Simulation and analysis of lithology heterogeneity on CO₂ geological sequestration in deep saline aquifer: a case study of the Ordos Basin

A simplified two-dimensional axisymmetric model was established based on a typical continental sedimentary basin in China to simulate the thermal evolution of wellbore and reservoir during the injection of CO₂ by taking consideration of lithology heterogeneity of reservoir. By comparing with two simple one-dimensional theory models, the lithology heterogeneity influence on CO₂ mass flow rate distribution along depth in the wellbore is identified. Results suggested that the interaction of multiple layers in the heterogeneous reservoir will influence the CO₂ mass flow rate distribution along depth in the wellbore so as to impact the corresponding temperature and pressure evolution in the wellbore and reservoir. Layer burial depth (or relative location), porosity, permeability and thickness are all important factors that affect CO₂ mass flow rate in wellbore. The variation of CO₂ mass flow rate in the wellbore will change the CO₂ temperature flowing into each layers through impact the heat extraction from rocks, compressibility of CO₂ and potential energy loss, and by varying the CO₂ hydrostatic pressure and pressure drop due to friction to determine the CO₂ injection pressure. Layer burial depth, porosity, permeability and thickness are all important factors that affect the CO₂ mass flow rate distribution in the wellbore. This study may help deepen our understanding of CO₂ flow and thermal evolution in the actual heterogeneous reservoir and provide important knowledge supplement for the liquid injection (especially CO₂) into underground, such as deep saline aquifer, depleted oil/gas reservoir and coal bed.