TESTING THE VIABILITY OF SUPERCRITICAL CO2 AS A FRACKING FLUID BY COMPUTING ITS CHEMICAL INTERACTION WITH VARIOUS MINERALS
We plan on using molecular modeling to compare water and scCO2 interactions with illite (a common component of the Marcellus Shale and other shale gas formations). We are deriving the interfacial energies of illite with scCO2 and water (i.e., the energy of interaction between the two components) from these simulations at pressure and temperature relevant to shale gas extraction (e.g. T=60oC and P=300 bar). The interfacial energies are important because they can give us a better idea of what creates larger and more complex fractures. For instance, a fluid with a smaller interfacial energy with the shale can be expected to yield a larger fracture network because it would be able to enter the shale more easily and flow throughout the rock. As fluid is added and the pressure in the rock builds up, it would then produce a greater fracture network.
We would expect that the interaction energy between illite and CO2 will be smaller than the interfacial energy with water. This is because the supercriticality of CO2 will cause the compound to interact less with the K atoms at the surface of the illite grains. We believe that this lower interfacial tension is the factor that leads to a higher complexity of fractures with scCO2, because the scCO2 is better able to diffuse into nanopores and nucleate fractures compared to water.