Methodology development for modeling heterogeneous conductivity fields for a sandstone type uranium deposit, central Japan

Abstract

A methodology for modeling heterogeneous conductivity fields has been developed for the Tono sandstone type uranium deposit in Japan. The main purpose of this study is to test the hypothesis that the heterogeneity of uranium deposition is predominantly controlled by the heterogeneity of the fluid flow system. Three numerical techniques — Kriging, Multi-Kernel Modulation and Self-affine fractal simulation — have been studied. Krining and Multi-Kernel Modulation were applied in order to characterize the broad horizontal spatial structures. Self-affine fractal simulation was used to represent a high resolution vertical section through the ore body. Modeling of the flow and uranium concentration in the heterogeneous self-affine conductivity field was carried out.The results of this study show that:(1) fine resolution of the heterogeneous field can be applicable for the simulation by comparison with the calculated particle distributions with observed uranium concentration;(2) groundwater flow modelling is applicable to show that the location and magnitude of groundwater flow is constrained by heterogeneity of hydrological structure;(3) techniques such as the Self-affine fractal method can be used to simulate the influence of hydrological heterogeneity on the uranium concentration in sedimentary rock; and(4) the heterogeneity of the uranium concentration is most likely controlled by the spatial distribution of variation in the hydraulic conductivity field.