Experimental and modeling study of the interaction between a crushed marl caprock and CO2-rich solutions under different pressure and temperature conditions

Flow-through experiments using columns filled with three crushed samples (marly limestone, bituminous black shale and marl), which constitute the Hontomín caprock unit, were conducted under different PTotal-pCO2 (atmospheric: 1-10− 3.5 bar, subcritical: 10-10 bar and supercritical: 150-37 bar) conditions and T (25 and 60 °C) using gypsum-undersaturated and gypsum-equilibrated solutions to evaluate the Hontomín caprock reactivity. 1D reactive transport modeling of the results enabled us (1) to better understand the overall processes that bring about the large dissolution of calcite, minor dissolution of aluminosilicates and the precipitation of gypsum, kaolinite, zeolites and some aluminum and iron oxides and oxyhydroxides and sulfates and (2) to evaluate their implication for the hydrodynamic properties of the caprock. An increase in porosity over the column length, which mostly occurred near the inlet, was calculated.