Method for tilt (roll) and pitch estimation in a multi-sensor streamer

摘要

A method for estimating a tilt angle β(t) of at least one given particle motion sensor nearly collocated, in a multi-sensor streamer for seismic prospection, with a pressure sensor. The given particle motion sensor has two orthogonal sensing axes Y and Z in a plane orthogonal to a longitudinal axis of the streamer. The tilt angle is formed by the Z sensing axis and a reference vertical axis Z0. The method comprises, for the given particle motion sensor, a step of computing a first estimate β₀ of the tilt angle, comprising, while the streamer is being towed: obtaining (41) first data measured by the pressure sensor nearly collocated with the given particle motion sensor; obtaining (42) second and third data measured by the given particle motion sensor along the sensing axes Y and Z respectively; for at least two values of a rotation angle θ, rotating (45) the second and third data by the rotation angle θ, to obtain rotated second and third data; and computing (46-410) a particular value θ_max among the at least two values of the rotation angle, which maximizes, over at least one frequency, a coherence function between the first data and the rotated third data, or between the first data and velocity data resulting from an integration of the rotated third data, the particular value θ_max being equal to said first estimate β₀. Step of computing a first estimate β0 of said tilt angle is processed independently of any seismic signal.