Our objective was to build and operate the first node management system for the deployment and retrieval of autonomous ocean bottom seismic (OBS) nodes on the sea floor in the deepwater Atlantis field area of the Gulf of Mexico. Nodal OBS systems collect wide-azimuth seismic data to provide improved imaging of subsalt reservoirs. The system was to operate across the Sigsbee Escarpment, an area of rugged topography with depths ranging from 1,200 to 2,300 m. The final node management system consisted of surface and subsurface operations. Surface operations employed a gantry crane, controlled from a raised operator stand on deck, for maneuvering nodes onto the deck of a marine vessel and into storage and charging containers. A robotic manipulator arm, also controlled from the operator stand, was mounted to allow access to both an ROV system and a node storage basket. The manipulator loaded the nodes onto a multi-conveyor deployment skid that fit under the ROV. When the ROV reached the sea floor, the robotic manipulator planted the nodes in succession. The ROV later returned to the node site, and the manipulator retrieved the nodes. Using two ROVs allowed the operation to proceed continuously. The use of 3D terrain profiling software, images from a camera mounted on the manipulator arm, and an enhanced inertial navigation system aided in precisely locating deployment and retrieval positions. Modeling and physical testing of the system and its components ensured that the system would be safe and would operate as expected.
This paper is one of a group of papers that collectively describe the development of a novel deepwater ocean bottom seismic (OBS) acquisition technology that has been successfully applied at a commercial scale over the Atlantis Field in the Gulf of Mexico. Taken together these papers present a case history in how a staged development process, rigorously managed, can substantially accelerate the pace of E&P innovation. This case history records the development of this technology from definition of the problem to execution of an â??at-scaleâ?? field trial.
The ocean bottom seismic (OBS) acquisition survey of the Atlantis field, deepwater Gulf of Mexico, represents the first use of autonomous nodes to collect seismic data from a deepwater environment. Autonomous nodes are seismic recording units, placed in an array on the sea floor, to collect wide-azimuth seismic data for improved imaging of subsalt reservoirs.
As an integral part of this pioneering project, the task of managing the OBS nodes offered opportunities and challenges in developing new equipment or using existing equipment in new ways and, most particularly, combining equipment components into a workable and safe operational system.