The fractures of Keshen area are widely distributed controlled by northern Crassus faults and southern Baicheng faults. In the study area Cretaceous Bashijiqike formation are divided into three members. Due to the deep burial of the target member in Keshen area, most wells do not meet the third member in the drilling operations. The first and the second member reservoirs formed in a tectonic quiet epoch, which mainly developed underwater distributary channel sand bodies of Braided river delta front, are the favorable reservoir belts. However, because of deep burial diagenesis, the reservoirs are characterized by low porosity and low permeability, and low porosity and extra-low permeability. Fractures developed as a result of tectonic forces. So finding well-developed fractures high permeability reservoirs is the main purpose at present natural gas exploration stage in the study area. By the studies on the impact of fractures distribution rule and development characteristics on porosity, permeability and saturation of the reservoirs, they will contribute to evaluate reservoirs, find the high quality reservoirs and oil and gas prospect district.
In view of the research status and existing problems above, colligating with the achievement of predecessors on this subject and taking full advantage of the imaging logging, normal logging, normal thin sections, casting thin sections, X-ray and SEM analysis data, fractures distribution and quantitative description are studied. Fractures can be divided into straight fractures, high dip-angle fractures, low dip-angle fractures, netted fractures(irregular fractures), and filled fractures by using imaging logging fracture identification method on the basis of core scale logging. Combining with cores observation which are from the key cored well, summarize the imaging logging response characteristics of all kinds of fractures and set up corresponding imaging logging identification charts. By applying software interpretation platform, quantitatively descript the parameters of the fractures, accurately divide the fractures types, and identify the fractures at non-coring intervals and non-coring wells. Predict the fractures distribution rule of the first and the second member of Bashijiqike formation in the vertical and horizontal directions and search for the high quality reservoirs. The study aims at improving the exploration efficiency and reduce the cost by providing geologic bases for oil and gas exploration in Keshen gas field.
Key words: imaging logging; fractures distribution rule; high-qualify reservoirs；Keshen area; Bashijiqike formation
