Virtual Source Array for Subsurface Imaging
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Solution Overview
Problem
Existing controlled-source electromagnetic survey methods face challenges such as unfocused subsurface excitation, long electrode wire lengths, operational difficulties, and limited sensitivity to vertical features, which hinder effective imaging of subsurface formations, especially in complex geological backgrounds and stacked reservoirs.
Innovation Solution
A method using short dipole sources to simulate the signal of a concentric ring or radial bipole source array, reducing electrode wire length and enhancing spatial resolution by varying source configurations and integrating receiver data with Green's function techniques, allowing for imaging of subsurface resistivity and anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If concentric electrode rings are used to focus electromagnetic energy on subsurface targets, then imaging precision is improved, but electrode wire length increases dramatically
Solution Approach 1:
The patent uses a small number of physical dipole sources to create virtual concentric ring sources through mathematical modeling and signal processing. Instead of physically constructing the full concentric electrode rings, the system copies the electromagnetic response that would be produced by such rings using simplified dipole sources positioned at strategic locations, thereby achieving the same imaging precision with dramatically reduced wire length.
Solution Approach 2:
The patent segments the complex concentric ring source array into a smaller number of discrete dipole sources. By dividing the functional requirements of the full ring array into contributions from individual dipoles and using superposition principles, the system achieves equivalent imaging performance with fewer physical components and reduced material requirements.
2Measurement precision
If concentric electrode rings are deployed to achieve focused subsurface excitation, then imaging precision is improved, but operational difficulty increases
Solution Approach 1:
The patent replaces the complex operational requirements of deploying and positioning long concentric electrode rings with a simplified setup using few dipole sources. The virtual ring array is copied through computational methods rather than physical deployment, eliminating difficulties in wire handling, positioning accuracy, and ensuring uniform grounding along extensive wire lengths.
3Length of stationary object
If radial bipole sources are used to reduce electrode wire length, then wire requirements are reduced, but sensitivity to vertical features is limited
Solution Approach 1:
The patent assigns different orientations and positions to individual dipole sources in the virtual array, with each dipole contributing differently to the overall electromagnetic field. By varying the local characteristics of each source element and using appropriate weighting in the superposition, the system achieves both reduced wire length and enhanced sensitivity to vertical subsurface features.
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
This approach significantly reduces electrode wire requirements, improves spatial resolution, and enables accurate characterization of subsurface resistivity over a broader range of depths, including detection of reservoir resistivity anisotropy, while minimizing operational challenges and amplifier saturation effects.
Implementation Method 1
A first dipole source located at a first source excitation location corresponding to a first bipole source is activated, and an electromagnetic signal recorded
Implementation Method 2
the diffusive nature of low frequency electromagnetic wave propagation in the earth
Data Source
AI summary
This invention relates generally to a method of simulating the signal of an electromagnetic source using one or more dipole sources. In the method a dipole source is located at an excitation location corresponding to a segment of the electromagnetic source to be simulated. The dipole source is activated, and an electromagnetic signal recorded at one or more receiver locations. This process is repeated for additional excitation locations corresponding to additional segments of the electromagnetic source. The data from the sequence of dipole source excitation locations is processed to determine the simulated signal of the electromagnetic source.