First Wide-azimuth Time-lapse Seismic Acquisition Using Ocean Bottom Seismic Nodes at Atlantis Field – Gulf of Mexico

The world's first ocean bottom seismic (OBS) node-on-node time-lapse monitor survey was acquired at Atlantis Field in the Gulf of Mexico in 2009. The baseline survey, acquired in 2005-2006, was the first large-scale deepwater OBS survey employing autonomous nodes (Beaudoin and Ross, 2007). Following first oil in October 2007, studies were initiated for a time-lapse survey to monitor production changes in the Atlantis reservoir. The baseline survey demonstrated that remotely-operated vehicles (ROVs) could deploy and recover autonomous nodes with high positional accuracy even in the presence of severe bathymetric challenges. This capability underpinned the design, planning and execution of a highly repeatable monitor survey. For the monitor survey, an ROV deployed 500 nodes to a subset of the original 1628 baseline node locations. These 500 monitor locations were chosen to image the expected area of reservoir changes after careful analysis of image quality as baseline data were progressively decimated. The ROV deployed 91% of the nodes to within 5 meters of their respective baseline locations and 98% within 10 meters. This remarkable geometric repeatability within a producing field has laid the foundation for highly repeatable monitor surveys even in challenging seafloor environments.