RF Applicator for in situ heating
First Claim
1. The method of producing organic products from a body of oil shale beneath an overburden comprising:
- generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz;
transmitting said energy via a first transmission line having a first characteristic impedance through a first impedance transformation structure to a second transmission line which has a second characteristic impedance and which extends through said overburden and which is coupled to a radiating structure through a second impedance transformation structure positioned in said body of oil shale and substantially impedance matched to said transmission line; and
varying the impedance matching of said first impedance transformation structure to compensate for changes in temperature of said oil shale body.
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Accused Products
Abstract
A coaxially fed applicator for in situ RF heating of subsurface bodies with a coaxial choke structure for reducing outer conductor RF currents adjacent the radiator. The outer conductor of the coaxial transmission line supplying RF energy to the radiator terminates in a coaxial structure comprising a section of coaxial line extending toward the RF radiator from the termination for a distance approaching a quarter wavelength at the RF frequency and a coaxial stub extending back along the coaxial line outer conductor from the termination for a distance less than a quarter wavelength at said frequency. The central conductor of the coaxial transmission line is connected to an enlarged coaxial structure approximately a quarter of a wavelength long in a region beyond the end of the outer conductor coaxial choking structure.
168 Citations
19 Claims
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1. The method of producing organic products from a body of oil shale beneath an overburden comprising:
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generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz; transmitting said energy via a first transmission line having a first characteristic impedance through a first impedance transformation structure to a second transmission line which has a second characteristic impedance and which extends through said overburden and which is coupled to a radiating structure through a second impedance transformation structure positioned in said body of oil shale and substantially impedance matched to said transmission line; and varying the impedance matching of said first impedance transformation structure to compensate for changes in temperature of said oil shale body.
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2. The method of producing organic products from a body of oil shale beneath an overburden comprising:
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generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz; transmitting said energy via a first transmission line having a first characteristic impedance through a variable impedance matching structure to a second transmission line having a sound characteristic impedance and extending through said overburden to couple said energy through an impedance matching structure to a radiating structure positioned in said body of oil shale; and varying the frequency of said energy to vary the pattern of said energy radiated into said body of oil shale.
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3. The method of producing organic products from a body of oil shale beneath an overburden comprising:
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generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz; transmitting said energy via a first transmission line having a first characteristic impedance through a variable impedance matching structure to a second transmission line having a second characteristic impedance ad extending through said overburden to couple said energy through an impedance matching structure to a radiating structure which is positioned in said body of oil shale; and varying the frequency of said energy to compensate for changes in the impedance of said oil shale body to said energy.
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4. The method of producing organic products from a body of oil shale beneath an overburden comprising:
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generating electrical energy in the frequency range between 100 Kilohertz and 100 megahertz; transmitting said energy via a first transmission line having a first characteristic impedance through a variable impedance matching structure to a second transmission line having a second substantially different characteristic impedance from that of said first transmission line and extending through said overburden to couple said energy through an impedance matching structure to a radiating structure positioned in said body of oil shale; varying the frequency of said energy to vary the pattern of said energy radiated into said body of oil shale; and adjusting said variable impedance matching structure to reduce the power on said first transmission line reflected from said second transmission line and/or said radiating structure.
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5. The method of producing organic products from a body of oil shale beneath an overburden comprising:
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generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz; transmitting said energy via a first transmission line having a first characteristic impedance through a variable impedance matching structure to a second transmission line having a second characteristic impedance and extending through said overburden to couple said energy through an impedance matching structure to a radiating structure positioned in said body of oil shale while sensing the reflected power on said second transmission line; and varying the impedance matching of said structure as a function of said reflected power.
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6. A system for radiating energy into a subsurface body comprising:
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a coaxial transmission line extending from the surface of said body to an RF applicator; said coaxial transmission line comprising inner and outer cylindrical conductors and said inner conductor being attached to a cylindrical radiating element at a point below the lower end of said outer conductor, said outer conductor being attached to an impedance matching element having a first tubular member extending upwardly parallel to said outer conductor and a second tubular member extending downwardly parallel to said inner conductor; the maximum diameter of said radiating element being substantially larger than the average diameter of the outer conductor of said transmission line; and the upper end of said first tubular member being displaced from the lower end of said second tubular member a length equal to an odd number of quarter wavelengths of the operating wavelength of said radiating energy system.
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7. A radiating system comprising a coaxial transmission line having a radiating element connected to the inner conductor of said transmission line and a cylindrical conductive structure connected to the outer conductor of said transmission line, said conductive structure comprising:
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a first upwardly extending tubular member coupled to the lower end of said outer conductor and extending parallel to said outer conductor and a second downwardly extending tubular member coupled to the lower end of said outer conductor and extending parallel to said inner conductor; and the diameter of said conductive structure being substantially greater than the average diameter of the inner surface of the outer conductor of said transmission line. - View Dependent Claims (8, 9)
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10. A system for transferring RF energy into a subsurface body comprising:
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a coaxial transmission line extending from the surface of said body to an RF applicator; said coaxial transmission line comprising inner and outer cylindrical conductors; said inner conductor being attached to a cylindrical radiating element at a point below the lower end of said outer conductor and said outer conductor being attached to a conductive structure surrounding the end of said outer transmission line, said conductive structure having a first tubular member extending upwardly parallel to said outer conductor and a second tubular member extending downwardly parallel to said inner conductor; the maximum diameter of said conductive structure being substantially greater than the average diameter of the inner conductive surface of said outer conductor of said coaxial transmission line; and means for supplying said transmission line with said RF energy.
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11. A system for producing organic products from a body of oil shale beneath an overburden comprising:
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means for generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz; means for transmitting said energy via a first transmission line having a first characteristic impedance through a variable impedance matching structure to a second transmission line having a second characteristic impedance; said second transmission line extending through said overburden and being coupled to a radiating structure positioned in said body of oil shale through an impedance transition; and means for varying the frequency of said energy.
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12. A system for radiating RF energy into a subsurface body comprising:
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means for generating said RF energy; a coaxial transmission line extending from the surface of said body to an RF applicator for supplying said applicator with said energy; said coaxial transmission line comprising inner and outer cylindrical conductors; said inner conductor being attached to a cylindrical radiating element extending below the lower end of said outer conductor; and the lower end of said outer conductor being attached to an impedance matching structure having a first tubular member extending upwardly parallel to said outer conductor and a second tubular member extending downwardly parallel to said inner conductor and having a maximum diameter which is substantially larger than the average diameter of the conductive inner surface of said outer conductor; said radiating element attached to said inner conductor being disposed in said system a distance below the end of said conductive structure wherein said distance between the upper end of said radiating element and the lower end of said second tubular member is a quarter wavelength of the operating wavelength of said system.
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13. A subsurface radiating system comprising a coaxial transmission line having a radiating element connected to the inner conductor of said transmission line and a coaxial impedance transformation structure connected to the outer conductor of said transmission line, said impedance transformation structure comprising a first tubular member coupled to the lower end of said outer conductor and extending upwardly parallel to said outer conductor and a second tubular member coupled to the lower end of said outer conductor and extending downwardly parallel to said inner conductor;
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the second tubular member of said structure having a maximum diameter substantially greater than the average diameter of the inner conductive surface of said outer conductor. - View Dependent Claims (14, 15, 16, 17)
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18. A system for producing organic products from a body of oil shale beneath an overburden comprising:
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means for generating electrical energy in the frequency range between 100 kilohertz and 100 megahertz; means for supplying said energy via a first coaxial transmission line having a first characteristic impedance through a variable impedance matching structure to a second coaxial transmission line having a substantially different characteristic impedance from that of said first transmission line; said second transmission line extending through said overburden to supply said energy through an impedance matching structure to a radiating structure positioned in said body of oil shale; said radiating structure comprising a radiating element connected to the inner conductor of said second transmission line; said impedance matching structure comprising a first tubular member coupled to the lower end of an outer conductor of said second transmission line extending upwardly parallel to said outer conductor and a second tubular member coupled to the lower end of said outer conductor extending downwardly parallel to said inner conductor; and the diameter of said impedance matching structure being substantially greater than the average diameter of the outer conductor of said second transmission line. - View Dependent Claims (19)
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Specification