Tomographic inversion of checked events on seismic migrated data uses depth migration before addition of seismic data is determined for a number of field speeds

摘要

Depth migration before addition of seismic data is determined for a number of field speeds. To determine the depth and droop of the reflector, those speed fields which minimize the gap to horizontal of the depth/distance offset curve or of the depth/angle curve, are selected. The reflector depth is determined for different displacements or angles. Method for producing a speed model of a subsoil in which: (a) on a group of seismic traces, acquired to the right of the subsoil, a depth migration is started before addition of data. The migration is started by means of a start speed model and allows determination of one or more trace collections each of which describe the subsoil directly below a surface point; on the trace collection obtained from the migration one or more events, which are reflected to the considered surface point, are marked. For each event mark a depth and reflector slope and reflector slope to the right of the surface point; start a ray trace between the reflector and the surface point to determine collection of acoustic-receiver source pairs as well as characteristic data for the path and gradient times which correspond to the traced rays associated with these pairs; afterwards start a process in which an iterative profile migration is started; migrate kinematically the path and gradient time data by means of speed field parameters; characterize the alignment of the produced migrated points, start parameters; the iterative process selects the parameters for the speed field which optimize the alignment of the migrated points.