A Study Of Reinjection Of Geothermal Resources In The Geothermal Reservoir Of The Wumishan Group In Tianjin

There is continual concern about hydraulic,hydrochemical and temperature features of deep-seated geothermal reservoirs under the conditions of geothermal reinjection.This paper mainly analyzes the reinjection in the carbonate resevior of the Wumishan Group in Tianjin under the condition of reservoir dynamic field distribution of plane,vertical distribution characteristics and the influence of the injection,the temperature field distribution of plane,vertical distribution characteristics and influenced by injection,field of plane distribution characteristics,exploration chemical characteristics and vertical distribution characteristics of geothermal fluid in geothermal wells,etc.By 2016,there were 236 geothermal wells(including 90 reinjecton wells)and 90 exploration-reinjecetion systems in the geothermal reservoir of the Wumishan Group in the Tianjin area.The steady flow temperature of the geothermal wells ranges from 70 to 113 ?.The geothermal fluids quality is good and mainly used for heating and domestic water.The geothermal flow of heating and domestic water accounts for 78.2% and 78.2% of the proportion of the total annual production,respectively.At the present stage,the utilization scale is large,and the reinjection rate is increasing year by year.There is still a long distance between the distance from the 100% exploration and reinjection balance.Geothermal reinjection well is generally used with three open holes and four open holes.In order to ensure the effect of recharge,the naked-eye length is basically 500 m.Analyses of 2 pairs of typical exploration and reinjecetion systems show that the reinjection effect on the geothermal reservoir in the plane is reflected in the local area.Through the analysis of the dynamic monitoring data for many years,it is found that the backgrouting can slow down the reservoir pressure of geothermal wells with hydraulic connections.According to the pressure data of geothermal wells,the reservoir pressure increases with the increase of the well depth.Analyses of the steady flow dynamic observation data of geothermal well wellhead temperature show that the temperature difference is not large both the steady flow temperature of geothermal well wellhead and well completion,continuous injection on the influence of reservoir plane is small,and the reservoir temperature recovers quickly.The temperaturess of stable flow geothermal well wellhead of HX-25,HX-14 and DC-40 are basicly stable at 89?,92? and 98-99?.During the current monitoring period,the fluid temperature of geothermal wells has not changed significantly due to a long-term exploration or reinjection.The geological and numerical model of the Wumishan Group reservoir are established and the reservoir pressure field and temperature field of simulation forecast analyses are carried out,and the simulation results show that the recoverable amount of the thermal fluid for the development and utilization of geothermal resources and the actual production relations is not big,but the injection quantity is more intuitive.If we want to increase the reservoir fluid production,it is necessary to solve the reservoir injection amount and increases the reinjection rate.The thermal reservoir temperature of the reinjection wells was basically restored during the non-exploration period,so that the fluid temperature of the geothermal wells did not change significantly due to a long-term mining or reinjection.The conclusion is consistent with the analysis results of the dynamic observation data and the temperature data.Comparison with water quality data of many years indicates that the chemical properties of geothermal fluid of the Wumishan Group reservoir are stable.Except the a certain fluctuation,the main ion contents did not obviously changed due to human production or injection in reinjection wells or drilling wells in the concentrated exploration area.It is necessary to further increase the intensity of reinjection to maintain the sustainable development and utilization of the Wumishan Group reservoir.Reinjection can effectively alleviate the trend of reservoir pressure decline in the future and make the geothermal of resources high quality sustainable in the development and utilization.