Abstract: The chang 6¹ low permeable reservoir in Yanchang Formation in the Upper Triassic is the main oil layer in Wuqi area. According to outcrop, drilling core observations, thin-section analysis, and the paleomagnetic orientation method of the drilling cores, the authors have done a detail description and statistics of the tectonic fractures qualitatively and quantitaively. The authors find that the well-developed fractures are NE and NW directions which are regional conjugated high-angle tectonic fracture system. The density of tectonic fractures is 0.4-1.9 unit per meter, the most of tectonic fractures are tensional and mostly filled (about 57%). The invalid tectonic fractures are in dominant (about 68%). Based on finite element simulation method, together with rock burst method and strain energy method, the predicted math model of tectonic fracture is established. The authors quantitatively predict and evaluate the distribution and development degree of tectonic fractures according to the model. The fracture development, sub-development and un-development areas have been separated, and tensile-shear fracture directions are predicted. These results supply important geological references for the further petroleum exploration in Wuqi area.

Key words: tectonic fractures, quantitative prediction, Chang 6¹ low permeable reservoir, Wuqi area, Ordos Basin