A Discussion on the Fracture Characteristics and Controlling Factors of the Ma5_1 Reservoir in Changqing Gas Field

The Ma5 1 reservoir is the main gas reservoir in changqing gas field. The main fracture types of reservoir are four types: vertical, oblique, horizontal and braided. Although there are lots of fracture types in Ma5 1 reservoir , the main types that have a great influence on the percolation flow of the reservoir are two types, i.e., structural fracture and weathered fracture. The formation stages of fracture in Ma5 1 reservoir are mainly three, i.e., (1) Caledonian stage, in which all kinds of weathered fractures have been formed; (2) mid stage of Yanshan movement, which is an important structure ruptured stage; (3) Late Yanshan stage to early Himalayan stage. In this paper, geological factors forming fractures are studied and analyzed, it is summarized as that,the formation of the weathered fractures is mainly related to the occurrence of the rock strata, but the formation of structural fracture is related to the condition of palaeo stress field and the mechanics property of rock itself.