Abstract: Deep saline aquifer is a complex multi-components and multiphase flow system after CO2 injection. CO2 advection happens because of pressure gradient and velocity difference and dries out water in saline aquifer, which changes phases of the components and causes salt precipitation. The precipitated salt clogs the pore space in aquifer and decreases CO2 injectivity, so it is very important to research the effect on dry-out problem and site selection. 2D radial model is built and multiphase fluid flow function is established. By considering relative permeability function and capillary pressure function, the effects of CO2 injection rate, salty in aquifer, input maximum capillary pressure and characteristic parameters of capillary pressure on dry-out problem are studied. The dry-out problem can be quantitatively described by solid saturation. Results show that CO2 migration separates the aquifer into three domains: dry-out domain, gas and liquid mixture domain and liquid saline aquifer domain. The dry-out problem happens nearby the injection well. If capillary pressure is considered, the solid saturation will increase when injection rate decreases, salty in aquifer increases, or capillary pressure increases. As a result, increasing CO2 injection rate, injecting water into aquifer before CO2 injection, and decreasing capillary pressure by choosing a large pore size homogenous formation can avoid the clogging of pore space with salt precipitation, which enhances CO2 injectivity.

Key words: dry-out, inversed flow, solid saturation, capillary pressure, pore size