基于CFD的填砾抽灌同井数值模拟

摘要

文章根据已有的填砾抽灌同井砂箱实验台,建立了两种不同尺寸的多区域耦合三维CFD模型,选取了热源井的抽水温度、逐时取热量和累计取热量进行模型验证.热源井抽水温度实验值与模拟值的吻合度较高,两种模型25 min内热源井累计取热量的相对误差分别为3.28%和5.56%.分析结果表明:砂箱的几何尺寸会对含水层流场和温度场的变化造成影响;回填砾石区会发生流贯通,中间隔断区的宽度与抽、回水区的间距会影响回水进入抽水区的速率,因此,应增大回水区与砂箱上顶板之间以及热源井与砂箱四壁之间的距离;应当增大中间隔断层的宽度以及抽、回水区的间距,以此来延缓流、热贯通的形成.%Based on the existing forced external circulation standing column well(FECSCW) sandbox experimental table, two multi-zone coupled 3D CFD models in different sizes were established.The models were validated by outlet water temperature (OWT), hourly heat absorption quantities (HHAQ) and accumulative heat absorption quantities (AHAQ) of thermal well. The experimental value of OWT and HHAQ agree well with the simulation value. The relative error of AHAQ in 25 min is 3.28% and 5.56% respectively. The results show that the size of the sandbox will affect the aquifer flow/temperature field. The backfill gravel zone will induce the flow transfixion, while the width of the seal zone (WSZ) and the distances between pumping and injection screens (DPIS)will affect the rate of inlet water entering the pumping screen.Therefore,it should increase the distance between injection screen and upper roof of sandbox,and the distance between thermal well and the walls. Moreover, the WSZ and DPIS need increase too, in order to reducing the flow/thermal transfixion.