The Evolution of an OBS Node – From North Sea Tests to Final Design

Abstract

A new design of ocean-bottom seismometer (OBS) system has been developed and tested that can provide high quality data in challenging deep-marine exploration and production areas.Each node records the pressure signal with a hydrophone and three components of seabed motion using geophones. The new units are self-contained recording stations, and are deployed by a remotely operated vehicle (ROV). They record seismic data on the seafloor for an extended period while a source vessel shoots lines above. Because they are autonomous, there are no cables joining the stations together. The nodes are therefore well-suited to working in congested waters, even right up to, or perhaps under, production structures. They also render 4D surveys practical because the ROV can redeploy the units close to their previous sites to ensure a high level of repeatability.The new nodes are differentiated from other types by improved levels of safety and efficiency; this is inherent in the compact, long-endurance, integrated modular design. The units also deliver high vector-fidelity thanks to excellent coupling to the seabed.We discuss the considerations, compromises, development and testing of these new OBS units.