Fourier finite-difference migration of prismatic waves for steeply dipping structure imaging with dip-guided amplitude-matched fusion

Abstract Accurate imaging of steeply dipping structures is critical for hydrocarbon reservoir identification and fault characterization in complex regions. However, conventional imaging methods based on primary reflections often fail to resolve near-vertical and overturned interfaces due to limited acquisition aperture and survey geometry. To address this limitation, we propose a dip-guided amplitude-matched fusion Fourier finite-difference (FFD) migration method for prismatic waves (PFFD). The method exploits prismatic waves, which can be observed in seismic data acquired over complex structures, especially near steep or near-vertical interfaces, and can provide complementary information for imaging steep structures. The method uses conventional migration results as the reflectivity model and constructs prismatic-wave propagation paths using an FFD operator. The flexible extrapolation range reduces computational cost. In addition, accurate separation of upgoing and downgoing wavefields suppresses non-target propagation paths. To mitigate imaging artifacts and amplitude distortion, we employ omnidirectional plane-wave destruction (OPWD) to extract dip attributes. These attributes, combined with prior spatial constraints, then guide region selection and main-lobe root-mean-square (RMS) amplitude matching for image fusion. Numerical results demonstrate that the proposed method significantly improves steep-structure imaging. It compensates for the limitations of one-way wave-equation migration (OWEM) at large dips and outperforms prismatic-wave reverse time migration (PRTM) in poorly illuminated steep-dip regions.