Setiawan, Fnu (2019-11). CO2 Storage Capacity Estimation in Depleted Gas Reservoirs with Water Drive using Material Balance and Convection Diffusion Model. Master's Thesis.
Thesis
COv2 sequestration in depleted gas reservoir is an option to reduce the COv2 emissions. It is specifically good because of data availability, safe trap mechanism, and high ratio of COv2 storage capacity per pore volume. One method to estimate the COv2 storage capacity is using a material balance model. However, previous studies have not included the effect of COv2 solubility in water in the calculations. It is an important variable to consider because COv2 dissolved in water changes water properties affecting the estimation especially for gas reservoirs with water drive. In this study, the effect of COv2 solubility in water to the COv2 storage capacity in depleted gas reservoir with water drive is analyzed. A method to estimate the COv2 storage capacity considering the COv2 solubility in water is developed. The method is an iterative method based on material balance model which is divided into production and injection stages, Van Everdingen-Hurst aquifer model, and a modified convection diffusion model. The COv2 storage capacities are estimated using conventional material balance and this iterative method. The results are compared to analyze the effect of COv2 solubility in water. Generally, COv2 solubility in water changes the water properties which makes the storage capacity lower compared to the result from conventional material balance estimation. The difference between the results are a function of several variables including aquifer and reservoir properties, such as: radial aquifer-reservoir ratio; aquifer permeability; temperature; salinity, and injection rate. Moreover, because COv2 dissolves in water, some of the COv2 is stored in the aquifer through convection and diffusion. The amount of COv2 stored in the aquifer is far smaller than the amount of COv2 stored in the gas reservoir, but the absolute value is still significant. I developed a method to estimate COv2 storage capacity in depleted gas reservoir with water drive while considering COv2 solubility in water. It is important because it may help avoiding storage capacity over-estimation by the conventional method. The estimation is also one of important parameters necessary to design COv2 storage facilities.
