非完整井对单井注抽试验测算地下水流速影响机理

Effect Mechanistic of Partially Penetrating Well on Single-Well Push-Pull Tests for Groundwater Velocity Estimation

为了探究非完整井结构对单井注抽试验测算地下水流速的影响机理,采用COMSOL Multiphysics软件建立非完整井条件下的单井注抽试验数值模型,分析了非完整井滤管长度与位置对穿透曲线的影响.同时开展了非完整井单井注抽试验室内试验研究,并利用数值模型拟合示踪剂穿透曲线来进一步验证模型的可靠性.结果表明:滤水管长度越短,示踪剂穿透曲线早期浓度越低;滤水管位置越靠近含水层上部,穿透曲线早期的浓度越高;参数反演误差分析表明数值模型能较好地反演地下水流速、孔隙度以及弥散度.总体而言,非完整井附近复杂流场导致溶质空间的不均匀分布,进而对穿透曲线有显著影响,增大传统完整井模型的参数反演误差;而本文建立的非完整井单井注抽试验模型拟合精度高,能够适用于非完整井条件下的单井注抽试验.

For the purpose of analyzing the influencing mechanism of partially penetrating well on single-well push-pull(SWPP)tests,this study employed COMSOL Multiphysics to develop a numerical model of SWPP test,in which the impacts of the length and location of screen on breakthrough curves(BTCs)were investigated.Meanwhile,a laboratory experiment of SWPP test with partially penetrating well was conducted,verifying the reliability of the proposed model by fitting the observed and simulated BTCs.The results show that a shorter screen length leads to a lower concentration of BTC in the early stage;meanwhile a shorter unscreened segment near the top of aquifer results in a lower concentration in the early stage.Additionally,the error analysis of parameter inversion indicates that the numerical model is quantified for the estimations of groundwater flow velocity,porosity and dispersion by fitting BTCs.Overall,the complicated flow field in the vicinity of partially penetrating wells leads to a non-uniform spatial distribution of solute,which has a significant effect on the BTCs and increases the parameter inversion error if using the traditional fully penetrating well model.Nevertheless,the SWPP test model developed in this paper has high fitting accuracy and can be applied to SWPP test under partially penetrating conditions.