Annual Performance Report On The Demonstration Reinjection Project In Sandstone Geothermal Reservoir At Dezhou City

Low-medium temperature water type geothermal resource is suitable to provide heat energy for residential seasonal heating needs, and reinjection of the cooled chemical composition no- changed geothermal tail water back into the geothermal reservoir is a necessary procedure to maintain the sustainable utilization and to prevent environmental pollution. But the reinjection in sandstone geothermal reservoir is a delicate project. The paper summarized the general performance of the demonstration reinjection project in sandstone geothermal reservoir at Dezhou city which operated continuous since 2016. Up to now, the project maintained a 6 consecutive years of nearly 100% reinjection rate. The distance between the pumping well and the reinjection well is 178m, the temperature of the geothermal tail water is around 35℃, and the temperature of geothermal water at the pumping outlet is around 55℃, the average pumping and reinjection rate is about 60m3/h to accommodate the heating needs of 52 000 m2 of residential buildings . There some slightly temperature fluctuations of the geothermal water observed at the pumping outlet, but without a stable downward trend, which suggested no thermal breakthrough occurs. The tracer test of Molybdenum ammonium acid shows a suspicious tracer travel time span of 320 days with a slight rise of Molybdenum ion concentration at the pumping well. The temperature loggings in the reinjection well showed slight temperature rise during off heating season, which suggested there is a weak heat replenish from ambient surround rock mass. The successful reinjection practices in the demonstration project draw a conclusion that long term reinjection in the sandstone geothermal reservoir is viable.