Multifactor optimization of supercritical CO₂ geothermal system based on Taguchi method

Utilizing supercritical CO₂ (sCO₂) for heat extraction is a novel method of geothermal development, which can not only improve heat extraction efficiency, but also achieve the benefit of carbon sequestration. But the performance of sCO₂ geothermal system (SCGS) is simultaneously affected by multiple factors, while current research primarily focuses on the influence of a single factor, neglecting the comprehensive effect of multiple factors. Furthermore, the influence degree of various factors is not yet clear. Therefore, this paper aims to conduct multifactor optimization on SCGS. Six crucial impact factors are determined and three evaluation parameters representing heat extraction capacity, heat extraction stability, and carbon sequestration capacity of SCGS are selected. Taguchi method is used to gain the value combinations of impact factors for the optimal single and comprehensive performance of SCGS, as well as the influence rank of various factors. The research results indicate that the factors combination for the optimal comprehensive performance of SCGS is: T_in (5 ℃), P_in (26 MPa), P_out (10 MPa), D (700 m), T₀ (150 ℃), k (70 mD). In addition, well spacing and reservoir temperature have the greatest impact on the comprehensive performance of SCGS, reflecting that well selection and geological exploration before geothermal extraction are of great significance. The relevant research results of this paper can provide theoretical guidance and technical support for the design and promotion of SCGS, which is conducive promote the efficient and sustainable development of geothermal resources.