In situ radio frequency selective heating system

• US 4,457,365 A
• Filed: 08/10/1981
• Issued: 07/03/1984
• Est. Priority Date: 12/07/1978
• Status: Expired due to Fees

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Kasevich, Raymond S., Dwyer, Arthur S., Kolker, Myer
• Primary Examiner(s): Novosad, Stephen J.
• Application Number:
  US06/291,667
• Time in Patent Office: 1,058 Days
• Field of Search: 166/60, 166/59, 166/65 R, 166/248, 166/52, 166/68, 166/302, 166/242, 219/10.55 R, 219/10.65, 219/10.81
• US Class Current: 166/60
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/17 Interconnecting two or more wells by fracturing or otherwise attacking the formation E21B43/2405, E21B43/247 take precedence
• 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

The process and apparatus for extracting the products of kerogen in situ from an oil shale body by supplying energy selectively to the kerogen by high frequency electric fields in the frequency range between 100 kilohertz and 1000 megahertz at an intensity which heats the kerogen to a temperature range between 250° C. and 500° C. to allow pyrolysis of the kerogen prior to substantial heat transfer to the surrounding mineral portions of the oil shale. A plurality of groups of spaced radiators produce the electric fields for heating the kerogen. A dipole radiator in the subsurface formation is supplied with electromagnetic energy through a transmission line from an energy generator on the surface.

Claims

1. A system for producing subsurface heating of a formation comprising:

a plurality of groups of predetermined spaced radiators extending through an overburden into a region to be heated; and

means for supplying said radiators with electrical energy at intensities and a frequency which produce electrical fields directed toward a common region in said formation which heat selected organic portions of said formation at a more rapid rate than said heat is transferred by conduction from said organic portions to predominantly inorganic portions of said formation adjacent to said organic portions.

2. The system in accordance with claim 1 wherein said radiators are positioned on the order of a half wavelength apart of said frequency in said formation.

3. The system in accordance with claim 2 wherein said radiators have parasitic reflecting elements positioned adjacent said radiators and separated therefrom by less than a quarter wavelength of said frequency to direct said radiation toward said common region of said formation to be heated.

4. The system in accordance with claim 3 wherein said parasitic radiation elements comprise apertures through which liquids in said formation may be collected.

5. The system in accordance with claim 4 wherein means are provided for pumping said liquids through parasitic radiation elements to the surface of the overburden.

6. A radiating system for radiating electromagnetic wave energy into a subsurface formation comprising:

a coaxial line extending from the surface into said subsurface formation;

a dipole radiator coupled to said coaxial line in said subsurface formation;

one dipole half of said radiator being connected to the outer conductor of said coaxial line with the space between the free end of said one dipole half and said outer conductor being filled with a dielectric comprising a solid dielectric; and

the dielectric constant of said solid dielectric substantially reducing the maximum field gradient at the electrode surface of said dipole radiator.

7. The system in accordance with claim 6 wherein:

the region between both halves of said dipole radiator is substantially entirely filled with a solid comprising a dielectric having a high dielectric strength at temperatures above 250°

C.

8. The system in accordance with claim 6 wherein:

the central conductor of said coaxial line is hollow and is attached to the other half of the dipole radiator.

9. The system in accordance with claim 6 wherein:

said coaxial line is inside a casing extending through an overburden into said subsurface formation.

10. A radiating system for heating a subsurface formation comprising:

a dipole radiator in said formation supplied with electromagnetic energy through a transmission line extending from the surface through an overburden to said subsurface formation and coupled to said radiator; and

means for collecting products of pyrolytic decomposition of said formation comprising a ceramic cylinder which is positioned in the electric field radiated from said radiator in said formation and having an aperture through which fluids comprising said pyrolytic decomposition products flow.

11. The system in accordance with claim 10 wherein:

said formation comprises oil shale.

12. A radiating system for heating a subsurface formation comprising:

a radiator in said formation supplied with electromagnetic energy through a transmission line extending from the surface through an overburden to said subsurface formation and coupled to said radiator;

means for collecting products of pyrolytic decomposition of said formation comprising a ceramic cylinder which is positioned in the electric field radiated from said radiator in said formation and which has apertures through which fluids comprising said pyrolytic decomposition products flow; and

said transmission line comprising a coaxial line whose inner conductor is connected to one half of dipole radiator and whose outer conductor is connected to the other half of said dipole.

13. A radiating system for heating a subsurface formation comprising:

a radiator in said formation supplied with electromagnetic energy through a transmission line extending from the surface through an overburden to said subsurface formation and coupled to said radiator;

means for collecting products of pyrolytic decomposition of said formation comprising a ceramic cylinder which is positioned in the electric field radiated from said radiator in said formation and which has apertures through which fluids comprising said pyrolytic decomposition products flow;

said transmission line comprising a coaxial line whose inner conductor is connected to one half of a dipole of said radiator and whose outer conductor is connected to the other half of said dipole; and

said inner and outer conductors of said transmission line are electrically connected to said dipole halves in a central region of said dipole in a region surrounded by a body of high dielectric strength ceramic.

14. A system for radiating electromagnetic wave energy into a subsurface formation comprising:

a plurality of coaxial lines extending from the surface into said subsurface formation;

dipole radiators coupled to said coaxial lines in said subsurface formation;

said dipole radiators comprising upper dipole halves connected to the outer conductors of said coaxial lines with the spaces between the upper and lower halves of said radiators being filled with solids comprising high strength dielectrics.

15. The system in accordance with claim 14 wherein:

said dielectrics have a high dielectric strength at temperatures above 250°

C.

16. The system in accordance with claim 14 wherein:

the central conductors of said coaxial lines are hollow and are attached to the lower halves of said dipole radiators with hollow passages in said lower dipole halves communicating with the hollow interiors of said central conductors for conducting fluids between said formation and said surface.

17. The system in accordance with claim 14 wherein:

said coaxial lines extend through an overburden over said subsurface formation; and

casings surround said coaxial lines in said overburden.

18. The system in accordance with claim 14 wherein:

a ceramic cylinder for collecting pyrolytic decomposition products is positioned in the electric fields radiated from said radiators.

19. The system in accordance with claim 14 wherein:

said inner and outer conductors of said transmission lines are electrically connected to said dipole halves in central regions of said dipoles which regions are surrounded by high dielectric strength ceramic blocks.

20. A system for producing subsurface heating of a formation comprising:

a plurality of spaced radiators extending through an overburden into a region to be heated; and

means for supplying said radiators with electrical energy at intensities and a frequency which produce electrical fields in said formation which heat selected organic portions of said formation wherein said radiators have parasitic reflecting elements positioned adjacent said radiators and separated therefrom to direct said radiation toward a common region of said formation to be heated.

21. A system in accordance with claim 20 wherein:

said parasitic reflecting elements positioned adjacent said radiators are separated therefrom by less than a quarter wavelength of said frequency.

22. The system in accordance with claim 21 wherein:

said radiators contain apertures through which liquids in said formation may be collected.

23. A radiating system for heating a subsurface formation comprising:

a dipole radiator comprising a pair of radiating elements, one of such elements having apertures therein, said radiator being disposed in said formation supplied with electromagnetic energy through a transmission line extending from the surface through an overburden to said subsurface formation and coupled to said radiator; and

means for collecting fluid products of pyrolytic decomposition of said formation which flow through the apertures in the one of the radiating elements to a collecting means.

24. A system for producing subsurface heating of a formation comprising:

a plurality of groups of spaced radiators extending through an overburden into a region to be heated;

means for supplying said radiators with electrical energy at intensities and a frequency which produce electrical fields in said formation which heat selected organic portions of said formation at a more rapid rate than said heat is transferred by conduction from said organic portions to predominantly inorganic portions of said formation to adjacent to said organic portions; and

said radiators being positioned on the order of a half wavelength apart of said frequency in said formation.

25. A system for producing subsurface heating of a formation comprising:

a plurality of groups of spaced radiators extending through an overburden into a region to be heated;

means for supplying said radiators with electrical energy at intensities and a frequency which produce electrical fields in said formation which heat selected organic portions of said formation at a more rapid rate than said heat is transferred by conduction from said organic portions to predominantly inorganic portions of said formation adjacent to said organic portions;

said radiators being positioned on the order of a half wavelength apart of said frequency in said formation; and

said radiators having parasitic reflecting elements positioned adjacent said radiators and separated therefrom by less than a quarter wavelength of said frequency to direct said radiation toward a common region of said formation to be heated.

26. The system in accordance with claim 25 wherein said parasitic radiation elements comprise apertures through which liquids in said formation may be collected.

27. The system in accordance with claim 26 wherein means are provided for pumping said liquids through parasitic radiation elements to the surface of the overburden.