Characterizing North Sea Chalk Using Elastic Full-Waveform Inversion

This technical report presents a comparison between elastic and acoustic full-waveform inversion (FWI) methodologies applied to an ocean-bottom survey in the Buzzard area of the UK North Sea, focusing on high-resolution velocity model building over complex geological settings. The study highlights the limitations of conventional acoustic FWI in accurately modeling subsurface parameters in the presence of strong velocity contrasts, particularly in chalk deposits. The report details how elastic FWI provides a more reliable velocity update, demonstrating improved agreement with well data and reduced discrepancies in reflectivity estimations compared to acoustic methods. The findings indicate that elastic FWI effectively captures the complexities of the chalk geology, yielding a clearer and more accurate representation of subsurface features, including hydrocarbon-bearing sands below the Base Cretaceous Unconformity. The results advocate for the use of elastic FWI in areas where traditional methods struggle due to elastic effects, ultimately enhancing subsurface imaging and modeling accuracy.