Ordos Basin, Northwest Shiqianfeng Formation High Resolution Sequence Stratigraphy

Ordos Basin is one of the most potential gas reservoir regions in China. Over-20-year exploring practice, some gas reservoirs have been discovered one by one from Taiyuan Formation Shanxi Formation and Lower Shihezi Formation in Upper Paleozoic. Along with the further studying, industrial gas current has been gained from Shiqianfeng Formation of the Upper Permian. However, the exploring degree of the Shiqianfeng Formation in Ordos Basin is relative lower, at the same time, the studying on sedimentary facies and sequence stratigraphy still need a further research.Aim at the above problems and important research value, in this thesis, the article apply the basic theories and methods of Sedimentology, High-resolution sequence stratigraphy and Petroleum Geology to research the sedimentary system, high-resolution sequence stratigraphy and lithofacies paleogeography characteristic of Shiqianfeng Formation north-west of the Ordos Basin, and offer important basic data to further gas exploration in the Shiqianfeng Formation of the Ordos Basin.According to the rock type, sedimentary structure, section architecture, physical geology and geochemistry indicators, fluvial sedimentary system, delta sedimentary system and lacustrine sedimentary system can be identified in the Shiqianfeng Formation. We particularly discussed the sedimentary characteristic and cross section structure of every microfacie in each sedimentary system. At the same time, according to the color and geochemistry characteristic of the rock, we believe that the research region is a drought, torridity and oxidation continent lacustrine environment.On the basis of detailed facies division and depositional array, taking the theory of high-resolution sequence stratigraphy as a direction, through comprehensive analysis of the field section cores well logs and the discriminating of the sequence interface, the Shiqianfeng Formation can be divided into four-grade base-level cycle sequences .many short sequence cycles, 14 middle sequence cycles(MSC), 5 long sequence cycles(LSC) and 1 super-long sequence cycles(SLSC). Based on this, we bat around every base-level cycle facies sequence and structure character, according to the structure of the system tract, the short-term, middle-term and long-term cycles sequence have two basic types, upward deepening non-symmetry(type A) and symmetry(type C).On basis of the above research, using rising half cycle of long sequence cycle as mapping units, respectively mapped the rising half cycle lithofacies paleogeography...