Azimuthal anisotropy analysis of multiazimuth P-wave seismic data — An example from the Rock Springs Uplift, Wyoming, USA

Abstract

Our study area in Rock Sprigs Uplift, Wyoming, lies close to the carbon dioxide ([Formula: see text])-producing Jim Bridger power plant, and hence it is a good site for carbon sequestration. Two subsurface reservoirs within this area are being analyzed for their capability of long-term carbon storage. The presence and orientation of fractures within a reservoir and the associated seal govern the efficiency and long-term effectiveness of [Formula: see text] storage. The presence of natural fractures gives rise to seismic anisotropy that is related to the fracture orientation and density. This work analyzed P-wave multiazimuth seismic amplitude and well data from a potential carbon sequestration site for the anisotropy analysis. Using prestack waveform inversion, accurate azimuthal velocities were obtained for offset-to-angle transformation and to compute azimuthal angle gathers. These angle gathers were then stacked for each azimuth and analyzed for azimuthal anisotropy to estimate the fracture orientation and relative fracture density. Finally, by corroborating the results of the seismic azimuthal analysis with well data, it was confirmed that the results from the azimuthal analysis of the angle stacks are related to the fracture orientation and density.