| Taking the Carboniferous and Permian tight sandstone reservoirs in Daniudi gas field of the Ordos basin as research objects, based on the regional geological background, guided by the theory of reservoir geology, using the identification and quantitative statistics of rock thin sections under the microscope, electron scan microscope(ESM), cathode luminescence, X-ray diffraction(XRD), measurement of homogeneous temperature for inclusions, and the other analytical techniques together, combined with research results of burial and thermal evolution history of Daniudi gas field, this thesis studies the diagenesis characteristics and the diagenetic evolutionary stages, analyzes the single factor influencing the physical properties, establishes the diagenetic evolution history of tight sandstone’s porosity, and the diagenetic evolution quantitative model pattern corresponding to diagenetic facies.Based on the identification of thin sections under the microscope, combined with all sorts of analytical techniques indoor, this study defines that the reservoir rock types are quartz sandstone and lithic sandstone and lithic quartz sandstone, the primary reservoir space is the secondary pores which include particle dissolution pore, cement dissolution pore, Kaolinite intercrystal pore and a small number of micro cracks, and the diagenesis types mainly include compaction, cementation, metasomatic alteration, dissolution and so on, recognizes three-stage of quartz overgrowth, two-stage of calcite cementation, three-stage of microfracture and three-stage of fluid filling. Combined with burial and thermal evolution history, the author according to time sequence divides the process of diagenetic evolution into four stages: fast compaction, acid and alkali alternating, densification and after the dense phase.The author respectively from the buried depth, sedimentary and diagenesis which is controlling the reservoir properties analyzes every single factor and defines the impact of various factors on the physical properties. Under the degree of influence of different sedimentary facies, which are in the same range of depth(dissolution is not development) on the physical properties of reservoirs, establish the original compaction curve of pores, in which the sorting range of different granularity sandstone is from 1.6 to 2.0 and that of lithic sandstone is 1~1.6, 1.6~2.0, 2.0~2.13 and more than 2.13 with less than 6% content of cements. Based on calculating the original porosity, the compaction rate, the cementation rate, the dissolution rate, the diagenetic synthetical coefficient and so on, quantitative analysis diagenetic intensity of reservoirs. Then using grey correlation method the author calculate the porosity calculation formula of reservoirs which is under the condition of pure compaction, and the grey correlation degree and weight coefficient which is between the parameters of main controlling factors and the porosity, so get the porosity calculation formula under multi-factor controlled.According to different diagenetic facies, targeting on the rock thin sections of casting, based on the morden reservoir pore structure, with the method of reservoir property recovery in geological history period under the restriction of "reservoir diagenetic evolution sequence-reservoir pore structure", combined with burial and thermal evolution history and diagenetic evolution sequence, adopt the technology of image analysis of man-machine interactive, using the principle of inversion and back-stripping, the author restores the reservoir porosity and pore structure of the main diagenetic stage in geological history period, finally establishes the diagenetic evolution quantitative model pattern of different diagenetic facies, and thinks that the mechanism of densification of reservoirs are mechanical compaction and calcareous, silicious and clay cement. |
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