Abstract:

The two-dimensional radial model of CO₂-water-rock reaction in carbon sequestration of Yancheng Group under section sandstone layer in Subei basin is built based on TOUGHREACT parallel version. The mineral sequestration potential in reservoir is evaluated. The influence of grid subdivision precision and anisotropy of reservoir on mineral sequestration simulations is analyzed. The simulation results show that dawsonite, calcite and siderite, significantly precipitated in the process of CO₂ sequestration. The total mass of CO₂ sequestrated by mineral trapping is as high as 34.0% after 5 000 a. The grid resolution has little impact on the reaction path of minerals sequestration, however, the total amount of CO₂ mineral sequestration with coarser grid is overestimated comparing to that with finer grid. The discretion of the vertical permeability (k_v) would lead to a more rapid horizontal migration of injected CO₂ to the middle and bottom, which results in an incretion in solubility trapping and mineral trapping for a short period of time. However, for a long term, with the increasing instability of the system due to CO₂ dissolution, the vertical convective mixing becomes significant, it turns out to be a significant inhibition of convection by decreasing k_v. It shows that the mineral sequestration calculated by middle k_v value model is higher than the larger k_v and smaller k_v value model after 1 000 a.

Key words: mineral sequestration of CO2, grid subdivision precision, anisotropy, Subei basin