The Sedimentary Microfacies And Reservoir Characteristics In The Yan10,Yan9 Formation Of The No.1 Oilfield In The West Of Ordos Basin

The No.1 oilfield is located in the west of Ordos Basin, it has been text and pilot product in the Yan10, Yan9 formation, and have good exploration and development. But the research area has poor basic geological study, especially sedimentary microfacies and control facrors of reservoir property. It has limitation to further waterflooding and improve recovery efficiency. This paper takes reservoir sedimentology, petroleum geology etc. as the guide theory, using logging, SEM analysis, thin section and mercury analysis to study formation characteristics, structural features, sedimentary microfacies and reservoir characteristics in the Yan10, Yan9 formation of the No.1 oilfield. It gets the following points:(1) Yan10, Yan9 formation subdivided into Yan10?Yan 101?Yan 92?Yan 91 formation. Every formation has similar structural features and good succession. The terrain presents high in east and low in west, and develops some nose uplift of east-west.(2) The research area at the filling sedimentary environment for Yanchang formation in Yan10 period, its sedimentary thickness of sand is big. The structural environment is turbulent under the effection of Yanshan movement I period. This area was located in the Mengshan Ancient River in YanlO period, material source is northwest. Its sedimentary facies are fluvial facies, it can subdivided into channel deposit, channel sand bank, and washland. In Yan9 period, the filling was finished, structural and sedimentary environment is stable, sedimentary thickness is small. The lake invasion scope is wide, Ancient Rivers in Yan10 period were disappeared in Yan9 period. The sedimentary facies of research area are delta plain, it divided into five sedimentary microfacies: distributary channel, interchannel, flood fan, natural levee and swamp. The material source is northwest.(3) YanlO formation is mainly consisted by quartz arkose sandstone and lithic feldspar sandstone, particle size variation is big, sorting features is general, roundness is good. Yan9 formation is mainly consisted by lithic feldspar sandstone, sorting features and roundness is good. The pore types are mainly intergranular pores, secondly is dissolution pore.(4) The diagenetic sequence in YanlO and Yan9 formation is:machinery compaction ? clastic particles were surrounded by clay membrane ? microcrystal calcite sediment ? quartz secondary increase ? feldspar and lithic corrosion ? authigene kaolinite formation ? dolomite cementation ? embedded crystal calcite formation ? calcite metasomatism.(5) Sedimentation and diagenesis have an important influence on the reservoir property, especially diagenesis. Porosity of Yan10 reservoir is average lose 20.73% in the effection of compaction, by cementation lose 10.92%, and increase 6.94% in the dissolution. Porosity of Yan9 reservoir is average lose 20.01% in the effection of compaction, by cementation lose 10.87%, and increase 8.05% in the dissolution. The study proved that Yan10 and Yan9 reservoir belongs to ? type reservoir.