地中炭素貯蔵のための地震監視の改善方法を発見(New study finds a way to improve seismic monitoring for geologic carbon storage)

2024-07-11 ロスアラモス国立研究所(LANL)

＜関連情報＞

• https://discover.lanl.gov/news/0711-geologic-carbon-storage/
• https://www.nature.com/articles/s43247-024-01493-6

地中炭素貯留の信頼できるモニタリングのためのCO2岩石物理モデリング CO2 rock physics modeling for reliable monitoring of geologic carbon storage

Neala Creasy,Lianjie Huang,Erika Gasperikova,William Harbert,Tom Bratton & Quanlin Zhou
Communications Earth & Environment Published:17 June 2024
DOI:https://doi.org/10.1038/s43247-024-01493-6

Abstract

Monitoring, verification, and accounting (MVA) are crucial to ensure safe and long-term geologic carbon storage. Seismic monitoring is a key MVA technique that utilizes seismic data to infer elastic properties of CO₂-saturated rocks. Reliable accounting of CO₂ in subsurface storage reservoirs and potential leakage zones requires an accurate rock physics model. However, the widely used CO₂ rock physics model based on the conventional Biot-Gassmann equation can substantially underestimate the influence of CO₂ saturation on seismic waves, leading to inaccurate accounting. We develop an accurate CO₂ rock physics model by accounting for both effects of the stress dependence of seismic velocities in porous rocks and CO₂ weakening on the rock framework. We validate our CO₂ rock physics model using the Kimberlina-1.2 model (a previously proposed geologic carbon storage site in California) and create time-lapse elastic property models with our new rock physics method. We compare the results with those obtained using the conventional Biot-Gassmann equation. Our innovative approach produces larger changes in elastic properties than the Biot-Gassmann results. Using our CO₂ rock physics model can replicate shear-wave speed reductions observed in the laboratory. Our rock physics model enhances the accuracy of time-lapse elastic-wave modeling and enables reliable CO₂ accounting using seismic monitoring.