Improving the 4D Signal Inside the SOA at Eldfisk Using RTM Pseudo-Offset Gathers
Leila Bencherif-Soerensen, Z. Li, K. McCluskey, A. Ratcliffe · 2023
Summary Seismically obscured areas are observed in the P-wave imaging of ocean bottom node data acquired over the Eldfisk area of the Norwegian North Sea. These are mainly caused by gas chimneys that overlie the anticlinal structures of the reservoir. Due to its ability to better handle complex velocity models, reverse time migration (RTM) produces better structural imaging of these obscured areas than Kirchhoff pre-stack depth migration. Further, RTM can be modified to output ‘pseudo-offset-gathers’ that offer a post-imaging domain for subsequent processing before final stacking. This work presents a time-lapse imaging case study using a recent, state-of-the-art, velocity model build, involving complex velocity, anisotropy and attenuation updates, and applies the ‘pseudo-offset-gather-based’ RTM concept to two vintages of Eldfisk data. The results show an improved 3D image and 4D response from the final stack of the RTM ‘pseudo-offset-gather-based’ data, both in structural aspects and signal-to-noise, compared to an equivalent Kirchhoff or ‘stack-based’ RTM product.