Evaluating Ocean-bottom Seismic Acquisition in the North Sea - A Phased Survey Design Case Study

Abstract

Ocean-bottom seismic (OBS) is experiencing a resurgence of popularity in the North Sea. This is due in part to recent advances in acquisition equipment and operational efficiency as well as advances in geometry design and processing algorithms. Using two recent case examples, we review the key stages of the evaluation process and share the derived conclusions. The primary goal of these studies was to investigate and validate the image improvement associated with an OBS survey. The studies helped establish the optimal OBS geometry design by benchmarking it against legacy data as well as a number of alternative towed streamer and ocean-bottom acquisition solutions. The secondary goal of these studies was to increase the understanding of OBS acquisition options that is, ocean-bottom node (OBN) acquisition and ocean-bottom cable (OBC) acquisition. Using a multiphase feasibility study, which integrates geometry design, illumination analysis, and finite-difference modelling, we were able to successfully evaluate the suitability and value of OBS for a number of seismic acquisitions in the North Sea. By investigating the natural sampling, illumination characteristics, and processing considerations of each geometry, we were able to design and optimise an OBS geometry that met the imaging and operational challenges of each area.