The influence of CO2 partial pressure on the stability of dawsonite-based on water-rock physical experiment and numerical simulation

Dawsonite has the potential to serve as a significant mineral for carbon sequestration in geological storage, and its stability in the reservoir is determined by intricate fluid-rock interactions. Thus, it is crucial to elucidate the mechanism that influences the stability of dawsonite. In this study, a natural dawsonite-bearing sandstone in Dongying Sag was utilized for CO2-H2O-Rock interaction experiments and TOUGHREACT numerical simulations at varying CO2 pressures. Additionally, the CO2 fugacity value acting on the sandstone in the reactor experiment was corrected using thermodynamic analysis. By systematically analyzing the dissolution response and elemental composition evolution of dawsonite through techniques such as scanning electron microscopy observation and energy spectrum analysis, X-ray diffraction analysis, hydrochemical analysis, and dawsonite stability indicator parameters, the influence mode on the stability of dawsonite was clarified. The atomic ratio of dawsonite in each experimental group (between Al:O = 1:3 and Al:O = 1:2) suggested that gibbsite and boehmite were formed after the dissolution of dawsonite under high CO2 pressure. When pCO2 <= 7.3 MPa or pCO2>8.3 MPa, increasing the CO2 pressure could enhance the thermal stability of dawsonite and inhibit its decomposition. However, when pCO2 was between 7.3 MPa and 8.3 MPa, the reaction equilibrium was disrupted, and a considerable amount of dawsonite was dissolved and transformed into new minerals. Both physical experimentation and numerical simulation indicated that dawsonite achieved a stable state at pCO2 = 7.3 MPa and 120 degrees C.