A Conceptual Subsurface Risk Management and Measurement, Monitoring and Verification Design for an Offshore Carbon Capture and Storage Site in Japan

ABSTRACT: This paper presents a case study on the conceptual subsurface risk management and measurement, monitoring, and verification (MMV) design for an offshore CCS carbon capture and storage (CCS) site in Japan. Based on the available geological and carbon dioxide (CO2) numerical simulation results, preliminary risk assessment and risk management analyses were conducted for this site. This risk management analysis identified the key monitoring tasks of MMV. The MMV design was subsequently conducted to develop a site-specific and risk-based MMV plan to proactively address the potential subsurface risks for the given site. The paper describes the workflow of conceptual subsurface risk management and MMV design, summarizes the key considerations and findings, and sets examples for conducting similar evaluations for other CCS projects. 1. INTRODUCTION The Government of Japan announced the goal of achieving carbon neutrality by 2050, and carbon capture and storage (CCS) is considered a critical part of the overall solution to achieve the goal. In 2023, seven potential offshore CCS projects were selected by the government as the first initiative for the CO2 storage feasibility study toward the commencement of commercial CCS operations by 2030. Subsurface risk management and related MMV design are critical parts of the feasibility study, as the success of a CCS project relies on the long-term containment of the injected CO2 in the storage complex. In this context, conceptual subsurface risk management and MMV design were conducted at one of the candidate sites located offshore Japan by leveraging the enriched knowledge of worldwide CCS guidelines and regulations on CCS subsurface risk management and MMV planning. 2. INTRODUCTION OF THE STORAGE SITE The offshore carbon storage site, located around the Tokyo metropolitan area, was selected by INPEX for potential CCS operations. CO2 will be transported by onshore and offshore pipelines from emitters located in the metropolitan area. The injection operation is planned to start in 2030 and continue for more than 30 years, with a target injection rate of approximately 1.0 million tonnes per annum (Mtpa). Considering the water depth around the potential CCS site, the platform injection concept was selected. The target storage aquifer in the site employs a continuous and thick, deep- and shallow-water marine sedimentary succession.