Reservoir Characterization Of Chang-6 Oil Reservoir Set Of Panguliang

The exploration of oil and gas has been gonging on for nearly one century in the Ordos Basin. The research of basin's basic theory and productive experience indicates that the sandstone reservoir with good permeability is the base and the various traps are the conditional factor of Mesozoic oil accumulation. In the present research, therefore, identification of the shape of permeable sands seems very important. In a word, it's of great significance in the theory and in practice to find out the location, shape and extending direction of lacustrine delta and characteristics of different microfacies in the Upper Triassic Yanchang Formation.Based on the careful strata correlation and division of Chang-6 Formation of Panguiang in Jing'an Oil Field, the article discusses the structure characteristics, the sand body shape and distribution and the microfacies feature of Chang-6 Oil Set , analyses the physical properties and heterogeneities of the reservoir which is classified three types as I, II and III type, summarizes the relation between microfacies, sandbody distribution and physical properties, evaluates the reservoir from the flow unit aspect, reveals the affecting feature of oil concentration.Depending on the above studies, the following conclusions can be obtained:1) Chang-6 Oil Reservoir Set of Panguliang is a set of continental clastic sediment composed of lacustrine and deltaic system in which estuarine bar is not well developed. There are 7 sedimentary microfacies that can be recognized, including underwater distributive river course, estuarine bar, submerged natural levee, etc.2) On the basis of high-resolution sequence stratigraphy, distinguished basic level and base-level cycle, Chang-6 Formation can be divided into 6 strata and 15 substrata, consequently the isochronous formation structure is set up.3) The sandbody distribution, physical properties, pore structure and heterogeneities are affected by the microfacies. At the center part of underwater distributive river course, the petrophysics and physical properties are both better than that at the edge of the microface.4) The Chang 61 2-3 substrata and the substrata of Chang 62' member which show the better porosity, permeability, and better pore structure; display lower permeability variation coefficient, dart-coefficient and contrast-coefficient and good connecting sandbody so the horizontal heterogeneities is weaker; whereas manifest strongerinner-heterogeneities due to the numerous intermediates; present stronger inter-heterogeneities caused by the greater frequency of sandbody. The reservoir heterogeneities are mainly controlled by the intensity of hydronamic force, sedimentary mode, the ingredient and content of the filler, i.e., depositional environment is the most important factor.5) Chang-6 Reservoir can be classified three types as I, II and III, among which I type is the best one with best porosity , permeability and oil saturation. There aremore I type reservoir in Chang 62 1-2, Chang 621-3, Chang 62 2-1 substrata than that in other substrata. The distributive area of I and II type reservoir in each substrata are the same distributing range with that of underwater distributive course and estuarine bar.6) By using cluster analysis, Chang-6 Oil Set can be classified three different flow units as A, B and C type, among which A type flow unit is the best one with best seepage character. Chang 63 member is mainly consisted of C type flow unit, however Chang 62 is composed of A and B type mostly.