Electromagnetic surveying
First Claim
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1. A method of determining the nature of a subterranean stratum which comprises the steps:
- deploying an electric dipole transmitter antenna;
applying an electromagnetic (EM) field to the stratum using the transmitter;
measuring the current and voltage at the transmitter antenna terminals during the EM transmission;
calculating the input impedance of the transmitter antenna from the measured current and voltage;
using changes in the impedance to calculate the resistivity of the stratum; and
determining the nature of the stratum from the resistivity.
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Abstract
A method of determining the nature of subterranean strata. The transmitter antenna is towed by vessel at a distance h above the sea floor. The antenna omits a wave field whose strength is proportional to the current delivered to the antenna and this is monitored. The input voltage to the antenna is also measured and changes in antenna impedance are calculated. Changes in antenna impedance are used together with seismic information to determine the nature of the subsea strata.
238 Citations
14 Claims
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1. A method of determining the nature of a subterranean stratum which comprises the steps:
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deploying an electric dipole transmitter antenna; applying an electromagnetic (EM) field to the stratum using the transmitter; measuring the current and voltage at the transmitter antenna terminals during the EM transmission; calculating the input impedance of the transmitter antenna from the measured current and voltage; using changes in the impedance to calculate the resistivity of the stratum; and determining the nature of the stratum from the resistivity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification