Electro-thermal process for promoting oil recovery

Claim 2

An improved electro-thermal method for stimulating oil recovery from a porous and substantially homogeneous underground oil bearing formation having at least two regions respectively penetrated by first and second spaced apart bore holes, comprising the steps of; a. locating an electrode in the first bore hole at an approximately medial elevation of the proximate region of said formation, said electrode being sufficiently small to constitute effectively a point source of resistance heating; b. immersing said electrode in a pressurized conductive liquid thereby to form an expanding body of liquid surrounding said electrode and constituting an electroconductive path between the electrode and the oil bearing formation; c. applying unipolarity voltage between said electrode and an exposed conductor proximate the second bore hole, with the polarity of said electrode being positive relative to said conductor, the resulting unidirectional current through said porous formation having sufficiently high current density at the surface of said electrode to heat said liquid body appreciably above the surrounding ambient temperature of said formation as said liquid body expands; and d. thereafter extracting oil from one of said bore holes.

Claim 3

The method of claim 1 wherein oil is extracted from said second borehole.

Claim 4

The method of claim 1 wherein said electrode comprises a relatively short cylindrical body, the length of said body being less than one-half the depth of said proximate region.

Claim 5

The method of claim 1 wherein the magnitude of the applied voltage is 200 volts or higher.

Claim 6

The method of claim 1 including the step of supplying electroconductive water through the first borehole to the vicinity of said electrode.

Claim 7

The method of claim 5 wherein said water is injected into said first borehOle at a pressure sufficient to maintain the volume rate of flow of the injected water at a predetermined desired value.

Claim 8

The method of claim 5 including the step of applying sufficiently high voltage between said electrode and said conductor to heat the fluid in the vicinity of said electrode to substantially above 250* Fahrenheit.

Claim 9

The method of claim 7 wherein said fluid is supplied under sufficient pressure to maintain the heated fluid between the electrode and the oil-bearing formation in a liquid state.

Claim 10

The method of claim 1 wherein said exposed conductor comprises a metal liner in said second borehole.

Claim 11

The method of claim 1 wherein said exposed conductor is positioned in said formation proximately adjacent said second borehole.

Claim 12

An improved electro-thermal method of stimulating oil recovery from an underground oil-bearing formation that is penetrated by first and second spaced-apart boreholes, said first borehole having a casing whose lower end terminates near the top of the formation, comprising the steps of: a. joining the upper end of a tubular liner of insulating material to the lower end of the casing in said first borehole; b. suspending an electrode in a cavity in the formation below said liner; c. injecting electroconductive fluid through said liner to said cavity; d. applying unipolarity voltage between said electrode and a region of the oil bearing formation that is penetrated by the second borehole, with the polarity of the electrode being relatively positive; and e. extracting oil from said second borehole.

Claim 13

An improved electro-thermal method of stimulating oil recovery from an underground oil-bearing formation that is penetrated by first and second spaced-apart boreholes, said first borehole having a casing whose lower end terminates near the top of the formation, comprising the steps of: a. joining the upper end of a tubular liner of insulating material to the lower end of the casing in said first borehole; b. suspending an electrode in a cavity in the formation below said liner; c. injecting electroconductive fluid through said liner to said cavity; d. applying unipolarity voltage between said electrode and a region of the oil bearing formation that is penetrated by the second borehole, with the polarity of the electrode being relatively positive; and e. extracting oil from said second borehole.

Claim 14

The method of claim 11 including the step of disposing an insulated cable in said first borehole for connecting said electrode to the positive pole of a source of d-c electric power.

Claim 15

The method of claim 11 wherein said tubular liner has a relatively small inside diameter.

Claim 16

In an improved electro-thermal method for stimulating oil recovery from a porous and substantially homogeneous underground oil bearing formation that is penetrated by first and second bore holes each having a casing and a tubing string disposed therein, said bore holes communicating with horizontally spaced apart regions of said porous formation, the steps of: a. introducing through the first bore hole and positioning at an approximately medial elevation in the corresponding region of said formation and electrode comprising an electroconductive body having a substantially noncorrodable surface, said electrode being sufficiently small to constitute effectively at point source of resistance heating; b. supplying electroconductive liquid through the tubing string in the casing of said first bore hole to the vicinity of said electrode, said liquid forming an expanding body of liquid electrolyte in the porous formation surrounding said electrode; c. electrically insulating said electrode from the casing of said first bore hole; d. passing electric current through said liquid body and said formation between said electrode and the casing of said second bore hole, said current being sufficient to raise the temperature of said liquid body appreciably above the ambient temperature of said formation; and e. withdrawing oil from the tubing string in the casing of said second bore hole.

Claim 17

In an improved electro-thermal method for stimulating oil recovery from a porous and substantially homogeneous underground oil bearing formation that is penetrated by first and second bore holes each having a casing and a tubing string disposed therein, said bore holes communicating with horizontally spaced apart regions of said porous formation, the steps of: a. introducing through the first bore hole and positioning at an approximately medial elevation in the corresponding region of said formation and electrode comprising an electroconductive body having a substantially noncorrodable surface, said electrode being sufficiently small to constitute effectively at point source of resistance heating; b. supplying electroconductive liquid through the tubing string in the casing of said first bore hole to the vicinity of said electrode, said liquid forming an expanding body of liquid electrolyte in the porous formation surrounding said electrode; c. electrically insulating said electrode from the casing of said first bore hole; d. passing electric current through said liquid body and said formation between said electrode and the casing of said second bore hole, said current being sufficient to raise the temperature of said liquid body appreciably above the ambient temperature of said formation; and e. withdrawing oil from the tubing string in the casing of said second bore hole.

Claim 18

The method of claim 14 in which said voltage is obtained from a d-c electric power source whose positive pole is connected by an insulated cable to said electrode.

Claim 19

An improved electro-thermal method for stimulating oil recovery from a porous and substantially homogeneous underground bearing formation comprising the steps of; a. locating an electrode at an approximate medial elevation of a first region of said formation, said electrode being sufficiently small to constitute effectively a point source of resistance heating; b. maintaining about and in contact with said electrode, by a process of regulated flow, a pressurized hydrous electrolyte of a composition having the essential characteRistics of connate water present in said formation, said pressurized electrolyte forming an expanding body of liquid in the porous formation surrounding said electrode, c. passing unidirectional current between said electrode and an exposed conductor located in another region of said formation, said other region being spaced from said first region and the polarity of said electrode being positive relative to said conductor , said current being sufficient to raise the temperature of said liquid body appreciably above the ambient temperature of said formation; and d. extracting oil from one of said regions.

Claim 20

An improved electro-thermal method for stimulating oil recovery from a porous and substantially homogeneous underground bearing formation comprising the steps of; a. locating an electrode at an approximate medial elevation of a first region of said formation, said electrode being sufficiently small to constitute effectively a point source of resistance heating; b. maintaining about and in contact with said electrode, by a process of regulated flow, a pressurized hydrous electrolyte of a composition having the essential characteRistics of connate water present in said formation, said pressurized electrolyte forming an expanding body of liquid in the porous formation surrounding said electrode, c. passing unidirectional current between said electrode and an exposed conductor located in another region of said formation, said other region being spaced from said first region and the polarity of said electrode being positive relative to said conductor , said current being sufficient to raise the temperature of said liquid body appreciably above the ambient temperature of said formation; and d. extracting oil from one of said regions.

Claim 21

The method of claim 16 including the step of supplying said hydrous electrolyte through a borehole which penetrates said first region.

Claim 22

The method of claim 17 including the step of regulating the supply of said hydrous electrolyte so that it flows at a volume rate which varies with the product of the magnitude of said applied voltage and the magnitude of electric current between said electrode and said conductor.

Claim 23

The method of claim 17 in which said hydrous electroltye is formation water.