A Methodology of Shot Point Regularization and Trace Interpolation in 3DVSP

Due to limitations of surface conditions and/or acquisition budgets, shot points are often irregular and/or spatially under-sampled in many 3DVSP surveys. The irregularity and insufficiency of shot points in can considerably degrade the imaging quality of VSP data, resulting in, for example, the presence of acquisition footprints, lower resolution, and smaller imaging coverage. Most regularization/interpolation methods developed for surface seismic data are not applicable to the 3DVSP data. This is due to that VSP survey has (1) a vertically fixed and limited number of borehole receivers, and (2) complex wavefields containing downgoing and upgoing wave modes. This paper describes a new methodology to perform shot point regularization and trace interpolation for 3DVSP data. Our methodology consists of four steps: (1) separating VSP data into upgoing reflection wavefield; (2) performing anisotropic VSP NMO correction to align the upgoing refection events over different offsets; (3) regularizing shot points by cubic trace interpolation from the NMO corrected reflection wavefield; and (4) reversing NMO correction to regularized and interpolated traces for a final VSP image. We use a 3DVSP dataset with a highly irregular shot point pattern demonstrates that the imaging quality has been significantly improved after the shot point regularization and trace interpolation.