EXPERIMENTAL STUDY ON THE EFFECT OF SUPERCRITICAL CO2 ON SHALY CAPROCKS

Petrophysical properties such as porosity and pore size distribution are critical parameters in seal integrity of the caprock. The effect of interactions between CO2, brine, and minerals constituting the caprock, have a significant influence on the effectiveness of the caprock sealing properties. Alteration of caprock integrity leads to environmental problems and bringing into question the effectiveness of the program altogether. In this study, shale samples were exposed to supercritical CO2 (scCO2) at in-situ pressure, temperature, and salinity condition, representative of a CO2 storage operation in Southwest Hub, Western Australia. Petrophysical properties of the samples are analysed with several methods to track the changes after exposure of samples to CO2. With this approach, we show that in the context of tight samples, the alteration of caprock minerals could result in either porosity enhancement or diminishment. Pore size distribution curves form nuclear magnetic resonance (NMR), low-pressure nitrogen adsorption (LPNA), and mercury injection capillary pressure (MICP) tests indicate an increase in pore volume, except for relatively tighter, clay-rich samples.