The Principle of Density Differences Drive Geothermal Water to Move and the Short Range Recharge Model of Geothermal Water in Hilly Area

Abstract

The thermal reservoir of a geothermal well in a rift subsidence basin with depth of 2148m belongs to the lower Tertiary sandstone. Pumping test results: the initial water table is 8.7m under ground, the initial water temperature is 50Ž; in the 80m3/h pumping conditions for 34h, the water temperature is 56Ž, water table is 5.2m under ground,e.i. upthrow of 2.5m; 2 minutes later, the well begins to flow itself and water temperature is 61Ž, water outflow yield is about 60 m3/h; after 46 hours, the water outflow yield is to the max 90m3/h and for 8h while the water head is 9.2 m above the ground and the water temperature is 67Ž. The author puts forward the idea that the movement mechanism of the groundwater is caused by the density differences from different temperatures. Based on this idea, the authors propose the short range recharge model of geothermal water in flat terrain hilly area. The model explains the coexistence mechanism of recharge and discharge (hot springs) zones can be at same altitude. Considering the temperature is an important driving force of groundwater movement, the paper puts forward and demonstrates that the hot springs can expose at higher lands while the recharge zone being situated lower lying areas.