Method and apparatus for electrically heating a subsurface formation

• US 3,874,450 A
• Filed: 12/12/1973
• Issued: 04/01/1975
• Est. Priority Date: 12/12/1973
• Status: Expired due to Term

• Current Assignee: Loyd R. Kern
• Original Assignee: Loyd R. Kern
• Inventors: Kern, Loyd R.
• Primary Examiner(s): Novosad, Stephen J.
• Application Number:
  US05/424,099
• Time in Patent Office: 475 Days
• Field of Search: 166/248,250,302,57,60,65
• US Class Current: 166/248
• CPC Class Codes: E21B 43/2401 by means of electricity

Abstract

One or more wellbores extending from the surface into a subterranean electrically conductive formation are each provided with a deviated bottom section extending laterally for a predetermined distance with respect to the vertical axis of the wellbore and in a predetermined direction. The deviated section is filled with electrolyte adapted to electrically contact the formation along its interface with the deviated section. Insulated conductive means are introduced within the electrolyte from the surface so that the electrolyte effectively constitutes an electrode to which a suitable source of potential may be connected at the surface through the conductive means. Passage of current to and from this effective electrode through the formation as part of a closed circuit establishes a heated zone, which extends laterally from the wellbore in the direction of the deviated section.

Claims

1. The method of electrically heating a subterranean electrically conductive formation comprising the steps of:

a. drilling a first and a second wellbore downwardly from the surface in substantially vertically spaced apart relation to within said formation, b. further drilling each of said first and second wellbores to form respective first and second deviated sections thereof extending laterally in a direction transverse to the direction between the vertical axes of said first and second wellbores, c. establishing respective first and second electrode means within said first and second deviated sections adapted to communicate with said formation along its interface with said first and second deviated sections, d. providing first and second conductive means extending from the surface within said first and second wellbores to contact said first and second electrode means respectively, and e. applying a voltage potential between said first and second electrode means through said first and second conductive means, whereby a current is adapted to pass through the formation between said first and second electrode means.

2. The method of claim 1 wherein said first and second deviated sections of wellbore are uncased.

3. The method of claim 1 wherein said first and second deviated sections are at least partially filled with electrolyte defining said first and second electrode means.

4. The method of electrically heating a subterranean electrically conductive formation comprising the steps of providing a wellbore extending from the surface within said formation, said wellbore having an upper vertical section and a lower deviated section extending from the bottom of said upper vertical section laterally for a predetermined distance from the vertical axis of said vertical section and in a predetermined direction, establishing first electrode means within said deviated section in electrical communication with said formation along the interface between said formation and said deviated section, providing first conductive means extending from the surface within said wellbore in contact with said first electrode means, establishing second electrode means within said wellbore and insulated therein from said first electrode means, providing second conductive means extending from the surface within said wellbore and adapted to support said second electrode means at a predetermined height above said first electrode means, providing a communication path between said second electrode means through said wellbore into said formation, interconnecting said first and second conductive means at the surface to a source of voltage potential, whereby a current is adapted to flow in a substantially vertical direction through the formation between said first and second electrode means.

5. In the art of electrically heating an electrically conductive formation by positioning a pair of spaced apart electrodes therein and passing a current therebetween through the formation, the method of increasing the linearity of the current paths between said electrodes comprising the steps of positioning at least one of said electrodes within a deviated section of wellbore extending laterally within said formation in a direction transverse to the direction between said pair of electrodes and establishing electrical continuity between said at least one electrode and the surrounding formation substantially over the interface between said formation and said deviated wellbore section.

6. In the art of electrical heating of an electrically conductive formation by passage of an electric current therethrough, the improvement comprising:

a. a wellbore extending from the surface downwardly into the formation consisting of an upper vertical section and a lower deviated section extending from the bottom of said upper vertical section laterally for a predetermined distance from said upper vertical section and in a predetermined direction, b. an electrolyte adapted to at least partially fill said lower deviated section and to thereby communicate with said formation along the interface thereof with said lower deviated section, c. an insulating oil filling said wellbore above the level of said electrolyte, d. conductive means extending within the wellbore from the surface and adapted to contact said electrolyte, and e. means for connecting a source of electrical potential to said electrolyte through said conductive means.

7. In the art of electrical heating of an electrically conductive formation by passage of an electric current therethrough, the improvement comprising:

a. a wellbore extending from the surface downwardly into the formation consisting of an upper vertical section and a lower deviated section extending from the bottom of said vertical section laterally for a predetermined distance from said vertical section and in a predetermined direction, b. electrode means within said deviated section adapted to communicate with said formation along the interface with said deviated section, c. conductive means extending within the wellbore from the surface and adapted to contact said electrode means, d. additional electrode means positioned within the vertical section of said wellbore and situated at a predetermined height above said deviated section, e. additional conductive means extending within the wellbore from the surface and adapted to support said additional electrode means, f. means extending laterally through the wellbore into the formation adjacent said additional electrode means to establish electrical communication between said formation and said additional electrode means, g. means for insulating said electrode means and additional electrode means from each other within said wellbore, and h. means for connecting a source of electric potential serially with said electrode means and said additional electrode means through said conductive means and additional conductive means respectively whereby a current is adapted to flow through the formation between said electrode means and additional electrode means responsive to the application of said electrical potential.

8. The apparatus of claim 7 wherein said additional electrode means is a steel bar, and said additional conductive means is a wire.

9. The apparatus of claim 8 wherein said means establishing communication between said additional electrode means and said formation is a quantity of electrolyte adapted to surround said steel bar.

10. The apparatus of claim 9 wherein said wellbore is provided with a centralized tube coextensive with the vertical section thereof, said centralized tube being insulated from said wellbore, said conductive means being adapted to extend through said centralized tube to the bottom of said vertical wellbore section, and said additional conductive means being adapted to extend externally of said centralized tube and partially above said vertical wellbore section.