正烷烃、姥鲛烷与植烷对沉积环境的指示意义——以山东济阳坳陷下第三系为例

SEDIMENTARY ENVIRONMENTAL SIGNIFICANCE OF NORMAL ALKANE AND THE RATIO OF PRISTANE TO PHYTANE

烃源岩和原油有机地球化学成分中的正烷烃特征与沉积环境类型有密切关系。比较典型的正烷烃分布有４ 种类型：①后峰型奇碳优势正烷烃，一般内陆湖泊三角洲平原沼泽相、湖沼相正烷烃属这种类型；②前峰型奇偶优势正烷烃，一般海相和较深湖相正烷烃属这种类型；③双峰型奇偶优势正烷烃，一般海陆过渡相和内陆湖泊三角洲相正烷烃属这种类型；④偶碳优势正烷烃，一般咸水湖相或盐湖相正烷烃属这种类型。姥鲛烷／植烷（ ｗ（Ｐｒ）／ｗ（Ｐｈ））值对于判断原始沉积环境氧化—还原条件有重要意义。根据正烷烃分布特征和姥鲛烷、植烷特征对山东济阳坳陷沙四上亚段的４ 口钻井岩心进行了分析，结果表明，其正烷烃类型有①，②，④型，结合ｗ（Ｐｒ）／ ｗ（Ｐｈ） 值和ＣＰＩ（Ｃａｒｂｏｎ ＰｒｅｆｅｒｅｎｃｅＩｎｄｅｘ）值进行分析。

The characteristics of normal alkanes ( n \|alkanes) and the ratio of pristane to phytane are related to the sedimentary environments. The four types of n \|alkanes are recognized: ① back\|crest odd\|predominant n \|alkanes, generally occurring in the inland lake\|delta plain bog and lacustrine bog; ② front\|crest odd\|even\|predominant n \|alkanes, generally occurring in marine and deep\|lake facies; ③ bimodal odd\|even\|predominant n \|alkanes, generally occurring in paralic facies and inland lake deltas; and ④ even\|predominant \%n\%\|alkanes, generally occurring in saline lakes or salt lakes. The ratio of pristane to phytane is mainly used to determine the oxidation\|reduction condition of the sedimentary environments. According to the analysis data of four wells, the types of alkanes of the upper part of the 4th member in the Shahejie Formation of the Paleogene in the Jiyang Depression of Shandong province belong to ①, ② and ④ types. The ratio of pristanel to phytane and CPI (Carbon Preference Index) values show that the sedimentary environments of the strata are weakly\| to strongly\|reducing inland brackish to saline lakes.