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Flying 300 underwater Planes and other Oil Industry Innovations

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If you have a question about this talk, please contact Dr Nigel Bennee.

Exploring for oil and gas reserves begins with seismic exploration in which a picture of the subsurface is obtained using acoustic imaging. For marine seismic exploration this involves a boat towing sources and receivers. The acoustic signal from the sources propagates through the water, and then into the earth, where it is reflected at boundaries between rock types. The reflected signals are recorded on hydrophones within long cables, towed at about 10m below the sea surface. These cables can be extremely long, 12km or more, and 10 to 20 cables are often simultaneously towed behind the boat, approximately 50 m apart. A typical arrangement will contain 40,000 to 100,000 hydrophones, which are all simultaneously recording the reflected signals. Keeping all these cables in the correct position is a major challenge and is achieved by small underwater planes (called birds) placed periodically along the cables. In all, there are several hundred underwater birds distributed amongst all the cables. Each bird can force the cable to locally change depth or horizontal position. However, to achieve the correct physical geometry, required to ensure accurate acoustic data is gathered, all the birds must be instructed in concert. This talk describes the remarkable simultaneous flying of these hundreds of birds; and how they are coordinated to respond to changes in sea currents, the trajectory of the boat, and other factors. It will also explain the multi-level control system, how the system is designed to cope with critical events and how an accurate estimate of the position of the equipment being towed is achieved. Dr. Simon Bittleston invented these underwater birds, and the complete dynamic control system, which allow this massive acoustic array to be placed accurately whilst being towed.

This talk is part of the Cambridge Society for the Application of Research (CSAR) series.

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