Abstract: In the Tahe Oilfield, the Ordovician carbonate reservoirs are deep-buried with high overburden pressure, which might cause fracture closure. The critical fluid pressure of fracture closure was 37-42 MPa in the Tuofutai area. The comparisons between production statistics and production phenomenon proved the existence of fracture closure. The main factors influencing closure included reservoir burial depth, fracture dip and the angle between fracture trend and maximum principal stress. During production process, some pressure-maintaining measures such as reducing pressure drop and injecting a amount of water could slow crack closing speed. Acidification measures could benefit oil wells to regain some diversion capacity by etching fractures.