Electrical isolation of subterranean casing section

Abstract

A method and apparatus for electrically-enhanced oil recovery from an oil-bearing subterranean formation are provided. An isolation opening extends around the circumference of a casing to provide a separation of the inflow section from an adjacent section of the casing. A portion of the oil-bearing formation disposed on the outside of the isolation opening is removed to form a void in the oil-bearing formation adjacent the isolation opening. A material having less electrical conductivity than the casing is inserted into the void and the isolation opening to form an insulative barrier.

1 . In a recovery apparatus employing electrical enhanced oil recovery from an oil-bearing formation, the apparatus comprising a wellhead having a hollow casing extending through at least one non-oil-bearing formation into the oil bearing formation, the casing having an inflow section with at least one inflow opening into the oil-bearing formation for extracting oil using electrically enhanced oil recovery, the method for improving the efficiency of the extracting by forming an electrical isolation barrier within the oil-bearing layer adjacent the inflow opening of casing, comprising the steps of
 providing an isolation opening extending around the circumference of the casing to provide a separation of the inflow section from an adjacent section of the casing,   removing a portion of the formation disposed on the outside of the isolation opening to form a void in the oil-forming formation,   providing a quantity of material into the void and the isolation opening to form an insulative barrier.   
     
     
         2 . The method of  claim 1  including the steps of
 providing a second isolation opening extending around the circumference of the casing on the opposite side of the inflow opening to provide access between the formation outside the casing and the interior of the casing, 
 removing a portion of the formation disposed on the outside of the isolation opening to form a second void in said formation, 
 providing a quantity of insulative material sufficient to fill said second void and the second isolation opening and filling said second void and said isolation opening with said flowable material, and 
 treating the flowable material to solidify the flowable material contained within the second void and the second isolation opening to form a second isolation barrier. 
 
     
     
         3 . The method of  claim 1  wherein said isolation barrier and said adjacent casing sections have interior surfaces, including the further step of
 shaping the interior surface of said isolation barrier to conform to the interior surfaces of the adjacent casing sections. 
 
     
     
         4 . The method of  claim 1  including the further step of
 providing a hollow cylindrical insulating liner formed of an electrical insulation material, and applying the liner over the inward surface of said isolation barrier. 
 
     
     
         5 . The method of  claim 1  including the further steps of
 providing passages on the inner surface of said liner, and closing the passages by a mandrel positioned within the inner surface. 
 
     
     
         6 . The method clam  1 , wherein the casing comprises multiple sections, each having a hollow cylindrical shell of an electrically conductive material, wherein the step of providing an isolation opening is performed by removing a 360 degree ring of the conductive material of the hollow cylindrical shell. 
     
     
         7 . The method of  claim 6  wherein said step of removing a 360 degree ring is performed by cutting away the electrically conductive material. 
     
     
         8 . The method of  claim 6  wherein the step of removing a 360 degree ring is performed by applying a chemical material to the ring to dissolve the same. 
     
     
         9 . In a recovery apparatus employing electrical enhanced oil recovery from an oil-bearing formation, the apparatus comprising a wellhead having a hollow casing extending through at least one non-oil-bearing formation, the casing having an inflow section with at least one inflow opening into the oil-bearing formation for extracting oil using electrically enhanced oil recovery, the method for improving the efficiency of the extracting by forming electrical isolation barriers within the oil-bearing layer on opposite sides of the inflow opening of the casing, comprising the steps of
 forming isolation openings extending substantially 360 degrees about the circumference of the casing on opposite sides of said inflow openings to provide access between the oil-bearing formation and the interior of the casing,   removing a portion of the oil-bearing formation disposed on the outside of each opening of said casing to form voids in said formation,   providing a quantity of flowable material sufficient to fill said voids and said isolation openings and injecting said material into said voids and said isolation openings, and   treating said flowable material to solidify said flowable material contained within said voids and said isolation openings to form isolation barriers interrupting electrical communication between the inflow section and the reminder of said casing.   
     
     
         10 . Recovery apparatus for extracting oil using electrical enhanced oil recovery from an oil-bearing formation comprising a wellhead having a hollow casing with multiple sections extending through at least one non-oil-bearing formation into the oil bearing formation, the casing having an inflow section with at least one inflow opening in registry with the oil-bearing formation for extracting oil using electrically enhanced oil recovery, said inflow section being separated from an adjacent one of said multiple sections by a ring-shaped opening extending around the circumference of the casing, and
 an isolation barrier mounted in said ring-shaped opening to maintain the physical continuity of the casing and operable to improve the efficiency of the extracting,   the barrier comprising electrically non-conductive material isolating said inflow section from the adjacent section,   the barrier having an interior dimension substantially similar to the interior dimension of the casing sections on both sides of the barrier, and an exterior dimension extending beyond the exterior circumference of said casing sections and into the formation surrounding said ring-shaped opening between said adjacent casings sections.   
     
     
         11 . Recovery apparatus according to  claim 10  wherein said isolation barrier material has flowable state when it is first inserted into said ring-shaped opening and into the formation surrounding said opening, and is curable into a solid state when the insertion is complete.