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.