Westerngeco L.l.p.

Services Petroliers Schlumberger

Westerngeco Seismic Holdings Limited

Francois Daube

Henrik Bernth

Mark Rainbow

Mark Schlumberger House Rainbow

A number of seismic stacks are precomputed () for known velocity fields. The velocity fields are chosen to span the range of velocities of interest. The stacks are then arranged () in the 3D memory of a graphics computer () using time and position as first dimensions and the index of the velocity field as the last dimension. In such 3D space, any velocity field to be used for stacking appears as a surface (S) within a volume. Projecting the seismic stacks onto that surface provides the seismic line stacked for the velocity field of interest.

Velocity analysis on seismic data

A method of generating a semblance panel comprises summing two or more gathers of traces. The dip of the reflector is taken into account in the summation process, and this prevents semblance peaks from becoming smeared during the summation process and so allows a greater number of gathers to be used to generate the semblance panel. In an embodiment of the invention the dip is determined from the seismic data. Alternatively, the reflector dip used in the summation process may be obtained from pre-existing data acquired at the survey location, or the reflector dip may be already known. The invention can be applied to seismic data containing events from more than one reflector.

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Houston, TX, United States of America

Francois Daube