四川盆地侏罗系凉高山组河道砂岩成藏共性与差异

Commonalities and differences of hydrocarbon accumulation in channel sandstones of Jurassic Lianggaoshan Formation, Sichuan Basin

  • 摘要: 为破解四川盆地不同区块侏罗系凉高山组致密砂岩高效勘探开发面临的关键问题,明确油气富集模式与主控因素以指导后续勘探部署,以川北巴中、川东复兴地区凉高山组河道砂岩为研究对象,综合运用钻井岩心、测井、地震及生产动态等多类型、多尺度资料,开展系统的石油地质条件对标分析与成藏过程精细解剖。研究表明:凉高山组油气富集部位多位于优质泥页岩生烃中心与相控孔隙型储层的空间叠合部位,普遍发育油气同产的挥发性油藏—凝析气藏;据此建立“近源充注、砂体输导”与“混源充注、断砂输导”两类油气成藏模式,明确研究区河道砂岩油气富集受构造演化、源储配置、烃源岩热演化程度等多因素耦合控制。对比分析表明,川北巴中与川东复兴地区在压力系统、凝析油含量、油气富集层位及富集强度上存在显著区域差异。系统提出不同地区凉高山组油气成藏的核心共性与关键区域差异,明确构造南北分异主控天然气成藏富集模式、油气来源及烃源岩热演化程度制约气藏特征及流体地球化学性质、源储匹配关系影响油气富集层系与富集程度。研究成果可为相似地质背景下侏罗系河道砂岩油气高效勘探开发提供针对性的理论支撑与参考。

     

    Abstract: To address the key issues in the efficient exploration and development of tight sandstones in the Jurassic Lianggaoshan Formation across different blocks of the Sichuan Basin, and to clarify the hydrocarbon accumulation models and main controlling factors for guiding subsequent exploration deployment, this study took the channel sandstones of the Lianggaoshan Formation in Bazhong (northern Sichuan) and Fuxing (eastern Sichuan) areas as the research objects. Multi-type and multi-scale data, including drilling cores, well logging, seismic data, and production performance, were comprehensively utilized to conduct systematic benchmarking analysis of petroleum geological conditions and detailed examination of hydrocarbon accumulation processes. The study revealed that the hydrocarbon-rich zones of the Lianggaoshan Formation were mostly located at the spatial overlapping areas of high-quality shale hydrocarbon-generating centers and facies-controlled porous reservoirs, generally developing volatile oil reservoir-condensate gas reservoir with co-production of oil and gas. Based on this, two types of hydrocarbon accumulation models, namely "near-source charging and sandbody migration" and "mixed-source charging and fault-sand migration", were established. It was clarified that the hydrocarbon enrichment of channel sandstones in the study area was controlled by the coupling of multiple factors such as structural evolution, source-reservoir configuration, and thermal evolution degree of source rocks. Comparative analysis indicated that significant regional differences were observed between the Bazhong area in northern Sichuan and the Fuxing area in eastern Sichuan in terms of pressure systems, condensate oil content, hydrocarbon-rich horizons, and enrichment intensity. The core commonalities and key regional differences in the hydrocarbon accumulation of the Lianggaoshan Formation across different areas were systematically refined. The study clarified that the north-south structural differentiation primarily controlled the natural gas accumulation and enrichment model, the hydrocarbon source and thermal evolution degree of source rocks constrained gas reservoir characteristics and fluid geochemical properties, and the source-reservoir matching relationship affected the hydrocarbon-rich horizons and enrichment degree. The research findings can provide targeted theoretical support and reference for the efficient exploration and development of Jurassic channel sandstone hydrocarbons in similar geological settings.

     

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