Subsurface Electromagnetic Mapping via Resistivity Scenario Evaluation
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Solution Overview
Problem
Current electromagnetic subsurface mapping techniques, such as CSEM surveying, provide low resolution images that obscure individual subsurface features and structures, making it difficult to accurately identify hydrocarbon reservoirs and other geological formations due to the large and indeterminate nature of resistivity clouds.
Innovation Solution
The system generates and evaluates resistivity scenarios using additional data sources like seismic and well data to refine the resistivity images, allowing for the identification of features near or below the resolution of electromagnetic data, thereby enhancing the geologic reasonableness and accuracy of subsurface mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If CSEM surveying uses low frequency electromagnetic waves to survey large subsurface areas, then large area coverage is achieved, but resolution of subsurface features deteriorates to approximately one hundred meters
Solution Approach 1:
The patent segments the subsurface area into multiple survey lines and uses multiple electromagnetic transducers positioned at different locations along each line. This allows the large area to be covered through systematic division into manageable survey segments, maintaining resolution by ensuring adequate sampling density within each segment while achieving broad coverage through the combination of multiple segments.
Solution Approach 2:
The patent transitions from traditional 2D CSEM surveying to 3D electromagnetic surveying by deploying transducers in three-dimensional space with multiple depths and horizontal positions. This dimensional expansion allows simultaneous coverage of large areas while maintaining high resolution through volumetric sampling of the subsurface.
2Area of stationary object
If electromagnetic transducers are used to collect data at multiple locations, then area coverage increases, but data processing complexity increases
Solution Approach 1:
The patent implements iterative inversion processes where initial models are refined based on misfit calculations between observed and predicted electromagnetic data. The system uses feedback loops to adjust model parameters, evaluate goodness-of-fit metrics, and progressively improve the subsurface model until convergence criteria are met, systematically managing the complexity of processing data from multiple transducer locations.
3Measurement precision
If multiple electromagnetic transducers are deployed to improve resolution, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent divides the transducer array into multiple independent modules or groups, each capable of operating semi-autonomously. This segmentation reduces the complexity of controlling and managing a large number of transducers by breaking them into manageable units, while still achieving high resolution through the combined data from all segments.
Solution Approach 2:
The patent employs a sufficient number of transducers to achieve the required resolution threshold rather than deploying maximum possible transducers. By determining the minimum adequate sampling density needed for the target resolution, the system avoids unnecessary complexity while maintaining measurement precision through optimized transducer spacing and positioning.
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 provides more detailed and accurate subsurface mapping by resolving the ambiguity of resistivity clouds, enabling better characterization of hydrocarbon reservoirs and other geological features, improving the understanding of subsurface structures not previously possible with existing methods.
Implementation Method 1
an electromagnetic source, typically producing electromagnetic waves in the 0.01 Hz to 1 Hz range, introduces electromagnetic energy into the subsurface and multiple electromagnetic transducers collect electromagnetic energy that is reflected and/or refracted by subsurface structure, features, etc.
Implementation Method 2
CSEM surveying exploits the differences in resistivity of various subsurface media (e.g., rock formations, shale, sand, briny water, hydrocarbons, etc.) for providing subsurface mapping
Data Source
AI summary
Systems and methods which provide electromagnetic subsurface mapping to derive information with respect to subsurface features whose sizes are near to or below the resolution of electromagnetic data characterizing the subsurface are shown. Embodiments operate to identify a region of interest (203) in a resistivity image generated (202) using electromagnetic data (201). One or more scenarios may be identified for the areas of interest, wherein the various scenarios comprise representations of features whose sizes are near to or below the resolution of the electromagnetic data (204). According to embodiments, the scenarios are evaluated (205), such as using forward or inverse modeling, to determine each scenarios' fit to the available data and further to determine their geologic reasonableness (206). Resulting scenarios may be utilized in a number of ways, such as to be substituted in a resistivity image for a corresponding region of anomalous resistivity for enhancing the resistivity image (207).