Simulation Study of Hydraulic Fracturing Using Super Critical CO2 in Shale

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Abstract The history of using fracturing fluid of carbon dioxide is more than three decades. Since literature concerning the application of fracturing with carbon dioxide first have been published in 1982, and utilize carbon dioxide in American shale fracturing have been success in early 1990s. Nowadays the application of fracturing fluid in shale hydraulic fracturing is general slick water, however, carbon dioxide will play an important role in shale hydraulic fracturing in the next 30 years, not only because shale gas production is rising all over the world, but also the water resources is increasingly scarce and greenhouse gas emission is increasing. Universal Distinct Element Code (UDEC) was used to simulate pressurized cracks and hydraulic fracturing in shale with super critical carbon dioxide in this paper. First part compares the displacements of crack surface with three different fracturing fluids, water, slick water and carbon dioxide, based on assuming uniform fluid pressure, certain elastic medium, Young's modulus, Poisson's ratio, and different size of planar crack. In the second part, the assumption of Young's modulus and Poisson's ratio which reflect shale properties, brittleness and fracability were changed, and fracturing effect with super critical carbon dioxide in different shale are simulated, crack displacement were compared in these assumptions. The simulation results suggest that viscosity of hydraulic fluid influence formation of hydraulic fractures and super critical carbon dioxide need more volume of fracturing fluid to contribute same crack displacement. Meanwhile, the performance of different shale fracability with super critical carbon dioxide fracturing fluid shows shale fracability index ranges in this model, and to some extent, using carbon dioxide as fracturing fluid have more economic and environmental significance.