Integrated velocity and attenuation model building: Sakhalin case study

Abstract

Shallow gas accumulations with varied spatial distribution and scales cause amplitude loss and phase distortion in seismic images in underlying reservoir intervals. We present an integrated velocity and attenuation (defined by the quality factor Q) model-building workflow to address the imaging challenges in a shallow-water data set acquired offshore Sakhalin Island, Russia. As part of the workflow, we use full-waveform inversion (FWI) to capture fine details of the velocity and Q models. We achieve a step change in image quality improvement and amplitude fidelity enhancement by leveraging the workflow. This image enhancement improves subsurface interpretation and influences well placement, subsurface model building, and depletion plan optimization. Key to this success is not only the advanced model-building tool kit, which includes FWI and tomography, but also the optimal integration of the tools specifically tailored for the geologic setting and imaging challenges offshore Sakhalin Island.