Porosity and permeability development in compacting chalks during flooding of nonequilibrium brines: Insights from long-term experiment

Abstract

We report the complete chemical alteration of a Liège outcrop chalk core resulting from a 1072 flow-through experiment performed during mechanical compaction at 130°C. Chemical rock-fluid interactions alter the volumetric strain, porosity, and permeability in a nontrivial way. The porosity reduced only from 41.32% to 40.14%, even though the plug compacted more than 25%. We present a novel analysis of the experimental data, which demonstrates that the geochemical alteration does not conserve the volume of the solids, and therefore, the strain is partitioned additively into a pore volume and solid volume component. At stresses beyond yield, the observed deformation can be explained by grain reorganization reducing the pore space between grains and solid volume changes fromthe rock-fluid interactions. Themechanical and chemical effects are discussed in relation to the observed permeability development.