The Yimeng Region Of Ordos Basin, The Developmental Characteristics Of Paleozoic Sandstone Reservoir

Applied with core description, geophysical logging interpretation, thin section determination, Scanning Electron Microscope, reservoir lithology and physical property analysis and other analytic machinery,The sandstone reservoirs micro-characteristic of Shanxi Formation and Xiashihezi Formation of upper Palaeozoic in Yimeng exploration area in Ordos Basin are studied deeply.The main reservoir sand bodies for oil and gas have 3 filiation in shanxi Formation of upper Palaeozoic in Yimeng exploration area... Distributed widly in H8.The valid source rockes of upper Paleozoicly distribute in Carboniferous and lower Permian on longitudinal section, organic abundance is heavier and the types of source rock are mainly typeⅢ. The solube organic matters character of mudstone distinguished expressly from coal, which organic matters of dark argillite can be preserved better because of higher sedimentary water salinity. The result of thermal imitation demonstrate that both the coal and dark argillite have stronger ability to the gasous hydrocarbon and the coal have specific ability to liquid hydrocarbon in upper Paleozoic.lithic sandstone and quartz sandstone is main rock type, composition maturity and structural maturity are mid-poor, The grain size parameter is 0.25-0.5mm In Shanxi Formation and Xiashihezi Formation In Yimeng exploration area, the content of matrix is high and change is stability, the content of cement are mainly clay mineral: illite, kaolinite, chlorite films, and carbonate minerals: ferrocalcite, calcite, dolomite, siderite and silica etc.The reservoir characteristics of petrology have differentiation in different region in Yimeng exploration area.Remnant intergranular porosity, intergranular dissolution porosity, intragrnular dissolution porosity, filling constituents dissolution porosity, authigenic mineral intercrystal porosity are main pore types.Reservoir combination of pore have dissolution-pore and micro-pore, intergranular porosity and inter-crystal pores, dissolution pore and composite pores. Pore texture can be classified as following: low drainage capillary pressure and big throat type, middle drainage capillary pressure and big throat type, middle drainage capillary pressure and small throat type, high drainage capillary pressure and small throat type, evolution of pore structure be control with diagenesis. in the north region of Yimeng area. The diagenesis of the upper palaeozoic can been divided into the early diagenetic stage (stage B), and the late diagenetic stage(stage A, B, C), but the south area mainly been in the late diagenetic stage(stage A, B).Reservoir are mainly influenced by sedimentary facies, tectonics and diagenesis. The main reservoir sand bodies for oil and gas distributed in region of channel and distributary channel in delta plain microfacies. physical property of Reservoir fine with increases to content of quartz and feldspar and be bad with increases to content of cuttings, as a whole, quartz sandstone had best of physical property of Reservoir, intergranular porosity and mineral intercrystal porosity the second is lithic sandstone, the others are Feldspar-lithic sandstone and lithic -Feldspar sandstone. The main is intergranular porosity and mineral intercrystal porosity in quartz sandstone and mineral intercrystal porosity mainly in lithic sandstone. Shanxi Formation and Xiashihezi Formation is low-pore and low-permeability reservoir and heterogeneity of sandy reservoir is very serious, physical property of Reservoir is the best in north region deteriorated in south.Studying the parameter of pore and permeability comprehensively and consulting prevenient study results of evaluation of reservoir, the reservoir is classified four types:Ⅰ,Ⅱ,Ⅲ,Ⅳ. typeⅠis dominant on the north region,TypeⅡ-Ⅲis appeared the south region, have self-producing and self-reserving primary reservoir and below-producing and above-reserving primary reservoir, types of advantage trap is lithology-structures trap and lithologic trap.It could be inferred from above-mention that It also sprediet the favorable reservoir position to be explored in this area, which provide the credibility geology gist for further exploration and exploitation.