Apparatus and method for in situ heat processing of hydrocarbonaceous formations

• US RE30,738 E
• Filed: 02/06/1980
• Issued: 09/08/1981
• Est. Priority Date: 02/06/1980
• Status: Expired due to Term

• Current Assignee: IIT Research Institute (Alion Science & Technology Corp.)
• Original Assignee: IIT Research Institute (Alion Science & Technology Corp.)
• Inventors: Taflove, Allen, Bridges, Jack
• Primary Examiner(s): NOVOSAD, STEPHEN
• Application Number:
  US06/118,957
• Time in Patent Office: 580 Days
• Field of Search: 166/248, 166/60, 166/57, 166/302, 166/245, 166/50, 166/52, 166/65 R, 219/10.55 R, 219/10.65, 219/10.81
• US Class Current: 166/248
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/2401 by means of electricity
• CPC Class Codes: E21B 43/305 comprising at least one inclined or horizontal well

Abstract

The disclosure describes a technique for uniform heating of relatively large blocks of hydrocarbonaceous formations in situ using radio frequency (RF) electrical energy that is substantially confined to the volume to be heated and effects of dielectric heating of the formations. An important aspect of the disclosure relates to the fact that certain hydrocarbonaceous earth formations, for example raw unheated oil shale, exhibit dielectric absorption characteristics in the radio frequency range. In accordance with the system of the invention, a plurality of conductors are inserted in the formations and bound a particular volume of the formations. The phrase "bounding a particular volume" is intended to mean that the volume is enclosed on at least two sides thereof. Electrical excitation is provided for establishing alternating electric fields in the volume. The frequency of the excitation is selected as a function of the dimensions of the volume so as to establish a substantially non-radiating electric field which is substantially confined in the volume. In this manner, volumetric dielectric heating of the formations will occur to effect approximately uniform controlled heating of the volume.

Claims

1. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising:

a plurality of conductive means inserted in said formations and bounding a particular volume of said formations;

electrical excitation means for establishing alternating electric fields in said volume;

the frequency of said excitation means being selected as a function of the volume dimensions so as to establish substantially non-radiating electric fields which are substantially confined in said volume;

whereby volumetric dielectric heating of the formations will occur to effect approximately uniform heating of said volume.

2. A system as defined by claim 1 wherein the frequency of said excitation is in the radio frequency range.

3. A system as defined by claim 2 wherein said conductive means comprise opposing spaced rows of conductors disposed in opposing spaced rows of boreholes in said formations.

4. A system as defined by claim 3 wherein the conductors of each row comprise spaced elongated conductors.

5. A system as defined by claim .[.4.]. .Iadd.20 .Iaddend.wherein said excitation is applied as a voltage as between the conductors of the outer rows and the conductors of the central row.

6. A system as defined by claim 4 wherein said electrical excitation is a source of current applied to at least one current loop in said volume.

7. A system as defined by claim 4 wherein said electrical excitation is applied across at least one electrical dipole in said volume.

8. A system as defined by claim 4 wherein the conductors of the central row are of substantially shorter length than the conductors of the outer rows so as to reduce radiation at the ends of said conductors.

9. A system as defined by claim 8 wherein the frequency of said excitation is selected such that a half wavelength of electromagnetic energy in the region beyond the center conductor is substantially greater than the spacing between the outer rows to give rise to a cutoff condition in said region.

10. A system as defined by claim 9 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

11. A system as defined by claim 9 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

12. A system as defined by claim 8 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

13. A system as defined by claim 8 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

14. A system as defined by claim 2 wherein said excitation in applied as to a voltage as between different groups of said conductive means.

15. A system as defined by claim 2 wherein said electrical excitation is a source of current applied to at least one current loop in said volume.

16. A system as defined by claim 2 wherein said electrical excitation is applied across at least one electrical dipole in said volume.

17. A system as defined by claim 2 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

18. A system as defined by claim 2 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

19. A system as defined by claim 1 wherein said conductive means comprise opposing spaced rows of conductors disposed in opposing spaced rows of boreholes in said formations.

20. A system as defined by claim 19 wherein said rows of conductors comprise three spaced rows of conductors.

21. A system as defined by claim 20 wherein the conductors of each row comprise spaced elongated conductors.

22. A system as defined by claim 21 wherein said excitation is applied as a voltage as between the conductors of the outer rows and the conductors of the central row.

23. A system as defined by claim 22 wherein the conductors of the central row are of substantially shorter length than the conductors of the outer rows so as to reduce radiation at the ends of said conductors.

24. A system as defined by claim 23 wherein the frequency of said excitation is selected such that a half wavelength of electromagnetic energy in the region beyond the center conductor is substantially greater than the spacing between the outer rows to give rise to a cutoff condition in said region.

25. A system as defined by claim 21 wherein said electrical excitation is a source of current applied to at least one current loop in said volume.

26. A system as defined by claim 25 wherein the conductors of the central row are of substantially shorter length than the conductors of the outer rows so as to reduce radiation at the ends of said conductors.

27. A system as defined by claim 26 wherein the frequency of said excitation is selected such that a half wavelength of electromagnetic energy in the region beyond the center conductor is substantially greater than the spacing between the outer rows to give rise to a cutoff condition in said region.

28. A system as defined by claim 21 wherein said electrical excitation is applied across at least one electrical dipole in said volume.

29. A system as defined by claim 20 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

30. A system as defined by claim 29 wherein said rows of conductors are inserted in said formations at angles such that said rows are closer together at far ends thereof to compensate for attenuation of the electrical field at said far end.

31. A system as defined by claim 20 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

32. A system as defined by claim 31 wherein said means for modifying the electric field pattern comprises means for modifying the effective length of the conductors of the central row.

33. A system as defined by claim 32 wherein said means for modifying the effective length of the conductors of the central row comprises means for physically shortening the length of said conductors.

34. A system as defined by claim 32 wherein said means for modifying the effective length of said conductors comprises means for electrically modifying the effective length thereof.

35. A system as defined by claim 20 wherein said rows of conductors are inserted in said formations at angles such that said rows are closer together at far ends thereof to compensate for attenuation of the electrical field at said far end.

36. A system as defined by claim 19 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

37. A system as defined by claim 19 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

38. A system as defined by claim 19 wherein said rows of conductors are inserted in said formations at angles such that said rows are closer together at far ends thereof to compensate for attenuation of the electrical field at said far end.

39. A system as defined by claim 1 wherein said excitation is applied as a voltage as between different groups of said conductive means.

40. A system as defined by claim 39 wherein the conductors of the central row are of substantially shorter length than the conductors of the outer rows so as to reduce radiation at the ends of said conductors.

41. A system as defined by claim 1 wherein said electrical excitation is a source of current applied to at least one current loop in said volume.

42. A system as defined by claim 1 wherein said electrical excitation is applied across at least one electrical dipole in said volume.

43. A system as defined by claim 1 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

44. A system as defined by claim 43 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

45. A system as defined by claim 1 further comprising means for modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

46. A method for in situ heating of hydrocarbonaceous earth formations, comprising the steps of:

forming a plurality of boreholes which bound a particular volume of said formations;

inserting elongated electrical conductors in said boreholes; and

introducing electrical excitation to said formations to establish alternating electric fields in said volume;

the frequency of said excitation being selected as a function of the volume dimensions so as to establish substantially non-radiating electric fields which are substantially confined in said volume;

whereby volumetric dielectric heating of the formations will occur to effect approximately uniform heating of said volume.

47. A method as defined by claim 46 wherein the frequency of said excitation is in the radio frequency range.

48. A method as defined by claim 47 wherein the step of introducing electrical excitation comprises applying a voltage as between different groups of said conductors.

49. A method as defined by claim 47 wherein the step of introducing electrical excitation comprises applying electrical current to at least one current loop in said volume.

50. A method as defined by claim 47 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

51. A method as defined by claim 47 further comprising the step of modifying the electric field pattern so as to average the electric field intensity in said volume to enhance the uniformity of heating of said volume.

52. A method as defined by claim 51 wherein the step of modifying the electric field pattern comprises the step of modifying the effective length of some of said conductors.

53. A method as defined by claim 47 further comprising the step of withdrawing through said boreholes the valuable constituents resulting from said heating.

54. A method as defined by claim 47 wherein said dielectric heating is continued to heat said volume to a temperature below the temperature required for extraction of valuable constituents from said volume, and further comprising the steps of applying further nonelectrical heating means to said volume and withdrawing through said boreholes valuable constituents from said volume.

55. A method as defined by claim 46 wherein said boreholes are formed in opposing spaced rows in said formations.

56. A method as defined by claim 55 wherein said rows comprise three spaced rows.

57. A system for in situ heat processing of an oil shale bed, comprising:

a plurality of conductive means bounding a particular volume of said bed;

electrical excitation means for establishing alternating electric fields in said volume;

the frequency of said excitation means being selected as a function of the volume dimensions so as to establish substantially non-radiating electric fields which are substantially confined in said volume;

whereby volumetric dielectric heating of the bed will occur to effect approximately uniform heating of said volume.

58. A system as defined by claim 57 wherein the frequency of said excitation is in the radio frequency range.

59. A system as defined by claim 57 wherein the frequency of said excitation is in the range between about 1 MHz and 40 MHz.

60. A system as defined by claim 59 wherein said conductive means comprise opposing spaced rows of conductors disposed in opposing spaced rows of boreholes in said bed.

61. A system as defined by claim 60 wherein said rows of conductors comprise three spaced rows of conductors.

62. A system as defined by claim 61 wherein the conductors of the central row are of substantially shorter length than the conductors of the outer rows so as to reduce radiation at the ends of said conductors.

63. A system as defined by claim 62 wherein the frequency of said excitation is selected such that a half wavelength of electromagnetic energy in the region beyond the center conductor is substantially greater than the spacing between the outer rows to give rise to a cutoff condition in said region.

64. A system as defined by claim 59 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

65. A system as defined by claim 57 wherein said conductive means comprise opposing spaced rows of conductors disposed in opposing spaced rows of boreholes in said bed.

66. A system as defined by claim 57 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the l/e attenuation distance of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

67. A system for in situ heat processing of a tar sand deposit, comprising:

a plurality of conductive means inserted in said deposit and bounding a particular volume of said deposit;

electrical excitation means for establishing alternating electric fields in said volume;

the frequency of said excitation means being selected as a function of the volume dimensions so as to establish substantially non-radiating electric fields which are substantially confined in said volume;

whereby volumetric dielectric heating of the deposit will occur to effect approximately uniform heating of said volume.

68. A system as defined by claim 67 wherein the frequency of said excitation is in the radio frequency range.

69. A system as defined by claim 68 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the skin depth of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction.

70. A system as defined by claim 67 wherein the frequency of said excitation is selected as a function of the electrical lossiness of the formations in said volume to be sufficiently low such that the skin depth of the electric field in any direction in said volume is more than twice the physical dimension of said volume in that direction. .Iadd. 71. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising:

a waveguide structure comprising a plurality of elongate electrodes and configured such that the direction of propagation of aggregate modes of wave propagation therein is approximately parallel to an elongate axis of said electrodes and bounding a particular volume of earth formations as a dielectric medium bounded therein; and

means for supplying electromagnetic energy to said waveguide structure at a frequency selected to confine said electromagnetic energy in said structure and to dissipate said electromagnetic energy to the earth formations, thereby to substantially uniformly heat the bounded volume. .Iaddend..Iadd. 72. A system for in situ heat processing of hydrocarbonaceous earth materials, comprising;

a waveguide structure having an elongate shape which penetrates and bounds a particular volume of earth formations therein and wherein the aggregate direction of propagation of electromagnetic wave modes in said structure is in a direction approximately parallel to an elongate axis of said structure; and

means for supplying electromagnetic energy to said waveguide structure at a frequency selected to confine said energy and to dissipate said electromagnetic energy to said bounded volume thereby to substantially uniformly heat said bounded volume. .Iaddend. .Iadd. 73. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising;

field confining means bounding a particular volume of earth formations and forming an elongate waveguide structure having a direction of aggregate electromagnetic wave propagation mode direction in a direction approximately parallel to an elongate axis of said structure; and

means for supplying electromagnetic energy to said waveguide structure at a frequency to confine said electromagnetic energy in said structure and to cause dielectric heating of said bounded volume to a substantially uniform degree. .Iaddend..Iadd. 74. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

a plurality of electrodes placed in a pattern bounding a particular volume of hydrocarbonaceous earth formation, said pattern defining a waveguide structure having said volume bounded therein as a dielectric medium; and

,

means for applying an alternating current to said electrodes in the frequency range of the order of 100 kilohertz to 100 megahertz, the frequency of said current being selected as a function of a volume dimension so as to establish substantially non-radiating and uniform electromagnetic fields in said volume, thereby obtaining volumetric dielectric heating of said volume to a temperature sufficient to permit production of hydrocarbonaceous components thereof. .Iaddend. .Iadd. 75. A system of in situ heat processing of hydrocarbonaceous earth formations comprising;

a pattern of conductors bounding a particular volume of hydrocarbonaceous earth formation, said pattern defining an unbalanced transmission line structure having said bounded volume integral therewith as a dielectric medium; and

means for supplying alternating current in the frequency range of the order of 100 kilohertz to 100 megahertz, to said conductors, the frequency of said current being selected as a function of at least one volume dimension so as to establish substantially non-radiating electromagnetic fields in said volume. .Iaddend..Iadd. 76. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

a substantially tri-plate pattern of electrodes placed in a particular volume of hydrocarbonaceous earth formation and forming a waveguide structure having said volume bounded therein as a dielectric medium wherein adjacent portions of electrodes within a plate are at approximately the same potential; and

means for supplying a time varying electric field in the frequency range from 100 kilohertz to 100 megahertz to said electrodes so as to establish substantially non-radiating electric fields in said volume. .Iadd. 77. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

waveguide means formed by a pattern of electrodes placed in a particular volume of hydrocarbonaceous earth formation to bound said volume therein as a dielectric medium; and

means for supplying alternating current to said waveguide structure at a frequency of the order of from 100 kilohertz to 100 megahertz to effectively confine electromagnetic fields in said structure and to effect substantially uniform dielectric heating of said volume. .Iaddend..Iadd. 78. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

an unbalanced transmission line structure deployed in a particular volume of hydrocarbonaceous earth formation, said structure bounding said volume and employing said formation material as a dielectric medium therein; and

means for supplying electrical energy having a frequency of the order of from 100 kilohertz to 100 megahertz to said transmission line structure, thereby confining said energy in said structure and providing dielectric heating to a controllable degree in said volume. .Iaddend. .Iadd. 79. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

a waveguide structure formed by bounding a particular volume of earth formations with a pattern of electrodes bounding said volume and including said volume as a dielectric medium therein; and

means for establishing alternating electromagnetic fields in the frequency range between 100 kilohertz and 100 megahertz in said bounded volume, the frequency of said alternating fields being selected as a function of a volume dimension, thereby causing volumetric dielectric heating of said volume to an approximately uniform degree. .Iaddend..Iadd. 80. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

electrode means bounding a particular volume of earth formations in such a manner as to comprise a waveguide structure having said volume bounded therein as a dielectric medium; and

means for supplying electromagnetic energy to said waveguide structure at a frequency selected to confine said energy substantially in said volume and to cause heating of said volume by displacement currents to a substantially uniform degree in said volume. .Iaddend. .Iadd. 81. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising;

electrode means bounding a particular volume of earth formations in such a manner as to comprise an unbalanced transmission line structure having said volume bounded therein as a dielectric medium; and

means for supplying electromagnetic energy to said unbalanced transmission line at a frequency selected to cause heating of said volume by displacement currents to a substantially uniform degree in said volume. .Iaddend..Iadd. 82. A system for in situ heat processing of hydrocarbonaceous earth formations comprising;

electrode means bounding a particular volume of earth formations in such a manner as to comprise an approximately tri-plate transmission line structure having said volume bounded therein as a dielectric medium; and

means for supplying electromagnetic energy to said triplate transmission line structure at a frequency and field intensity selected to cause heating of said volume to a substantially uniform degree in said volume without significant heat loss to the adjacent unbounded regions and without electrical breakdown of said bounded volume. .Iaddend. .Iadd. 83. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising

a waveguide structure comprising a plurality of electrodes bounding a particular volume of earth formations as a dielectric medium bounded therein; and

means for supplying electromagnetic energy to said waveguide structure at a frequency selected to dissipate said electromagnetic energy substantially only to said bounded medium thereby to substantially uniformly heat said bounded volume. .Iaddend..Iadd. 84. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising;

an unbalanced transmission line structure comprising a plurality of electrodes bounding a particular volume of earth formations as a dielectric medium bounded therein; and

means for supplying electromagnetic energy to said unbalanced transmission line structure at a frequency selected to substantially confine said energy to said structure and to dissipate said electromagnetic energy to said dielectric medium by displacement current heating thereof, thereby to substantially uniformly heat said bounded volume without significant heat loss to the adjacent unbounded regions and without electrical breakdown of said bounded volume. .Iaddend. .Iadd. 85. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising;

an approximately tri-plate transmission line structure comprising a plurality of electrodes bounding a particular volume of earth formations as a dielectric medium bounded therein; and

means for supplying electromagnetic energy to said approximately tri-plate transmission line structure at a frequency and field intensity selected to dissipate said electromagnetic energy to said dielectric medium, thereby to substantially uniformly heat said bounded volume without significant heat loss to the adjacent unbounded regions and without electrical breakdown of said bounded volume. .Iaddend..Iadd. 86. A system for in situ heating a volume of hydrocarbonaceous earth formation to an elevated temperature comprising;

electrical excitation means for providing an electrical waveform of a frequency of the order of from 100 kilohertz to 100 megahertz;

a conductor array located approximately centrally in said volume to which the electrical waveform is applied, said central conductor array comprising a line of conductors inserted in boreholes in the formation, wherein adjacent conductors in the line are separated by a distance of about 1/8 of a wavelength of less of the electrical waveform; and

a bounding conductor array comprising at least one line of electrical conductors inserted in boreholes in the formation, adjacent of said conductors in a line being separated by about 1/8 of a wavelength or less of the electrical waveform wherein bounding conductors are at approximately the same potential as the adjacent unbounded earth formations whereby radiation of electrical energy outside the volume of the hydrocarbonaceous earth formation is minimized. .Iaddend..Iadd. 87. A method of heating a volume of hydrocarbonaceous earth formations to an elevated temperature comprising;

applying an electrical waveform to a first row of elongated conductors penetrating a volume of the formation, adjacent conductors being separated by a distance less than 1/8 of the wavelength of the electrical waveform;

confining the electromagnetic field in the volume by bounding said volume with at least two rows of elongated conductors, adjacent conductors in a row being separated by a distance less than 1/8 of the wavelength of the electrical waveform; and

varying at least one of;

(a) the frequency of the electrical waveform;

(b) the physical length of individual conductors in a row of conductors, (c) the series capacitance of conductors in a row;

(d) the effective electrical length of conductors in a row;

to facilitate uniform heating of the formation in the direction of the principal axis of the elongated conductors. .Iaddend..Iadd. 88. A method for in situ heat processing of hydrocarbonaceous earth formations comprising the steps of;

placing a plurality of electrodes into a particular volume of hydrocarbonaceous material in a pattern which bounds said volume and defines an unbalanced transmission line structure having said bounded volume present as a dielectric medium bounded therein;

applying alternating current at a radio frequency on the order of from 100 kilohertz to 100 megahertz to said electrodes, said radio frequency being chosen as a function of a volume dimension so as to establish substantially non-radiating electromagnetic fields which are substantially confined in said volume, thereby effecting approximately uniform heating of said volume to a temperature sufficient to permit production of

71. hydrocarbonaceous components thereof. .Iaddend..Iadd. 89. A method for in situ heating processing of hydrocarbonaceous earth formations comprising the steps of:

placing a plurality of electrodes into a particular volume of hydrocarbonaceous material in a pattern which bounds said volume and defines a waveguide structure having said bounded volume present as a dielectric medium bounded therein;

applying alternating current at a radio frequency on the order of 100 kilohertz to 100 megahertz to said electrodes, said radio frequency being chosen as a function of at least one volume dimension so as to establish substantially nonradiating electromagnetic fields which are substantially confined in said volume, thereby effecting approximately uniform heating;

modifying the electromagnetic field pattern so as to time average the electromagnetic field in said volume to enhance the uniformity of heating of said volume. .Iaddend. .Iadd. 90. A method for in situ heat processing of hydrocarbonaceous earth formations, comprising the steps of;

forming a plurality of holes which bound a particular volume of hydrocarbonaceous material and spaced from each other so as to define an approximately triplate structure having said bounded volume of hydrocarbonaceous material present as a dielectric medium bounded therein;

inserting electrical conductors into said holes; and

,

applying alternating current at a radio frequency on the order of from 100 kilohertz to 100 megahertz to said conductors, said radio frequency being chosen as a function of at least one volume dimension so as to establish substantially nonradiating electromagnetic fields which are substantially confined in said volume, thereby effecting approximately uniform heating of said volume. .Iaddend..Iadd. 91. A method for in situ heat processing of hydrocarbonaceous earth formations, comprising the steps of;

enclosing a particular volume of earth formations on at least two sides thereof with a plurality of spaced electrodes to define a waveguide structure having said enclosed volume present therein as a dielectric medium; and

establishing alternating electromagnetic fields in the frequency range between 100 kilohertz to 100 megahertz in said enclosed volume, the frequency of said alternating fields being selected as a function of a volume dimension, so as to establish substantially non-radiating, confined, electromagnetic fields in said volume, thereby causing volumetric dielectric heating of said volume to effect approximately

72. uniform heating of said volume. .Iaddend..Iadd. 92. A method for in situ heat processing of hydrocarbonaceous earth formations comprising the steps of:

bounding a particular volume of earth formations with a waveguide structure comprising elongate electrodes having outer electrodes which are at approximately the same potential as the adjacent unbounded earth formations; and

propagating electromagnetic energy through the waveguide structure in an aggregate mode of propagation generally parallel to the direction of an elongate axis of said electrodes, thereby substantially confining the electromagnetic energy in the waveguide structure and uniformly heating the bounded volume of earth formations. .Iaddend. .Iadd. 93. A method for in situ heat processing of hydrocarbonaceous earth formations, comprising the steps of;

bounding a particular volume of earth formations with a transmission line structure having an inner elongate shaped propagating electrode structure and an outer elongate shaped electrode structure which is at approximately the same potential as the adjacent unbounded earth formations; and

propagating modes of electromagnetic energy in said structure in an aggregate direction generally parallel to an elongate axis of said propagating electrodes, thereby confining said electromagnetic energy in said bounded volume and uniformly heating said bounded volume. .Iaddend..Iadd. 94. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising;

a multi mode cavity structure comprising a plurality of elongate electrodes and configured such that the direction of wave propagation of a particular mode is parallel to an elongate axis of at least one set of said electrodes, said multi mode cavity structure bounding a particular volume of earth formations as a dielectric medium bounded therein wherein the outermost electrodes are at approximately the same potential as the adjacent unbounded earth formations; and

means for supplying electromagnetic energy to said multi mode cavity structure at a frequency selected to confine said electromagnetic energy in said structure and to dissipate said electromagnetic energy to the earth formations;

thereby to substantially uniformly heat the bounded volume. .Iaddend..Iadd. 95. The system of claim 94 and further including means for time averaging said electromagnetic energy along the direction of propagation, thereby to enhance the uniformity of heating of the bounded volume of earth formations. .Iaddend..Iadd. 96. A system for in situ heat processing of hydrocarbonaceous earth formations, comprising;

a waveguide structure having a plurality of rows of conductors, the spacing of conductors in a row being less than the spacing of said rows of conductors and bounding a particular volume of earth formations as a dielectric medium bounded therein; and

,

means for supplying electromagnetic energy to said waveguide structure at a frequency selected to dissipate said electromagnetic energy substantially only to said bounded medium, thereby to substantially uniformly heat said bounded volume. .Iaddend..Iadd. 97. The system of claim 96 and further including means for time averaging said electromagnetic energy along a direction of its propagation in said waveguide structure. .Iaddend.