Researches on the reinjection of Dongli Lake bedrock reservoir in Binhai New Area, Tianjin

The Wumishan Formation is the main development and utilization reservoir in the Donglihu district of Binhai New Ar-ea, Tianjin. There are 11 geothermal wells, and static level falls by the depth of 3m annaully due to the concentrated development and utilization. For the purpose of alleviating water level falling, geothermal fluid waste water has been used for reinjection; never-theless, the falling of the water level remains relatively fast. The Dongli Lake area is rich in surface water, the treated lake water is used for reinjection to increase the amount of reinjection in rich water period, and the concentrated reinjection system has been built in this area. A reinjection well was digged to carry out reinjection test and the largest reinjection of the well is 152m³/h. TOUGH2.0 software is adopted to establish the numerical model in the study area and simulate dynamic field and temperature field characteristics of two kinds of reinjection mode under the condition of the heating period and non-heating period. Reinjection rate is 30×10⁴m³/a in the heating period averagely for 120 days, the reinjection water temperature is 20℃ and the natural reinjection modde is adopted. The reinjection rate is 40×10⁴m³/a in the non-heating period for averagely 120 days, the reinjection water tem-perature is 20℃ and the natural recharge mode is adopted. This paper forecasts the dynamic field and temperature field characteris-tics of the study area under the conditions of the absence of lake water reinjection and the existence of water injection for 1 year and 5 years. The results show that increasing lake water reinjection can reduce heat reservoir pressure dropping rate and has no sig-nificant influence on the temperature field.