Achieving the dual carbon goals of peaking by 2030 and neutrality by 2060 is significantly aided by the growth of coal measure gas research and development, especially for China to optimize its primary energy consumption. We critically review the distribution, geological characteristics, methods of liberation and then recovery by hydraulic fracturing of coal measure gas in China and present a roadmap to optimize this recovery. The gas-bearing system is the focus of this recovery, but this system is embedded within its sedimentary environment and modulated by tectonic and hydrogeological controls that affect gas exploration and recovery. However, to improve the development of coal measure gas in China, bottleneck problems remain to be solved, such as accurately predicting reservoir behavior in dessert regions, optimizing well patterns, and deploying optimal horizontal well trajectories. Additionally, the technology breakthroughs on deep co-production of coal measure gas, automatic fracturing and intelligent drainage are imminent. Basically, developing new techniques and conducting improved geological surveys are essential to ensure the sustainable supply of coal measure gas resource. Thus, this review presents a comprehensive introduction to coal measure gas resources in China, of utility to academic researchers and engineers in enhancing the understanding of the current situation and in projecting future development.

Shale contains a certain amount of natural fractures, which affects the mechanical properties of shale. In this paper, a bonded-particle model in particle flow code (PFC) is established to simulate the failure process of layered shale under Brazilian tests, under the complex relationship between layer plane and natural fracture. First, a shale model without natural fractures is verified against the experimental results. Then, a natural fracture is embedded in the shale model, where the outcomes indicate that the layer plane angle (marked as α) and the angle (marked as β) of embedded fracture prominently interfere the failure strength anisotropy and fracture pattern. Finally, sensitivity evaluations suggest that variable tensile/cohesion strength has a changeable influence on failure mechanism of shale, even for same α or/and β. To serve this work, the stimulated fractures are categorized into two patterns based on whether they relate to natural fracture or not. Meanwhile, four damage modes and the number of microcracks during the loading process are recognized quantitatively to study the mechanism of shale failure behavior. Considering the failure mechanism determines the outcome of hydraulic fracturing in shale, this work is supposed to provide a significant implication in theory for the engineering operation.