Estimating rock physical parameters using anisotropic 3D seismic data to characterize unconventional Vaca Muerta oil shale deposits in the Neuquèn Basin, western Argentina

Abstract

Summary Acquisition and processing of wide azimuth large offset and high fold (WA/LO/HF) 3D seismic data in the Aguada Federal concession is presented. Preserved amplitude/azimuthal workflows (e.g. anisotropy analysis, pre-stack elastic inversion, reservoir characterization) facilitate the quantitative interpretation. Layering, fracture distribution and stress cause measurable velocity anisotropy. Well ties and residual normal move-out help to determine the anisotropy parameters (η, e and δ). Non-hyperbolic 4th-order move-out improves flattening of gather reflections. Sinusoidal residual move-out on common-offset, common-azimuth gathers is diagnostic for HTI anisotropy. Azimuthal Residual Move-out (ARMO) on gathers improves the seismic quality. Anisotropic 3D tomographic raytracing and velocity model building increase the depth imaging efficiency. The new processing better focuses the seismic reflections and boosts higher frequencies. The migration repositions the energy in depth and the mismatch of geologic markers at the well locations is reduced. Higher fidelity datasets are better suited for seismic inversion, reservoir characterization and fracture prediction. The anisotropic workflow serves to estimate Vp, Vs, density, total organic contents, Young’s modulus E and pore pressure. Delineation of Vaca Muerta sweet spots is thus made possible. Seismic anisotropy analysis allows optimization of the well landing point, selection of well spacing and a preferred trajectory orientation.