Switches for downhole electrocrushing drilling

Abstract

A downhole drilling system is disclosed. The downhole drilling system may include a bottom-hole assembly having a pulse-generating circuit and a switching circuit within the pulse-generating circuit, the switching circuit comprising a solid-state switch. The downhole drilling system may also include a drill bit having a first electrode and a second electrode electrically coupled to the pulse-generating circuit to receive a pulse from the pulse-generating circuit.

What is claimed is: 
     
         1 . A downhole drilling system, comprising:
 a bottom-hole assembly including:
 a pulse-generating circuit; and 
 a switching circuit within the pulse-generating circuit, the switching circuit comprising a solid-state switch; and 
   a drill bit including a first electrode and a second electrode electrically coupled to the pulse-generating circuit to receive a pulse from the pulse-generating circuit.   
     
     
         2 . The downhole drilling system of  claim 1 , wherein the solid-state switch is a silicon-carbide switch. 
     
     
         3 . The downhole drilling system of  claim 1 , wherein the solid-state switch is one of a gallium-arsenide switch and a silicon switch. 
     
     
         4 . The downhole drilling system of  claim 1 , wherein the solid-state switch is located within a circular cross-section of the bottom-hole assembly. 
     
     
         5 . The downhole drilling system of  claim 1 , wherein the switching circuit comprises a plurality of solid-state switches coupled together in parallel. 
     
     
         6 . The downhole drilling system of  claim 1 , wherein the switching circuit comprises a plurality of solid-state switches coupled together in series. 
     
     
         7 . The downhole drilling system of  claim 6 , wherein the switching circuit further comprises an additional solid-state switch coupled in parallel with each respective solid-state switch of the plurality of solid-state switches coupled together in series. 
     
     
         8 . The downhole drilling system of  claim 6 , further comprising a plurality of grading resistors, each of the plurality of grading resistors coupled in parallel to a corresponding solid-state switch of the plurality of solid-state switches. 
     
     
         9 . The downhole drilling system of  claim 6 , further comprising a plurality of capacitors, each of the plurality of capacitors coupled in parallel to a corresponding solid-state switch of the plurality of solid-state switches. 
     
     
         10 . The downhole drilling system of  claim 1 , wherein the drill bit is integrated within the bottom-hole assembly. 
     
     
         11 . The downhole drilling system of  claim 1 , wherein the drill bit is one of an electrocrushing drill bit and an electrohydraulic drill bit. 
     
     
         12 . A downhole drilling system, comprising:
 a bottom-hole assembly including:
 a pulse-generating circuit; and 
 a switching circuit within the pulse-generating circuit, the switching circuit comprising a magnetic switch; and 
   a drill bit including a first electrode and a second electrode electrically coupled to the pulse-generating circuit to receive a pulse from the pulse-generating circuit.   
     
     
         13 . The downhole drilling system of  claim 12 , the magnetic switch comprising a primary coil and a supermendur core. 
     
     
         14 . The downhole drilling system of  claim 12 , the magnetic switch comprising a primary coil and a Metglas core. 
     
     
         15 . The downhole drilling system of  claim 12 , wherein the pulse-generating circuit includes a plurality of switching circuits, each of the plurality of switching circuits comprising a magnetic switch. 
     
     
         16 . The downhole drilling system of  claim 12 , further comprising a reset generator coupled to the magnetic switch. 
     
     
         17 . The downhole drilling system of  claim 16 , the magnetic switch further comprising a secondary coil coupled to receive a constant current from the reset generator to transition the core from a saturated state to a non-saturated state. 
     
     
         18 . The downhole drilling system of  claim 16 , the magnetic switch further comprising a secondary coil coupled to receive a reset pulse from the reset generator to transition the core from a saturated state to a non-saturated state. 
     
     
         19 . The downhole drilling system of  claim 12 , wherein the magnetic switch is located within a circular cross-section of the bottom-hole assembly. 
     
     
         20 . The downhole drilling system of  claim 19 , further comprising a thermally conductive encapsulant surrounding the magnetic switch, the thermally conductive encapsulant adjoins the outer wall of a drilling fluid channel within the circular cross-section of the downhole pulsed-power drilling tool. 
     
     
         21 . The downhole drilling system of  claim 12 , wherein the drill bit is integrated within the bottom-hole assembly. 
     
     
         22 . The downhole drilling system of  claim 12 , wherein the drill bit is one of an electrocrushing drill bit and an electrohydraulic drill bit. 
     
     
         23 . A method, comprising:
 placing a drill bit downhole in a wellbore;   providing electrical power to a pulse-generating circuit coupled to a first electrode and a second electrode of the drill bit;   closing a switch located downhole within the pulse-generating circuit to charge a capacitor that is electrically coupled between the first electrode and the second electrode;   forming an electrical arc between the first electrode and the second electrode of the drill bit;   discharging the capacitor via the electrical arc;   fracturing a rock formation at an end of the wellbore with the electrical arc; and   removing fractured rock from the end of the wellbore.   
     
     
         24 . The method of  claim 23 , wherein the switch is a solid-state switch. 
     
     
         25 . The method of  claim 23 , wherein the switch is a magnetic switch including a primary coil and a supermendur core. 
     
     
         26 . The method of  claim 25 , further comprising applying a reset pulse to a secondary coil of the magnetic switch to transition the core from a saturated state to a non-saturated state. 
     
     
         27 . The method of  claim 25 , further comprising applying a constant current to a secondary coil of the magnetic switch to transition the core from a saturated state to a non-saturated state.