脱羟基维生素E类化合物在成熟原油中检出及潜在地球化学意义

Detection and potential geochemical significance of methyltrimethyltridecylchromans in mature crude oils

脱羟基维生素E类化合物是一类通常作为未熟—低熟源岩或原油可靠标志的生物标志化合物。然而,在渤海湾盆地东濮凹陷南部马厂地区成熟原油中检测出了较为丰富的脱羟基维生素E类化合物。为了探究成熟原油中脱羟基维生素E类化合物的富集成因模式,详细地分析了其在原油样品中的分布特征,并充分结合马厂地区的构造演化特征、烃源岩分布与热演化史、原油样品的其他有机分子化合物特征以及原油围岩的黏土矿物组合与催化特征,总结出2种成因模式:一是成熟原油中混入了少量携带着脱羟基维生素E类化合物的未熟—低熟可溶物;二是储层中黏土矿物的演化机制降低了脱羟基维生素E类化合物的分解速率和程度。

Methyltrimethyltridecylchromans(MTTCs)are found to be relatively abundant in the mature crude oils from Machang area,south of Dongpu Depression,Bohai Bay Basin.In order to explore the enrichment mechanism of MTTCs in crude oils,a detailed study was performed to check its distribution characteristics in the crude oil samples.Integrated with tectonic evolution history,distribution characteristics and thermal history of source rocks,molecular fingerprints characteristics of crude oils and catalytic characteristics and combination features of clay minerals in wall rock of crude oils,two enrichment models have been proposed:(1)The crude oils were mixed with a small amount of immature-low mature soluble bitumen containing MTTCs;(2)Evolutionary mechanism of clay minerals in the reservoir could reduce the decomposition rate and degree of MTTCs resulting in relatively enrichment of MTTCs.