Analyzing Of Genesis Of Low Permeability And Effects On Physical Property In Extremely Lower Permeable Reservoirs

This paper takes the Chang-6 reservoir of Yan25 Area in An'Sai Oilfield as an example, using different theories and techniques of many subjects including sequence stratigraphy, sedimentary, petroleum geology, reservoir geology, petroleum reservoir engineering, and so on. aiming at the reservoir geological character, on the base of the basic geological study, by selecting large number of different core samples to do many experiments, recognize the microcosmic pore-structure and property character of this area impersonally, and quantificationally show the genesis of low permeability and the main factors affecting on physical property, so as to be the academic base of developing the low permeable reservoir efficiently and accurately.The main fruits and cognition are as follows:1 .On the base of collecting and neatening some data about this area, using sequence stratigraphy theory and the traditional method of cycle correlation, combining core observation with well log interpretion, set up subtle stratum contrasting framework section, and Chang-6 formation is divided nine substratums from top to bottom. At the same time analysed the character of the distributing of sandstone, physical properties and oil saturation of different substratums.2.Studied the characters of the sedimentary microfacies based on the known sedimentary facies. The research area is delta front aggradation controlled by North-West headstream, There are three kinds of sedimentary microfacies in research area, including underwater distributive river course, estuarine bar and distributive bay. The underwater distributive river course is preponderant, and it is the main reservoir in research area. Simultaneously analysed the character of the distribution of roomage and plane of different sedimentary microfacies.3.Studied the reservoir characters of the research area, including the character of lithology, microcosmic pore-structure and diagenesis;and analysed the character of heterogeneity from inner, inter and microcosmic. Otherwise by using the cluster analysis mathematical method, the research reservioir can be classified three different types that represent different physical property, so there is a comprehensive cognition about the research area.4.Based on the above contents, investigated the genesis of low permeability and the main factors affecting on physical property. By using many testing means, such asgeneral physical property, casting slice, image granularity, image pore, mercury injection, scanning electron microscopy, X-ray diffraction, sensitivity, oil-water displacement and relative permeability, and so on. combining ration Statistics with determine the nature description, aiming at this reservoir analysed detailedly from aggradation, diagenesis and micro-crack concretely.