Methods and apparatus for adaptive source electromagnetic surveying
AssigneePGS Geophysical AS
InventorsDougal Kennedy, Mattias Sudow, Robert Juhasz
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Abstract
Disclosed are methods and apparatus for adaptive source electromagnetic (EM) surveying. In accordance with one embodiment, a source waveform signal is generated, and an outgoing EM signal which is based on the source waveform signal is transmitted using an antenna. A responsive electromagnetic signal is detected using at least one electromagnetic sensor, and a receiver waveform signal based on the responsive electromagnetic signal is obtained. A feedback control signal which depends on at least one input signal is determined. Based on the feedback control signal, the source waveform signal is adapted. Other embodiments, aspects, and features are also disclosed.
Claims21
A method for electromagnetic surveying of a subsurface formation, the method comprising:
- generating a source waveform signal;
- transmitting an outgoing electromagnetic signal which is based on the source waveform signal;
- detecting, using at least one electromagnetic sensor, a responsive electromagnetic signal;
- obtaining a receiver waveform signal which is based on the responsive electromagnetic signal;
- determining a feedback control signal which depends on at least one input signal, wherein the at least one input signal comprises the receiver waveform signal;
- and
- adapting the source waveform signal based on the feedback control signal,
- wherein determining the feedback control signal comprises:
- determining an Earth's frequency response signal by deconvolving the receiver waveform signal with the source waveform signal;
- and
- determining a frequency shift of the Earth's frequency response signal.
An apparatus configured for electromagnetic surveying of a subsurface formation, the apparatus comprising:
- a transmitter configured to transmit an outgoing electromagnetic signal based on a source waveform signal;
- a receiver configured to detect a responsive electromagnetic signal so as to obtain a receiver waveform signal;
- a feedback controller configured to determine a feedback control signal based on at least one input signal,
- wherein the transmitter is further configured to adapt the source waveform signal using the feedback control signal;
- and
- an adjustable source generator in the transmitter, the adjustable source generator being configured to adjust generation of the source waveform signal based on the feedback control signal and generate a broadband signal having at least one pronounced frequency peak.
An apparatus configured for electromagnetic surveying of a subsurface formation, the apparatus comprising:
- a transmitter configured to transmit an outgoing electromagnetic signal based on a source waveform signal;
- a receiver configured to detect a responsive electromagnetic signal so as to obtain a receiver waveform signal;
- and
- a feedback controller configured to determine a feedback control signal based on at least one input signal,
- wherein the transmitter is further configured to adapt the source waveform signal using the feedback control signal, and
- wherein the feedback controller is further configured to determine an Earth's frequency response signal by deconvolution of the receiver waveform signal with the source waveform signal and to find a frequency shift of the receiver waveform signal by measuring a frequency shift of an amplitude minimum in a frequency-amplitude spectrum of the Earth's frequency response signal.
Dependencies are inferred from the claim text.