CSEM Survey Data Analysis Using Seismic Structural Constraints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Controlled-source electromagnetic (CSEM) survey techniques provide poor spatial resolution for subterranean resistivity profiles, making it difficult to accurately distinguish between hydrocarbon and aqueous pore fluids, especially when they have similar mechanical properties, and existing methods to improve resolution are not reliably solvable or confidence-measurable.
Innovation Solution
A method involving the analysis of CSEM data to generate probability density functions (PDFs) for electromagnetic parameters, using structural information from seismic surveying to enhance spatial resolution, iteratively refining these PDFs based on acceptance criteria to provide both parameter estimates and error estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CSEM survey techniques are used to determine subterranean resistivity profiles, then information on reservoir content can be obtained, but spatial resolution is poor making it difficult to accurately distinguish between hydrocarbon and aqueous pore fluids
Solution Approach 1:
The patent combines CSEM survey data with seismic survey data to create an integrated analysis approach. By merging the electromagnetic resistivity information from CSEM with the structural and spatial resolution information from seismic surveys, the method achieves both accurate reservoir content identification and high spatial resolution that neither technique could achieve alone.
Solution Approach 2:
The patent uses seismic survey data as an intermediary to enhance the CSEM results. The seismic data provides structural framework and spatial context that acts as a mediator to interpret the CSEM resistivity measurements, enabling accurate differentiation of pore fluid contents while maintaining high spatial resolution.
2Measurement precision
If CSEM techniques are used, then estimates of electric resistivity can be provided, but the results have relatively poor spatial resolution compared to seismic techniques
Solution Approach 1:
The patent merges CSEM resistivity measurements with seismic structural data to produce integrated subsurface models. This combination allows the preservation of accurate resistivity estimates from CSEM while achieving the high spatial resolution characteristic of seismic techniques, thereby resolving both reliability and precision requirements simultaneously.
3Measurement precision
If structural information from seismic surveying is integrated with CSEM data, then spatial resolution is enhanced, but the complexity of data analysis increases
Solution Approach 1:
The patent performs preliminary processing and interpretation of both CSEM and seismic data separately before integration. By preparing the datasets in advance with preliminary models and interpretations, the actual integration process becomes more manageable and less complex, as the data are pre-organized and pre-analyzed.
Solution Approach 2:
The patent divides the integrated analysis into distinct segments: seismic data processing, CSEM data processing, and integration/interpretation phases. This segmentation allows each dataset to be analyzed using optimized methods before combining them, reducing the overall analytical complexity compared to attempting simultaneous integrated processing.
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 enhances the spatial resolution of CSEM data to match the resolution of structural information, providing statistically derived estimates with confidence measures, improving the interpretation of subterranean resistivity profiles and aiding in hydrocarbon reservoir identification.
Implementation Method 1
CSEM techniques involve transmitting an EM signal into the seafloor, generally using a horizontal electric dipole (HED) source (transmitter), and measuring the response at EM receivers (detectors)
Implementation Method 2
the presence of relatively more conductive structures in the subterranean strata will, in general, lead to weaker EM fields seen at the detector. This is because of the increased attenuation of fields in the conductive structure
Data Source
AI summary
A method of analyzing controlled source electromagnetic (CSEM) survey data to determine probability density functions (PDFs) for values of an electromagnetic parameter at locations in a subterranean region of interest is provided. Structural features in the subterranean strata are identified, e.g. from seismic survey data. An initial PDF for values of the electromagnetic parameter is then assigned to each feature. Models specifying values for the parameter in each structural feature are generated by sampling the PDFs. A subset of the models are deemed acceptable based on an acceptance criterion. The PDF for each feature is modified based on values for the parameter in the subset of accepted models to generate replacement PDFs for each feature. The process may be iterated a number of times to generate final PDFs for values of the electromagnetic parameter in the structural features identified in the subterranean region of interest.