Origin of the regional fracturing in Yanchang epoch, Shanganning basin,significance for geology of oil and gas

The Yanchang Epoch of Triassic in Shanganning basin underwent multiple compressive and uplifting deformations,which led to four sets of regional fracturing.The EW,NW striking and NS,NE striking fractures constitute a conjugate shear system,responding the Yanshanian NWW compression and Himalayan NNE compression.Because of the heterogeneity of rocks,EW and NS striking fractures were developed in the mid north area,whereas NW and NE striking fractures were developed in the south.These fractures are major controls over the permeability of oil reservoirs,therefore significant for exploration and planning of oil and gas resources in the area.