Dual coil for electromagnetic sounding of layered earth
First Claim
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1. A device for measuring subsurface electrical conductivity, the device comprising:
- a first sensor coil having a first effective area and a first bandwidth;
a second sensor coil having a second effective area smaller than the first effective area and a second bandwidth greater than the first bandwidth;
wherein the second sensor coil is coupled to the first sensor coil at a position having an amount of overlap with the first coil and at a position where mutual inductance between the first and second sensor coils is substantially zero; and
further comprising a transmitter coil for generating a primary field, wherein the first sensor coil and the second sensor coil are configured to measure a resulting secondary field generated by a subsurface.
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Abstract
Methods and systems for measuring subsurface electrical conductivity, using first and second sensor coils. The second sensor coil has a smaller effective area and a greater bandwidth than the first sensor coil. The first and second sensor coils are positioned with respect to each other to achieve zero or near zero mutual inductance.
6 Citations
19 Claims
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1. A device for measuring subsurface electrical conductivity, the device comprising:
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a first sensor coil having a first effective area and a first bandwidth; a second sensor coil having a second effective area smaller than the first effective area and a second bandwidth greater than the first bandwidth; wherein the second sensor coil is coupled to the first sensor coil at a position having an amount of overlap with the first coil and at a position where mutual inductance between the first and second sensor coils is substantially zero; and further comprising a transmitter coil for generating a primary field, wherein the first sensor coil and the second sensor coil are configured to measure a resulting secondary field generated by a subsurface. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A device for measuring subsurface electrical conductivity, the device comprising:
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a first sensor coil having a first effective area and a first bandwidth; a second sensor coil having a second effective area smaller than the first effective area and a second bandwidth greater than the first bandwidth; wherein the second sensor coil is coupled to the first sensor coil at a position having an amount of overlap with the first coil and at a position where mutual inductance between the first and second sensor coils is substantially zero; wherein the second sensor coil is moveably coupled to the first sensor coil for adjusting the amount of overlap between the first and second coils; and wherein the second sensor coil is moveable from a storage configuration of the device where the device has a reduced footprint and the mutual inductance between the first and second sensor coils is substantially non-zero, to an operating configuration of the device where the mutual inductance between the first and second coils is substantially zero.
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8. A device for measuring subsurface electrical conductivity, the device comprising:
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a first sensor coil having a first effective area and a first bandwidth; a second sensor coil having a second effective area smaller than the first effective area and a second bandwidth greater than the first bandwidth; wherein the second sensor coil is coupled to the first sensor coil at a position having an amount of overlap with the first coil and at a position where mutual inductance between the first and second sensor coils is substantially zero; wherein the second sensor coil is moveably coupled to the first sensor coil for adjusting the amount of overlap between the first and second sensor coils; wherein the second sensor coil is slideably moveable relative to the first sensor coil; and wherein a common longitudinal axis is shared by the first and second sensor coils, the longitudinal axis passing through respective centers of the first and second sensor coils, and wherein the second sensor coil is moveable along the common longitudinal axis.
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9. A method of measuring subsurface electrical conductivity of a target site, the method comprising:
positioning a first sensor coil to measure electrical conductivity of the target site, the first sensor coil having a first effective area and a first bandwidth;
positioning a second sensor coil to measure electrical conductivity of the target site, the second sensor coil having a second effective area smaller than the first effective area and a second bandwidth greater than the first bandwidth;
the first and second sensor coils being positioned with respect to each other to reduce mutual inductance between the first and second sensor coils to substantially zero;
while keeping both the first and second sensor coils in position, obtaining measurements of electrical conductivity from the first and second sensor coils, wherein one of the first and second sensor coils is firstly positioned and the other of the first and second sensor coils is secondly positioned, the secondly positioning comprising adjusting overlap between the first and second sensor coils to achieve substantially zero mutual inductance.- View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of measuring subsurface electrical conductivity of a target site, the method comprising:
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positioning a first sensor coil to measure electrical conductivity of the target site, the first sensor coil having a first effective area and a first bandwidth; positioning a second sensor coil to measure electrical conductivity of the target site, the second sensor coil having a second effective area smaller than the first effective area and a second bandwidth greater than the first bandwidth; the first and second sensor coils being positioned with respect to each other to reduce mutual inductance between the first and second sensor coils to substantially zero; while keeping both the first and second sensor coils in position, obtaining measurements of electrical conductivity from the first and second sensor coils, wherein the first and second coils are positioned to share a common longitudinal axis passing through respective centers of the first and second coils.
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Specification