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Structurally-Constrained 3D Anisotropic CSEM Resistivity Inversion with Crossgradient Criterion: Proof-Of-Concept Study
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
Summary
Conventional anisotropic 3D CSEM inversion faces major challenges. The typically reconstructed ?h and ?v models often have conflicting depth structures that are difficult to explain in terms of subsurface geology. In integrated hydrocarbon exploration it is highly desirable to reduce ambiguity or subjectivity in depth interpretation of ?h and ?v models and also achieve comparability with other coincidentally-located subsurface models. Geological intuition suggests that the level and form of anisotropy would vary from one rock unit to another but a given 3D reservoir or anomalous rock mass would have the same boundary for ?h and ?v. This geological condition is met by incorporating an objective cross-gradient constraint in the formulation of the 3D anisotropic inverse problem implemented here in a nonlinear conjugate gradients algorithm. Using CSEM data from a fold-thrust setting, we demonstrate that it yields models that have a common depth structure and hence reduced ambiguity in geological interpretation. The use of a priori information and structural constraints to resolve interpretational non-uniqueness differentiates our approach from the more conventional regularized 3D electromagnetic inversion approaches. The structural-coupling procedure described here can also be applied to the inversion of land CSEM survey data or other tensor property measurements.
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