An Improved Approach in Modeling Injection-Withdraw Test of the Partially Penetrating Well

Single Well Injection-Withdraw (SWIW) test has been widely used to estimate physical and chemical parameters of aquifer due to its advantages of low budget, less time consuming and easy to operate. However, the complex flow fields near the wellbore pose challenges in solving the model of the SWIW test, especially for partially penetrating wells. Currently, three methods included in MODFLOW/MT3DMSwere used to deal with this problem:traditional WELL module, high permeability WELL module and MNW module, which respectively represent three types of commonly used numerical methods. However, it was found that all of these models were based on assumptions which might not be satisfied in the actual applications. In this study, a new method was developed by coupling the MNW module and high permeability WELL module. The case studies demonstrated the accuracy of the new model of the SWIW test. Meanwhile, we employed the new model to investigate two assumptions included in the previous studies, and found that:(1) the influence of the well screen location on the results was not negligible. (2) The assumption of the steady-flow field used in the traditional mathematical model of SWIW will cause non-negligible errors when the ratio of permeability coefficient to storage coefficient is small.