Numerical simulation of CO2 sequestration in sandstone aquifers with feedback effect of salt precipitation: A case study of Ordos Basin

Abstract

Salt precipitation is an important issue for CO2 sequestration in deep aquifers.At present, most numerical simulations ignore the feedback effect of the changes in the porosity and permeability caused by the salt precipitation on fluid flow.In this paper, taking Liujiagou Formation in Ordos Basin as an example, a two-dimensional model is established using TOUGH2 code.By modifying the source code of the program, the model can consider the feedback effect of salt precipitation on fluid flow.The simulation results show that after the CO2 injection into the Liujiagou Formation for 20 years, salt precipitation makes the formation pressure near the injection well increase by 0.87MPa and the corresponding injectivity loss of the formation is 7.17%.The salinity has the greatest influence on salt precipitation and its feedback, followed by CO2 injection rate, and permeability has the least influence.When the salinity is high, solid salt saturation increases significantly, resulting in a great decrease in the permeability.In this study, when the salinity was 0.24, the salt precipitation caused an injectivity loss by 45.32% and the pressure buildup up to 12.14 MPa.Therefore, special attention should be paid to the salt precipitation caused by high salinity and its feedback effect during CO2 storage.

Keywords

• co2 geological storage
• salt precipitation
• permeability decrease
• formation pressure
• injectivity
• tough2