ENGINEERING PRACTICE OF GEOTHERMAL RECHARGE TECHNOLOGY FOR LELING SANDSTONE THERMAL STORAGE

Geothermal well recharge is one of the main measures to maintain the production capacity of geothermal field, and sandstone reservoir recharge is a very difficult work. Taking the Leling area as an example, the permeability, porosity, throat characteristics and rock mechanical properties of sandstone thermal reservoirs were studied to clarify the main geological controlling factors that affecting the recharge of sandstone thermal reservoirs. The numerical simulation model of "one mining one irrigation" geothermal development system is established to study its heat transfer characteristics. The results show that the physical properties and water quality characteristics of sandstone thermal reservoir in Leling area meet the sandstone recharge conditions. The larger the distance between the mining and filling wells is, the longer the time required for the thermal breakthrough of the mining wells is, and the smaller the variation range of the mining temperature is. When the reinjection volume of the reinjection well is 65 m³ per hour, the reasonable well spacing with the production well is about 300 m. When the horizontal well distance is constant, with the increasing of flow, geothermal water connection time is faster, the average porosity >30%, the average permeability > 1100 mD, the average cumulative thickness of sand layer is greater than 195 m is more conducive to geothermal tail water recharge. In geothermal reinjection field test, the reinjection rate is 100%, the maximum reinjection volume is 82 m³ per hour and reinjection operation is stable.