The key mechanical problems on hydraulic fracture in shale

Shale gas is unconventional natural gas stored in shale in free or absorbed form, and sometimes in free fluid phase. The exploitation of shale gas has become a promising field of green energy development in China. Although great success has been achieved in shale gas revolution in North America with the technique of hydraulic fracturing, only 5~15% of the stored oil and gas could be exploited. In order to improve the production of shale oil and gas, a huge challenge accompanied with great opportunities is presented to the mechanics researchers. Based on the recent study results of our research group, this paper introduces and summarizes the key mechanical problems of shale hydraulic fracturing from the aspects of theory, numerical simulation and experiment. The main contents include developing a large-object experiment, establishing the shale constitutive model and fracture mechanics theory, and developing the numerical simulation method for coupling fracture mechanics and fluid mechanics of fracture network. The investigation on hydraulic fracture is of great significance and innovation and will lay a solid foundation for the physical experiment model, fracture mechanics theory and numerical simulation techniques of effective exploitation of shale gas in China.