Microstructural characteristics of wellbore cement and formation rocks under sequestration conditions

Five rock samples of different lithology (quartzitic sandstone, eolian sandstone, shale, limestone and anhydrite) were selected for the examination. The prepared samples composed of well bore cement and rock were exposed to CO2-saturated brine, under static conditions. Basing on the shape of the gas adsorption isotherms the classification of the materials (cement and rocks) was performed. In the case of the rocks classified as macroporous, because of the porosity characteristics close to those of cement, the CO2 saturated brine flow is uniform in both materials (cement and rock), and the dissolution and precipitation processes are less intense. The obtained results seem to be very useful for predicting the integrity of wellbore, in case of different caprock and reservoir rock.