Method for enhanced subsurface electromagnetic sensitivity
AssigneeElectromagnetic Geoservices Asa
InventorFrank Agnar Maao
Life of this patent
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Abstract
A method for measuring an enhanced electromagnetic field response, especially in a submarine environment, for the purposes of subsurface data acquisition and processing. An electromagnetic field is applied to subterranean strata at two or more different frequencies, a response at each frequency is detected, and the responses at different frequencies are resolved. The differences in the phase and/or amplitude of the responses are analyzed and the nature of the strata is determined. The same method can be used to determine the hydrocarbon content of a reservoir via the use of a borehole.
Claims27
A method of determining a nature of strata beneath a seabed comprising:
- applying an electromagnetic field by a transmitter to the strata at two or more different frequencies;
- detecting by a receiver an electromagnetic field response at each frequency;
- processing the field by resolving the field responses at the different frequencies;
- producing differences by subtracting responses at different frequencies, where the difference between each of the two or more frequencies is in the range 0.005 to 5.0 Hz;
- and
- analyzing these differences in their phase and/or amplitude and thereby deriving the nature of the strata, where the method can be applied to magnetic as well as electric field measurements.
A method of monitoring a reservoir via a borehole comprising:
- applying an electromagnetic field by a transmitter to the reservoir at two or more different frequencies;
- detecting by a receiver an electromagnetic field response at each frequency;
- processing the field by resolving the field responses at the different frequencies;
- producing differences by subtracting responses at different frequencies, where the difference between each of the two or more frequencies is in the range 0.005 to 5.0 Hz;
- and
- analyzing these differences in their phase and/or amplitude and thereby determining the hydrocarbon content of the reservoir, where the method can be applied to magnetic as well as electric field measurements.
Dependencies are inferred from the claim text.