Deposition System Research For Chang 9 Chang 10 Oil-bearing Beds Of The Yanchang Formation

This paper investigates the Yanchang formation Chang 9 Chang 10 oil bearing beds in Triassic system of Ordors basin, using theories as sedimentology and geology. This paper also systemly investigates the sediment source, dividing of sedimentary microfacies, sedimentary facies and its distributions, Chang 9 Chang 10's paleogeographic evolution was reconstructed all basin.Based analysis, on outcrop observation, core description, single well-log and sequence connecting-well section, the Chang 9 Chang 10 oil bearing beds can be divided into four kind of sedimentary facies such as lakes, rivers alluvial fans and deltas Furthermore, eleven kind of sedimentary facies are identified, namely shore and saucer fan, half-depth lake, underwater sedimentary fan, delta plain, delta front, meander riverbed, braided riverbed, flood plain, top fan, middle fan, foot fan. we conclude that main sedimentary facies of Chang 9 Chang 10 oil bearing beds is sedimentary of lacustrine, wide-dastic river-delta and kinds of fans in edge of basin. all kinds of sedimentary facies belt in the plane trend from annular deviding, the distributions of the sand bodies are controlled by deposition system. Southeast deposition system's sand bodies' configuration that has low component and textural maturity presents a band sharp of east-west and northeast-southwest trend from Huangxian to Zhengning. Northeast system's sand bodies which have good continuity present a northeast-southwest trend in the plane.Combining with the analysis of geological background of the study area, the paleogeographic evolution and evolvement has been resumed, exposing the rules of distribution of sedimentary facies and the rules of the evolution of paleogeography in the research areas. Protracting firstly sedimentary facies map of Chang 9 that divided into tow segment, and Chang 10, which is divided into three. By analyzing the fossils, sedimentary structure, sedimentary cycle, rhythmic bedding and other criteria, we preliminarily established paleogeography evolutionary characteristics which had influenced Chang 8's paleogeography evolution of Chang 9 Chang 10 oil bearing beds in the whole basin.