Impact Analysis of Multiple Parameters on Fracture formation during Volume Fracturing in Coalbed Methane Reservoirs

Uniaxial and triaxial compression, Brazilian splitting and three-point bending tests have been carried out to determine the mechanical parameters of the coal reservoir in Jiaozuo coal mining district, Henan Province, China. Based on the experimental results and combined with the target reservoir geological characteristics, a 3D geological mechanical model has been established to analyse the hydraulic fracture propagation during volume fracturing using MEYER software. Effects of the modulus of coal rock, difference between horizontal principal stresses, fracturing fluid viscosity and fracturing fluid injection rate on the fracturing network geometry are studied. Results show that fracturing network development intensity in the coalbed methane (CBM) reservoir is determined both by the geological conditions and the hydraulic fracturing parameters. The intensity of fracturing in the CBM reservoir is positively related with the elastic modulus of the coal rock, and is inversely proportional to the difference between the two horizontal principal stresses. Increasing fluid viscosity reduces the fracturing area. Low injection rate is beneficial to improving hydraulic treatment areas when it is larger than that required to guarantee that the crack extends. The results can provide a case reference for optimization design of volume fracturing and productivity prediction analysis of CBM reservoirs.