Advanced Well Log Analyses Using Image Data at the Nagaoka CO2 Injection Site

Abstract

This paper discusses advanced well log data analyses to obtain refined geological model for CO2 sequestration. In order to evaluate the safety of stored CO2 in the ground, a reasonable geological model is required. Well log data is very helpful to evaluate geophysical parameters and to build detail geological model. However, the number of wells at geological CO2 storage sites is smaller compare to oil/gas field in generally. Therefore, it is preferred that as much as information is extracted from well log data. In this paper we introduced analyzing techniques for image log data, and conducted structural and sedimentological analysis at the Nagaoka CO2 injection site. From the image log of FMI logging, Sandspect analysis evaluating the histogram of resistivity value was conducted. From the T2 distribution of NMR logging, factor analysis was employed. The results from these analyses revealed the heterogeneity in the reservoir, and this heterogeneity was consistent with the depositional process of the reservoir and monitoring results during the CO2 injection. We concluded that these advanced analyses could provide useful information on the reservoir characterization for geological CO2 storage.