Reconnaissance Processing to Understand Potential Value of Converted Waves - Experiences from Culzean

The focus of many ocean bottom seismic surveys is improved P-wave imaging using the hydrophone and vertical components. The horizontal components also record potentially valuable converted wave (C-wave) arrivals. The sensitivity of C-waves can provide insights into the rock properties and stress environment of not only the reservoir but also the overburden. C-wave processing projects often take significant time and sometimes produce disappointing results. We share our experiences conducting rapid reconnaissance processing to assess the potential value and challenges of conducting C-wave processing to constrain the geomechanical model of the HPHT Culzean Discovery. The geologic environment is conducive to obtaining high quality C-wave results although is more challenging beneath the top chalk. The full azimuth sampling available from the high density ocean bottom cable survey facilitates velocity analysis, assessment of shear wave splitting and illumination near a salt dome adjacent to the field. The shear wave splitting fast azimuth variations found in the shallowest layers are similar to the principle horizontal stress directions predicted from geomechanical modelling. Such evaluations can be conducted quickly and in parallel to fast track P-wave processing to allow early and more informed decisions about including the horizontal component data in the full production processing flow.