Prediction of fractures of seam No.3 in northern Shizhuang, Qinshui basin

Northern Shizhuang, an important area for CBM production, is located in the southeast of Qinshui basin. As the primary seepage channel, fractures in coal seams make a great significance for the enrichment and production of CBM. The direction of the fold axes in sem No.3 is nearly NS, while a group of conjugate shear fractures was developed in outcrops, of which the dominant direction is NW and nearly EW, followed by nearly NS. According to the structural features, the stress field of Yanshanian was mainly compression from SEE105°. The stress in well points was calculated by using the hydraulic fracturing method, the direction of the maximum horizontal principal stress which is NE55°, was determined by restoring the original position through paleomagnetic and according to the velocity anisotropy. Considering the coal structure and surface topography as the main influencing factors, using the finite element method to simulate Yanshanian and the present stress field, and the precision is high. By using elastic mechanics theory to calculate fracture parameters, the porosity and permeability of SEAM No.3 in northern Shizhuang is generally small. In general, the porosity and permeability in central anticlinal area > central flat area > eastern monoclinic area > central synclinal area > western district, the simulation results were consistant with the measured data and single well gas production line, the credibility was high.