Reservoir Characteristics And Reservoir-forming Regularity In Chang-6 Member Of Li-79 Block In ZI-bei Oil Field

Chang-6 member of Li-79 block in ZI-bei Oil Field in Ordos Basin is taken as the study object in this thesis. Under the guidance of theories of sedimentology?petroleum geology?geochemistry and well logging geophysics, on the basis of abundant data from geology?drilling?logging?oil testing, adopting the combination of geology?geophysics?geochemistry and technique methods of academic researeh indoors combined with practice research and investigations in the field, using many testing methods and analytical techniques, Chang-6 member of Li-79 block of ZI-bei Oil Field is deeply studied in strata?structure?sediment?and characteristic of reservoir and oil storage. Based on these methods, the paper discusses the regularity and controlling factors of the distribution and accumulation of oil - gas systerm in the study area. The main understanding and conclusions are as follows:(1) Acording to "marker layer?cyclic correlation?step control", Chang-6 group is divided into 3 sub- groups,:Chang-61?Chang-62 and Chang-63. Acording to the secondary cyclic correlation, Chang 61 and Chang 62 sub-groups are divided into Chang-611?Chang-612?Chang-619 and Chang-621?Chang-622 respectively, and then the detailed stratigraphic framework of the whole region is builded. The establishment and analysis of top surface structural maps show that the study area is a broad west-dip monocline, and the structure characteristics of each period has a certain continuity.(2) According to the analysis of facies signs, such as rock types and features, sedimentary structure, fossils, logging facies and other criteria in the study area, the deposition system of Chang-6 member is a delta plain sedimentary system. Based on the sedimentary background of study area, and using the analysis of geology characteristics and logging facies, the distribution pattern of sandstone thickness and sandstone percentage in the plane section are discussed comprehensively, and furtherly Chang-6 deposition system is divided into two sedimentary microfacies:distributary channel and flood plain swamp.(3) Starting from the four Properties relations study, based on well testing results and statistical results of geological parameters of the core, the recognition criterion of oil and water reservoir is concluded, the interpretation equation on porosity and initial oil saturation is builded, and the low criterion of effective thickness is defined. (4) The method of multi-parameters clustering eanalysis is adopted for reservoir token and synthetical evaluation in this paper, which makes the criteria more reasonable.The parameters include porosity?permeability?flowing interval exponent?reservoir quality?normalizing porosity. Different flow unit corresponds to different quality reservoir, so flow unit can be used for evaluating and tokening reservoir. This evaluation method not only takes full account of the geological nature of the reservoir, but also takes the characteristics of the reservoir project into consideration,which is more conducive to the synthetical evaluation of reservoir and the meticulous exploitation of oil field.(5) The research on granularity?flakes?properties.etc show that the sandstone of reservoir in the study area is mainly fine-graded feldspar sandstone and the reservoir sandstone has reached the late diagenesis A period. The type of porosity is mainly intergranular pore, and the composition of pore-throat is the small pore with micro-throat type. In general, the type of reservoir is low porosity-extra-special low permeability-extra low porosity-ultra-low-permeability reservoir. The research on unhomogeneity of reservoir also shows the unhomogenenity is strong. Analyzing the controlling factors to reservoir, sedimentary microfacies is the main factor controlling and affecting the distribution of reservoir in the study area.(6) The result of analysis on property of oil, water.etc show that the oil of Chang-6 member in the study area belongs to the conventional oil from terrestrial facies with low density, medium viscosity, medium freezing point and low sulfur content. And the type of formation water in the study area belongs to calcium chloride(CaCl2).The total saltiness of formation water is comparatively high and the sandstones of reservoir act as water-wet.The results of high pressure properties of the reservoir show that the type of trap is lithologic trap which belongs to normal temperature and low pressure system with the elastic-soluble gas driving oil.(7) Through the study of inclusion thermometry thermal history of the basin?illite dating and other methods, it can be confirmed that the forming date of Chang-6 reservoir of Zl-bei Oil Field is Early Crataceous, and especially the application of illite dating methods is a new quantitative result, which is the first quantitative outcome in Mesozoic reservoirs in the Ordos Basin and deepens the study on chronology of Hydrocarbon accumulation futher more.(8) The research also concludes the regularity of the accumulation of Chang-6 reservoir., which shows that the study reservoir is controlled by delta plain distributary channel where is considered as the most important deposition area. The fine regional cap rock of Chang4+5 also supplys the good barrier conditions.(9) According to the type and distribution of Chang-6 reservoir, based on the previous studies, the research concludes that there are two oil-gas accumulation models:one is the sandstone lens reservoir,the other is sandstone updipping wedge-out reservoir.