An efficient 3D wave-equation pre-stack time migration for high-density and wide-azimuth data

Abstract

Abstract The sharp increase in data size of the high-density and wide-azimuth seismic acquisition makes seismic processing routines very challenging. To reduce the turn-around time of pre-stack time migration (PSTM) for large-scale field data (terra to petabyte size), we present an efficient wave-equation PSTM that is an approximate version of the double-square-root (DSR) migration for moderate lateral velocity variation. By converting the DSR dispersion relation into the vertical-time domain and ignoring an offset-dip term, a novel common-offset ray parameter wave-equation PSTM is developed. Meanwhile, the common-offset ray parameter data (i.e. offset plane waves) can be formed by applying the linear Radon transform to the common middle point CMP) gathers. To enhance the signal-to-noise ratio of the conventional Radon transform, we integrate the Radon transform result over azimuth, yielding azimuth-independent offset plane waves that are well suited to irregular sampling and uneven offset distribution. Furthermore, the split-step Fourier method is introduced to extrapolate the wavefield efficiently. Since the pre-stack migration of common-offset ray parameter data is migrated independently, the common image gathers (CIGs) can be generated naturally by sorting the migrated sections by ray parameters. A 3D high-density field data test demonstrates the efficiency and effectiveness of the proposed method, making it very promising for industrial-sized data processing.