Method and system for marine seismic acquisition

A method for acquiring seismic data, the method comprising:

• towing a streamer spread including first and second streamers, each of the first and second streamers having at least one seismic receiver and at least one position control device;
• towing a seismic source located within an area underlined by the streamer spread and configured to generate seismic waves;
• and
• controlling with the position location devices a streamer separation DS between the first and second streamers so that the streamer separation DS varies along a length of the spread to comply with a given survey characteristic,
• wherein the streamer spread is towed by a first vessel and the source is towed by a second vessel, and
• wherein the streamer separation varies from a front-end value DS(F) at a front-end of the spread, to a middle of the spread value DS(O), to a back-end value DS(B) at a back-end of the spread, and the middle of the spread value is smaller than the front-end value and smaller than the back-end value.

A method for acquiring seismic data, the method comprising:

• calculating plural streamer separations DS between first and second streamers of a spread so that the streamer separation DS varies along a length of the spread to comply with a given survey characteristic;
• calculating forces to be applied by birds, which are located on the first and second streamers, to maintain the streamer separations DS along the length of the spread;
• and
• programming the birds to hold the forces during a seismic survey to maintain the streamer separations DS while the first and second streamers move through the water,
• wherein there is a streamer separation DS(F) at a front-end of the spread, a streamer separation DS(O) at a middle of the spread, and a streamer separation DS(B) at a back-end of the spread, and the streamer separation at the middle of the spread is smaller than the streamer separations at the front-end and the back-end.