There is an increasing trend to dispose acid gases (H2S and CO2) generated from natural gas processing by geologic sequestration. Industry and government must carefully assess the compatibility of the formation matrix and fluids, with the intended injection stream, to ensure safe and efficient facility operations. We investigated cores subjected to acid gasflooding using X-Ray computed tomography (CT) analysis. The changes in pore morphology, pore size, and pore distribution were examined. Results indicated that the porosity roughly doubled and pore size increased substantially. Visually distinct areas of the core suggested that changes in porosity were non-uniform, probably due to the natural heterogeneity in the rock and/or regions of nonuniform flooding due to lack of pore interconnectivity in the matrix. Detailed CT image analysis revealed traces of halite (NaCl) probably due to the desiccation of the initial water saturation by the highly under-saturated injected gas. Our results suggest that changes in porosity are not attributed to dissolution processes but due to fine dislodgement and desiccation. Consequently, the permeability and porosity increases were the result of physical processes rather than chemical ones.