Field mapping and seismic analysis of fractures

Near-surface fractured carbonates and a subsurface fractured coal bed were studied to predict the strike of the dominant natural fracture systems. These predictions are based on measuring seismic azimuthal anisotropy.;Analysis of a 3-D seismic survey, recorded on outcropping carbonates, gave a measure of near surface azimuthal velocity anisotropy (9%) in fractured carbonates with the fast velocity sub-parallel to structural strike. This agrees with field mapping of fracture data, which shows the dominant fracture pattern is Type 2 fold-associated fractures oriented sub-parallel to the fold axis.;Azimuthal AVO in coal beds was also studied based on multi azimuth walkaway VSP data. Measuring three azimuthal AVO gradients helped to quantify an estimate of the dominant face cleat strike. The results show that the dominant face cleat trend is NW-SE. This is interpreted to be a possible localized fault block with a draped anticline on the fault to create observed cleat trend.