Electromagnetic induction heater

Abstract

A heating device for heating underground soil including a conductor housed in a conductive casing, where when at least one driving current is supplied to the conductor, the conductor generates at least one magnetic field that induces at least one induced current in the casing. The driving currents are of a frequency sufficient to cause the induced currents to generate resistance in the casing, thereby increasing the temperature of the casing. A plurality of the heating devices may be arranged in an array to facilitate the heating of a zone of soil.

What is claimed is: 
     
         1 . A heating device for heating underground soil, comprising:
 a conductive casing having a first end, a second end, and a wall defining an inner bore extending the first and second ends, and a temperature;   a conductor, at least a part of the conductor being positioned in the inner bore, the conductor being electrically insulated from the casing; and   a power unit connected to the conductor through the first end, the power unit configured to convert power received from a power source into at least one driving current and supply the at least one driving current to the conductor,   wherein the conductor is configured to generate at least one magnetic field when the at least one driving current is supplied thereto to create at least one corresponding induced current in the casing, and wherein the at least one driving current is of a frequency sufficient for the at least one induced current to encounter resistance in the casing to increase the temperature.   
     
     
         2 . The heating device of  claim 1 , wherein the conductor comprises one or more work coils. 
     
     
         3 . The heating device of  claim 2 , wherein the one or more work coils are helical coils. 
     
     
         4 . The heating device of  claim 2 , wherein each of the one or more work coils are positioned at an axial location in the inner bore for increasing the temperature of the casing at the axial location. 
     
     
         5 . The heating device of  claim 2  wherein the one or more work coils are supported on a work coil support. 
     
     
         6 . The heating device of  claim 1 , wherein the conductor is a single-phase conductor and the power unit comprises one or more single-phase inverters. 
     
     
         7 . The heating device of  claim 1 , wherein the conductor is a three-phase conductor and the power unit comprises one or more three-phase inverters. 
     
     
         8 . The heating device of  claim 7 , wherein the conductor comprises three or more work coils axially arranged in series. 
     
     
         9 . The heating device of  claim 7 , wherein the conductor comprises sets of three or more interleaved work coils. 
     
     
         10 . The heating device of  claim 1 , wherein the casing is a metal tubular member. 
     
     
         11 . The heating device of  claim 1 , wherein the casing is made of a high permeability and high resistivity material. 
     
     
         12 . The heating device of  claim 1 , wherein the wall of the casing has an inner surface coated with refractory mortar. 
     
     
         13 . The heating device of  claim 1 , wherein the conductor is coated with refractory mortar. 
     
     
         14 . The heating device of  claim 1 , further comprising at least one capacitor connected in parallel or series with the conductor. 
     
     
         15 . The heating device of  claim 14 , wherein the frequency of the at least one driving current is about the same as the resonant frequency of a circuit formed by at least the conductor, the casing, and the at least one capacitor. 
     
     
         16 . The heating device of  claim 1 , further comprising:
 one or more temperature sensors positioned along the length of the casing; and   a controller for receiving data from the one or more temperature sensors, and in response to the data, modifying the at least one driving current.   
     
     
         17 . The heating device of  claim 1 , further comprising an outer sleeve supported on the conductive casing and defining an annulus therebetween for receiving a transport fluid. 
     
     
         18 . The heating device of  claim 1 , further comprising a cooling system for removing heat from the conductor. 
     
     
         19 . A system for heating one or more subterranean zones of soil comprising:
 a plurality of the heating device of  claim 1  arranged in an array.   
     
     
         20 . The system of  claim 19 , wherein the array is in a form of one or more triangles, with at least one of the plurality of the heating devices at each vertex of the one or more triangles. 
     
     
         21 . The system of  claim 20 , wherein the distance between adjacent heating devices is between about 5 feet and about 20 feet. 
     
     
         22 . A method of heating one or more subterranean zones of soil comprising:
 supplying at least one alternating driving current each having a frequency to a respective at least one conductive coil housed inside a conductive casing, the at least one conductive coil being electrically insulated from the conductive casing, and the conductive casing being positioned in the one or more subterranean zones; and   inducing at least one induced current in the conductive casing,   wherein the frequency is selected to cause the at least one induced current to generate resistance in the conductive casing to increase a temperature of the conductive casing.   
     
     
         23 . The method of  claim 22 , further comprising converting an alternating utility current to at least one direct current, and converting the at least one direct current into the at least one alternating driving current. 
     
     
         24 . The method of  claim 22 , wherein each of the at least one conductive coil is connected in parallel or series with a corresponding at least one capacitor and the frequency of each of the at least one driving current is about the same as a resonant frequency of a circuit formed by a respective one of the at least one conductive coil, its corresponding at least one capacitor, and the conductive casing. 
     
     
         25 . The method of  claim 22 , wherein the at least one alternating driving current is single-phase or three-phase. 
     
     
         26 . The method of  claim 22 , further comprising collecting temperature data from at least one sensor positioned on the conductive casing; and selectively modifying the at least one alternating driving current in response to the collected temperature data. 
     
     
         27 . The method of  claim 22 , further comprising injecting a transport fluid into an annulus defined between the conductive casing and an outer sleeve supported on the conductive casing. 
     
     
         28 . The method of  claim 22 , further comprising removing heat from the at least one conductive coil. 
     
     
         29 . The method of  claim 28 , wherein removing heat comprises passing a coolant through the at least one conductive coil.