Processing and imaging of a multi-petabyte OBN survey in the North Sea

Abstract

Summary The Utsira ocean-bottom node (OBN) survey was acquired during 2018/19 covering 1510 km2 over the Utsira high, which is ~90 nautical miles west of Stavanger. As it was acquired using several asynchronous triple-source vessels, deblending was an essential step to recover signal at target depths. Deblending also removed very strong nearby seismic interference, by using the interfering survey’s shot times, with as many as 14 active sources firing. Up-down deconvolution is a key step to address the challenges observed in the area as it achieves both free-surface multiple elimination and 3D signature deconvolution. A similar approach was developed to tackle the same issues for the down-going wavefield resulting in a more effective and efficient processing flow for imaging shallow targets than conventional techniques. The long offsets and rich azimuthal sampling of the wavefield meant FWI could solve model building and imaging challenges over a range of depths. Such challenges included shallow channels and deeper cemented sand injectites. This survey illustrates how advances in acquisition and processing technologies enable large-scale, high-density OBN surveys to be acquired and processed in accelerated time frames leading to new insights even in relatively well-explored areas.