Study On Kaifeng Deep Geothermal Pumping-recharging Based On Groundwater And Geothermal Coupling Simulation

As traditional fossil energy sources such as petroleum and coal have greater and greater impact on the environment,geothermal energy is gaining more and more attention as a green energy source.Because of its green and low-carbon renewable energy,it has great potential for future development.Kaifeng City is located in the Kaifeng Sag.The richness and development of geothermal resources are at the forefront in Henan Province.The development of geothermal resources has made great contributions to the promotion of local economic development and the improvement of residents 'lives.However,the long-term "only exploitation without tailwater recharge" is a problem that the development causes the groundwater level of the thermal reservoir to decrease year by year and the output of the geothermal well is insufficient.The recharge of geothermal tail water can effectively solve the above problems and achieve sustainable utilization of geothermal resources.In this paper,FEFLOW is used to establish a coupling model of groundwater flow and heat transport in the study area,to simulate and analyze different irrigation and irrigation conditions,and to analyze the sensitivity of the seepage field and temperature field to the parameters of permeability coefficient and rock thermal conductivity.The calculation of the four thermal reservoir resources and recoverable resources mainly draws the following conclusions:(1)When planning a geothermal well in the fourth thermal reservoir in the study area,in order to avoid thermal breakthrough,when the recharge temperature is 15 ? and the recharge rate is 30%,it is recommended that the geothermal pumping-irrigation well spacing should not be less than 200m;At 50%,the recommended geothermal pumping-irrigation well spacing should be 300m;when the recharge rate is 100%,the recommended geothermal pumping-irrigation well spacing should be 400 m.(2)The control variable method was used to simulate and analyze the effect of changes in recharge rate and recharge distance on the seepage field and temperature field.It was found that an increase in recharge rate can effectively reduce the water level in the mining well and decrease The area of the funnel is lowered,but the risk of thermal breakthrough of the mining well is increased;the smaller the well spacing,the better the effect of the recovery well compensation of the production well,the stronger the hydraulic connection between the production and irrigation wells,the higher the risk of thermal breakthrough.(3)The change of permeability coefficient has a great influence on the seepage field in mining and irrigation areas.At the end of the heating period with 50% increase in permeability coefficient and 50% decrease,the water level of the recharge well decreased by 6.4m and 10.6m compared with the same,while the water level of the pumping well increased by 14.3m and decreased by 24.6m,respectively.The field is less sensitive to changes in permeability coefficient.When the permeability coefficient increases by 50% or decreases by 50%,the change value of the pumping well temperature is less than 0.2? when the permeability coefficient is unchanged,and the change value of the distance from the cold front to the recharge well is less than 15 m.The sensitivity of the seepage field and temperature field to the change of rock thermal conductivity is low,and the thermal conductivity increases or decreases by 50%.At the end of the heating period,the pumping and recharge well water levels are less than 1m when the thermal conductivity is constant.While the temperature of the pumping well is less than 1°C when the thermal conductivity is constant,the change of the distance from the front edge of the cold front to the recharging well is less than 15 m.(4)The total amount of geothermal resources in the fourth thermal reservoir in the study area is 1.17×1019J,which is equivalent to about 3.99×108 t for standard coal.Based on the numerical model simulation of the appropriate well spacing for each recharge rate,the recoverable resources of the study area were calculated by the well layout plan and the average well layout plan,respectively.When the rates are 30%,50%,and 100%,the maximum recoverable heat of the fourth thermal reservoir is 4.86×1015J/a,2.20×1015J/a,1.23×1015J/a;under the well layout plan,the production volume is 100m3/h At the recharge rate of 30%,50%,and 100%,the maximum recoverable heat of the fourth thermal reservoir is 4.74×1016J/a,2.11×1016J/a,and 1.18×1016J/a.