3D prestack seismic data migration method

A method of performing prestack migration of seismic events for imaging a part of an underground zone from a series of a number Ns of seismic reflection cycles, comprising successive emission of elementary wavefields, each elementary wavefield defined by association of a seismic signal W(t) and of a point of emission defined in a series of points of emission Si with 1≦i≦Ns, seismic receivers located in positions Rji receiving seismic signals reflected by the underground zone in response to each of the wavefields, with signals received by each seismic receiver being recorded as time-dependent seismic traces dji(t), wherein for a given velocity model, the method comprises the following steps:

• a) defining a slowness vector p having components p1 and p2 assuming a series of previously defined values;
• b) defining, for a given slowness vector p and for a given point of emission Si, a time lag function t0(p, i);
• c) applying the time lag function t0(p, i) to each elementary wavefield associated with point of emission Si and forming a surface composite wavefield by spatiotemporal superposition of elementary wavefields to which such a time lag is applied;
• d) applying the time lag function t0(p, i) to seismic traces dji(t) marked by a pair (i,j) and forming a surface composite trace field by spatiotemporal superposition of the seismic traces to which the time lag is applied,
• e) performing migration of the surface composite trace field using the surface composite wavefield, by modelling propagation of the surface composite wavefield and retropropagation of the surface composite trace field, and combining the modelled propagation of the surface composite wavefield and the retropropagation of the surface composite trace field at any point of the zone to be imaged,
• f) repeating steps c) to e) for all values assumed by the components p1 and p2 of the vector p, and
• g) for any set value of the second component p2 of the vector p, stacking the results of combinations of the surface composite wavefield and the retropropagation of the surface composite tracer field to obtain a migrated image associated with the set value of p2, to thereby perform prestack migration.