Method and apparatus for tertiary recovery of oil

• US 4,199,025 A
• Filed: 06/17/1977
• Issued: 04/22/1980
• Est. Priority Date: 04/19/1974
• Status: Expired due to Term

• Current Assignee: Electroflood Company
• Original Assignee: Electroflood Company
• Inventors: Carpenter, Neil L.
• Primary Examiner(s): Novosad, Stephen J.
• Application Number:
  US05/807,739
• Time in Patent Office: 1,040 Days
• Field of Search: 166/248, 166/245, 166/268, 166/60, 166/65 R, 166/272, 166/303, 204/129
• US Class Current: 166/248
• CPC Class Codes: E21B 36/00 Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
• CPC Class Codes: E21B 36/001 Cooling arrangements
• CPC Class Codes: E21B 43/2401 by means of electricity
• CPC Class Codes: E21B 43/30 Specific pattern of wells, e.g. optimising the spacing of wells

Abstract

In one exemplar embodiment, method and apparatus include providing an electrode disposed in a plurality of insulated, spaced boreholes penetrating the oil formation. The plurality of electrodes in contact with a water electrolyte in the formation are connected to a source of AC electrical power for establishing a current flow between the spaced electrodes and through the oil bearing formation by means of the electrolyte. The electrodes are insulated from the earth structure surrounding the boreholes for preventing an electrical current path between the electrodes and the earth structure for isolating the electrical current path between the electrodes and the formation. When the AC current passing through the formation surpasses a minimum current density, AC disassociaton of the H₂ O of the electrolyte occurs and generates free hydrogen and oxygen which may be trapped in the formation for increasing the formation pressure, the oxygen gas may combine with carbon molecules to form carbon dioxide which may dissolve in the oil for enhancing the flow characteristics of the oil in the formation. The increased pressure in the formation will aid in driving the oil into producing boreholes spaced from the electrode boreholes.

Claims

1. A method of generating gases in situ in a fluid-bearing earth formation, comprising the steps of

establishing at least two spaced-apart boreholes extending into a subsurface earth formation containing both oil and an electrolyte dispersed therein,

disposing a separate electrode in each of said boreholes and into electrical contact with said oil and electrolyte in said formation,

insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

establishing an AC electrical current flow in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween for establishing a current density in the formation exceeding the minimum current density required to cause AC disassociation of the electrolyte, and

electrochemically generating free gases, at least one constituent of which is hydrogen, in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density.

2. The method described in claim 1, further including the step of trapping said free gases in said formation to increase the pressure in said formation acting on the oil therein.

3. The method described in claim 2, further including the steps of

establishing a producing borehole spaced from said at least two electrode boreholes and also extending into said subsurface earth formation, and

withdrawing oil from said formation through said producing borehole in response to said increased pressure in said formation.

4. The method described in claim 3, wherein said producing borehole is further spaced from an axis defined by said electrode boreholes.

5. The method described in claim 1, wherein said generated free gases include carbon dioxide.

6. The method as described in claim 5, wherein at least a portion of said free carbon dioxide gas is dissolved in the oil formation for lowering the viscosity of the oil and enhancing its flow characteristics in the formation.

7. The method described in claim 1, wherein said current flow between said electrodes is a flow of single-phase AC current.

8. The method described in claim 1, further including the step of circulating a cooling fluid within each of said boreholes containing said electrodes.

9. The method described in claim 1, further including the step of introducing a selected electrolyte into each of said spaced-apart electrode boreholes for aiding in establishing an electrical current path between said electrodes disposed therein and said formation electrolyte.

10. The method described in claim 1, further including the steps of

establishing a third borehole extending into said formation and spaced generally triangularly from said at least two spaced-apart boreholes containing said electrodes,

disposing a third electrode in said third borehole and into electrical contact with said oil and electrolyte in said formation,

insulating said third electrode from substantially all earth materials adjacent said third borehole and lying above said formation, and

interconnecting a three-phase AC current source to said electrodes with each electrode receiving a different phase thereof.

11. The method described in claim 10, further including the step of circulating a cooling fluid within each of said electrode boreholes.

12. The method described in claim 10, further including the step of introducing a selected electrolyte into each of said electrode boreholes for establishing an electrical current path between said electrodes and said formation electrolyte.

13. The method as described in claim 10, comprising the additional steps of

completing said at least three electrode wells in substantially a first triangular pattern,

establishing said AC current flow in said electrode wells in said first triangular pattern for a predetermined period of time,

completing another electrode well to form a second triangular pattern utilizing two of said at least three electrode wells in said first triangular pattern, and

establishing said AC current flow in said electrode wells in said second triangular pattern for a predetermined period of time.

14. The method as described in claim 13, further including the steps of

completing a series of additional electrode wells where each of said additional electrode wells forms substantially a subsequent triangular pattern in cooperation with at least two electrode wells operating in a prior triangular pattern, and

establishing said AC current flow in said electrode wells in each of said subsequent triangular patterns for a preselected time period.

15. A method as described in claim 14, wherein completing said series of additional electrode wells to form said subsequent triangular patterns includes

locating said electrode wells to obtain at least one larger triangular pattern formed by a plurality of said subsequent triangular patterns.

16. The method as described in claim 15, further including

establishing said AC current flow in said electrode wells at each apex of said at least one larger triangular pattern for a preselected time period.

17. The method described in claim 1, wherein said passage of said AC current through said formation electrochemically lowers the viscosity of the oil for enhancing its flow characteristics in the formation.

18. The method described in claim 1, wherein said passage of said AC current through said formation electrochemically causes the breaking of the physical bond of the oil and formation electrolyte from the formation matrix.

19. The method described in claim 1, further including the steps of

heating the electrolyte in the pore spaces of said formation matrix for increasing the conductivity of said electrolyte to permit greater current flow and rapidly increase the rate of heating of said electrolyte in said port spaces,

boiling the electrolyte within said pore spaces of said formation matrix to form steam and increase the electrical resistivity of the electrolyte in the pore space until substantially all current flow ceases within said pore space, and

arcing said AC current across said pore space of said formation matrix to decompose said electrolyte in the form of steam and electrochemically generate at least free hydrogen gas.

20. A method of increasing the internal pressure in a fluid-bearing earth formation, comprising the steps of

establishing at least two spaced-apart boreholes extending into a subsurface earth formation containing both oil and an electrolyte disposed therein,

disposing a separate electrode in each of said boreholes and into electrical contact with said oil and electrolyte in said formation,

insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

establishing an AC electric current flow in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween for establishing a current density in the formation exceeding the minimum current density required to cause AC disassociation of the electrolyte,

electrochemically generating free gases, at least one constituent of which is hydrogen, in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density, and

trapping said free gases in said formation to increase the pressure in said formation on said oil therein.

21. The method described in claim 20, further including the steps of

establishing a producing borehole spaced from said at least two electrode boreholes and also extending into said subsurface earth formation, and

withdrawing oil from said formation through said producing borehole in response to said increased pressure in said formation.

22. The method described in claim 20, wherein said generated free gases also include carbon dioxide.

23. The method as described in claim 22, wherein at least a portion of said free carbon dioxide gas is dissolved in the oil in the formation for lowering the viscosity of the oil and enhancing its flow characteristics in the formation.

24. The method described in claim 20, wherein said current flow between said electrodes is a flow of single-phase AC current.

25. The method described in claim 20, further including the step of circulating a cooling fluid within each of said electrode boreholes.

26. The method described in claim 20, further including the step of introducing a selected electrolyte into each of said spaced-apart electrode boreholes for aiding in establishing an electrical current path between said electrodes disposed therein and said formation electrolyte.

27. The method described in claim 20, further including the steps of

establishing a third borehole extending into said formation and spaced generally triangularly from said at least two spaced-apart boreholes containing said electrodes,

disposing a third electrode in said third borehole and into electrical contact with said oil and electrolyte in said formation,

insulating said third electrode from substantially all earth materials adjacent said third borehole and lying above said formation, and

interconnecting a three-phase AC current source to said electrodes with each electrode receiving a different phase thereof.

28. The method described in claim 27, further including the step of circulating a cooling fluid within each of said electrode boreholes.

29. The method described in claim 27, further including the step of introducing a selected electrolyte into each of said electrode boreholes for aiding in establishing an electrical current path between said electrodes disposed therein and said formation electrolyte.

30. The method as described in claim 27, comprising the additional steps of

completing said at least three electrode wells in substantially a first triangular pattern,

establishing said AC current flow in said electrode wells in said first triangular pattern for a predetermined period of time,

completing another electrode well to form a second triangular pattern utilizing two of said at least three electrode wells in said first triangular pattern, and

establishing said AC current flow in said electrode wells in said second triangular pattern for a predetermined period of time.

31. The method as described in claim 30, further including the steps of

completing a series of additional electrode wells where each of said additional electrode wells forms substantially a subsequent triangular pattern in cooperation with at least two electrode wells operating in a prior triangular pattern, and

establishing said AC current flow in said electrode wells in each of said subsequent triangular patterns for each preselected time period.

32. A method as described in claim 31, wherein completing said series of additional electrode wells to form said subsequent triangular patterns includes

locating said electrode wells to obtain at least one larger triangular pattern formed by a plurality of said subsequent triangular patterns.

33. The method as described in claim 32, further including

establishing said AC current flow in said electrode wells at each apex of said at least one larger triangular pattern for a preselected time period.

34. A method of tertiary recovery of oil from a subsurface earth formation, comprising the steps of

establishing at least two spaced-apart boreholes extending into the subsurface earth formation containing both oil and an electrolyte dispersed therein,

disposing a separate electrode in each of said boreholes and into electrical contact with said oil and electrolyte in said formation,

insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

establishing an AC electrical current flow in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween for establishing a current density in the formation exceeding the minimum current density required to cause AC disassociation of said electrolyte,

electrochemically generating free gases, at least one constituent of which is hydrogen, in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density,

trapping said gases in said formation to increase the internal pressure in said formation,

establishing a producing borehole spaced from said at least two electrode boreholes and also extending into said subsurface earth formation, and

withdrawing oil from said formation through said producing borehole in response to said increased pressure in said formation.

35. The method described in claim 34, wherein said producing borehole is further spaced from an axis defined by said electrode boreholes.

36. The method described in claim 34, wherein said electrochemically generated free gases include carbon dioxide.

37. The method as described in claim 36, wherein at least a portion of said free carbon dioxide gas dissolves in the oil in the formation for lowering the viscosity of the oil and enhancing its flow characteristics in the formation.

38. The method described in claim 34, wherein said current flow between said electrodes is a flow of singlephase AC current.

39. The method described in claim 34, further including the step of circulating a cooling liquid within each of said boreholes containing said electrodes.

40. The method described in claim 34, further including the step of introducing a selected electrolyte into each of said spaced apart electrode boreholes for aiding in establishing an electrical current path between said electrodes disposed therein and said formation electrolyte.

41. The method described in claim 34, further including the steps of

establishing a third borehole extending into said formation and spaced generally triangularly from said at least two spaced-apart boreholes containing said electrodes,

disposing a third electrode in said third borehole and into electrical contact with said electrolyte in said formation,

insulating said third electrode from substantially all earth materials adjacent said third borehole and lying above said formation, and

interconnecting a three-phase AC current source to said electrodes with each electrode receiving a different phase thereof.

42. The method described in claim 41, further including the step of circulating a cooling liquid within each of said electrode boreholes.

43. The method described in claim 41, further including the step of introducing a selected electrolyte into each of said electrode boreholes for establishing an electrical current path between said electrodes and said formation electrolyte.

44. The method as described in claim 41, comprising the additional steps of

completing said at least three electrode wells in substantially a first triangular pattern,

establishing said AC current flow in said electrode wells in said first triangular pattern for a predetermined period of time,

completing another electrode well to form a second triangular pattern utilizing two of said at least three electrode wells in said first triangular pattern, and

establishing said AC current flow in said electrode wells in said second triangular pattern for a predetermined period of time.

45. The method as described in claim 44, further including the steps of

completing a series of additional electrode wells where each of said additional electrode wells forms substantially a subsequent triangular pattern in cooperation with at least two electrode wells operating in a prior triangular pattern, and

establishing said AC current flow in said electrode wells in each of said subsequent triangular patterns for a preselected time period.

46. The method described in claim 36, wherein said passage of said AC current through said formation electrochemically lowers the viscosity of the oil for enhancing its flow characteristics in the formation.

47. The method described in claim 36, wherein said passage of said AC current through said formation electrochemically causes the breaking of the physical bond of the oil and electrolyte from the formation matrix.

48. The method described in claim 34, further including the steps of

heating the electrolyte in the pore spaces of said formation matrix for increasing the conductivity of said electrolyte to permit greater current flow and rapidly increase the rate of heating of said electrolyte in said pore spaces,

boiling the electrolyte within said pore spaces of said formation matrix to form steam and increase the electrical resistivity of the electrolyte in the pore space until substantially all current flow ceases within said pore space, and

arcing said AC current across said pore space of said formation matrix to decompose said electrolyte in the form of steam and electrochemically generate at least free hydrogen gas.

49. The method as described in claim 34, further including the steps of

utilizing at least a portion of the oil withdrawn from said formation in a combustion process,

collecting the exhaust gases from combustion of said oil, and

introducing said exhaust gases into said formation for further increasing said formation pressure.

50. The method as described in claim 49, wherein at least a portion of said exhaust gases introduced into said formation are dissolved in the oil for lowering the viscosity of the oil and enhancing the flow characteristics of the oil in the formation.

51. The method as described in claim 49, further including the step of introducing compressed air into said formation for further increasing said formation pressure.

52. A method of tertiary recovery of oil from a subsurface earth formation, comprising the steps of

establishing at least two spaced-apart boreholes extending into the subsurface earth formation containing both oil and an electrolyte dispersed therein,

disposing a separate electrode in each of said boreholes and into electrical contact with said oil and electrolyte in said formation,

insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

establishing an AC electric current flow in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween for establishing a current density in the formation exceeding the minimum current density required to cause AC disassociation of the electrolyte,

electrochemically generating free gases, at least one constituent of which is hydrogen, in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density,

trapping said gas in said formation to increase the internal pressure in said formation,

establishing a producing borehole spaced from said at least two electrode boreholes and also extending into said subsurface earth formation,

withdrawing oil from said formation through said producing borehole in response to said increased pressure in said formation,

utilizing at least a portion of the oil withdrawn from said formation in a combustion process,

collecting the exhaust gases from the combustion of said oil, and

introducing said exhaust gases into said formation for further increasing said formation pressure.

53. The method as described in claim 52, wherein at least a portion of said exhaust gases introduced into said formation are dissolved in the oil for lowering the viscosity of the oil and enhancing the flow characteristics of the oil in the formation.

54. The method as described in claim 53, further including the step of introducing compressed air into said formation for further increasing said formation pressure.

55. The method described in claim 52, wherein said producing borehole is spaced from an axis defined by said electrode boreholes.

56. The method described in claim 52, wherein said electrochemically generated generated free gases and said exhaust gases include carbon dioxide.

57. The method described in claim 56, wherein at least a portion of said carbon dioxide is dissolved in the oil for lowering the viscosity of the oil and enhancing its flow characteristics within the formation.

58. The method described in claim 52, wherein said current flow between said electrodes is a flow of a singlephase AC current.

59. The method described in claim 52, further including the step of circulating a cooling liquid within each of said boreholes containing said electrodes.

60. The method described in claim 52, further including the step of introducing a selected electrolyte into each of said spaced-apart electrode boreholes for aiding in establishing an electriclal current path between said electrodes disposed therein and said formation electrolyte.

61. The method described in claim 52, further including the steps of

establishing a third borehole extending into said formation and spaced generally triangularly from said at least two spaced-apart boreholes containing said electrodes,

disposing a third electrode in said third borehole and into electrical contact with said electrolyte in said formation,

insulating said third electrode from substantially all earth materials adjacent said third borehole and lying above said formation, and

interconnecting a three-phase AC current source to said electrodes with each electrode receiving a different phase thereof.

62. The method described in claim 61, further including the step of circulating a cooling liquid within each of said electrode boreholes.

63. The method described in claim 61, further including the step of introducing a selected electrolyte into each of said electrode boreholes for establishing an electrical current path between said electrodes and said formation electrolyte.

64. The method as described in claim 61, comprising the additional steps of

completing said at least three electrode wells in substantially a first triangular pattern,

establishing said AC current flow in said electrode wells in said first triangular pattern for a predetermined period of time,

completing another electrode well to form a second triangular pattern utilizing two of said at least three electrode wells in said first triangular pattern, and

establishing said AC current flow in said electrode wells in said second triangular pattern for a predetermined period of time.

65. The method as described in claim 64, further including the steps of

completing a series of additional electrode wells where each of said additional electrode wells forms substantially a subsequent triangular pattern in cooperation with at least two electrode wells operating in a prior triangular pattern, and

establishing said AC current flow in said electrode wells in each of said subsequent triangular patterns for a preselected time period.

66. The method described in claim 52, wherein said passage of said AC current through said formation electrochemically causes the breaking of the physical bond of the oil and electrolyte from the formation matrix.

67. The method described in claim 52, further including the steps of

heating the electrolyte in the pore spaces of said formation matrix for increasing the conductivity of said electrolyte to permit greater current flow and rapidly increase the rate of heating of said electrolyte in said pore space,

boiling the electrolyte within said pore spaces of said formation matrix to form steam and increase the electrical resistivity of the electrolyte in the pore space until substantially all current flow ceases within said pore space, and

arcing said AC current across said pore space of said formation matrix to decompose said electrolyte in the form of steam and electrochemically generate at least free hydrogen gas.

68. Apparatus for increasing the formation pressure of an oil bearing subsurface earth formation, comprising

at least two spaced boreholes drilled into the earth formation containing both oil and an electrolyte dispersed therein,

a plurality of electrodes, one each of which is disposed in each of said boreholes and into electrical contact with said oil and electrolyte in said subsurface earth formation,

casing of electrically insulating material set into each borehole for insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

a source of an AC electrical current connected to each of said electrodes for establishing an AC current in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween,

means cooperating with said source of AC current for establishing an AC current density in the formation exceeding the minimum current density required to cause AC disassociation of said electrolyte and electrochemically generate free gases, at least one constituent of which is hydrogen, in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density, and

means for trapping said generated gasses in said formation for increasing the formation pressure acting on the oil therein.

69. The apparatus as described in claim 68, further including a producing borehole drilled into said earth formation and spaced from said electrode boreholes for removing said oil from said earth formation.

70. The apparatus as described in claim 69, further including

means for utilizing at least a portion of said oil withdrawn from said earth formation in a combustion process,

means for collecting the exhaust gases from said combustion of said oil,

at least one borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing said exhaust gases into said formation through said borehole adjacent said electrodes for enhancing the flow characteristics of said oil and to further increase said formation pressure.

71. The apparatus as described in claim 70, further including

at least one additional borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing compressed air into said formation through said borehole for further increasing said formation pressure.

72. The apparatus as described in claim 69, further including

means for utilizing at least a portion of said oil withdrawn from said earth formation in a combustion process,

means for collecting the exhaust gases from said combustion of said oil,

at least one borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing said exhaust gases into said formation through said borehole adjacent said electrodes for enhancing the flow characteristics of said oil and to further increase said formation pressure.

73. The apparatus as described in claim 68, wherein said source of AC electrical current is a source of single-phase AC electrical current.

74. The apparatus as described in claim 73, further comprising

casing of electrically conducting material set into each of said boreholes within said subsurface earth formation and having perforations therein to allow said oil and electrolyte to flow into said casing, and

a seal disposed into the annular space between each of said electrodes and said electrically conducting casing adjacent the interface of the insulated borehole casing and said electrically conducting casing.

75. The apparatus as described in claim 74, wherein said electrodes comprise strings of tubing.

76. The apparatus as described in claim 75, further comprising

a source of a selected electrolyte,

means for introducing said selected electrolyte through said tubing strings into each of said boreholes for enhancing electrical contact between said tubing strings acting as electrodes and said formation electrolyte.

77. The apparatus as described in claim 76, further comprising means for cooling said insulating borehole casing adjacent the interface of said borehole casing and said electrically conducting casing.

78. The apparatus as described in claim 77, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes and spaced from said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and the annular space between said borehole casing, said electrode, and said string of tubing for cooling said insulating casing.

79. The apparatus as described in claim 77, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes concentrically surrounding said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode, said tubing having perforations therein adjacent said lower end,

a seal disposed into the annular space between each of said strings of tubing and said electrode adjacent the end of said string of tubing and below said perforations,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and said annular space betweens said strings of tubing and said borehole casing for cooling said insulating casing.

80. The apparatus as described in claim 73, further comprising

conventional casing set into each of said boreholes from the surface of the earth to a predetermined depth,

electrically insulating casing set into each of said boreholes between said conventional casing and said earth formation,

a string of electrically insulating tubing set into each of said boreholes concentrically surrounding each of said electrodes, and

a seal disposed into the annular space between said strings of insulating tubing and the lower end of said insulating casing of each borehole.

81. The apparatus as described in claim 80, further comprising a volume of insulating fluid introduced into the annular space between said borehole casing and said insulating tubing in each borehole.

82. The apparatus as described in claim 81, further comprising

a source of a selected electrolyte,

means for introducing said selected electrolyte through said strings of insulating tubing into said strings of insulating tubing into said boreholes in said earth formation for enhancing electrical contact between said electrodes and said electrolyte in the formation.

83. The apparatus as described in claim 80, further including

at least one additional borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing compressed air into said formation through said borehole for further increasing said formation pressure.

84. The system as described in claim 83, further including

means for utilizing at least a portion of said oil withdrawn from said earth formation in a combustion process,

means for collecting the exhaust gases from said combustion of said oil,

at least one borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing said exhaust gases into said formation through said borehole electrodes for enhancing the flow characteristics of said oil and to further increase said formation pressure.

85. The system as described in claim 84, further including

at least one additional borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing compressed air into said formation through said borehole for further increasing said formation pressure.

86. The apparatus as described in claim 68, wherein the number of insulated boreholes and electrodes is three and said source of AC electrical current is a source of three-phase AC electrical current, one phase of which is connected to each of said three electrodes.

87. The apparatus as described in claim 86, further comprising

casing of electrically conducting material set into each of said boreholes within said subsurface earth formation and having perforations therein to allow said oil and electrolyte to flow into said casing, and

a seal disposed into the annular space between each of said electrodes and said electrically conducting casing adjacent the interface of the insulated borehole casing and said electrically conducting casing.

88. The apparatus as described in claim 87, wherein said electrodes comprise strings of tubing.

89. The apparatus as described in claim 88, furthere comprising

a source of a selected electrolyte,

means for introducing said electrolyte through said tubing strings into each of said boreholes in said earth formation for enhancing electrical contact between said tubing strings acting as electrodes and said electrolyte in the formation.

90. The apparatus as described in claim 89, further comprising means for cooling said insulating borehole casing adjacent the interface of said insulating borehole casing and said electrically conducting casing.

91. The apparatus as described in claim 90, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes and spaced from said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and the annular space between said borehole casing, said electrode, and said string of tubing for cooling said insulating casing.

92. The apparatus as described in claim 90, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes concentrically surrounding said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode, said tubing having perforations therein adjacent said lower end,

a seal disposed into the annular space between each of said strings of tubing and said electrode adjacent the end of said string of tubing and below said perforations,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and said annular space between said strings of tubing and said borehole casing for cooling said insulating casing.

93. The apparatus as described in claim 68, wherein said electrodes and said insulated casing comprise

an insulated cable disposed in said boreholes, said cable having a metal conductor exposed to the subsurface formation, and

a supporting material having electrical insulating properties disposed in said borehole above said formation surrounding said insulated cable for supporting said cable in said borehole and further providing electrical insulation between said insulated cable and said overlying earth formations.

94. A system for tertiary recovery of oil from an oil bearing subsurface earth formation, comprising

at least two spaced boreholes drilled into the earth formation containing both oil and an electrolyte dispersed therein,

a plurality of electrodes, one each of which is disposed in each of said boreholes and into electrical contact with said oil and electrolyte in said subsurface earth formation,

casing of electrically insulating material set into each borehole for insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

a source of an AC electrical current connected to each of said electrodes for establishing an AC current flow in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween, and

means cooperating with said source of AC current for establishing an AC current density in the formation exceeding the minimum current density required to cause AC disassociation of said electrolyte and electrochemically generate free gases, including hydrogen and carbon dioxide, in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density, at least a portion of said carbon dioxide dissolving in said oil in said formation for lowering the viscosity of the oil and enhancing its flow characteristics in the formation,

means for trapping said generated gases in said formation for increasing the formation pressure acting on the oil therein, and

a producing borehole drilled into said earth formation and spaced from said electrode boreholes for removing said oil from said earth formation in response to said increased pressure and enhanced flow characteristics.

95. The apparatus as described in claim 94, wherein said electrodes and said insulated casing comprise

an insulated cable disposed in said boreholes, said cable having a metal conductor exposed to the subsurface formation, and

a supporting material having electrical insulating properties disposed in said borehole above said formation surrounding said insulated cable for supporting said cable in said borehole and further providing electrical insulation between said insulated cable and said overlying earth formations.

96. The system as described in claim 94, wherein said source of the AC electrical current is a source of single-phase AC electrical current.

97. The system as described in claim 96, further comprising

casing of electrically conducting material set into each of said boreholes within said subsurface earth formation and having perforations therein to allow said oil and electrolyte to flow into said casing, and

a seal disposed into the annular space between each of said electrodes and said electrically conducting casing adjacent the interface of the insulated borehole casing and said electrically conducting casing.

98. The system as described in claim 97, wherein said electrodes comprise strings of tubing.

99. The system as described in claim 98, further comprising

a source of a selected electrolyte,

means for introducing said electrolyte through said tubing strings into each of said boreholes for enhancing electrical contact between said tubing strings acting as electrodes and said electrolyte in said formation.

100. The system as described in claim 99, further comprising means for cooling said insulating borehole casing adjacent the interface of said borehole casing and said electrically conducting casing.

101. The system as described in claim 100, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes and spaced from said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and the annular space between said borehole casing, said electrode, and said string of tubing for cooling said insulating casing.

102. The system as described in claim 100, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes concentrically surrounding said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode, said tubing having perforations therein adjacent said lower end,

a seal disposed into the annular space between each of said strings of tubing and said electrode adjacent the end of said string of tubing and below said perforations,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and said annular space between said strings of tubing and said borehole casing for cooling said insulating casing.

103. The system as described in claim 96, further comprising

conventional casing set into each of said boreholes from the surface of the earth to a predetermined depth,

electrically insulating casing set into each of said boreholes between said conventional casing and said earth formation,

a string of electrically insulating tubing set into each of said boreholes concentrically surrounding each of said electrodes, and

a seal disposed into the annular space between said strings of insulating tubing and the lower end of said insulating casing of each borehole.

104. The system as described in claim 103, further comprising insulating fluid introduced into the annular space between said borehole casing and said insulating tubing in each borehole.

105. The system as described in claim 104, further comprising

a source of a selected electrolyte,

means for introducing said electrolyte through said strings of insulating tubing into said boreholes in said earth formation for enhancing electrical contact between said electrodes and said electrolyte in the formation.

106. The system as described in claim 94, wherein the number of insulated boreholes and electrodes is three and said source of AC electrical current is a source of three-phase AC electrical current, one phase of which is connected to each of said three electrodes.

107. The system as described in claim 106, further comprising

casing of electrically conducting material set into each of said boreholes within said subsurface earth formation and having perforations therein to allow said oil and electrolyte to flow into said casing, and

a seal disposed into the annular space between each of said electrodes and said electrically conducting casing adjacent the interface of the insulated borehole casing and said electrically conducting casing.

108. The system as described in claim 107, wherein said electrodes comprise strings of tubing.

109. The system as described in claim 108, further comprising

a source of a selected electrolyte,

means for introducing said electrolyte through said tubing strings into each of said boreholes in said earth formation for enhancing electrical contact between said tubing strings acting as electrodes and said electrolyte in the formation.

110. The system as described in claim 109, further comprising means for cooling said insulating borehole casing adjacent the interface of said insulating borehole casing and said electrically conducting casing.

111. The system as described in claim 110, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes and spaced from said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and the annular space between said borehole casing, said electrode, and said string of tubing for cooling said insulating casing.

112. The system as described in claim 110, wherein said cooling means comprises

a string of tubing disposed into each of said insulated boreholes concentrically surrounding said electrode, the lower end of said string of tubing terminating adjacent said seal between said casing of each borehole and said electrode, said tubing having perforations therein adjacent said lower end,

a seal disposed into the annular space between each of said strings of tubing and said electrode adjacent the end of said string of tubing and below perforations,

a source of cooling fluid, and

means for circulating said cooling fluid through said strings of tubing and said annular space between said strings of tubing and said borehole casing for cooling said insulating casing.

113. The system as described in claim 94, further including

means for utilizing at least a portion of said oil withdrawn from said earth formation in a combustion process,

means for collecting the exhaust gases from said combustion of said oil,

at least one borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing said exhaust gases into said formation through said borehole adjacent said electrodes for enhancing the flow characteristics of said oil and to further increase said formation pressure.

114. The system as described in claim 113, further including

at least one additional borehole drilled into said earth formation and spaced from said electrode boreholes, and

means for introducing compressed air into said formation through said borehole for further increasing said formation pressure.

115. A method of generating gases in-situ and treating a subsurface fossilized mineral fuel bearing formation containing an electrolyte dispersed therein, comprising the steps of

establishing at least two spaced-apart boreholes extending into the subsurface formation,

disposing a separate electrode in each of said boreholes and into electrical contact with the fossilized mineral fuel and the electrolyte in the formation,

insulating said electrodes from substantially all earth materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said formation electrolyte,

establishing a preselected level of an AC electrical current in said electrical circuit composed of said insulated electrodes and said formation electrolyte lying therebetween for establishing a current density in the formation exceeding the minimum current density required to cause AC disassociation of the electrolyte, and

electrochemically generating free gases in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density for treating said fossilized mineral fuel material and forming recoverable fluid hydrocarbon products.

116. The method described in claim 115, wherein said generated free gases include hydrogen and oxygen.

117. The method described in claim 115, wherein said generated free gases include carbon dioxide.

118. A method of generating gases in-situ and treating a subsurface fossilized mineral fuel bearing formation comprising the steps of

establishing at least two spaced-apart boreholes extending into the subsurface formation,

introducing a selected electrolyte into the subsurface formation for establishing an electrically conductive path between each of said boreholes and the formation and between said boreholes,

disposing a separate electrode in each of said boreholes and into electrical contact with said fossilized mineral fuel and said electrolyte in the formation,

insulating said electrodes from substantially all each materials adjacent said boreholes and lying above said subsurface earth formation to establish an electrical circuit composed of said insulated electrodes and said electrolyte,

establishing an AC electrical current flow in said electrical circuit composed of said insulated electrodes and said electrolyte lying therebetween for establishing a current density in the formation exceeding the minimum current density required to cause AC disassociation of the electrolyte, and

electrochemically generating free gases in said subsurface earth formation between said boreholes as a function of current density in said formation exceeding said minimum current density for treating said fossilized mineral fuel material and forming recoverable fluid hydrocarbon products.

119. The method described in claim 118, wherein said generated free gases include hydrogen and oxygen.

120. The method in claim 118, wherein said generated free gases include carbon dioxide.