Bulk Heating a Subsurface Formation

Abstract

Systems and methods for bulk heating of a subsurface formation with at least a pair of electrode assemblies in the subsurface formation are disclosed. The method may include electrically powering the pair of electrode assemblies to resistively heat a subsurface region between the pair of electrode assemblies with electrical current flowing through the subsurface region between the pair of electrode assemblies; flowing a shunt mitigator into at least one of the pair of electrode assemblies; and mitigating a subsurface shunt between the pair of electrode assemblies with the shunt mitigator. Mitigating may be responsive to a shunt indicator that indicates a presence of the subsurface shunt.

1 . A method for bulk heating a subsurface formation with at least a pair of electrode assemblies in the subsurface formation, the method comprising:
 electrically powering the pair of electrode assemblies to resistively heat a subsurface region between the pair of electrode assemblies with electrical current flowing through the subsurface region between the pair of electrode assemblies;   flowing a shunt mitigator into at least one of the pair of electrode assemblies; and   responsive to a shunt indicator, mitigating a subsurface shunt between the pair of electrode assemblies with the shunt mitigator, wherein the shunt indicator indicates a presence of the subsurface shunt.   
     
     
         2 . The method of  claim 1 , wherein the flowing occurs after determining the presence of the subsurface shunt. 
     
     
         3 . The method of  claim 2 , wherein the determining comprises measuring between the pair of electrode assemblies at least one of an electrical conductivity-related parameter, a thermal parameter, and a fluid permeability-related parameter. 
     
     
         4 . The method of  claim 2 , wherein the determining comprises determining that an average electrical conductivity of the subsurface region is at least 0.01 S/m. 
     
     
         5 . The method of  claim 2 , wherein the shunt mitigator is configured to increase the electrical resistivity of at least a portion of the pair of electrode assemblies near the subsurface shunt. 
     
     
         6 . The method of  claim 5 , wherein the shunt mitigator is selected to at least one of decompose in response to the shunt indicator, polymerize in response to the shunt indicator, and melt in response to the shunt indicator. 
     
     
         7 . The method of  claim 5 , wherein the shunt mitigator is selected to chemically react, in response to the shunt indicator, with at least one of the pair of electrode assemblies, the subsurface region, and the subsurface shunt. 
     
     
         8 . The method of  claim 5 , wherein the shunt mitigator is selected to undergo a state change in response to the shunt indicator. 
     
     
         9 . The method of  claim 8 , wherein the shunt mitigator undergoes a state change, and the state change is at least one of an electromagnetic state change, an electromagnetic phase transition, a paramagnetic transition, and a paraelectric transition. 
     
     
         10 . The method of  claim 2 , wherein the shunt mitigator includes a composite shunt mitigator, wherein the composite shunt mitigator includes a first material that defines a first functional relationship between an electrical property of the first material and the shunt indicator, and wherein the composite shunt mitigator includes a second material that defines a second functional relationship between a property of the second material and the shunt indicator. 
     
     
         11 . The method of  claim 10 , wherein the electrical property of the first material includes at least one of electrical conductivity, electrical admittivity, electrical resistivity, electrical impeditivity, electric susceptibility, electric permittivity, magnetic susceptibility, and magnetic permeability. 
     
     
         12 . The method of  claim 10 , wherein the property of the second material includes at least one of electrical conductivity, electrical admittivity, electrical resistivity, electrical impeditivity, electric susceptibility, electric permittivity, magnetic susceptibility, magnetic permeability, density, viscosity, volume, rigidity, and chemical activity. 
     
     
         13 . A method for bulk heating a subsurface formation with at least a pair of electrode assemblies in the subsurface formation, the method comprising:
 electrically powering the pair of electrode assemblies to resistively heat an in situ resistive heater, wherein the in situ resistive heater is a subsurface region of the subsurface formation between the pair of electrode assemblies;   upon determining a presence of a subsurface shunt between the pair of electrode assemblies, forming a modified in situ resistive heater by mitigating the subsurface shunt; and   electrically powering the pair of electrode assemblies to resistively heat the modified in situ resistive heater.   
     
     
         14 . The method of  claim 13 , wherein the mitigating includes injecting a fluid to chemically alter an electrical property of the subsurface shunt. 
     
     
         15 . The method of  claim 14 , wherein the fluid includes at least one of molecular oxygen, carbon dioxide, an oxidizing gas, and a gasification gas. 
     
     
         16 . The method of  claim 13 , wherein the mitigating includes injecting an electrically insulating liquid into the subsurface shunt. 
     
     
         17 . A subsurface formation, comprising:
 at least a pair of electrode assemblies;   wherein each electrode assembly of the pair of electrode assemblies includes an electrically conductive material; and   wherein at least one electrode assembly of the pair of electrode assemblies includes a shunt mitigator that is selected to undergo a state change in response to a shunt indicator.   
     
     
         18 . The subsurface formation of  claim 17 , wherein the shunt indicator indicates a presence of a subsurface shunt between the pair of electrode assemblies. 
     
     
         19 . The subsurface formation of  claim 17 , wherein the shunt indicator is at least one of a temperature difference in the subsurface region, a temperature gradient in the subsurface region, a current density in the subsurface region, a current gradient in the subsurface region, a current density in the subsurface shunt, an electrical conductivity of the subsurface shunt, an electrical admittivity of the subsurface shunt, an electrical resistivity of the subsurface shunt, an electrical impeditivity of the subsurface shunt, a point temperature of at least one electrode assembly, a point temperature near the subsurface shunt, and an average temperature of the subsurface shunt. 
     
     
         20 . The subsurface formation of  claim 17 , wherein the shunt mitigator undergoes a state change, and the state change is at least one of an electromagnetic state change, an electromagnetic phase transition, a paramagnetic transition, and a paraelectric transition.