Research On Sedimentary Characteristics Of Chang6&7of The Yanchang Formation In Tongchuan-fuxian Area Of Ordos Basin

In this Paper, Chang6&7oil formation of Triassie Yanchang Formation inTongchuan-Fuxian Area of Ordos basin is elected as the object of study, based on the previousresearch results and exploration data and guided by fundamental sedimentological theory andmeans, the paper studies the source direction, sedimentary facies types and distribution ofsedimentary facies of Upper Triassic Yanchang Formation Chang6&7on the basis ofgeophysics, geochemistry, basin analysis and ancient landscape restoration, combinedoutcrops, cores and well logging data.The Ordos Basin is a multi-cyclic sedimentational, petroliferous craton basin. Currentresearch all over the world shows the triassic Yanchang formation is the main oil layer ofOrdos Basin. Chang6&7reservoir group lies in the third part of the Upper Triassic Yanchangformation, and the development and distribution of its source rocks and reservoir stratu arecontrolled by depositional environment. Therefore the research of Fuxian-TongchuanChang6&7deposition will provide theoretical and technical support to oil and gas explorationof the this area.In the course of the partition and contrast of Yanchang formation,3primary marker bedsare searched firstly, which distribute steadily in the whole area. The Chang6&7could bedivided into3layers, following the principles that contrasting the big sections firstly, thensmall sections, being controlled by cycle, consulting the thickness, etc.Throught standardization of well logs, integrated all area GR logging characteristics.Then based for the more accurate identification of lithologic features and logging faciescharacteristics. Based the inorganic geochemistry analysis of the Chang7concludes thedepositional environment the semi-deep lake to deep lacustrine, brackish and stronglyreducing environment.Based on outcrop observation, core description single well facies and comparison ofconnecting-well sections, combined with rock type, sedimentary texture, structure,paleontology, sedimentary cycle,etc, the paper points out that the main facies developed instudy area of Chang6&7Formation are lake facies and delta facies, which can further devidedinto3types of subfacies and9types of microfacies. Fluvial and detailed analysis on spatial－temporal distribution and characteristics about various kinds of sedimentaryfacies,depositional sub facies and sedimentary micro-facies.