Development of deep geothermal energy and its influence on geothermal water flow field: Taking the development of deep geothermal energy in Lankao County for an example

In order to study the influence of deep geothermal energy development on the flow field of thermal reservoir, deep geothermal energy development in Lankao County is selected as the research object. The geological structure and regional structure of the study area since Cenozoic are analyzed, and the of geothermal exploitation and existing problems in the area are investigated. According to the types of geothermal energy, the characteristics of the Quaternary(Q), Neogene Minghuazhen Formation(N₂) and Neogene Guantao Formation(N₁) are analyzed. The conditions of fault distribution, thermal reservoir development and water-resisting boundary in the area are found out by using controlled-source audio-frequency magnetotelluric sounding. The parameters of thermal reservoir in different positions are found by field test and measurement, the amount of geothermal resources in each layer by region are calculated. The mathematical model is established according to the mining mode, boundary conditions and hydrogeological parameters. By numerical simulation, it is predicted that the flow field of Q reservoir will revert to the original flow field model in 2023, the funnel effect of N₂ thermal reservoir flow field continues to weaken, the funnel effect of N₁ thermal reservoir flow field is obvious and its distribution is irregular. To control the influence of geothermal resource exploitation on environment, the methods of closed cycle geothermal utilization, pressure reinjection in the same layer, rational distribution of wells and comprehensive utilization of multi-layer geothermal are put forward, which provides a reference for the development of geothermal resources and environmental protection in local and surrounding areas.