| Ordors basin is a large one of a multi-tectonic systems, multicycle evolutions and multi-sedimental typies. The foults and folds are very developed in the edge, but inter the basin, the structure are relatively simple. Mesozoic oil and gas reserviors in Ordors Basin mainly distributed in Yanchang Formation of Late Triassic and Yan’an Formation of Early Jurassic. Zhenjing oil field is located on the south-west of Ordors Basin. Oil set chang9in the Upper Triassic Yanchang formation is one of the main oil producing strata. With the developing of the farther studies in chang9reservoir, it has become the core issue of fine reservoir description which is Sedimentary facies distribution of understanding of the law and sand body microfacies determine the spatial distribution.The paper follow a path from point to line, to surface, to area, and adopts several advanced geologic theories and technologies, such as reservoir sedimentology, high-resolution sequence stratigraphy, to describe the reservoir characteristics. Based on the analyse of core observation, sedimentary structure, petrological characteristics, logging facies and single well facies, it implies that zhenjing area develops Braided river delta front in the sedimentary period of chang9. the front mainly develops the microfacies of underwater distributary channel、 channel mouth bar、underwater interdistributary bay. At the premise of establishing isochronous Stratigraphic framework, in terms of Carved out of every single well sedimentary microfacies, build a small layer of sedimentary microfacies planar distribution diagram sedimentary micro-facies characteristics of study in all directions, as well as the region of the sedimentary evolution of the characteristics and laws.Feldspathic lithic sandstone is the main composition of sandstones reservoir zhenjing area. Argillaceous matrix, Calcite is the main fillings. The Chang9reservior sandstone is of Medium reservoir structure maturity, middle-good sorting, middle-fine granularity.Consequently, the relationships between lithology, physical properties, oil saturation and electricity, are presented distinctly in mathematics equation or chart performance. On the basis of electrical clear relationship between the various factors parses the lithologic physical information. Then reservoir properties are researched accurately combined with regional geological features. The equation of acoustic travel time, porosity, and permeability is gained with the use of linear regression and the crossplot in order to calculate the well reservoir sandstone porosity and permeability values.In the study reservoir is of area, the physical properties is particullaly bad, the special medium porosity and low permeability, average permeability is1.37×10-3μm2, mainly located between the0.05×10-3μm2-2.5×10-3μm2. Contrast to the change trends of the por and perm, it shows that porosity and permeability has a good correlation. In the back groud of poor good por and perm, some well may appear relative high value area with good properties conditions.Based on the research of rock-type, sedimentary faces, physical distribution, reservoir lithology, grain size and pore characters, the reservoir of the study area is classified as three categories:type I, type II and type III. Type I and type II are mainly developed in the main channel activity area or the junction of branch river, where have a better permeability condition. Type III is mainly developed in the the edge of channel, having a poor permeability condition. On the basis of these, combining with distribution of oil and gas, the favorable exploration blocks are predicted that can be used for exploration and development... |
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