Patent ID: 7345951
Filing Date: 2008-03-18
Classification: G01V

Abstract:
1. A method for updating a distribution model of propagation velocities of seismic waves in an underground formation by determining specular source/receiver pairs associated with image points obtained from images of the underground formation resulting from multi-offset records, as a function of time, of seismic waves emitted and picked up by an acquisition device comprising seismic sources and seismic receivers coupled at the surface with the underground formation, the seismic waves being reflected by geologic interfaces of the formation, the method of the determining the specular source/receiver pairs comprising: (a) defining a selection of image points of the images of the formation comprising at least one image point and adjacent points; (b) carrying out a prestack depth migration for the selection of image points wherein data relative to the sources and receivers of the acquisition device, ray parameters of rays defined between any source/image point pair and the ray parameters of rays defined between any receiver/image point pair are determined and stored and, for at least one image point of the selection: (c) determining, for the at least one image point, a local slope of at least one seismic event corresponding to reflections impacting one of the geologic interfaces of the formation; (d) determining specular source/receiver pairs associated with the at least one image point, by comparing the local slope associated with the image point with ray parameters associated with the image point; and (e) modifying the distribution model of the propagation velocities of the seismic waves in the underground formation according to the determined specular source/receiver pairs.