Depositional System Of Chang 7 Oil Formation Of The Triassic Yanchang Formation In Ordos Basin

This paper's object of study is Chang 7 oil formation of Triassic Yanchang Formation in Ordos basin.Research method is based on the use of sedimentary petrology and petroleum geology as the main theoretical guidance,while collecting the basis of materials,still collecting field profiles and drilling the core sample,the outdoor describe photographic and indoor experiment analysis,combining logging curves and logging interpretation etc material, painted sandstone clastic component content variation,Ree distribution of patterning, single-well lithology lithofacies bar chart, well-tie profiles contrast map, planar distribution map of sedimentary facies and sand body. The purpose is to make clear further system of object of study on formation characteristics, the provenance, sedimentary system, distribution of sand body and sedimentary microfaces, eventually to build a deposition pattern.The results show that the Ordos basin Chang 7 oil formations tendency in the northeast is thin, southwest and northwest is thick,the largest stratum thickness of DingBian—HuaChi regional from side to center be thinning; Sedimentary is from the northeast, northwest, southwest and southern provenance, in northeast and southwest are most extensive; Main development lakes, delta depositional system, lake sedimentary system from shore-lacuatrine and half deep lake—phase composition, deep lake has large-scale development in turbidite fan, delta depositional system from delta plain and delta front-phase composition; Sand body form inherited sedimentary facies exhibition, the shape's character of northeast delta depositional system is flake, bird foot, Sand body sectors-connecting is good, in front of the bird foot shape, sand body size in the Southwest is small and be a ribbon in the northeast.Chang 7 oil formation sedimentary from early's heyday to the cuts of late, basin's lake area reduced gradually, shore-lacuatrine line near the center of basin, half to deep-lake line in northwest from never closed to close, but delta area continuously increasing and accumulate to the lake center, plain area and front sand body accordingly had development, sand body extension farther and farther, the turbidite fan which development in lacustrine area is increased,at the same time, the fan and fan articulated enhanced.