Research on Fracture Propagation by Cryogenic Volume Fracturing Based on Dem

Due to the defects of active water fracturing fluid properties and the particularity of coal in the structure and mechanical properties, the conventional hydraulic fracturing is not applicable to high-rank coal seam, which is prone to the problems of excessive extension of fracture height, short effective propped fracture length. This paper introduces cryogenic technology into the coalbed methane(CBM) fracturing and puts forward a new cryogenic volume fracturing technology, whose mechanism is: alternative injecting water and cryogenic fluid by small rate to freeze the water in the fracture and cleat, temporary plugging fracture to divert, forming complex fracture networks to increasing CBM production. In this paper, the discrete element method (DEM) is adopted to establish a two-dimensional fracture propagation model to simulate cryogenic volume fracturing in CBM. The different injection temperature and pressure are simulated to study fracture propagation rules. The results show that with injection pressure increasing and temperature reducing, fracture networks become more complex and larger. Cryogenic volume fracturing can form ice temporary plugging to effectively increase the network complexity and SRV.