摘要
车排子地区紧邻沙湾凹陷和四棵树凹陷,油源条件优越,具有多层系含油特点,前人对该区原油油源认识存在较大分歧。本次研究在研究区原油生物标志物分析基础上,结合金刚烷异构化指标和正构烷烃单体碳同位素分布,对车排子地区原油油源进行了分析。结果表明,车排子地区存在3类原油:(1)Ⅰ类原油为新近系沙湾组轻质油,表现为侏罗系来源特征,Pr/Ph比值大于2.0,原油碳同位素值偏重,δ(13)^C值大于−28.0‰,姥鲛烷(Pr)、植烷(Ph)和三环萜烷含量较低,Pr/nC17和Ph/nC18比值小于0.3,不含β-胡萝卜烷,三环萜烷/藿烷比值分布在0.08~0.18之间,C_(24)四环萜烷/C_(26)三环萜烷比值分布在1.61~3.81之间,ααα20R规则甾烷具有C_(27)和C_(29)规则甾烷优势,呈C_(27)>C_(28)<C_(29)分布;金刚烷异构化指标IMA值在0.30~0.38之间,IDMA-1值在0.45~0.49之间,正构烷烃单体碳同位素分布曲线呈“下降”型,即随碳数增加正构烷烃碳同位素值逐渐变轻;(2)Ⅱ类原油分布于白垩系到石炭系,表现为二叠系下乌尔禾组来源特征,Pr/Ph比值小于1.3,原油碳同位素值偏轻,δ(13)^C值小于−30.0‰,Pr、Ph和三环萜烷含量相对较高,Pr/nC17和Ph/nC18比值大于0.4,具有中等含量的β-胡萝卜烷,三环萜烷/藿烷比值分布在0.32~1.20之间,C_(24)四环萜烷/C_(26)三环萜烷比值分布在0.25~0.77之间,ααα20R规则甾烷具有C_(29)规则甾烷优势,呈C_(27)<C_(28)<C_(29)分布,金刚烷异构化指标IMA值在0.49~0.53之间,IDMA-1值在0.51~0.53之间,正构烷烃单体碳同位素分布曲线呈“山谷”型,随碳数增加,正构烷烃碳同位素值呈先降低后增加的趋势;(3)Ⅲ类原油分布于新近系沙湾组生物降解稠油,表现为二叠系和侏罗系混源特征,生物标志物特征介于Ⅰ类和Ⅱ类原油之间,原油碳同位素值偏轻,δ(13)^C值小于−30.0‰,三环萜烷含量较高,三环萜烷/藿烷比值分布在0.87~1.32之间,表现为二叠系来源特征,C_(24)四环萜烷/C_(26)三环萜烷比值分布在1.25~1.51之间,ααα20R规则甾烷具有C_(27)和C_(29)规则甾烷优势,呈C_(27)>C_(28)<C_(29)分布,正构烷烃单体碳同位素分布曲线呈“下降”型分布,表现为侏罗系来源特征。
The Chepaizi area is adjacent to the Shawan Sag and Sikeshu Sag.It has superior oil source conditions and is characterized by multi-layered oil-bearing characteristics.However,previous studies have not clearly defined the crude oil source in this area.Based on analysis of crude oil biomarkers in the study area,this study combined the isomerization index of adamantane and the compound-specific carbon isotope distribution of n-alkane to analyze crude oil sources in the Chepaizi area.The results showed that there are three types of crude oil in the Chepaizi area.(1)Type crude oils are light oils distributed in the Neogene Shawan Formation,whichⅠare characterized by Jurassic origin,a Pr/Ph of greater than 2.0,heavy crude oil carbon isotope values,δ(13)^C values greater than−28.0‰,low Pr,Ph,and tricyclic terpene contents,and Pr/nC17 and Ph/nC18 values of less than 0.3.Type I crude oils do not containβ-carotane,have tricyclic terpene/heptane ratios of 0.08 to 0.18,and have C_(24) tetracyclic terpene/C_(26) tricyclic terpene ratios of 1.61 to 3.81.ααα20R regular sterane has the advantage of C_(27) sterane and C_(29) sterane,showing a distribution of C_(27)>C_(28)<C_(29).The adamantane isomerization index(IMAI)values are between 0.30 and 0.38,and the IDAMI-1 values are between 0.45 and 0.49.The compound-specific carbon isotope distribution curve of n-alkane is declining,and the carbon isotope values of n-alkane decrease gradually as the carbon number increases.(2)Type II crude oils are distributed in the Cretaceous to Carboniferous,and are characterized by Permian origin,Pr/Ph of less than 1.3,lighter crude oil carbon isotope values,δ(13)^C values of less than−30.0‰,high Pr,Ph,and tricyclic terpene contents,Pr/nC17 and Ph/nC18 values of greater than 0.4,a medium content ofβ-carotane,tricyclic terpene/heptane ratios of 0.32 to 1.20,and C_(24) tetracyclic terpene/C_(26) tricyclic terpene ratios of 0.25 to 0.77.ααα20R regular sterane has the advantage of C_(29) sterane,showing a distribution of C_(27)<C_(28)<C_(29).The IMAI values are between 0.49 and 0.53,and the IDAMI-1 values are between 0.51 and 0.53.The compound-specific carbon isotope distribution curve of n-alkane is valley-shaped,and the carbon isotope value of n-alkane decreases first and then increases as the carbon number increases.(3)Type III crude oils are biodegradable heavy oils distributed in the Neogene Shawan Formation,which have mixed source characteristics of Permian and Jurassic,lighter crude oil carbon isotope values,δ(13)^C values of less than−30.0‰,high contents of tricyclic terpenes,tricyclic terpene/heptane ratios of 0.87 to 1.32,and C_(24) tetracyclic terpene/C_(26) tricyclic terpene ratios of 1.25 to 1.51.ααα20R regular sterane has the advantage of C_(27) sterane and C_(29) sterane,showing a distribution of C_(27)>C_(28)<C_(29).The compound-specific carbon isotope distribution curve of n-alkane is declining,and the carbon isotope values of n-alkane decrease gradually as the carbon number increases.
作者
李二庭
靳军
米巨磊
何丹
王明
李际
马万云
王海静
LI Er-ting;JIN Jun;MI Ju-lei;HE Dan;WANG Ming;LI Ji;MA Wan-yun;WANG Hai-jing(Research Institute of Experiment and Testing,Xinjiang Oilfield Company,PetroChina,Karamay 834000,China;Key Laboratory of Conglomerate Reservoir Exploration and Development,CNPC,Karamay 834000,China)
出处
《地球化学》
CAS
CSCD
北大核心
2021年第5期492-502,共11页
Geochimica
基金
新疆维吾尔自治区重点实验室开放课题(2017D04023)。
关键词
油源对比
单体烃碳同位素
金刚烷
生物标志物
车排子地区
oil source correlation
compound-specific carbon isotope
diamondoid
biomarker
Chepaizi area
