Research on monitoring methods and technical systems of CO2 mineralization in basalt formation

Abstract

CO2 storage in basalt formation has received much attention as one of the new CO2 geological storage methods worldwide. It has been successfully implemented in Iceland and the United States. During the process of carbon storage in basalt, CO2 is transformed into solid minerals, which differs significantly from carbon storage in sandstone reservoirs in terms of CO2 injection method, burial depth, and physical property requirements of reservoir cap. Significant differences are also found in both monitoring schemes. By studying the Wallula basalt storage project in the United States and the Carbfix mineralization storage project in Iceland, this study compared and summarized the monitoring schemes of basalt storage for different CO2 injection phases (supercritical and gas dissolved state). The monitoring systems of basalt storage, saline aquifer storage, oil and gas reservoir storage were further compared. The storage monitoring system for sandstone reservoir focuses on the structural integrity of the CO2 reservoir and evaluating the change of CO2 concentration along the potential leakage path. The monitoring period is usually more than 50 years. In contrast, basalt mineralization and storage technology focus on the mineralization reaction of “water-CO2-basalt”. Its monitoring system is mainly to describe the property changing pattern of each substance from downhole fluid (chemical compositions, tracer concentrations, pH, etc.) during the storage cycle. Moreover, it evaluates the degree of mineralization reaction and the storage efficiency of basalt qualitatively and quantitatively. Finally, based on the systematic and comprehensive monitoring scheme of saline aquifer and oil and gas reservoir storage, the basalt-CO2 mineralization storage monitoring technology is analyzed systematically and a complete set of basalt-CO2 mineralization storage monitoring scheme and process is summarized. By comparing different CO2 storage monitoring systems, this study proposes a universal “subsurface-wellbore-surface-ground” monitoring scheme for basalt-CO2 mineralization: monitoring scope, purpose, program, and alert system. This provides basic information for the future basalt-CO2 mineralization storage demonstration project.

Keywords

• basalt
• co2
• mineralization storage technology
• monitoring technology
• monitoring system