Borehole-to-Surface Resistivity Mapping via EM Coupling
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Solution Overview
Problem
Current borehole-to-surface electromagnetic (BSEM) surveys face challenges with accurate geolocation, alignment, and interference issues, leading to measurement errors and increased installation time, particularly when dealing with deeper subsurface formations and safety concerns related to operating a borehole source.
Innovation Solution
Deploying an electromagnetic source in a borehole and an array of surface electric field sensors aligned radially, measuring electromagnetic fields at two depths and synthesizing radial and tangential components to correct for measurement errors and reduce interference, allowing for improved resistivity mapping with reduced power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional BSEM surveys use 1000 or more measurement points with buried electrodes, then measurement coverage and data quality improve, but installation time and geolocation accuracy requirements increase significantly
Solution Approach 1:
The patent replaces the mechanical burial system with an electromagnetic coupling system. Surface electrodes measure vertical electric field components through electromagnetic induction rather than direct physical contact, eliminating the need for digging holes and burying electrodes at each measurement point. This substitution dramatically reduces installation time while maintaining measurement precision through the electromagnetic field relationship described in the patent.
2Length of stationary object
If borehole source operations are conducted at greater depths, then subsurface imaging depth improves, but safety risks and operational complexity increase
Solution Approach 1:
The patent introduces surface electrodes as an intermediary measurement system that couples to the borehole source through electromagnetic fields. This intermediary approach allows the borehole source to operate at greater depths for improved imaging coverage while surface measurements are taken safely without requiring personnel or equipment in hazardous deep borehole environments, thus maintaining reliability while extending imaging depth.
3Loss of time
If surface electrodes are used instead of buried electrodes, then installation time reduces, but measurement accuracy may be affected by surface conditions
Solution Approach 1:
The patent changes the measurement parameter from direct contact potential difference (requiring buried electrodes) to vertical electric field component measurement through electromagnetic coupling. By measuring the vertical component Ez at the surface through the relationship described in the patent, the system achieves accurate resistivity mapping without the need for buried electrodes, thus reducing installation time while maintaining precision through the electromagnetic field relationship.
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 enables faster and more accurate installation of sensor arrays, reduces cultural noise interference, and lowers safety risks associated with borehole operations, enhancing the depth and resolution of subsurface resistivity mapping while minimizing setup time and costs.
Implementation Method 1
an electromagnetic source is deployed in a borehole... An electromagnetic field is transmitted from the source... the transmitted electromagnetic fields from the source... are measured with the deployed electromagnetic field sensors
Data Source
AI summary
Resistivity in subsurface earth at locations kilometers away from wells in the reservoirs is mapped and monitored. An electromagnetic source with an electrode is deployed a borehole in the reservoir, and a group of sensors at counter electrodes is deployed at a number of other locations radially spaced at some distance from the well. The source transmits a current which flows to the counter electrodes causing an electromagnetic field which is sensed at the sensors. The source is activated at different depths in the well and ratios of the electromagnetic field sensed with the source at different depths used to obtain data to map the resistivity. The sensors are capable of sensing electromagnetic fields along two orthogonal axes, and the measurements at a sensor along these axes used to reduce undesirable effects of noise and other factors on the data measurements.