Borehole Seismic Imaging
AVO analysis is widely used for hydrocarbon detection, lithology identification, and fluid content analysis, due to the fact that changes in seismic reflection amplitude with increasing offset can be affected by different lithology and fluid properties above and below a reflector.
Borehole seismic methods allow for improved AVO analysis over surface seismic measurement. This is due to the fact that the downhole geophones can be positioned very close to the zone of interest, resulting in the seismic energy only travelling through the unconsolidated near-surface zone once – this results in much broader bandwidth data being measured by the geophones. Since the geophones are very close to the reflection point, they measure very accurately the downgoing wavelet, which allows a deterministic waveshaping deconvolution operator to be designed, which removes propagation effects such as attenuation and multiples. S/N is also higher due to the geophones being located in a quiet borehole environment, rather than on surface.