Determination of Multiples in Surface Seismic Data Using Zero Offset Vertical Seismic Profiling (ZVSP) Techniques

In seismic exploration, one of the major tasks is to construct an image of the subsurface based on a limited amount often obscured and unreliable data. With conventional surface seismic data, we can often only guess at the measurements of the subsurface, but vertical seismic profiling (technique of placing the receiver at the depth in the well bore) enables us to measure the behavior of seismic wavelets as they propagate through the subsurface by shortening the path between the seismic source and the receiver. VSP provides a more accurate technique of imaging sub-surface targets with a higher resolution than conventional surface seismic technique. Various processing steps were applied in generating a One-dimensional (1-D image corridor) seismic section of the data, the corridor stack is then shifted to the frequency of the surface seismic data and a tie is generated. Multiples reflections and true primary reflections were then identified on the surface seismic data. From the results obtained using zero vertical seismic profiling, multiples were identified at offset time 1.32ms, 1.59ms, 1.71ms, 1.80ms and 1.82ms respectively across the section while true reflections were identified at 1.20ms.1.40ms, 1.92ms and 2.19ms respectively. This clearly shows the ability of the technique to differentiate multiples from true reflections in a seismic data or section. Zero-offset vertical seismic profiling survey provide detailed images of the subsurface both around the borehole and ahead of the drill bit which particularly helpful in aiding drilling strategies.