A method for obtaining a volumetric image of a geological structure present in subsoil, the method comprising:
- activating a plurality of seismic sources to generate a plurality of seismic waves;
- acquiring a plurality of traces by registering with a plurality of seismic sensors and processing in one or more computers seismic waves reflected by the geological structure;
- creating in the one or more computers a shot gather from the plurality of traces for each activation position of each seismic source;
- grouping in the one or more computers the seismic sources into a plurality of groups of N seismic sources each, N being a finite, positive integer, the N seismic sources of each group in the plurality of groups having a reciprocal distance such as to be contained in a circumference having a diameter lower than a predefined maximum distance;
- grouping in the one or more computers the groups of seismic sources into super-groups of N groups each, such that each super-group includes N2 seismic sources and a reciprocal distance between barycentres of any two distinct groups of seismic sources belonging to a single super-group is greater than a predefined minimum distance;
- effecting in the one or more computers N migrations for each super-group to obtain a partial volumetric image for each of the N groups in the super-group, wherein for each migration, a composite N-order shot gather is migrated through a numerical processing based on a seismic source selected from the group, thus obtaining an overall migration of N2 seismic sources using N distinct migrations, wherein the migration of each N-order shot gather focuses each reflection registered in each shot gather, in a corresponding point of the subsoil in which the reflection originated, by
- numerically modelling in the one or more computers a contemporaneous propagation of seismic waves generated by activating the seismic sources of the group to obtain a first wave field in each point of the volumetric image in relation to the positions of the seismic sources and with respect to time,
- back-propagating in depth the registered reflections in the one or more computers to obtain a second wave field in each point of the volumetric image in relation to the positions of the seismic sources and with respect to time,
- combining the first wave field and the second wave field in the one or more computers to obtain the partial volumetric image;
- and
- combining the partial volumetric images obtained from the migrations of the composite N-order shot gathers in the one or more computers to attain an overall volumetric image of the geological structure.