The Regional Tectonic Characteristic Of Southeast Sichuan Basin And Its Control To Oil And Gas Reservoir

The Southeast Sichuan Basin's hydrocarbon zones are mainly Permian and Triassic, which has been explored and developed for more than forty years, and it has reached the late stage of production. On the basis of the theory about the anticline reservoir there have less and less exploration areas for prospecting, yet greater potential oil and gas resources. As a result it's necessary and urgent to further understanding southeast Sichuan basin's tectonic characteristics and flaw system distribution rule which have the bigger oil and gas reserves in order to gain the larger new reserves. According to the observation and interpretation of the geologic sections and the former studies of this region and the analysis of its seism and log data, the paper discusses the regional tectonic characteristics of southeast Sichuan basin and its control to oil and gas reservoirs from the aspects of kinematics and dynamics. The paper analyses the regional structures of Southeastern Sichuan Basin on the base of the interpretation of the four actual metrical geologic sections and the advanced experience. The area is made up of three groups of tectonics of which trends are severally northeastern, transmeridional and southern-northern, it is brush structure on plane, which also named ejective folds on vertical section. The middle-high and steep structures of northeastern ward and eastern-western ward are a part of Huayingshan tectonic belt extending to south. And to the south, its structures and folds are gradually flattened and superposed with eastern-western folds, which named cross-superposition structure. Based on Sichuan basin's structure-stratum frame and mechanics background, From the aspects of kinematics and dynamics, the author discussed the formation mechanism of southeast Sichuan structures, including ejective folds, brush structure and cross-superposition folds and the formation process of Luzhou ancient apophysis; Combined with east Sichuan basin high and steep structure zones, the paper analyses "two floors"tectonic characteristics. With regional mechanics background and structural mode, Through the studies of the structures of Indosinian, Yanshanian and Himalayan, The author considers that Northeastern structures of southeast Sichuan and southern-northern structures in the north of Luzhou and Qijiang are formed by superposition of the structures of Indosinian, Yanshanian and Himalayan, while the southern-northern structures in the area of Luzhou are formed in the early of Himalayan, and the eastern-western structures are formed in the late of Yanshanian. Following the analysis of the oil source, reservoir and caprock, the paper discussed the conditions of migration, Reservoir and gas accumulation in Permian Maokou Formation and Triassic Jialingjiang Formation. From dynamics background and tectonic characteristics, the author discussed the regional structure and its control to oil and gas reservoir:①Structural evolution stages and gas distribution;②Fissure and gas distribution;③Luzhou ancient apophysis and oil-gas distribution;④Brush structure and its control to oil and gas reservoir;⑤Relation between tectonic superposition and oil-gas. Based on the research synthetically, the paper discussed the new exploration areas in this region. Southeast Sichuan basin hidden and buried structure and fissure is new way for oil and gas. This region is also the source of oil and gas in early Paleozoic, therefore it is a very good prospect for oil and gas in early Paleozoic stratum.