Pulsed power drilling with multiple selective drilling fluids

Abstract

An apparatus that is part of a drill string for drilling a wellbore in a subsurface formation, comprises a drill bit that includes at least one electrode coupled to a power source, the at least one electrode to periodically emit an electrical discharge based on electrical pulses received from the power source; and a first port to output a first type of drilling fluid having a dielectric that is different from a dielectric of a second type of drilling fluid to flow downhole for removal of cuttings, wherein the electrical discharge is to be transmitted through the first type of drilling fluid and through a rock of the subsurface formation.

1 . An apparatus that is part of a drill string for drilling a wellbore in a subsurface formation, the apparatus comprising:
 a drill bit that includes at least one electrode coupled to a power source, the at least one electrode to periodically emit an electrical discharge based on electrical pulses received from the power source; and   a first port to output a first type of drilling fluid having a dielectric that is different from a dielectric of a second type of drilling fluid to flow downhole for removal of cuttings, wherein the electrical discharge is to be transmitted through the first type of drilling fluid and through a rock of the subsurface formation.   
     
     
         2 . The apparatus of  claim 1 , wherein the second type of drilling fluid is to flow through a second port that is positioned uphole from the first port. 
     
     
         3 . The apparatus of  claim 2 , wherein the drill bit is part of a bottom hole assembly (BHA) such that an annulus is defined to be between a wall of the wellbore and the BHA, wherein the second port is positioned on the BHA such that the second type of drilling fluid is output from a position uphole from a face of the drill bit and out to the annulus. 
     
     
         4 . The apparatus of  claim 1 , wherein the first type of drilling fluid has a higher dielectric than a rock of the subsurface formation. 
     
     
         5 . The apparatus of  claim 1 , wherein the first type of drilling fluid has a higher dielectric than the second type of drilling fluid. 
     
     
         6 . The apparatus of  claim 1 , wherein a volumetric flow rate of the first type of drilling fluid is less than a volumetric flow rate of the second type of drilling fluid. 
     
     
         7 . The apparatus of  claim 1 , wherein the first port is located at a face of the drill bit. 
     
     
         8 . A system that includes a drill string for drilling a wellbore in a subsurface formation, the system comprising:
 a drill bit comprising at least one electrode coupled to a power source, the at least one electrode to periodically emit an electrical discharge based on electrical pulses received from the power source;   a first port to output a first type of drilling fluid having a dielectric that is different from a dielectric of a second type of drilling fluid to flow downhole for removal of cuttings, wherein the electrical discharge is to be transmitted through the first type of drilling fluid and through a rock of the subsurface formation;   an inner conduit configured to convey a first type of drilling fluid from a surface of the wellbore to downhole such that the first type of drilling fluid is to be output from the first port; and   an outer conduit into which the inner conduit is to be housed, wherein the outer conduit is to convey a second type of drilling fluid between the surface of the wellbore and downhole.   
     
     
         9 . The system of  claim 8 , wherein the second type of drilling fluid is to flow through a second port that is positioned uphole from the first port. 
     
     
         10 . The system of  claim 8 , wherein the first type of drilling fluid has a higher dielectric than a rock of the subsurface formation. 
     
     
         11 . The system of  claim 8 , wherein the first type of drilling fluid has a higher dielectric than the second type of drilling fluid. 
     
     
         12 . The system of  claim 8 , wherein a volumetric flow rate of the first type of drilling fluid is less than a volumetric flow rate of the second type of drilling fluid. 
     
     
         13 . The system of  claim 8 , wherein the first port is located at a face of the drill bit. 
     
     
         14 . A method comprising:
 positioning a drill string in a wellbore formed in a subsurface formation, wherein the drill string comprises a drill bit having at least one electrode coupled to a power source, and a first port;   periodically emitting an electrical discharge from the at least one electrode based on electrical pulses received from the power source;   pumping, at least partially in parallel with emitting the electrical discharge, a first type of drilling fluid down the wellbore through the first port; and   pumping a second type of drilling fluid down the wellbore to remove cuttings from the wellbore, wherein a dielectric of the first type of drilling fluid is different from a dielectric of the second type of drilling fluid.   
     
     
         15 . The method of  claim 14 , wherein pumping the second type of drilling fluid down the wellbore comprises pumping the second type of drilling fluid down the wellbore to be output from a second port that is positioned uphole from the first port. 
     
     
         16 . The method of  claim 15 , wherein the drill bit is part of a bottom hole assembly (BHA) such that an annulus is defined to be between a wall of the wellbore and the BHA, wherein the second port is positioned on the BHA such that the second type of drilling fluid is output from a position uphole from a face of the drill bit and out to the annulus. 
     
     
         17 . The method of  claim 14 , wherein the first type of drilling fluid has a higher dielectric than a rock of the subsurface formation. 
     
     
         18 . The method of  claim 14 , wherein the first type of drilling fluid has a higher dielectric than the second type of drilling fluid. 
     
     
         19 . The method of  claim 14 , wherein pumping the first type of drilling fluid down the wellbore through the first port comprises pumping the first type of drilling fluid down the wellbore through an inner coil tubing from a surface of the wellbore. 
     
     
         20 . The method of  claim 14 , wherein a volumetric flow rate of the first type of drilling fluid is less than a volumetric flow rate of the second type of drilling fluid.