Azimuthal Velocity Analysis and Shale Gas Reservoirs

Shale gas reservoirs have become important hydrocarbon targets for oil and gas companies. Fractures and stress fields play important roles in the development of shale gas reservoirs. New seismic analysis methods enable geoscientists to map fracture patterns and associated permeability changes, allowing E&P operators to better target highly productive zones within these tight, heterogeneous reservoirs. Horizontal transverse isotropy (HTI) is an important issue for shale gas reservoirs and can be an effect of such things as vertical aligned fractures or unequal horizontal stresses. Azimuthal velocity analysis allows the measurement of HTI effects in wide azimuth seismic data and the determination of important azimuthal velocity anisotropy attributes. Calibration of the anisotropy attributes with well data can provide information regarding fracture density and orientation as well as horizontal stresses, thereby allowing geoscientists to predict sweet spots in shale gas reservoirs.