一种有效的油气成藏研究手段——有机包裹体生物标志物分析:以渤海中部沙东南构造带为例

Practical methodology for study petroleum accumulation - Biomarker analysis of petroleum within fluid inclusion: A case for south-east Shaleitian structure zone

包裹体生物标志物分析实现了包裹体烃与储层烃的直接对比,是目前最有效的有机包裹体成分分析方法之一。由于一般情况下成熟早期原油密度较高,其中高分子量的生物标志物浓度亦高,因此,虽然该方法为群体包裹体分析结果,事实上包裹体生物标志物主要反映早期烃流体的特征,因而该方法可用于追朔油气成藏过程中石油组成的变化。本文详细介绍了压碎法包裹体烃生物标志物分析方法,并应用该方法分析了渤海中部沙东南构造带油气成藏过程。认为沙垒田凸起上CFD11-1油田的原油为沙河街组与东营组下段混合来源,其成藏过程是:早期沙河街组一段、三段形成的成熟度低到中等的油首先充注在近凹陷的构造中(如CFD18-2构造),晚期(上新世时)东营组下段成熟油及沙河街组生成的高成熟油充注近凹的构造,并将早期注入的成熟度相对低的油向构造高部位排驱,排驱过程中有部分晚期生成的油气混合一起进入浅层,在远离凹陷的凸起上成藏(CFD11-1油藏)。作者认为,在近凹的低凸起及潜山构造是寻找轻质油和天然气的有利区带。

The biomarker analysis by crushing host mineral is one of the best analysis technique for petroleum inclusion composition analysis. It allows directly comparison for petroleum within inclusions with product oil. In general, the oil is heavier in early mature, the C-21(+) biomarker compounds content is higher in lower mature petroleum than in higher ones. So the results show mainly the information of early petroleum evolution stage despite this method has to extract a group of petroleum inclusions into GC/MS system, and it can be used to deduce the change of oil composition. In this paper, we present the biomarker analysis of bearing-oil inclusions in detail. And we have studied the oil/gas accumulation history in east-south Shaleitian structure zone, Bohai golf basin. It is suggested that the oil of CFD11-1 oilfield generate from Shahejie formation and Lower Dongying member. The petroleum accumulation process as follows. First, low to middle mature petroleum charged into reservoir near the sag ( e. g. CFD18-2), then the higher mature hydrocarbon of Lower Dongying member and Shahejie formation charged into reservoir, the petroleum of filled later expulsive ones early migrate to swell. Some lighter hydrocarbon mixed with low to middle maturity oil and accumulate in the reservoir on swell (CFD11-1). The writer believed that structure near the sag is more beneficial for the light oil and gas exploration.