Study on geothermal extraction method and control factors of extraction effect in high temperature goaf

In order to rationally utilize the goaf geothermal resources, a goaf heat extraction system and a goaf extraction and injection geothermal utilization method were put forward. The numerical model of temperature-seepage field of goaf was established. The controlling factors affecting the effect of extraction were determined, and the variation law of temperature field in goaf was revealed in the process of extraction. Orthogonal experiment-variance analysis was used to analyze the influence degree of each influencing factor on the extraction effect. The results show that the cold front in the temperature field of the goaf firstly develops from the area with high porosity to the area near the extraction well, while the temperature drops slowly in the area with small porosity. The order of influence degree about each factor on extraction is injection flow rate > injection temperature > pumping well length > pumping pressure.