地下水观测井井筒效应的多场耦合数值模拟

利用3种不同水流运移方程分别模拟井管附近不同区域的水流运动, 基于流量守恒原理实现不同流态区域边界的耦合, 建立了有代表性的观测井-含水层系统场景; 利用建立的耦合模型模拟了观测井-含水层系统中水头的分布, 基于模型模拟数据分析了观测井井筒存在对含水层局部水头分布及地下水水质采样和环境监测结果的影响; 还分析了地下水三维水流强度、观测井井径以及含水层介质参数等对井筒效应的影响规律: 井筒效应在粘土等渗透系数和比单位贮水系数相对较小的含水层介质中更为明显, 其影响随着三维水流强度及观测井井径的增加而增大; 进行了上述参数的敏感性分析, 指出对于同一参数其在不同区间的敏感性比例不同, 对于不同参数观测井井径的敏感性比例最大, 因此在地下水环境监测的工程实践中减小观测井井径是相对快速且有效提高监测和采样精度的方法. 

A Coupled Darcy-Brinkman-NS Simultation Model of Wellbore Effect of an Monitor Well

In this paper, three different flow equations, namely, Darcy law, Brinkman equation and Navier-Stoke equation, are employed to simulate the water movement with different flow conditions within and around the wellbore in a confined aquifer. Based on the principles of continuity, three different flow equations are coupled. The coupled model is used to simulate the impact of wellbore in aquifer on the head distribution and water movement. Results indicate that the influence of wellbore increases with the strength of three-dimensional flow and wellbore diameter. In addition, being compared with the sandy soil aquifer, wellbore effect is more obvious in clay or similar aquifers with lower permeability and smaller storage coefficient. By conducting parameter sensitivity analysis, it also can be found that the sensitivity ratio differs in different value zones for the same parameter, while for different parameters, wellbore effect is more sensitive to well diameter than other parameters.