Volume 57

Study on the Long-term Storage Mechanism and Migration of Carbon Dioxide in the Pearl River Mouth Basin, Eastern South China Sea Li Fangfang, Cai Zhenghua, Gao Zhenglong, Liu Cheng, Xuan Tao, Ma Zhanqi

Abstract

This study investigates the long-term phase change, migration, and sequestration mechanisms of CO2 in deep saline aquifers, using X Oilfield in the South China Sea as a case study. Through integrated laboratory experiments and numerical simulations, we demonstrate that (1) hydrodynamic and residual trapping are primarily governed by two-phase relative permeability and capillary pressure, (2) dissolution trapping is strongly influenced by temperature, pressure, and salinity conditions, and (3) mineral trapping correlates with feldspar and clay mineral content. Laboratory experiments provided essential thermodynamic and kinetic parameters for site-specific numerical simulations. The simulation results reveal that during the early injection phase, 60% of the injected CO2 remains in a supercritical state while 38% dissolves into formation brine, predominantly accumulating near the wellbore and causing localized pH reduction. Over time, dissolution increases significantly, followed by mineralization reactions. After 1,000 years, mineral trapping accounts for over 21% of the total sequestered CO2.

Keywords sequestration mechanism, migration and evolution law, capture and sequestration, dissolution trapping, mineral trapping