文摘
Flooding carbon dioxide into oil reservoirs is a promising technique for improving the pressure of a reservoir when it is depleted through primary and secondary production. In the context of global warming, it is a viable method for geological storage of CO2 emissions. Once CO2 is injected into a reservoir, it is forced to come into partial contact with formation water. To estimate the rate of CO2 transfer and the total amount of CO2 dissolved in the formation water, correct estimation of CO2 diffusivity is required. In this study, the rate of CO2 diffusion in water was experimentally determined in a PVT cell using the pressure depletion method at reservoir conditions (temperature: 50–75 °C and pressure: 17,450 kPa). As expected, the rate of CO2 diffusion in water increases with increasing temperatures. In addition, the impact of salinity of the water on the rate of CO2 diffusion was investigated. A significant decrease in the rate of CO2 diffusion was found with increasing salinity. Subsequently, a diffusion model describing the experiments was developed to predict the behavior of CO2 diffusivity under simulated conditions. Unique correlations between CO2 diffusion coefficients and water at different temperatures and salinities were obtained using the results of modeling.
