Peservoir-forming pattern of "four-storey" hydrocarbon accumulation in Anchang syncline of northern Guizhou Province

The Sinian-Paleogene period in South China developed several sets of hydrocarbon source rocks. Because of the multistage tectonic movements, the preservation conditions of oil and gas are poor. Over the past 60 years, oil and gas survey in complex structure areas outside the basins has not made a major breakthrough except for Sichuan, Jianghan and Subei basins. Based on field geological survey, geophysical exploration and researches on hydrocarbon accumulation conditions, the authors hold that, because the Wufeng-Longmaxi Formation has well-developed organic matter-rich shale, moderate thermal evolution, Shiniulan Formation provides good reservoir, and syncline wing is blocked by reverse faults, the shale gas, oil and gas accumulation conditions are very favorable. Well Anye-1 made the "four-storey" type oil and gas breakthrough in the Shiniulan Formation, Wufeng-Longmaxi Formation, Baota Formation and Qixia Formation. In the Shiniulan Formation, more than 10×10⁴ m³ industrial gas is produced everyday. New areas, new layers and new types are therefore opened up for oil and gas exploration in South China. The breakthrough of well Anye-1 confirms the fact that there exist the reservoir-forming conditions for the coexistence of conventional and unconventional oil and gas in the complex structure areas outside the basins in northern Guizhou and southeastern Chongqing. These achievements are of great significance for the development of residual syncline oil and gas exploration in the adjacent areas.