In-line walkaway VSP processing and integration

During July 2002 a large vertical aperture land walkaway data set (154 levels) was acquired simultaneously with<br>3D surface seismic operations. The objectives were to acquire data for 1) calibrated surface seismic processing, 2) high<br>resolution imaging near the borehole and 3) AVO measurements. This paper deals with the computations relevant to<br>integrated surface processing; with model calibration and in-line walkaway data processing for imaging and AVO.<br>Input to surface seismic processing came in several forms: an effective anisotropic velocity model derived from<br>direct times to guide velocity analysis, a calibrated model for ray-based spreading, transmission and Q compensation<br>applied prestack, modeling for optimum mute design and simulations and corridor stacks for borehole match-driven<br>optimized demultiple processing.<br>Walkaway processing includes surface-consistent vector wavefield processing, inverse Q filtering, elastic<br>wavefield separation and deconvolution done in the t-p domain. The Kirchhoff migration uses exact 1D VTI dynamic<br>ray-tracing and includes options for processing-consistent amplitude handling. Our processing sequence for AVO<br>analysis employs common shot separation and deconvolution to avoid mixing in offset.