For complex reservoirs it is almost imperative to have wide azimuth data.
Planted Ocean Bottom Seismic Nodes
Traditional marine seismic, for exploration as well as for production purposes, is carried out by towing one or more hydrophone sensor cables (streamers) behind a vessel. The acquired data are based on pressure waves (acoustic waves) only, with a narrow azimuth (range of angles of view) concentrated in the direction of the streamers. However, to image a complex reservoir (underneath salt bodies, etc.), it is almost imperative to have access to data of wider azimuth. Also, the ability to be able to acquire shear waves, in addition to pressure waves, would give much more information
about possible fracturing of the reservoir, as well as important rock physical parameters. To address these challenges for detailed seismic surveys (i.e. those used for development and production purposes), the state of the art technology up till now has been to use ocean bottom cables (OBC) with geophone sensors instead of streamers, making it possible in theory to acquire the whole wave field (i.e. both pressure and share waves with much wider azimuth). However, in congested areas and deep waters, the use of OBC is logistically difficult and costly. In addition the quality of the data might not be optimal, due to bad coupling of the geophone sensors with the sea bottom.
Traditional marine seismic, for exploration as well as for production purposes, is carried out by towing one or more hydrophone sensor cables (streamers) behind a vessel. The acquired data are based on pressure waves (acoustic waves) only, with a narrow azimuth (range of angles of view) concentrated in the direction of the streamers. However, to image a complex reservoir (underneath salt bodies, etc.), it is almost imperative to have access to data of wider azimuth. Also, the ability to be able to acquire shear waves, in addition to pressure waves, would give much more information
about possible fracturing of the reservoir, as well as important rock physical parameters. To address these challenges for detailed seismic surveys (i.e. those used for development and production purposes), the state of the art technology up till now has been to use ocean bottom cables (OBC) with geophone sensors instead of streamers, making it possible in theory to acquire the whole wave field (i.e. both pressure and share waves with much wider azimuth). However, in congested areas and deep waters, the use of OBC is logistically difficult and costly. In addition the quality of the data might not be optimal, due to bad coupling of the geophone sensors with the sea bottom.
Our concept is based on independent autonomous receivers that will be planted into the seabed by one or more remotely operated vehicles (ROV), avoiding easily obstructions like platform legs, pipelines, etc., that might exist on the sea bottom. Since our nodes are planted into the seabed and correctly oriented, at predetermined positions, good coupling with the subsurface is secured and the receivers will be shielded from environmental noise, generated by all kind of industrial activity taking place on an typical offshore oil field. ROV’s can also operate in ultra deep waters (several thousand meters) where it is impossible to work with OBC cables.
