Multi-objective Optimization of Geothermal Extraction from the Enhanced Geothermal System in Qiabuqia Geothermal Field, Gonghe Basin

A geothermal demonstration exploitation area will be established in the Enhanced Geothermal System of the Qiabuqia field, Gonghe Basin, Qinghai-Xizang Plateau in China. Selection of operational parameters for geothermal field extraction is thus of great significance to realize the best production performance. A novel integrated method of finite element and multi-objective optimization has been employed to obtain the optimal scheme for thermal extraction from the Gonghe Basin. A thermal-hydraulic-mechanical coupling model (THM) is established to analyze the thermal performance. From this it has been found that there exists a contraction among different heat extraction indexes. Parametric study indicates that injection mass rate (Q(in)) is the most sensitive parameter to the heat extraction, followed by well spacing (WS) and injection temperature (T-in). The least sensitive parameter is production pressure (p(out)). The optimal combination of operational parameters acquired is such that (T-in, p(out), Q(in), WS) equals (72.72 degrees C, 30.56 MPa, 18.32 kg/s, 327.82 m). Results indicate that the maximum electrical power is 1.41 MW for the optimal case over 20 years. The thermal break has been relieved and the pressure difference reduced by 8 MPa compared with the base case. The optimal case would extract 50% more energy than that of a previous case and the outcome will provide a remarkable reference for the construction of Gonghe project.

Automated summary

This study focuses on geothermal system development in the Gonghe Basin of the Qinghai-Xizang Plateau, and employs a novel integrated method of finite element and multi-objective optimization to obtain the optimal thermal extraction scheme. It also identifies the most sensitive operational parameters for heat extraction and reveals the potential for increased energy extraction in the optimal case compared to previous scenarios.