川西坳陷源内油气成藏主控因素及模式:以孝泉-丰谷构造带须家河组五段为例

Main Controlling Factors and Models of Hydrocarbon Accumulation in the Source of Western Sichuan Depression:Taking Xu 5th Member of Xujiahe Formation in Xiaoquan-Fenggu Structural Belt as an Example

上三叠统须家河组是四川盆地川西坳陷的主力烃源岩系,而孝泉-丰谷构造带须家河组五段则是川西坳陷致密砂岩气勘探开发的新领域.利用地质、录井、钻井、分析化验等资料,结合盆地模拟技术,在须五段内部烃源岩、储集层特征以及其发育构造-沉积背景分析的基础上,探讨了孝泉-丰谷构造带须家河组五段源内成藏的主控因素,并建立了相应模式.须五段泥页岩连续稳定分布,有机质丰度高,有机质类型以Ⅲ为主,总体上处于成熟-高成熟阶段;砂岩储层总体为特低孔特低渗致密储层;沉积相以三角洲前缘亚相为主.须五段源内成藏主控因素为烃源岩控制气藏范围和规模,有利相带决定了优质储层发育位置,源储配置关系控制油气富集程度,异常高压有效保存和改造;总结其成藏模式为源内短距离垂向叠覆运聚模式.

Xujiahe Formation of the Upper Triassic is the main source rock series of the West Sichuan depression, while Xujiahe Formation of the Xiaoquan-Fenggu structural belt is a new field of exploration and development of tight sandstone gas in the West Sichuan depression. Based on the data of geology, logging, drilling and analysis, combined with basin simulation technology, and the analysis of source rock, reservoir characteristics and its development structure sedimentary background in the fifth member of Xujiahe Formation, Xiaoquan Fenggu structural belt, this paper discusses the main controlling factors of reservoir formation in the fifth member of Xujiahe Formation, and establishes the corresponding model. The shale of Xuwu member is continuously and stably distributed, with high organic matter abundance. The type of organic matter is mainly III, which is generally in the stage of maturity to high maturity. The sandstone reservoir is generally ultra-low porosity and ultra-low permeability tight reservoir, and the sedimentary facies is mainly delta front subfacies. The main controlling factor of hydrocarbon accumulation in Xuwu member is that the source rock controls the range and scale of gas reservoir, the favorable facies zone determines the location of high quality reservoir, the source reservoir configuration relationship controls the degree of oil and gas enrichment, and the abnormal high pressure is effectively preservation and reservoir reconstruction;the accumulation mode is summarized as short-distance vertical superposition accumulation mode in the source.