Unconstrained 3D Anisotropic CSEM Resistivity Inversion: Industry Benchmark
M.A. Meju, R.V. Miller, S. Shukri, N.K.S. Mansor, J.H.W. Kho and S. Shahar
Event name: 80th EAGE Conference and Exhibition 2018
Publication date: 11 June 2018
Info: Extended abstract, PDF ( 1.11Mb )
Price: € 20
Resistivity anisotropy remains the bane of CSEM exploration and the results of an industry-wide benchmark test of state-of-the-art 3D unconstrained anisotropic CSEM inversion conducted in December 2016-January 2017 supports this contention. The reconstructed VTI models of horizontal and vertical resistivities (?h and ?v) from 4 leading industry service providers have conflicting structures at depth and the resistivities do not match the anisotropic logs from a control well. The reconstructed TTI models of parallel and normal resistivities from a leading industry service provider only matched the ?h well log but not ?v log at the well location. It is practically expedient to reduce structural ambiguity in ?h and ?v models and also achieve structural compatibility with other collocated physical models of the subsurface. Some lessons can be learned from biomedical imaging where it was found that precise structural information is important for the reconstruction of anisotropic resistivities, consistent with the geophysical observation of Brown et al (2012). As a possible way forward, Meju and Fatah (2017) recently proposed the use of the cross-gradient technique to structurally constrain the joint recovery of anisotropic resistivities in geophysical inversion.