Azimuthal Pre-Stack 4D Time-Shift-Analysis: North Sea Case Study

Our new work expands the pre-stack 4D analysis workflows by Hatab and MacBeth (2023) taking the angle/offset dependency in 4D analysis to angle/offset and azimuth dependencies into account. This involves estimating and applying the 4D time-shift corrections directly in the pre-stack domain, enabling the generation of all 4D attributes in the pre-stack domain followed by stacking the results to obtain the 4D signature. This method facilitates the computation of ellipticity as a function of mean azimuth in each sector, offering insight into the anisotropy of the 4D attributes. We demonstrate the impact of this approach on a North Sea PRM dataset, our study emphasizes variable contributions from individual azimuth sectors and highlights the need for azimuthal analysis to address potential smearing when working in the post-stack domain. The results reveal that the variation in time shift with offset is less pronounced than with azimuth. Both isotropic and anisotropic behaviour is observed in the 4D attributes by fitting the azimuthal dependency to an ellipse. For this field, the gas cloud presents a significant challenge for this technique, requiring careful assessment of the results in those regions.