Joint VSP-surface Gaussian beam depth migration method and applications

In response to high-resolution imaging in complex geological structures, surface seismic imaging and vertical seismic profile (VSP) imaging mitigate illumination limitations inherent to either method alone, but are still subject to unbalanced image amplitude and structural distortion due to uneven illumination. To address this issue, a joint VSP-surface Gaussian beam depth migration method is proposed. First, a dynamic complementary mechanism is built for the surface and borehole wavefields, where illumination-based weighting factors are applied to balance their respective contributions and integrate their advantages. Second, a structural dip field is introduced to constrain the propagation paths of Gaussian beams, dynamically aligning their initial emission directions to be perpendicular to the local formation dip. Third, a dip-dependent weighting function is employed during the imaging stack to suppress scattering energy from non-geological directions, thereby enhancing the signal-to-noise ratio of the joint VSP-surface image. Applications to both synthetic and field data demonstrate that the joint VSP-surface Gaussian beam depth migration method produces superior images compared to those obtained using surface data alone and improves the imaging accuracy of complex structure.