Research Of Sedimentary Facies And The Distribution Of Sand Body Of The Triassic Yangchang Formation In Fuxian Exploration Area Of The Ordos Basin

Applied with outcrop observation, core description, geophysical logging interpretation, thin section determination, reservoir lithology and physical property analysis and other analytic machinery, the sedimentary facies of Yanchang Formation in Fuxian exploration area are studied deeply.Based on utilizing the stratum touching relations, the characters of facies cycle, the abrupt interface of facies, the regional characteristic interface (Maximum flooding surface), and overlapping fashion of the river channels sand and the regional good contrasting markers, the sequence interfaces had been identified after researching the sequence stratigraphy. Yangchang Formation are divided into a tectonic super sequence and 4 pieces of third class sequences, and are compared with traditional stratum partition.It makes sure that NE is the main direction of sediment provenance, the original rock are Wulashan group in uper Archeozoic and lower Proterozic Erdaoao group of high-grade metamorphic crystalline schist and gneiss in Yinshan mountain and Daqing mountain in the north of Ordos basin by the studying of the paleocurrent direction and the light and heavy minerals.Based on outcrop observation , core description , single log facies analysis and connecting-well section , combined with the rock types , depositional texture , structure , paleontology and sedimentary cycle , etc , the Upper Triassic Yanchang formation is composed of the lacustrine system and the delta system in Fuxian exploration area ,which are farther divided carefully them into 4 types sediment subfacies and 6 types sediment micfacies . Subaqueous distributary channel in delta front microfacies and subaerial distributary channel in delta plain microfacies are identified ,which are the main reservoir sand bodies for oil and gas of Yanchang Formation in Fuxian exploration area, the distribution of sand bodies are from northeast to southwest are dominated by sedimentary facies .The source rock and the distribution of the centre of oil generation all have well coincidence relation with the distribution of deep lake in research area . The property and distribution of reservoir is controlled by sedimentary system ,the sand body of subaqueous distributary channel in delta front microfacies and subaerial distributary channel in delta plain microfacies and turbidite fan are good reservoirs . The favorable source-reservoir-caprock group can be formed for the frequency of lacustrine transgression and regression . the favorable exploration area can be found out in the main oil-bearing beds in Yanchang formation by the analysis of sedimentary facies , the distribution of sandbody , the character of structure and the property of reservoir , etc .