Patent ID: 8203907
Filing Date: 2012-06-19
Classification: G01V

Abstract:
1. A method for generating a velocity model from seismic reflection data obtained from a subterranean survey region, said model giving seismic velocity as a function of location in the region, said method comprising: (a) generating a velocity model of the subsurface region for updating; (b) obtaining a migration velocity scan from the seismic data, said scan including a set of seismic images created by migrating the seismic data using a suite of test velocity models of the subterranean region; (c) selecting an optimal pick from the velocity scan, said optimal pick corresponding to a particular test velocity model and to a particular (x,y,z) location in the subterranean region; (d) computing imaging travel times from the selected optimal pick location to a plurality of locations on the subterranean region's surface using the test velocity model corresponding to the selected optimal pick, wherein rays corresponding to the imaging travel times from the selected optimal pick location to the plurality of surface locations include at least one non-specular ray; (e) determining a surface location corresponding to an emergence point of a zero-offset ray from the (x,y,z) location corresponding to the selected optimal pick, using the test velocity model corresponding to the selected optimal pick; (f) determining an update location in the velocity model for updating such that a zero-offset ray from the update location has substantially the same surface emergence location and travel time as the zero-offset ray from the (x,y,z) location corresponding to the selected optimal pick; (g) computing imaging travel times from the update location to the plurality of surface locations selected in step (d) using the velocity model; and (h) updating the velocity model to reduce any differences between the imaging travel times computed in (d) for the optimal pick and the corresponding travel times computed in (g) using the velocity model; wherein at least the computing imaging travel times steps are performed using a computer programmed to perform those steps.