The Study On Depositional Systems Of Triassic Yanchang Formation Chang 6-Chang 8 At Sancha-Heqi Area

Sancha - Heqi area is located in the Ordos Basin Tianhuan depression south of the region in 2004 were classified as Changqing Oilfield exploration off the main area, at the Triassic Yanchang Series expect Chang 6 - Chang 8 on oil exploration group has the breakthrough. However, Chang 6 - Chang 8 Group chief source reservoir , the deposition system, basic understanding of geological problems is still no consensus which on the western source of the most controversial, especially on the deposition of sand body distribution and the scope of the delta is still unclear.In this paper, the principle of modern sediment study, based on drilling through the core of the study area with observation and analysis of log and core through the typical characteristics of the micro-endoscopic observation and substantial information on the physical properties of the statistics and analysis, key research in the area of Yanchang Series Chang 6 - Chang 8 are sedimentary fades types, characteristics and distribution of sandbody laws and characteristics of the area were made aware of the major achievements and summarized as the following:1. To light and heavy mineral assemblage of the main level changes, combined with particle size statistics, regional deposition measured ancient background and direction of flow field analysis of the study area to Chang 6 at long, long period of Chang 8 layers of sedimentary source direction, consider the purpose of the study area layer of sediment from the main basin of the southwestern margin of Pangea.2. According to field observation and drilling and logging of core analysis, consider Sancha - Heqi area Yanchang Series Chang 6 - Chang 8 group of major oil development braided river delta and lacustrine depositional system system. By the electric characteristics of rocks, sedimentary structures, palaeontological features, profiles of the characteristics of the structure and logging, and further delineation of the delta front and semi-deep lake - deep lake subfacies, as well as two kinds of underwater distributary channel, separate inter-Bay, I like sand , four kinds of underwater natural levee microfacies, one of the underwater delta front distributary channel sandbody phase for the skeletons, the study area is the most important reservoir.3. General of Sancha - Heqi area properties analysis, Chang 6 - Chang 8 small layer between the group, the best properties is Chang 8₁ and Chang 6₁, and Chang 8₂, Chang 6₃ Chang 6₂ is worse the physical properties and long oil group 7 duration of the three layers Chang 7₁, Chang 7₂ ,Chang 7₃ is worst properties.4. Sedimentary facies based on the results of research, combined with the physical properties of reservoir parameters and the distribution of sandstone thickness, oil saturation and collected information on a small number of test oil, the Chang 8₂ Chang 8₁ Chang 6₃ Chang 6₂ and Chang 6₁-storey favorable section of a prediction block.