Understanding the carbon dioxide sequestration in low-permeability saline aquifers in the Ordos Basin with numerical simulations

Abstract

A carbon dioxide (CO2) capture and storage demonstration project was started in 2010 by injecting around 100 000 tonnes of super-critical CO2 per annum into a set of very low-permeability sandstone at depths of more than 1600 m in the northeastern Ordos Basin, China. Based on the site-specific geology and the observational data, a numerical injection model was developed in order to understand the hydrodynamic behavior of CO2 in the subsurface for evaluating reservoir performance. The results show that the model reasonably described the spreading of the CO2 plume. The Triassic Liujiagou sandstone aquifer is the most favorable storage formation for CO2 sequestration at the site of interest. After three years of injection of CO2, the maximum lateral migration distance of CO2 plume is about 550 m and the pressure build-up is about 13 MPa in the Liujiagou formation for the actual injection simulation. The major storage layer is at depths of 1690-1699 m, which contributes around 80% of injectivity of the entire reservoir system. The leakage of CO2 into the geological seals is negligible (<0.1%) over the entire simulation period. Regardless of the relatively good fit during the calibration period, the model overestimated the pressures associated with the injection thereafter.