大民屯凹陷烃源岩中高分子量烃的形成与分布特征

大民屯凹陷原油以高含蜡著称,对沙河街组低成熟烃源岩抽提物的高温气相色谱分析揭示了高分子量化合物的组成与分布特征。研究表明有机质的原始组成和沉积环境是形成高分子量烃类的主要控制因素。有机质含量较高的烃源岩(TOC>3.0%)显微组成中类脂组的含量较高,岩石抽提物不仅总量较高,而且含蜡量较高,但在蜡的组成上以中分子量的显晶蜡为主,形成于弱还原环境。有机质含量较低的烃源岩(TOC<2.0%)显微组成中镜质组的含量较高,岩石抽提物含量及含蜡量均较低,但在蜡的组成上高分子量的微晶蜡相对富集,形成于弱氧化环境。除正构烷烃外,岩石抽提物中还检出了含量较高的异构烷烃。 

ORGANIC GEOCHEMICAL INVESTIGATION OF PETROLEUM SOURCE ROCKS IN THE DAMINTUN DEPRESSION, EAST CHINA

High temperature GC analysis of high molecular weight hydrocarbons (HMWHCs) was performed on marginal mature source rock extractions from the Shahejie Formation, Damintun Depression, whose oil is parti cularly rich in wax. Organic composition and depositional environment are the main control factors for the formation of HMWHCs. The main maceral components in organic rich samples ( TOC >3.0%) are liptinite and exinite, deposited in relatively reduced environment. They contain high amount of waxes but dominated by macrocrystalline ones (centred at C 29 ). Those organic lean samples ( TOC <2.0%) are dominated by vitrinite, deposited in a slightly oxidized environment. They contain lower amount of waxes but relatively rich in microcrystalline components. Besides normal alkanes, high amounts of branched/cyclic hydrocarbons have been detected in the region above C 50 .