Areas In The Ordos Basin Huaqing Triassic Extended Leader Group 9 Reservoir Sedimentary Facies And Sand Body Distribution Rule Research

The Huaqing area is located in the southwest and south of the Ordos Basin. In the Mid-late Triassic, Yinshan upthrust was developed in the north margin of Ordos Basin, Qilian-Qinling upthrust was developed in the southwest and south margin of the Ordos Basin Ordos Basin. The Yanchang formation was deposited in the circumstance of semi-humid climate. The study area Chang9sediment was formed in this regional geological background.Based on relevant research results of the previous reaserchers, according to sandbodies distribution characteristics, the quantitative analysis of heavy minerals and sandstone detrital composition, the quantitative analysis of cathodeluminescence, and trace elements and rare earth elements analysis, and combined with the regional tectonic and geololical background closely, we did a reaserch about the provenance of Chang9formation. From the reaserch we have the conclusion that there’re two provenance systems which are Yanqing system and Zhengning system. The Yan-Qing provenance system derived from the mother rocks which is composed of the ancient metamorphic rock and magmatic rock in Longxi ancient land and ancient Qinqi folded belt; the Zhengning provenance system derived from the mother rocks which is composed of the ancient metamorphic rock and igneous rock in ancient Qinling Mountains.Depositional environments and sedimentary facies are congenital geological factors. which control the development and distribution of the sandstone reservoir. In this paper, the sedimentary facies and distribution are finely analyzed based on the informations of outcrop sections, drilling, core, logging and analysis, it is identified that the study area is mainly composed of braided delta, and subfacies of the braided delta plain and braided delta front are fined studied..Based on the geologic informations of outcrop, drill core and logging,the genetic types and characters of sandbodies in the Chang9formation of Yanchang group in Huaqing area of Ordos Basin were researched, and the controlling factors of sedimentation and distribution of the sandbodies were analyzed. The sandbodies in the research area mainly are composed of braided distributary channel sandbodies of braided delta plain and distributary channel, mouth bar, distal bar, frontal sheet sand of braided delta front. The palaeostructure and paleogeographic environment dominate the sedimentary facies and sandbodies spatial distribution, and sedimentary environment and sedimentary facies decide sandbodies types and characteristics.