环渤海平原区咸水源热泵系统对含水层孔隙结构变化的影响

Effects of the brackish water source heat pump system on the aquifers porous structure variation in the plain area around the Bohai Sea

针对环渤海平原区地下咸水层孔隙结构与矿物构成的特殊性,通过物理模拟试验,结合胶体稳定性理论,揭示咸水源热泵系统运行过程中引起咸水介质堵塞的诱导机制,探索咸水层孔隙结构的变化规律。研究结果表明:在含水介质的机械组成与孔隙结构相近的条件下,将咸水层原砂渗流砂柱与人造含水介质渗流砂柱进行比较,咸水层原砂渗流砂柱中各渗流单元相对渗透系数K/K0的变化时间相对滞后,试验结束时,两类渗流砂柱的K/K0分别为82.6%,109%,累计释放颗粒的质量分别为121,169 mg;利用CT扫描技术发现,在渗流试验过程中,咸水层孔隙结构呈现出非均质性的变化规律;由于含水层中的微小颗粒具有显著的胶体性状,因此含水层中颗粒间的静电作用力会使这些颗粒的稳定性得以增强;颗粒矿物构成与形貌特征是造成咸水介质孔隙结构变化的主要影响因素。

According to the particularity of porous structure and mineral composition in brackish aquifers of the plain area around the Bohai Sea, a infiltration simulation experiment was conducted, which, combining with related theories of colloid stability, explicated, the induced mechanism that gave rise to the aquifer medium blockage in heat storage mode, and then probed into the variation of the aquifer medium porous structure in the operational process of the brackish water source heat pump system. The study results indicate that the relative permeability coefficient （K/Ko） of per seepage element of brackish aquifer delays in variation time, compared with artificial aqueous medium sand column when the mechanical composition and porous structure of aquifer medium is similar. Additionally, there are significant differences in K/Ko trends can be found during this experiment. As for experiment results, the relative permeability coefficient of the whole aquifer medium K/Ko decreases to 82.6% and rises to 109% respectively, and the accumulation mass reaches 121 mg and 169 mg at the end of experiment. The heterogeneous regular pattern of brackish aquifers in porous structure during the heat storage process can be obtained by using the CT scanning technique. The impact of the electrostatic interaction forces on the stability of particles would be increased significantly due to the significant colloid properties of the micro-particle. The major factor that impacts the variation of porous structure in the aquifer medium is the diameter and morphology characteristics of the particle.