塔里木盆地塔北隆起英买力地区陆相原油分子地球化学特征及来源

Molecular geochemical characteristics and origin of continental oilsin Yingmaili area of Tabei uplift,Tarim Basin

尽管塔北隆起英买力地区陆相油气获得了重要突破,但油气成因类型及油源尚存在争议,根据分子地球化学及同位素参数,通过油源对比研究,明确了原油成因类型及来源。研究结果表明:研究区原油主要分为两种类型,其中第Ⅰ类原油广泛分布在除YM21井和YM46井外的其他地区,三环萜烷多以C_(21)为主峰,C_(24)四环萜烷含量相对较高,C_(24)Tet/C_(26)TT介于1.0~2.0,重排藿烷含量相对较低,该类原油与库车坳陷黄山街组烃源岩生物标志物特征类似;第Ⅱ类原油分布在YM21井和YM46井,原油中三环萜烷通常以C_(19)为主峰,C_(24)四环萜烷含量较高,明显高于第Ⅰ类原油,C_(24)Tet/C_(26)TT约为3,C_(30)重排藿烷/C_(30)藿烷约为0.5,该类原油与恰克马克组烃源岩生物标志物特征较为接近。此外,第Ⅰ类原油具有相对较轻碳同位素值,主要分布在-29.6‰~-28.2‰,第Ⅱ类原油具有相对偏重的碳同位素值,其同位素值约为-27‰,同位素特征也揭示第Ⅰ类原油和第Ⅱ类原油分别来源于黄山街组和恰克马克组烃源岩。

Although important breakthroughs have been made in continental oil and gas in Yingmaili area of Tabei Uplift,there are still disputes over the genetic type and oil source of the oil and gas.According to the molecular geochemical and isotopic parameters,the genetic type and source of crude oil are clarified through oil-source correlation study.The research results show that the crude oil in the study area is mainly divided into two types.ClassⅠcrude oil is widely distributed in areas other than YM21 and YM46 wells.The tricyclic terpenes of class I crude oil mostly have C_(21)as the main peak,the content of C_(24)tetracyclic terpanes is relatively high,the content of C_(24)Tet/C_(26)TT is between 1.0 and 2.0,and the content of diahopanes is relatively low.These features of biomarkers are similar to those of the source rocks of Huangshanjie Formation in Kuqa Depression.ClassⅡcrude oils are distributed in YM21 and YM46 wells.The tricyclic terpenes in crude oils usually take C_(19)as the main peak,and the abundance of C_(24)tetracyclic terpenes is significantly higher than that of classⅠcrude oils.The C_(24)Tet/C_(26)TT ratio is about 3,C_(30)diahopanes/C_(30)hopanes is about 0.5.This kind of crude oil is similar to the biomarker characteristics of source rocks of the Qiakemake Formation.In addition,classⅠcrude oil has relatively light carbon isotope value,which is mainly distributed in the range of-29.6‰~-28.2‰.ClassⅡcrude oil has relatively heavy carbon isotope value,and its isotope value is about-27‰.The isotope characteristics also reveal that the classⅠcrude oil and the classⅡcrude oil come from the source rocks of Huangshanjie Formation and Qiakmake Formation respectively.