Mechanical effect of CO₂ flooding of a sandstone specimen

An experimental campaign was carried out to investigate the applicability of the scratch test when studying the effect of CO₂ exposure on the mechanical strength of a Berea outcrop sandstone specimen. A water-alternating-gas scheme was chosen for a CO₂ flooding tests, using super-critical CO₂ and a 10% KCl brine. Subsequent bulk X-ray diffraction analysis showed decrease in feldspar and increase in dolomite content, when comparing the flooded specimen with dry and brine-saturated specimens. However, these mineralogical differences may be due to local heterogeneities rather than due to the CO₂ treatment itself. Scratch testing was used to assess unconfined compressive strength; no significant reduction in strength could be observed for the CO₂-exposed specimen as compared to a specimen that was only saturated with 10% KCl brine.