资源环境科技发展态势分析平台

We investigate mechanisms which enhance lateral methane (CH₄) plume migration in shallow aquifers that exhibit complex and multiscale sedimentary architecture. We show how heterogeneity in capillary pressure characteristics related to the sedimentary architecture causes gaseous CH₄ to spread over larger areas by retarding, deviating, or blocking upward buoyancy-driven CH₄ migration. Simplifying or ignoring capillary pressure heterogeneity thus leads to overestimation of leaked CH₄ to the atmosphere, and underestimation of mobile gaseous CH₄ in aquifer. We show, both qualitatively and quantitatively, that meter-scale sedimentary stratification contributes more to CH₄ plume migration than the millimeter- or centimeter-scale strata comprising them. Results indicate that the extent of gaseous CH₄ leakage, and its associated impacts on groundwater quality and global warming, cannot be accurately assessed unless the sedimentary architecture and resulting heterogeneity in capillary pressure are represented.