This case study highlights the successful development and implementation of a conceptual subsurface risk management and measurement, monitoring, and verification (MMV) plan for an offshore CCS site near Tokyo, Japan. By adhering to global CCS best practices, the project identified and managed 18 subsurface risks, resulting in a cost-effective and regulatory-compliant MMV plan.

Japan has set a target to reach carbon neutrality by 2050, with carbon capture and sequestration (CCS) being a central component of this strategy. As part of the national initiative, seven offshore CCS sites were earmarked for feasibility studies, with commercial operations anticipated by 2030. The project involves the transportation of liquid CO₂ via pipeline from the city to an offshore aquifer, where it will be injected and permanently stored at a rate of 1 million metric tons each year.

SLB was engaged to design a robust MMV plan for one of the offshore CCS sites near Tokyo. The objective was to develop a site-specific, risk-based MMV plan that addresses potential subsurface risks identified through comprehensive geological and numerical simulations. The MMV plan needed to align with global best practices and regulations to ensure the project's success in the long-term containment of the injected CO₂ within the storage complex and stakeholder acceptance.

The risk management analysis identified 18 potential subsurface risks, among which included wellbore blockage, vertical leakage, fault reactivation, and induced earthquakes. The Bowtie method was employed to develop a detailed risk management plan based on preliminary risk assessment results, while the Boston Square chart facilitated the evaluation of monitoring and measurement technologies based on cost-benefit analyses.

Key achievements of the project include:

• Risk-based MMV: The MMV plan was directly linked to the specific risks identified through Bowtie analysis, ensuring targeted and effective monitoring.
• Technology screening and selection: The Boston Square analysis allowed for the selection of appropriate monitoring technologies, balancing cost and benefit considerations.
• Dynamic area of review (AOR): The AOR was dynamically specified to set clear boundaries for the MMV program, enhancing focus and efficiency.
• Monitoring schedule planning: The implementation of monitoring technologies was meticulously planned to coincide with key project milestones, optimizing resource allocation.
• Site-specific MMV: Technologies were leveraged, and risk linkages were established to tailor the MMV plan to the specific site conditions.
• Cost estimation: Monitoring costs were estimated to assess their impact on overall project economics, aiding financial planning and stakeholder discussions.

Serving as a framework for other CCS projects globally, this approach demonstrates how integrating risk management with MMV design can lead to effective and compliant CCS operations. It ensures that potential subsurface risks are proactively managed, supporting ambitious carbon neutrality goals.