Increasing Reflection Coherency Through Improved Statics Corrections: An Iterative Tomographic Approach

Abstract

Computation and application of statics corrections have always been problematic on CMP reflection data, especially in highly weathered and structurally altered environments. Tomographic estimation of the velocity field within the weathered layer is a severely underdetermined problem, only to be exacerbated by the lack of a priori information of most survey sites. Statistically driven static techniques are sometimes considered implausible for specific subsurface conditions where compensating for severe static problems is necessary. Using turning-ray tomography to make static corrections (tomostatics) and iteratively developing the best tomographic model based on site-specific reflection arrivals will ultimately optimize the static correction for each source and receiver station. Cross-correlation statics routines that monitored changes in specific near-surface reflections during iterative application of tomostatics guided the selection of the best initial model. Combining statistical techniques with geologically based models of the subsurface increased the overall reflection coherency and accuracy of the final stacked section.