Flow characteristics and reaction properties of carbon dioxide in microtubules and porous media

Carbon dioxide reacts with porous media while flowing through them enhancing their permeability. Its flow behavior as well as the permeability enhancement effects were studied in synthetic cores, natural cores and microtubes with an inner diameter of 5 μm. The results show that the permeability of H₂O-saturated cores (containing carbonate ingredients) was enhanced by increasing the injection volume of a CO₂-H₂O solution. This enhancement is attributable to carbon dioxide’s corrosion, which is justified by SEM scanning. The same phenomenon occurs with a CO₂-H₂O solution in microtubes, but for a different reason. The gas flow velocity of carbon dioxide in microtubes was approximately 100% faster than that of nitrogen because of the scale and the squeezing effects. Carbon dioxide molecules dissolved in water accelerate the diffusion rate of water molecules within the boundary layer, which in turn diminishes the thickness of the water film and enlarges the effective pore size. This flow behavior facilitates the injection of carbon dioxide into low-permeability reservoirs for oil-displacement and formation energy buildup purposes. This behavior also increases the potential for carbon dioxide channeling or release from the formation. Supported by the “973” Project from the Ministry of Science and Technology of China (Grant No. 2006CB705805) and the National Key Technology R&D Program (Grant Nos. 2006BAB03B06 & 2007BAB17B0B)