Temperature limited heaters using modulated DC power
First Claim
1. A system configured to heat at least a part of a subsurface formation, comprising:
- an electrical power supply configured to provide modulated direct current (DC); and
a heater section comprising one or more electrical conductors electrically coupled to the electrical power supply and configured to be placed in an opening in the formation, at least one of the electrical conductors comprising ferromagnetic material;
wherein the heater section (a) provides a first heat output when electrical current is applied to the heater section below a selected temperature, (b) provides a second heat output approximately at and above the selected temperature during use, and (c) has a turndown ratio of at least 1.1 to 1; and
the system is configured to heat at least part of a subsurface formation.
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Accused Products
Abstract
The invention provides a system configured to heat at least a part of a subsurface formation. The system includes: an electrical power supply configured to provide modulated direct current (DC); and one or more electrical conductors configured to be electrically coupled to the electrical power supply and placed in an opening in the formation, wherein at least one of the electrical conductors has a heater section, the heater section comprising an electrically resistive ferromagnetic material configured to provide an electrically resistive heat output when electrical current is applied to the ferromagnetic material, and the heater section is configured to provide a reduced amount of heat near or above a selected temperature during use due to the decreasing electrical resistance of the heater section when the temperature of the ferromagnetic material is near or above the selected temperature, and the heater section has a turndown ratio of at least 1.1 to 1.
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Citations
30 Claims
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1. A system configured to heat at least a part of a subsurface formation, comprising:
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an electrical power supply configured to provide modulated direct current (DC); and a heater section comprising one or more electrical conductors electrically coupled to the electrical power supply and configured to be placed in an opening in the formation, at least one of the electrical conductors comprising ferromagnetic material; wherein the heater section (a) provides a first heat output when electrical current is applied to the heater section below a selected temperature, (b) provides a second heat output approximately at and above the selected temperature during use, and (c) has a turndown ratio of at least 1.1 to 1; and the system is configured to heat at least part of a subsurface formation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for heating at least a part of a subsurface formation, comprising:
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applying modulated direct current to a heater section to provide an electrically resistive heat output, the heater section comprising one or more electrical conductors electrically coupled to the electrical power supply and placed in an opening in the formation, at least one of the electrical conductors comprising ferromagnetic material; providing a first heat output when electrical current is applied to the heater section below a selected temperature; providing a second heat output approximately at and above the selected temperature during use, wherein the heater section has a turndown ratio of at least 1.1 to 1; and allowing heat to transfer from the heater section to a part of the subsurface formation. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A method for heating at least a part of a subsurface formation, comprising:
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applying modulated direct current to a heater section to provide an electrically resistive heat output, the heater section comprising one or more electrical conductors electrically coupled to the electrical power supply and placed in an opening in the formation, at least one of the electrical conductors comprising ferromagnetic material; wherein the electrical current is applied to (a) provide a first heat output when the heater section below a selected temperature, and (b) provide a second heat output when the heater section is approximately at and above the selected temperature, the second heat output at most 90% of the first heat output; and allowing heat to transfer from the heater section to a part of the subsurface formation.
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Specification