Anisotropic Wide Azimuth 3D Seismic Data for an Unconventional Shale Oil Project, Aguada Federal Block, Argentina

Seismic acquisition and processing is presented of a 3D dataset across the unconventional Vaca Muerta play in the Neuquén basin (Aguada Federal block, Argentina). More accurate depth imaging is made possible by adopting a Wide Azimuth, Large Offset and High Fold (WA/LO/HF) lay-out. Preserved amplitude and azimuth workflows were implemented that allow later quantitative seismic interpretation (anisotropy analysis, pre-stack elastic inversion and reservoir characterization).

Velocities anisotropy is related to layering, fracture distribution and the local stress pattern. The well ties and residual NMO hockey stick effect help to determine parameters like eta, epsilon and delta. Non-hyperbolic fourth order term polynomial moveout was applied for better flattening of reflections on the seismic gathers. A sinusoidal residual moveout on common offset, common azimuth gathers is diagnostic for a HTI anisotropy effect. The corrected gathers are used to estimate azimuthal anisotropy attributes.

Accurate anisotropic tomographic raytracing and velocity model building improves the depth imaging by better focusing reflections and boosting the higher frequencies. The migration repositions the energy in depth more effectively. Another advantage is that the mismatch of geologic markers at the well locations is improved. The higher fidelity dataset is better adjusted for seismic inversion, reservoir characterization and fracture prediction.