Enhanced heat extraction performance from deep buried U-shaped well using the high-pressure jet grouting technology.

Heat extraction from the single-well geothermal heating system (SWGHS) is significantly restricted by the high thermal resistance of the surrounding host rocks. To improve heat production efficiency of this geothermal system, the high-pressure jet grouting (HPJG) technology is proposed to enhance thermal output in deep buried U-shaped well (DBUSW) system. By means of this technology, an artificial jet grouting column (JGC) with high thermal conductivity is built near the horizontal well segment. The emphasize of this work is to evaluate the feasibility and efficiency of the proposed heat production method. Numerical simulations were conducted via a field validated model from in-situ experiments in Xian. Results demonstrated that average annual heat production rate is improved by about 22% in the 30-year heating period, with building an artificial JGC with 1.0 m radius near the wellbore. These results indicate that the proposed method is a promising strategy for enhancing thermal output in the DBUSW. Sensitivity analyses suggest heat production rate and outlet temperature are mainly controlled by the radius of the JGC, while very high JGC thermal conductivity has less effect. Given the field conditions, the suggested thermal conductivity and radius of artificial JGC is 30 W/m °C and 2.0 m, respectively. [ABSTRACT FROM AUTHOR]