Modeling research in low-medium temperature geothermal field, Tianjin

The geothermal reservoir in Tianjin can be divided into two parts: the upper one is theporous medium reservoir in the Tertiary system; the lower one includes the basement reservoir inLower Paleozoic and Middle-Upper Proterozoic. Hot springs are exposed in the northern mountainand confined geothermal water is imbedded in the southern plain. The geothermal reservoir is in-cised by several fractures. In recent years, TDS of the geothermal water have gone up along withthe production rate increasing, along the eastern fracture zone (Cangdong Fracture and West Bai-tangkou Fracture). This means that the northern fracture system is the main seepage channel ofthe deep circulation geothermal water, and the reservoir has good connection in a certain area anddefinite direction. The isotopic research about hydrogen and carbon chronology indicates that themain recharge period of geothermal water is the Holocene Epoch, the pluvial and chilly period of20 kaBP. The karst conduits in weathered carbonate rocks of the Proterozoic and Lower Paleozoicand the northeast regional fracture system are the main feeding channels of Tianjin geothermalwater. Since the Holocene epoch, the geothermal water stayed at a sealed warm period. Thetracer test in WR45 doublet system shows that the tracer test is a very effective measure forunderstanding the reservoir's transport nature and predicting the cooling time and transportvelocity during the reinjection. 3-D numerical simulation shows that if the reinjection well keeps asuitable distance from the production well, reinjection will be a highly effective measure to extractmore thermal energy from the rock matrix. The cooling of the production well will not be a problem.

Modeling research in low-medium temperature geothermal field, Tianjin

The geothermal reservoir in Tianjin can be divided into two parts: the upper one is the porous medium reservoir in the Tertiary system; the lower one includes the basement reservoir in Lower Paleozoic and Middle-Upper Proterozoic. Hot springs are exposed in the northern mountain and confined geothermal water is imbedded in the southern plain. The geothermal reservoir is in- cised by several fractures. In recent years, TDS of the geothermal water have gone up along with the production rate increasing, along the eastern fracture zone (Cangdong Fracture and West Bai- tangkou Fracture). This means that the northern fracture system is the main seepage channel of the deep circulation geothermal water, and the reservoir has good connection in a certain area and definite direction. The isotopic research about hydrogen and carbon chronology indicates that the main recharge period of geothermal water is the Holocene Epoch, the pluvial and chilly period of 20 kaBP. The karst conduits in weathered carbonate rocks of the Proterozoic and Lower Paleozoic and the northeast regional fracture system are the main feeding channels of Tianjin geothermal water. Since the Holocene epoch, the geothermal water stayed at a sealed warm period. The tracer test in WR45 doublet system shows that the tracer test is a very effective measure for understanding the reservoir's transport nature and predicting the cooling time and transport velocity during the reinjection. 3-D numerical simulation shows that if the reinjection well keeps a suitable distance from the production well, reinjection will be a highly effective measure to extract more thermal energy from the rock matrix. The cooling of the production well will not be a problem.