Three-dimensional hydrogeological parametrization using sparse piezometric data

[摘要] When modelling contamination transport in the subsurfaceand aquifers, it is crucial to assess the heterogeneities of the porousmedium, including the vertical distribution of the aquifer parameter. Thisissue is generally addressed thanks to geophysical investigations. As an alternative, a method is proposed using estimated hydraulic parametersfrom a 2D calibrated flow model (solely reliant on piezometric series) asparametrization constraints for a 3D hydrogeological model. The methodologyis tested via a synthetic model, ensuring full knowledge and control of itsstructure. The synthetic aquifer is composed of five lithofacies,distributed according to a sedimentary pattern, and functions in anunconfined regime. The level of heterogeneity for hydraulic conductivityspans 3 orders of magnitude. It provides the piezometric chronicles usedto inverse 2D flow parameter fields and the lithological logs used tointerpolate the 3D lithological model. Finally, the parameters of eachfacies (hydraulic conductivity and porosity) are obtained through anoptimization loop, which minimizes the difference between the 2D calibratedtransmissivity and the transmissivity computed with the estimated 3D faciesparameters. The method estimates values close to the known parameters, even with sparsepiezometric and lithological data sampling. The maximal discrepancy is45 % of the known value for the hydraulic conductivity and 6 % for theporosity (mean error 26 % and 3 %, respectively). Although themethodology does not prevent interpolation errors, it succeeds inreconstructing flow and transport dynamics close to the control data. Due tothe inherent limitations of the 2D inversion approach, the method onlyapplies to the saturated zone at this point.

[学科分类] 妇产科学