Effect of crustal stress on hydraulic fracturing in coalbed methane wells

The crustal stress and mechanics properties data from No.3 coal seam in the western Jincheng mining area were analyzed.With a finite-element method,the formation fracture pressure at borehole walls and natural fracture tips under different conditions of crustal stress was calculated.The effect of crustal stress on initiation pressure and azimuth was calculated.Initiation pressure and azimuth are related with the magnitude and direction of crustal stress.The influence degree of the angle between a natural fracture and the maximum horizontal principal stress on fracture pressure increases with increasing principal stress difference coefficient.In No.3 coal seam in the western Jincheng mining area,hydraulic main fractures are easy to occur when the coefficient exceeds 0.84,net-like fractures are easy to occur when the coefficient is less than 0.47,and initiation azimuth is related with natural fracture distribution when the coefficient is between 0.47 and 0.84.In difference areas,the coefficient used to analyze the initiation azimuth is difference.