The anisotropy of thin sand and shale laminations in a turbidite deposition complicates the analysis of such formations. Existing interpretation methods, such as low-resistivity-pay workflows or dominant rock typing based on a Thomas-Stieber diagram, can lead to errors in the calculation of storage and flow properties due to a complex mix of minerals, fluids and/or geology and deposition. To overcome these challenges, a multi- physics inversion-based interpretation of well logs sensitive to anisotropy and the distinct characteristics of the shales and sands is introduced; namely, tensor (triaxial) induction resistivities and nuclear magnetic resonance (NMR) are used to estimate storage and flow properties of these anisotropic formations. Firstly, well logs are used to estimate the anisotropy magnitude, i.e., volume of laminar shale, resistivity, and NMR transverse-relaxation time (𝑇2) corrected for thin shale-lamination effects. Secondly, the petrophysical properties of the sand laminae are calculated including lithology-independent NMR porosity, water saturation and permeability. Finally, the total-rock petrophysical properties are calculated using the volumetric relationships obtained from existing effective medium theories. The calculated petrophysical properties are then benchmarked against core porosity, water-saturation and permeability measurements and compared with standard interpretation methods to evaluate the improvement in the storage and flow-property estimations.
Eghbali et al. (Sat,) studied this question.