Development of New Methodologies for Fracturing of Shale Using Non-viscous Fluid

This thesis aims to obtain a comprehensive understanding and comparison of fracturing behaviour between water- and CO2- based fracturing. A series of experimental and numerical studies were conducted focusing on the mechanical, permeability and fracturing behaviours of reservoir rocks. Water invasion in the rock matrix can significantly decrease the matrix permeability and fracture permeability, due to the combined effects of softening, water blockage and phase trapping. Compared with water fracturing, CO2 fracturing tends to create more complex fracture networks and wider fracture apertures at lower breakdown pressure, which indicates its superiority in unconventional gas production enhancement.