Utilization of carbon dioxide gas for gas lift systems in geothermal wells

Abstract

Geothermal wells experience a decline in pressure between the bottomhole pressure and the wellhead pressure (during both static and dynamic conditions) due to friction and gravity. In some cases, this decline could be large, leading to reduced production rates. High wellhead pressures are necessary for maintaining high production rates and keeping the geothermal power plants operational. To address the pressure loss during fluid flow in geothermal wells, artificial lift techniques are employed, such as line shaft pumps and electrical submersible pumps (ESPs), which are widely used in Türkiye and globally. This study investigates the feasibility and potential benefits of using carbon dioxide gas lift systems in geothermal wells as an innovative artificial lift technique. The utilization of CO2 gas for gas lift in geothermal wells, though not widely researched and adopted, presents a promising approach to enhancing the productivity and efficiency of geothermal energy extraction. By integrating CO2 gas lift systems, operators can improve flow rates, increase overall system efficiency, and reduce operational costs. The study involves several stages, including the analysis of the thermodynamic behavior and solubility of CO2 in water at various pressures and temperatures encountered during geothermal fluid flow. Using Duan's solubility data, the solubility of CO2 in water was predicted with high accuracy through python coding techniques, covering pressures up to 2000 bar and temperatures of 533K. Additionally, geothermal pressure profiles, partial pressures of steam and CO2, and flash point pressures were simulated by python coding and validated, to understand the effects of varying CO2 mass fractions. It was discovered that increasing CO2 mass fractions reduced pressure losses, leading to higher wellhead pressures. This study's findings indicate that CO2 has a profound effect on the wellhead pressure. Therefore, CO2 gas lift systems may serve as a viable alternative to conventional artificial lift techniques. By addressing challenges such as declining productivity and operational inefficiencies, the integration of CO2 gas lift systems contributes to improved energy production and lower operational costs. This research provides a comprehensive understanding of the effects of CO2 on the production performance for geothermal wells.