Experimental and numerical study on hydraulic fracture propagation in coalbed methane reservoir

A true triaxial hydraulic fracturing system is built for carrying out fracturing stimulation experiments on cubic raw coal specimens to simulate the hydraulic fracturing by means of a vertical well in a coal seam. The effects of in-situ stress and injection rate on the hydraulic fracture propagation are analyzed. A three-dimensional hydraulic fracture numerical simulation model is developed to quantitatively study the effects of different geological and operational factors on the fracture propagation in coalbed methane (CBM) reservoirs. The results indicate that higher elasticity modulus and fracture toughness difference between coal and bedding show a strong inhibitory impact on the major fracture extension, but are good for forming more induced fractures. A smaller horizontal in-situ stress difference is beneficial in forming a crosscutting fracture network. A larger injection rate enhances the fracture size and the complexity of the fracture network. The experimental and numerical simulation study achievements can provide a case reference for optimization design of hydraulic fracturing and fracture network geometry control of CBM reservoirs.