Structure-Properties Correlations in Original and Hydrothermally Altered Rocks: Pore-scale Modeling Study Using Element Mapping and X-ray

Abstract

Reactive transport and hydrothermal alteration of rocks depend not only on boundary conditions, e.g., pressure, temperature and solution chemistry, but is also influenced by original rock structure. By structure we mean not only pore morphology and connectivity, but also spatial correlations of pore space and chemical elements/mineral phases. In this work we combine detailed structure information obtained using X-ray microtomography scanning with high resolutions, element mapping with µXRF-spectrophotometer, laboratory measurements on rock samples, and pore-scale modeling to characterize structure-properties correlations in original and hydrothermally altered rocks. We use such modern methods as local porosity theory analysis (connectivity of the pore space), correlation functions (spatial correlations between pore space and different mineral phases), different pore-scale modeling approaches to determine permeability and mechanical properties and connect them to structure data (spatial correlations and pore morphology estimated from pore-network extractions). As a result, it was shown that pore space morphology and connectedness affect precipitation/dissolution patterns, which, in turn, affect changes in physical properties. Pore-scale modeling techniques were found to be invaluable tools in characterizing changes in physical properties of altered rocks based on 3D structure information obtained using non-destructive microtomography scanning.