四川盆地北部二叠系茅口组沉积特征及油气意义

Sedimentary Characteristics of the Maokou Formation of the Permian in Northern Sichuan Basin and Its Petroleum Significance

基于地震资料精细解释成果,结合野外剖面及室内薄片观察,通过分析主要岩石类型及古生物、地球化学和地震相特征,对四川盆地北部二叠系茅口组沉积相展布特征进行研究,依据生物(屑)灰岩、礁灰岩和硅质岩等岩相发育规律以及地震地层结构和地层厚度变化特征,认为茅口组发育了开阔台地、台地边缘及斜坡—盆地等沉积亚相,总结出了开阔海夹点礁、开阔海夹点滩、台地边缘滩和灰质—硅质盆地等4种沉积微相组合,明确了沉积相纵向演化和平面展布规律。结果表明,台地边缘高能生物滩平面上呈条带状在剑阁—元坝—龙岗一带规模发育,生物(屑)灰岩的晶间溶孔、粒间溶孔和生物体腔孔发育,物性好,是优质储集层发育带;川西海槽和广元—旺苍海槽茅四段的硅质岩和泥岩有机碳含量高,则是优质生油岩,优越的沉积环境为该区油气成藏提供了有利的生油和储集条件。

Based on the fine seismic data interpretation result,combining the field sections and indoor thin-section observation,we study the depositional facies distribution characteristics,by analyzing the main rock types,paleontology,geochemical and seismic characteristics.On the basis of biological(chip)limestone,siliceous rocks and reef limestone development rule of the lithofacies and seismic stratigraphic structures and stratigraphic thickness variation characteristics,we find out that Maokou Formation has developed sedimentary facies of the open sea platform,marginal-platform shoals and slope-basin,summarize four kinds of sedimentary facies association,open sea platform with patch reefs,open sea platform with shaoal patch,the marginal-platform shoals and calcareous-siliceous basins.Land clarify the vertical evolution of sedimentary facies and plane distribution rule.The results show that the high-energy marginal-platform shoals present banding development in the Jiange-Yuanba-Longgang Area.The biological(chip)limestone develops the intercrystalline denudation pore,intergranular dissolved pore and biogenic body cavity pore,which is a high quality reservoir development zone with good phy sical properties.Maokou Formation(Member 4)in the western Sichuan trough and Guangyuan-Wangcang trough area sedimentary siliceous rock and mudstone is the high quality source rocks,the excellent sedimentary environment providing a favorable conditions for hydrocarbon accumulation oil source and reservoir.