The Researches Of Energy Storage And Recharge Aquifer Medium Space Structure In Brackish Aquifers

There is abundant underground brackish water resources buried at the shallowlayer as deep as100m-150m in most costal regions in China. The undergroundbrackish water resources have a huge reverses, large distribution range, shallowburied depth, and wonderful sealed condition which are all in favor of thecomprehensive application of energy storage and recovery in aquifer. At present, thereare few reports about the analysis research of the reasons and mechanism of thehydraulic conductivity of brackish aquifers during the inject-pumping process.Based on the basic principle of water-heat transferring in aquifer, this paperrevises and perfects the current numerical model of energy storage and recoverysystem in aquifers and establishes a three-dimensional couple numerical model ofgroundwater flow, heat transferring and solute movement, which fully make use of thesignificant variation of groundwater density and viscosity coefficient in energystorage and recovery in brackish aquifer. The revised couple numerical model ofgroundwater flow, heat transferring and solute movement is applied to simulate onebrackish aquifer storage and recovery system in Tianjin Binhai New Area and the datafrom simulation calculation fits the spot experiment results. The results show that thecoefficient of hydraulic conductivity has a same change with the geo-temperature and an oppositeone with salinity in brackish aquifers when the hydrogeology condition of brackish aquiferremains the same.Field experiment on the energy storage in brackish aquifers is the key measure toexplore the characteristics of this specific energy storage in aquifer. What’s more, it isthe best approach to studying water-heat transferring in aquifers. However, there isnot any such field experiment study in domestic China until now. Based on the resultsof site survey, this brackish aquifer energy storage and recovery system is establishedunder the existing site condition of experiment in the field.The regular feature of heatand mass transfer of porous medium during the process of energy storage in brackishaquifers shall be explored, which the possibility that the permeability coefficientvaries with the changes of temperature of recharge solution is proved. Thisexperiment also provides reference model and basic data for indoor experiment.By combining the actual experiment and theoretical analysis, a set of onedimensional infiltration sand column system is established. With a series of mutation and gradual experiments in temperature and salinities changes of recharge solution,the main reasons causing the changes of aquifer medium space structure andpermeability are explored based on double layer theory. The results show that,permeability is influenced by the temperature and salinity variation of rechargesolution as well as its change gradient. Take the temperature mutation experiment ofrecharge solution as example, the heterogeneousness of permeability in aquifermedium is revealed. In conclusion, when the recharge water remains the same, theregion of hyposmosis curtain in aquifer medium varies with the changes oftemperatures of recharge solution.Through simulating the heat storage of three dimension infiltration sand box, it isproved that, the permeability changes of aquifer medium is heterogeneous inhorizontal and vertical direction. By fixing and switching the locations of pumpingwell and injection well, it shows that the aquifer medium clay particle distribution andspace structure variations are irreversible. Under these two working modes, lowpermeability curtain occur in aquifer medium. However, where the low permeabilitycurtains lay is different according to its formation mechanism.