Experimental Research on Supercritical Carbon Dioxide Fracturing of Sedimentary Rock: A Critical Review

Supercritical carbon dioxide (ScCO₂) fracturing has great advantages and prospects in both shale gas exploitation and CO₂ storage. This paper reviews current laboratory experimental methods and results for sedimentary rocks fractured by ScCO₂. The breakdown pressure, fracture parameters, mineral composition, bedding plane angle and permeability are discussed. We also compare the differences between sedimentary rock and granite fractured by ScCO₂, ultimately noting problems and suggesting solutions and strategies for the future. The analysis found that the breakdown pressure of ScCO₂ was reduced 6.52%–52.31% compared with that of using water. ScCO₂ tends to produce a complex fracture morphology with significantly higher permeability. When compared with water, the fracture aperture of ScCO₂ was decreased by 4.10%–72.33%, the tortuosity of ScCO₂ was increased by 5.41%–70.98% and the fractal dimension of ScCO₂ was increased by 4.55%–8.41%. The breakdown pressure of sandstone is more sensitive to the nature of the fracturing fluid, but fracture aperture is less sensitive to fracturing fluid than for shale and coal. Compared with granite, the tortuosity of sedimentary rock is more sensitive to the fracturing fluid and the fracture fractal dimension is less sensitive to the fracturing fluid. Existing research shows that ScCO₂ has the advantages of low breakdown pressure, good fracture creation and environmental protection. It is recommended that research be conducted in terms of sample terms, experimental conditions, effectiveness evaluation and theoretical derivation in order to promote the application of ScCO₂ reformed reservoirs in the future.