Crack initiation and propagation in coalbed gas reservoir during hydraulic fracturing

The crack initiation and propagation calculation model during hydraulic fracturing in a coalbed methane reservoir with interlayers is established in this paper. The influence of coal elasticity modulus and fracturing fluid displacement on the fracture geometry are studied. Results show that the fracture initiation begins at the perforation interval. Stress inhomogeneity is detrimental for the formation of multiple cracks for the extension of the fracturing area. The cracks at the boundary have changed from less developed to more developed with increasing horizontal stress coefficient. The coal elasticity modulus and fracturing fluid displacement both play a determinative effect on fracture geometry. The study provides a reference basis for implementing hydraulic fracturing of low permeability coal seams with interlayers.