| Taking the reservoir of Ma 5th sub-member of Ordovician in the eastern Sugeli as research object, the thesis carries out a further study on the sedimentary facies, petrologic feature, reservoir space feature, diagenesis, reservoir porosity-permeability relation, reservoir classification and reservoir controlling factor. The thesis is based on such subjects as sedimentology, geology of carbonate reservoir, reservoir physics, and reservoir sedimentology, and such data as logging information, rock slice, scanning electron microscope, cathode luminescence as well as mercury intrusion analysis.The deposition of Ma 5th sub-member is mainly in epicontinental tableland facies and arid tidal flat environments. The sedimentary facies in this region can be divided into 3 subfacies, 8 secondary depositional subfacies and 13 lit hological types. The lithological types of Ma 5th sub-member are various. Through the thin slices identification and core analysis, the carbonate rocks in the study area mainly includes grain limestone, residual grain dolostone, crystalline dolostone and so on. Among the carbonate rocks, the reservoir performance of intergranular dolomite is the best, the residual-structure dolostone is good, and the limestone and breccia dolostone are the worst. The main reservoir spaces in Ma 5-5th sub-member are intergranular pore, cavity and seam from the secondary porosity. While there is nearly little other types of secondary porosity. Mid-crystal, fine-crystal and powder-crystal dolomite are the best with regard to reservoir development, physical properties, pore structure and mercury injection parameters. And intergranular pore is the main reservoir space.Through the observation and study of the data of drilling cores and thin slices in the region, and by using such test analysis methods as electron microscope, cath ode luminescence and X-ray diffraction analysis, the main diagenesis types in the research area have been studied in detail. It is considered that the main diagenesis types in the Ma 5-5th sub-member of the research area are dolomitization, degypsumization-dedolomitization, compaction pressure solution and dissolution, silicification, dissolution, filling, recrystallization and pyritization, etc. Different diageneses have different influences on reservoir space. Research shows that penecontemporaneous dolomitization fails to form favorable pores, while the intergranular holes, formed by burial dolomitization, constitute very important reservoir space in the research layer. Hypergene dissolution plays a big role in the increase of pores in the research layer. While because of occurring in a closed system, burial dissolution has a limited development on dissolution space.Taking advantage of such information as rock slices, rock casting thin sections, mercury injection curves and relative permeability curves, this thesis performs deep analysis on the objective layer reservoir, and concludes that among all kinds of lithology, thin-microtec dolomite has the biggest connected pore-throat radius and the mercury injection parameters. According to the capillary pressure curve, the parametric characteristics of pore structure and reservoir pore structure features, reservoirs can be classified into the following 4 types: reservoir Ⅰ, reservoir Ⅱ, reservoir Ⅲ and reservoir Ⅳ. Reservoir Ⅰ, Ⅱ, Ⅲ, Ⅳ have such porosity as > 5%, 2-5%, 0.5-2% and < 0.5%, respectively. And reservoir Ⅰ belongs to good reservoir. In the study area, reservoir Ⅰ and reservoir Ⅱ are locally developed in the well of Sudong 37-58. The most common reservoir Ⅲ are mainly developed in the well of Sudong 39-62C1 and Sudong 40-66. Reservoir is under the control of sedimentary microfacies, tectonism and dolomite distribution. The nose-like structure, formed by later tectonism, is beneficial to gas accumulation and is the main mode of gas accumulation in the study area. |
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