Research On Sedimentary Microfacies Of Chang 6 Oil-bearing Beds Of Yangchang Formation In Sai 160 Area South-West Of Wangyao District, Ansai Oilfield

Sai 160 area is located in south-west of Wangyao district of Ansai oilfild in the Shanbei slope of the south-east Ordos Basin. The Chang 6 oil-bearing beds is the main oil producing bed in the Ordos Basin. According to the characters of lithology, electricity and oiliness, the Chang 6 oil-bearing beds is subdivided into Chang 6\, Chang 6₂ and Chang 63. In study, Chang 6₁ is subdivided into Chang 6₁^1-1, Chang 6₁^1-2, Chang 6₁^1-3 and Chang 6₁² again. And the time correlation in sequence stratigraphic unit was realized according to the temporal rock markes.According to the analysis of the facies marks, such as petrosal kinds with the features, sedimentary structure, fossils, logging facies and other criteria in the study area, the analysis of the facies shows that the Chang 6 oil-bearing beds is a front-delta sedimentary system. The sedimentary microfacise include distributary channel, interdistributary deposits, distributary mouthbar, distal bar and front sand sheet.On the basis of regional geological background, the distribution pattern of sedimentary microfacies in the Chang 6 oil-bearing beds is distinguished and the palaegeographic environment is reconstructed by the analysis of sedimentary facies, logging facies, sandstone thickness and sandstone percent and other sedimentary character.Dividing the different scale sedimentary gyrations in Yanchang Formation and identifying sequence boundary by Sequence stratigraphy. Dividing and contrasting the stratums of Chang 6 oil-bearing beds by High-resolution sequence stratigraphy.The study show that: the reservoir sandstone is mainly made of feldspathic sandstones. Generally speaking, the reservoir is the one with low pore extra low permeability. The porosity is mainly the kind of intergranular pore and intragranular dissolved pore. The pore structure types are fine throat-small pore and micro-fine throat-small pore. The reservoir shows stronger unhomogeneity in the study area.Analyzing the controlling factors to reservoir, the result shows that sedimentary microfacies and diagenesis are the main factors of controlling and affecting distribution of reservoir in the study area.