Potential of Multilateral Closed Loop Geothermal Systems for Power Generation Using Water and Supercritical CO2

Abstract

Abstract The super-hot enhanced geothermal systems were simulated to generate remarkably high megawatts of electricity per well, while in practice, the extreme underground conditions proved to be challenging for long-term production operations. This paper presents a comprehensive investigation into Multilateral Closed Loop Geothermal Systems (CLGS) using water and supercritical CO2, targeting enhanced power generation in high-temperature geothermal environments up to 350°C, while eliminating production issues such as heavy corrosion and scale formation. Focused on optimizing system performance and ensuring well integrity, the study employs advanced flow and thermal models alongside mechanical simulation models to investigate the heat production performance of CLGS under different well design and production settings and examine the behavior of casing and cement under the subsurface temperatures. By exploring multilateral well completion techniques and varying operational parameters such as the number of laterals, injection pressure, and mass flow rate, the research identifies strategies to maximize energy recovery and minimize the levelized cost of electricity. Significant enhancements in power generation are demonstrated, particularly with the use of supercritical CO2, which despite its lower specific heat capacity, achieves higher temperature outputs at increased resource temperatures, effectively lowering electricity costs. Sensitivity analyses highlight the critical impact of well design on system efficiency, revealing optimal flow rates and the importance of insulated tubing to prevent heat loss. Structural modeling results further indicate potential failure risks due to stress concentrations at crucial lateral junctions in the well architecture. Key findings include a production temperature decline of 15-20°C after 20 years and significant economic benefits from increasing resource temperatures and the number of lateral sections. The paper underscores the potential of CLGS to significantly improve the economic and operational sustainability of geothermal power generation, offering robust insights into the strategic deployment of these systems in challenging geothermal environments.