Revealing new perspectives from vintage data using cutting-edge seismic imaging: An example from the deep-water Krishna-Godavari Basin, India

Abstract

In this study, we present a novel insight by reprocessing a legacy 3D deep-marine seismic dataset. We leveraged all aspects of the recorded wavefield from the legacy data, extracting valuable information to understand the complex subsurface through a multifaceted approach. We developed an efficient algorithm using direct arrivals and nonlinear refraction tomography to rectify the inherent anomalies in the geometry definition. Time-shift adjusted adaptive subtraction was adopted to optimally suppress multiples from the pre-stack wavefield. Through interpretative velocity analysis, geological layer consistencies were incorporated into the velocity model, which was further refined with reflection tomography and waveform inversion to enhance the resolution of the interval velocity field and improve the image within the complex structures. Local-angle domain wavefield separation migration was used to separately image the diffractions and also improve the continuity of the specular stacks. A novel application of tensor-based structure-oriented filtering attenuated the remnant multiples from the final stack. The final images indicate potential targets for hydrocarbon exploration. Intricate toe-thrust structures were revealed that were completely obscured in the legacy stacks, potentially highlighting an entirely new geological perspective. The study also indicates the presence of possible gas hydrates on fracture-filled host rocks, which strongly correlates with the findings of previous studies. Through this study, we justify the enduring value of the vintage datasets and the necessity of revisiting the same with advanced imaging technologies and optimal computational resources to generate fresh perspectives, unlock new prospects, and maintain sustainable exploration practices.