Temperature limited heaters with thermally conductive fluid used to heat subsurface formations

• US 20050269090A1
• Filed: 04/22/2005
• Published: 12/08/2005
• Est. Priority Date: 04/23/2004
• Status: Active Grant

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Vinegar, Harold J., Harris, Christopher Kelvin
• Granted Patent: US 7,383,877 B2
• Time in Patent Office: Days
• US Class Current: 166/302
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/12 Methods or apparatus for controlling the flow of the obtained fluid to or in wells E21B43/25 takes precedence; valve arrangements E21B34/00
• CPC Class Codes: E21B 43/122 Gas lift
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection
• CPC Class Codes: E21B 43/2401 by means of electricity
• CPC Class Codes: E21B 43/2405 in association with fracturing or crevice forming processes E21B43/247 takes precedence
• CPC Class Codes: E21B 43/38 in the well
• CPC Class Codes: H05B 3/141 Conductive ceramics, e.g. metal oxides, metal carbides, barium titanate, ferrites, zirconia, vitrous compounds

Abstract

Certain embodiments provide a system including a heater. The heater includes one or more electrical conductors. The heater is configured to generate a heat output during application of electrical current to the heater. The heater includes a ferromagnetic material. A conduit at least partially surrounds the heater. A fluid is located in a space between the heater and the conduit. The fluid has a higher thermal conductivity than air at standard temperature and pressure (STP) (0° C. and 101.325 kPa). The system is configured to provide (a) a first heat output below a selected temperature when time-varying electrical current is applied to the heater, and (b) a second heat output near or above the selected temperature when time-varying electrical current is applied to the heater.

Claims

1-83. -83. (canceled)

84. A system, comprising:

a heater comprising one or more electrical conductors, the heater configured to generate a heat output during application of electrical current to the heater, wherein the heater comprises a ferromagnetic material;

a conduit at least partially surrounding the heater;

a fluid located in a space between the heater and the conduit, wherein the fluid has a higher thermal conductivity than air at standard temperature and pressure (STP) (0°

C. and 101.325 kPa); and

wherein the system is configured to provide (a) a first heat output below a selected temperature when time-varying electrical current is applied to the heater, and (b) a second heat output near or above the selected temperature when time-varying electrical current is applied to the heater.

85. The system of claim 84, wherein the electrical conductor at least partially surrounds a non-ferromagnetic material.

86. The system of claim 84, wherein the fluid is helium.

87. The system of claim 84, wherein the fluid is helium and the space between the electrical conductor and the conduit is at least 50% by volume helium.

88. The system of claim 84, wherein a fluid pressure in the space between the electrical conductor and the conduit is at least 200 kPa.

89. The system of claim 84, wherein a fluid pressure in the space between the electrical conductor and the conduit is sufficient to inhibit arcing in the space.

90. The system of claim 84, wherein the system further comprises an AC power supply.

91. The system of claim 84, wherein the system further comprises a modulated DC power supply.

92. The system of claim 84, wherein the second heat output is at most 90% of the first heat output, the first heat output being at about 50°

C. below the selected temperature.

93. The system of claim 84, wherein the system further comprises a non-ferromagnetic material coupled to the ferromagnetic material, and the non-ferromagnetic material has a higher electrical conductivity than the ferromagnetic material.

94. The system of claim 84, wherein the selected temperature is approximately the Curie temperature of the ferromagnetic material.

95. The system of claim 84, wherein the selected temperature is within 25°

C. of the Curie temperature of the ferromagnetic material.

96. The system of claim 84, wherein the system has a turndown ratio of at least 1.1 to 1.

97. The system of claim 84, wherein at least one of the electrical conductors is elongated and configured such that electrically resistive sections at or near the selected temperature will automatically provide the second heat output.

98. The system of claim 84, wherein at least one of the electrical conductors is elongated and configured to provide heat output along a length of at least a portion of a wellbore.

99. The system of claim 84, wherein at least one of the electrical conductors is at least 10 m in length.

100. The system of claim 84, wherein the system is configured to allow heat to transfer from the heater to a part of a subsurface formation.

101. The system of claim 84, wherein the system is configured to be placed in an opening in a subsurface formation.

102. A method of heating a subsurface formation, comprising:

providing electrical current to a heater comprising an electrical conductor to provide an electrically resistive heat output, wherein the electrical conductor comprises a ferromagnetic material, a conduit at least partially surrounds the heater, and a fluid is located in a space between the heater and the conduit, the fluid having a higher thermal conductivity than air at standard temperature and pressure (STP) (0°

C. and 101.325 kPa); and

allowing heat to transfer from the heater to at least part of the subsurface formation such that the heater provides (a) a first heat output below a selected temperature when time-varying electrical current is applied to the heater, and (b) a second heat output near or above the selected temperature when time-varying electrical current is applied to the heater.

103. The method of claim 102, wherein the electrical conductor at least partially surrounds a non-ferromagnetic material.

104. The method of claim 102, wherein the fluid comprises helium.

105. The method of claim 102, wherein the fluid comprises helium, and wherein the space between the electrical conductor and the conduit comprises at least about 50% by volume helium.

106. The method of claim 102, wherein the fluid comprises helium, and wherein the space between the electrical conductor and the conduit comprises at least about 75% by volume helium.

107. The method of claim 102, wherein the fluid comprises helium, and wherein the space between the electrical conductor and the conduit comprises at least about 90% by volume helium.

108. The method of claim 102, wherein a fluid pressure in the space between the electrical conductor and the conduit is at least about 200 kPa.

109. The method of claim 102, wherein a fluid pressure in the space between the electrical conductor and the conduit is sufficient to inhibit arcing in the space.

110. The method of claim 102, further comprising providing time-varying electrical current to the heater.

111. The method of claim 102, further comprising providing the electrical current from an AC power supply.

112. The method of claim 102, further comprising providing the electrical current from a modulated DC power supply.

113. The method of claim 102, wherein the second heat output is at most 90% of the first heat output, the first heat output being at about 50°

C. below the selected temperature.

114. The method of claim 102, wherein the second heat output is provided without adjusting the amperage of the electrical current applied to the electrical conductor.

115. The method of claim 102, further comprising automatically providing the second heat output.

116. The method of claim 102, further comprising providing heat along a length of a wellbore in the subsurface formation.

117-536. -536. (canceled)