Characterization on reservoir complex and CO2 plume with Vp/Vs: Case study at Nagaoka site, Japan

This paper reports a relationship between P-wave to S-wave velocity ratio (Vp/Vs) and properties of rock at the reservoir of Nagaoka site. Seismic methods have been widely employed for site characterization and monitoring of CO2 behavior in the ground. In this method P-wave data are primarily used. However, S-wave velocity has independent properties from P-wave velocity, and it has been utilized to evaluate lithology of formations and gas saturation in the rocks. We investigated relationships between Vp/Vs and other rock properties before CO2 injection at Nagaoka geological storage site. The data analyses indicated that the Vp/Vs data could provide information that distinguishes shale volume and the degree of grain packing in rocks. The latter problem cannot be clarified by Vp data, therefore Vp/Vs data can be used in the detail characterization of the reservoir complex. (C) 2014 The Authors. Published by Elsevier Ltd.