneous spark over of the first and the second surge arrester components.  
     
     
         34 . The method as recited in  claim 25  further comprising the step of selecting the initiator from the group consisting of bridgewire initiators, exploding bridgewire initiators, exploding foil initiators, percussion type initiators and pressure actuated initiators.  
     
     
         35 . A method for delivering a discharge voltage impulse to an initiator that detonates a detonation cord connected to a plurality of shaped charges positioned in a wellbore, the method comprising the steps of: 
 positioning an impulse generator in a wellbore, the impulse generator including an input terminal, an output terminal coupled to the initiator, a plurality of capacitors connected in series between the input terminal and the output terminal, a plurality of first surge arrester components connected between each of the capacitors in series and a second surge arrester component positioned between the last one of the capacitors and the output terminal;    applying a charging voltage to the input terminal;    charging the plurality of capacitors in parallel through charging resistors; and    discharging the capacitors in series by the simultaneous spark over of the first and second surge arrester components, thereby delivering the discharge voltage impulse to the initiator via the output terminal.    
     
     
         36 . The method as recited in  claim 35  further comprising the step of triggering the impulse generator to enter regenerative latch up.  
     
     
         37 . The method as recited in  claim 35  further comprising the step of executing a voltage multiplication on the charging voltage to generate the discharge voltage impulse.  
     
     
         38 . The method as recited in  claim 35  wherein the plurality of first surge arrester components and the second surge arrester component comprise gas surge arrester tubes.  
     
     
         39 . The method as recited in  claim 35  wherein the plurality of capacitors comprise a ceramic material having a dielectric coefficient that increases with temperature.  
     
     
         40 . The method as recited in  claim 35  wherein the impulse generator further comprises a housing that provides a circuit ground.