Flowing partially penetrating well: solution to a mixed-type boundary value problem

A new semi-analytic solution to the mixed-type boundary value problem for a flowing partially penetrating well with infinitesimal skin situated in an anisotropic aquifer is developed. The solution is suited to aquifers having a semi-infinite vertical extent or to packer tests with aquifer horizontal boundaries far enough from the tested area. The problem reduces to a syste m of dual integral equations (DE) and further to a deconvolution problem. U nlike the analogous Dagan's steady-state solution [Water Resour. Res. 1978; 14:929-34], our DE solution does not suffer from numerical oscillations. T he new solution is validated by matching the corresponding finite-differenc e solution and is computationally much more efficient. An automated (Newton -Raphson) parameter identification algorithm is proposed for field test inv ersion, utilizing the DE solution for the forward model. The procedure is c omputationally efficient and converges to correct parameter values. A solut ion for the partially penetrating flowing well with no skin and a drawdown- drawdown discontinuous boundary condition, analogous to that by Novakowski [Can. Geotech. J. 1993; 30.600-6], is compared to the DE solution. The D-D solution leads to physically inconsistent infinite total flow rate to the w ell, when no skin effect is considered. The DE solution, on the other hand, produces accurate results. (C) 1999 Elsevier Science Ltd. All rights reser ved.