METHOD AND APPARATUS FOR ELECTRICAL HEATING OF HYDROCARBONACEOUS FORMATIONS

• US 3,862,662 A
• Filed: 12/12/1973
• Issued: 01/28/1975
• 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:
  US05/424,103
• Time in Patent Office: 412 Days
• Field of Search: 166/248,302,65,258
• US Class Current: 166/248
• CPC Class Codes: E21B 43/2401 by means of electricity

Abstract

A method and apparatus for electrically heating a subterranean hydrocarbonaceous formation situated between adjacent upper and lower layers having substantially lower resistivity than the formation itself. A pair of wells are drilled through the formation spaced apart at a preselected interval. A pair of electrodes are placed within the respective wellbores, one electrode being positioned above the formation in electrical contact with the upper layer, the other being positioned below the formation in electrical contact with the lower layer. A potential difference is established between the two electrodes causing an alternating current to flow through the formation along a plurality of laterally separated paths adapted to heat the formation with substantial uniformity between the two wellbores.

Claims

1. The method of electrically heating a subsurface formation situated between and immediately adjacent an upper and a lower layer each having a lower electrical resistivity than that of the formation comprising the steps of:

a. establishing a potential difference between a first and a second electrode means positioned respectively within the upper and lower layers and in electrical contact therewith and b. causing an alternating current to pass between said electrode means responsive to said potential difference along a plurality of paths through said formation determined by the relative resistivities of said formation and said upper and lower layers.

2. The method of claim 1 wherein said subsurface formation is hydrocarbonaceous.

3. The method of claim 1 including the step of increasing the linearity of the current paths between said electrode means by extending the effective area of contact between said electrode means and said upper and lower layers substantially parallel to the upper and lower boundaries of the formation.

4. The method of claim 1 wherein said first and second electrode means are situated respectively within first and second boreholes spaced apart at a predetermined interval.

5. The method of claim 4 including the step of electrically isolating each of said electrode means within said boreholes such that each of said current paths between said electrode means must include the upper and lower layers and traverse the formation intermediately therebetween.

6. The method of claim 5 including providing casings for said boreholes having nonconductive portions extending above and below said formation.

7. The method of claim 6 including providing perforations in said nonconductive portions adjacent said electrode means communicating with said upper and lower layers respectively.

8. The method of claim 7 including partially filling the boreholes with electrolyte surrounding said electrode means and extending within said perforations.

9. The method of claim 1 including first and second spaced apart boreholes extending respectively within said upper and lower layers, said first and second boreholes being provided respectively with a first and a second deviated section extending in the same sense and substantially parallel to the respective upper and lower boundaries of said formation, said first and second electrode means being situated respectively within said first and second deviated sections in electrical contact with said upper And lower layers substantially over the interface between said upper and lower layers and said first and second deviated sections.

10. The method of claim 9 additionally including the step of extending said deviated sections of said first and second boreholes transversely to the direction between said boreholes.

11. The method of claim 1 including positioning said first and second electrode means within a single borehole.

12. The method of claim 11 including providing said borehole with a laterally extending deviated section substantially parallel to the lower boundary of said formation, said second electrode means being situated within said deviated section in communication with said lower layer substantially over the interface between said lower layer and said deviated section.

13. Apparatus for electrically heating a subsurface hydrocarbonaceous formation situated between an upper and a lower adjacent layer each of lower electrical resistivity than that of said formation comprising:

a. first electrode means positioned in electrical contact with the upper layer;

b. second electrode means positioned in electrical contact with the lower layer;

c. first and second conductive means connected respectively to said first and second electrode means and extending to the surface; and

d. a source of alternating current voltage connected at the surface between said first and second conductive means adapted to produce an alternating current voltage gradient between said first and second electrode means whereby an alternating current is caused to flow between said first and second electrode means along a plurality of least resistance path through said formation.

14. Apparatus as in claim 13 including means for electrically isolating said first and second electrode means so that the available current paths between said electrodes each inclue the upper and lower layers and transverse the formation intermediately therebetween.

15. Apparatus as in claim 13 wherein said first and second electrode means are located respectively within first and second boreholes extending from the surface and spaced apart at a predetermined interval.

16. Apparatus as in claim 15 wherein said first and second boreholes are each provided with a deviated section extending in the same sense, substantially parallel to the respective upper and lower boundaries of said formation and transverse to the direction between said boreholes, and wherein said first and second electrode means are situated respectively within said first and second deviated sections in contact with said upper and lower layers respectively along the interface between said upper and lower layers and said respective first and second deviated sections.

17. Apparatus as in claim 15 including a casing within each of said boreholes, each of said casings comprising a conductive upper portion extending from the surface and a nonconductive lower portion joining the conductive portion and extending above and below the formation, separate fluid conductive means surrounding each of said electrode means respectively within said nonconductive portions, the remainder of said casings being filled with insulating material, and said nonconductive portions being provided with conductive paths therethrough adjacent said electrode means to permit electrical contact between said electrode means and said upper and lower layers, respectively, through said fluid conductive means.

18. Apparatus as in claim 15 wherein said nonconductive portions are provided with a plurality of perforations opposite said electrode means communicating with said upper and lower layers, respectively.

19. Apparatus as in claim 15 wherein said first and second electrode means are steel bars.

20. Apparatus as in claim 15 wherein each of said conductive means is a wire.

21. Apparatus as in claim 15 wherein each of said conductive means is a conductive tube.

22. Apparatus as in claim 13 wherein said first and second electrode means are conFined within a single wellbore.

23. Apparatus as in claim 22 further comprising a casing within said wellbore, a tube centralized within said casing, said first electrode means being supported by said first conductive means between said centralized tube and said casing, said second conductive means extending through said centralized tube and supporting said second electrode means in axial alignment therewith, separate conductive fluid means surrounding said first and second electrode means respectively, means for establishing a contact area between said fluid means and said upper and lower layers, respectively, and means within the casing for insulating said first and second electrode means from each other and from the formation.

24. Apparatus as in claim 23 wherein said wellbore is provided with a deviated section extending laterally for a predetermined distance, said deviated section being completely filled with said fluid conductive means surrounding said second electrode means.

25. Apparatus as in claim 13 additionally comprising first and second spaced apart wellbores extending respectively within said upper and lower layers, a first and second plurality of angularly spaced deviated wellbore sections extending laterally from the vertical axis of said first and second wellbores respectively, a first and second quantity of fluid electrolyte substantially filling said first and second plurality of angularly spaced deviated wellbore sections and defining said first and second electrode means, said first and second quantities of fluid electrolyte being adapted to communicate with said upper and lower layers respectively along their interfaces with said first and second plurality of deviated wellbore sections.