Statistical analysis of liquid seepage in partially saturated heterogeneous fracture systems

摘要: Field evidence suggests that water flow in unsaturated fracture systems may occur along fast preferential paths. However, conventional macroscale continuum approaches generally predict the downward migration of as a spatially uniform wetting front subjected to strong inhibition into partially saturated rock matrix. One possible cause this discrepancy be random geometry surfaces, and hence, irregular aperture. Therefore, numerical model was developed study investigate effects geometric features natural fractures on liquid seepage solute transport 2-D planar under isothermal, conditions. The were conceptualized heterogeneous porous media are characterized by their correlated permeability fields. A statistical simulator, which uses simulated annealing (SA) algorithm, employed generate synthetic Hypothesized expected relevant for behavior, such asperity contacts, considered SA algorithm. Most importantly, new perturbation mechanism order consider specifically spatial correlation near conditioning contacts. Numerical simulations fluid then performed these simulator TOUGH2, assuming matrix permeability, gas phase pressure, capillary/permeability hysteresis, molecular diffusion can neglected. Results simulation showed is localized flow, with bypassing, funneling, ponding. Seepage pattern dominated fraction contracts, shape, size, correlation. structure field less important than faster breakthrough observed higher normal stress, accompanied nonlinearly decreasing trend effective permeability. Interestingly, dispersion intermediate contacts; but it lower small or large fractions become if ponding becomes significant. Transport indicate tracers bypass dead-end pores travel paths have resistance. Accordingly, tracer curves show more spreading water. Further analyses suggest log-normal time fails fit water, good approximation tracer.