Abstract: The Ordovician carbonate reservoir in Hetianhe gas field of Bachu uplift, Tarim basin has strong heterogeneity and poor pore throat structure. Most of the karst caves and dissolved pores of the reservoir are filled, and the degree of fracture development becomes the main factor to determine the productivity of the gas field. According to the observation of fissures in the core, it is found that the fractures of the reservoir in the study area are mostly structural fractures. High-angle fractures are developed in the west, and both low-angle and high-angle fractures occur in the east. Based on dissection, occurrence and filling of fractures on the sections of outcrops and the comprehensive analysis on isotopes of oxygen and carbon of the fillings and fluid inclusions, it is considered that the fractures were formed in 3 periods such as early Hercynian movement, late Hercynian movement and Himalayan movement