3-D Static Corrections

The calculation of static corrections using the arrival times of refracted waves present in reflection seismograms by means of the method of Seismic Refraction Tomography (SRT) for 2D acquisition geometry has succesfully been applied to straight and crooked seismic lines. The redundancy as obtained by present day CDP shooting is used to estimate the variations in thickness and velocity of the weathered layer, which cause static shifts in the observed reflection times and hence distortions in the final stack. This paper deals with the extension of the method to any acquisition geometry, in particular 3D. After a short review of the basic theory we will highlight some aspects for 3D geometry. Then we discuss some implementation considerations after which real data examples will be shown. We conclude with observing that the method results in an improvement of the quality of the stacked section, especially for the 3D case where the conventionally obtained static corrections by means of refraction seismics do not account for the spatial variations in thickness and velocity of the weathered layer. This implies a pleasant 'fringe' benefit of the method, vz. that the shallow refraction survey may be omitted.