南堡凹陷1号构造源上油气成藏特征及控制因素分析

Above-source hydrocarbon accumulation in No.1 structure of Nanpu sag and its controlling factors

通过对南堡凹陷1号构造成藏条件、油气分布规律以及控藏因素系统分析认为:中浅层油气藏为源上油气藏,油气来自沙三段、沙一段和东三段。油气分布表现为平面上集中于构造主体部位,油源断层两侧相对富集,远离构造主体,油气分散;纵向上含油层位多,出油井段长,含油层段相对集中,距离烃源岩层越远,油气富集越少,油气主要聚集在区域性巨厚火山岩盖层之下的东一段和馆四段。油气分布特征与控制油气藏形成的多种因素密切相关:(1)继承性正向构造为油气运移的有利指向,与输导体系匹配的圈闭易于成藏;(2)油源断层是油气成藏的关键因素,它与骨架砂体组成的复合输导体系将油气输送到中浅层有利圈闭中;(3)局部低幅度构造、火山岩侧向封堵与直接封盖层是构造—岩性油气藏形成的有利因素;(4)良好的储集砂体类型和相带有助于油气富集,优先成藏。

According to the systematic analysis of hydrocarbon accumulation conditions, hydrocarbon distribution and reservoir-controlling factors, the shallow-middle reservoirs in No.1 structure of the Nanpu sag are above-source reservoirs where hydrocarbons came from the third and first members of Shahejie Formation and the third member of the Dongying Formation. Laterally, hydrocarbons are mainly distributed in the major part of the structure, and abundant on both sides of the oil-migrating fault; hydrocarbons are dispersed farther from the major part of the structure. Vertically, there are many oil-bearing horizons with long oil producing intervals, and the oil-bearing intervals are concentrated; the farther from the source rocks, the less hydrocarbons are accumulated; hydrocarbons are mainly endowned in the first member of Dongying Formation and the fourth member of Guantao Formation under the thick regional volcanic cap-rocks. The characteristics of hydrocarbon distribution are closely related to several reservoir-controlling factors. First, the inherited positive structure is a favorable destination of hydrocarbon migration, and hydrocarbons may probably accumulate within the traps with conducting system. Second, oil-migrating fault is a key element for hydrocarbon accumulation, and it constitutes a complex conducting system with the sand framework, through which hydrocarbons migrate into shallow-middle favorable traps. Third, local low-relief structure, lateral volcanic sealing and overlying cap-rocks are favorable factors for the formation of structural-lithologic reservoirs. Fourth, good reservoir sand types and facies belts are favorable for hydrocarbon accumulation.