Marine Electromagnetic Sensor Cable for Subsurface Electrical Property Measurement
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Solution Overview
Problem
Current marine electromagnetic geophysical surveying techniques, particularly frequency domain controlled source electromagnetic (f-CSEM) surveys, face limitations in accurately inferring subsurface Earth structure and electrical properties due to restricted data acquisition methods and interference from natural electromagnetic sources.
Innovation Solution
A marine electromagnetic sensor cable with sensor modules equipped with magnetic field sensors and electrodes arranged in a closed pattern to measure electric and magnetic fields, allowing for improved data acquisition and processing of transient controlled source electromagnetic responses, enabling the determination of magnetotelluric responses and electric field components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency domain controlled source electromagnetic (f-CSEM) surveying is used to measure subsurface electrical properties, then hydrocarbon reservoir detection capability is improved, but interference from natural electromagnetic sources reduces measurement precision
Solution Approach 1:
The patent extracts and removes the harmful natural electromagnetic source signals from the total electromagnetic field measurements by separating the controlled source response from the natural source background, thereby improving measurement precision of subsurface electrical properties
Solution Approach 2:
The patent uses an intermediary approach by introducing a marine electromagnetic sensor cable system that measures both controlled source and natural source electromagnetic fields, allowing the controlled source response to be isolated and extracted from the combined measurements
2Measurement precision
If autonomous recording stations are used for natural source electromagnetics, then measurement capability is improved, but device complexity and operational limitations increase
Solution Approach 1:
The patent merges natural source electromagnetic measurements with controlled source electromagnetic measurements into a single integrated marine sensor cable system, eliminating the need for separate autonomous recording stations and reducing overall system complexity
Solution Approach 2:
The marine electromagnetic sensor cable serves multiple functions by simultaneously measuring both natural source and controlled source electromagnetic fields, as well as providing subsurface electrical property characterization, thereby replacing multiple specialized systems
3Measurement precision
If comprehensive electromagnetic data acquisition is implemented using the marine sensor cable, then subsurface structure inference accuracy is improved, but data processing complexity increases
Solution Approach 1:
The patent segments the electromagnetic data acquisition into distinct components (controlled source response, natural source background, electric field measurements, magnetic field measurements) that can be processed and analyzed separately, thereby managing data processing complexity while maintaining inference accuracy
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the accuracy and efficiency of subsurface exploration by providing comprehensive electromagnetic data, allowing for better inference of subsurface structures and electrical properties, and reduces interference from natural sources, thereby improving hydrocarbon reservoir detection and mapping.
Implementation Method 1
imparting an electric field or a magnetic field into the Earth formations... The electric and/or magnetic fields are induced in response to the electric field and/or magnetic field imparted into the Earth's subsurface
Implementation Method 2
measuring electric field amplitude and/or amplitude of magnetic fields by measuring voltage differences induced in electrodes
Implementation Method 3
measuring voltage differences induced in electrodes, antennas and/or interrogating magnetometers
Data Source
AI summary
A method for measuring magnetotelluric response of the Earth includes measuring transient controlled source electromagnetic response of the subsurface below a body of water over a plurality of actuations of an electromagnetic transmitter. The transient response measurements are stacked. The stacked transient responses are subtracted from measurements of total electromagnetic Earth response over a time period including the plurality of transient response measurements to generate the magnetotelluric response.