Mining disturbance analysis and recharge scheme research of semi-trap deep circulation bedrock thermal reservoir
The Ordovician thermal reservoir in Liaocheng East Thermal Field is the preferred area for exploration and development of bedrock thermal reservoir in Shandong Province.In this paper,a regional deep-circulation fracture-karst bedrock thermal reservoir model of semi-structural trap is established by analyzing the geothermal characteristics of caprock,reservoir,water source,heat source and channel in the area.The analysis shows that the semi-trap deep circulation occurrence characteristics not only improve the hot water mineralization and trace elements,but also lead to the problems of strong reservoir sealing,large mining disturbance and difficult sustainable utilization.Based on the measured data of the observation wells in the area for many years,the empirical formula of mining depth reduction is established.The variation coefficient method and comprehensive index method are used to evaluate the disturbance of thermal reservoir mining in the area.It is considered that the exploitation of bedrock thermal reservoir in the area leads to the decrease of water level,water volume,reservoir pressure,temperature and service life.There are few secondary problems such as disturbance of water quality,land subsidence,thermal pollution,environmental pollution and cross-layer water source pollution.Combined with the regional reinjection test,the suitable local mining and reinjection schemes are discussed:centralized mining,gradient utilization,reinjection in the same layer,balanced mining and reinjection.The reinjection wells of bedrock thermal reservoirs in the area should be set in the range of 300-500 m around the mining well,and the tail water temperature should be 35-40 °C.This study provides a theoretical basis for the sustainable utilization of bedrock thermal reservoirs in the area.
bedrock thermal reservoirdeep circulationsemi-structural trapmining disturbancebalance in exploitation and reinjection
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