Numerical study of the effects of CO₂ gas in geothermal water on the fluid-flow characteristics in production wells

In this study, we numerically investigated the effects of CO2 gas in geothermal water and the scale deposition formed in the wellbore on the flow characteristics. Geothermal water that contains CO2 gas has the potential to produce calcite scale deposits in the wellbore. To prevent scale formation, scale inhibitor is injected below the flash point in the wellbore, which is a challenging job. Therefore, using a wellbore simulator to predict the depth of flash commencement and the effects of scale deposition above the flash point on flow characteristics is important. In our numerical simulations, we changed the values of the CO2 gas concentration to study its effect on the flow characteristics. The simulation results show that the presence of CO2 increases the flash pressure relative to that of pure water. A higher CO2 gas concentration in the water will initiate flashing at a lower depth than a lower CO2 concentration. However, when the presence of scale deposits in the wellbore is taken into account, the calculated wellhead pressure is lower than that in a wellbore without scale deposition.