鄂南地区中生界油气成藏体系划分与富集区预测

Mesozoic petroleum accumulation systems and play fairways in southern Ordos Basin

在典型油藏解剖的基础上,根据油气成藏体系概念和划分原则,结合烃源岩、源-储组合样式、油藏特征和成藏机制等,将鄂南地区中生界划分为近源成藏体系和远源成藏体系两类。前者油藏类型以岩性油藏为主,具有"近源成藏"特征,运移距离短,运移动力主要为异常压力,隐性输导,油气富集主控因素为优质烃源岩、有利储集体和构造背景,油气富集模式可概括为"近源相控";后者油藏类型以构造、构造-岩性油藏为主,具有"远源成藏"特征,运移距离长,运移主要动力为浮力,输导体系以通源断裂为主,油气富集主控因素为通源断裂、局部构造和有利砂体,富集模式可概括为"远源断控"。近源成藏体系源储空间呈"三明治"结构,直接大面积接触,具有"近水楼台"成藏优势,生烃高峰期与关键成藏期一致,油气就近大面积充注成藏,是下一步勘探首选领域。其中,长9-长8-长7近源成藏体系Ⅰ类富集有利区是大中型油气田重要的勘探方向。

According to the concept of ＂petroleum accumulation system＂,in combination with source rocks,source-reservoir relationship,reservoir characteristics and accumulation mechanism,we recognized two Mesozoic petroleum accumulation systems in the southern Ordos Basin,i.e.near-source system and far-source system.The near-source accumulation system is dominated by lithologic traps,and features in short migration distance,abnormal pressure as major driving force of migration,and implicit carrier system.Hydrocarbon accumulation in the near-source system is mainly controlled by high-quality source rocks and reservoirs as well as favorable structural setting,and the pattern of hydrocarbon accumulation can be described as ＂near-source and facies-control＂.The far-source system is dominated structural traps and structural-lithologic traps,and is characterized by long migration distance,buoyancy as the major driving force of migration and source rock-rooted faults containing the major carrier system.Hydrocarbon accumulation in the far-source system is mainly controlled by source rock-rooted faults,local structures and high-quality sandstone reservoirs,and the pattern of oil accumulation can be described as ＂far-source and fault-control＂.The source rock-reservoir relationship in the near-source system has a ＂sandwich-like＂ structure.The synchronism of peak hydrocarbon generation with hydrocarbon accumulation provides favorable conditions for widespread and large-scale hydrocarbon charging and accumulation near source rocks.The near-source systems are the priority of future exploration,and the top-ranking play fairways in the CH9-CH8-CH7 near-source systems are the important exploration targets for large-and medium-sized oil and gas fields.