Evaluation of CO₂ storage potential in Japan

Abstract

The “Investigation of potential sites for CO₂ storage in Japan” project, initiated in 2014, is a collaborative effort between the Ministry of Economy, Trade and Industry and the Ministry of the Environment. The project aims to identify multiple large-scale storage sites capable of holding over 100 million tons of CO₂. Japan CCS Co., Ltd. has been entrusted with the project, conducting activities such as seismic surveys, geological analyses, and numerical simulations for potential offshore storage sites in Japan. The evaluation of storage capacity, based on 3D seismic data until March 2023, estimates a total storage potential of around 16 billion tons across eleven sites. This assessment uses the volumetric method, focusing on the pore space capacity in the reservoir rock, without considering factors such as seal ability, injection well arrangement, injection properties, and CO₂ movement. We organized the sedimentary environment and geological age at geological analysis sites based on 3D seismic data and found that the reservoir layer offshore Japan is sandy splay/channel deposits from the Miocene to Pleistocene submarine ramp/slope apron system and delta system. The main candidates for the shielding layer are muddy sediments deposited in slopes and ocean basins during the transgressive period. In addition, we compared and discussed the injectivity（Kh）and the difference between formation pressure and formation fracture pressure from the simulation model at each site. In order to reduce uncertainty in assessing the amount of storage and to improve the accuracy of risk assessment, it is necessary to drill survey wells.