9 Oil Sedimentary Research Ordos Basin Yanchang

For investigates the core problem of sedimentary facies and characteristics and sand distribution rule for Yangchang Formation Chang9oil Formation in Triassic system of Ordors basin, using theories as sedimentology and geology, and the data of field geological profile, drilling, core, logging and well logging. Based on previous stratigraphic division, starting from the analysis of sedimentary background, areal distribution and sedimentary facies of Chang9oil Formation is analysied. There are many sedimentary facies types in Chang9oil Formation, such as braided river, meandering river, fan delta, braided river delta, meandering river delta, Lake six sedimentary subfacies, microfacies and so on. Chang92is shore and saucer fan. Chang91is semi-deep to deep lacustrine environment with the reason of basin subsidence and lake transgression. Based analysis genetic types and structure characteristics of sand bodies of different sedimentary facies, three kinds of sand bodies which is in different sedimentary environments and different genetic bodies are developed in Chang9oil Formation.①The sand which is related to delta plain environment and traction current effect, are mainly distributary channel, crevasse splay, natural levee, flood sill-like sand and so on.②The sand which is related to environment of delta front and traction current, are mainly underwater distributary channel, mouth bar, far sand dam, underwater crevasse splay, underwater natural levee, frontal sheet sand and so on.③The sand which is related to Lake shore shallow environment and sea and lake current transformation function, are mainly floodplains sheet sand and sandy beach bar sand bodies. Through summarizing Chang9oil Formation sand bodies distribution, it can be conclude that sand body with low compositional maturity and the structure of the medium-high maturity, grain size parameters and particle size distribution is complicated, the single sand body has five basic vertical structure style, multi-layer sand bodies development in a variety of vertical stack structure. On this basis, according to favorable reservoir belts, the pore and permeability and thickness of sand body and the test results, optimizing forecast reservoir groups A, B, C, D four favorable reservoirs zone of Chang9oil Formation in Ordos basin.