原油中C_(19-49)长链三环萜烷系列及其地球化学意义——以柴达木盆地西部英西地区原油为例  

C_(19-49)Extended Tricyclic Terpanes and Their Geochemical Significance in Crude Oils:A case of crude oils from the Yingxi area in the western Qaidam Basin

作　　者：包建平[1] 朱翠山[1] 杨茜[1] 陈琰[2] 周飞 张静 BAO JianPing;ZHU CuiShan;YANG Xi;CHEN Yan;ZHOU Fei;ZHANG Jing(Hubei Key Laboratory of Petroleum Geochemistry and Environment,Geochemistry Department,Yangtze University,Wuhan 434100,China;Exploration&Development Institute,Qinghai Oilfield,China National Petroleum Corporation,Dunhuang,Gansu 736202,China)

机构地区：[1]长江大学油气地球化学与环境湖北省重点实验室,地球化学系,武汉434100 [2]中石油青海油田分公司勘探开发研究院,甘肃敦煌736202

出　　处：《沉积学报》2024年第5期1765-1783,共19页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41772119)。

摘　　要：【目的】为了确定柴达木盆地西部英西地区古近系深部储层(E)原油的热演化程度和成因类型,【方法】利用色谱—质谱(GC-MS)和色谱—质谱—质谱(GC-MS-MS)技术,对其中的各类生物标志物、烷基菲和金刚烷类化合物的分布与组成特征进行了系统分析。【结果与讨论】分析结果表明该地区原油中正构烷烃系列均具有明显的偶碳优势,Pr/Ph比值低(<0.60),Ph/nC_(18)比值高(>1.30),伽马蜡烷含量高,伽马蜡烷指数介于0.90~1.36,属于典型咸水湖相原油,这与研究区古近纪的沉积特征一致。但依据不同原油中长链三环萜烷系列的分布与组成特征,可将他们分成两类:一类原油中C_(19-49)长链三环萜烷系列异常丰富,C_(19-30)TT/C_(27-35)H比值大于1.60,C_(23)TT/C_(30)H>1.40,并伴随有高甾藿比(>4.50)和高β-胡萝烷/nC_(37)比值(>3.20),表明藻类是其主要原始生烃母质;另一类原油中C_(19-30)长链三环萜烷系列含量中等,C_(19-30)TT/C_(27-35)H比值小于0.50,C_(23)TT/C_(30)H<0.55,其甾藿比相对较低(<2.0)、β-胡萝卜烷含量中等,β-胡萝烷/nC_(37)比值小于1.50,可见此类原油中藻类的贡献明显低于前一类原油。对比它们的甾、萜烷和金刚烷类化合物成熟度参数,发现这两组原油的成熟度相近,其对应的R_(o)值介于1.1%~1.3%,即它们形成于生油高峰之后、凝析油气形成以前这一演化阶段。【结论】影响研究区原油中长链三环萜烷系列相对丰度的主要因素是原始生烃母质,而非成熟度,因而它在研究区具有指示原油成因类型的作用,在后续油气勘探中应重点关注。[Objective]To determine the maturity and origin of crude oils from the Yingxi area,western Qaidam Basin,[Methods]the distribution and composition of various biomarkers,alkyl phenanthrenes and diamondoid hydrocarbons were analyzed in detail by gas chromatography-mass spectrometry(GC-MS)and gas chromatography-mass spectrometry-mass spectrometry(GC-MS-MS).[Results and Discussion]The analytical results demonstrate that these oils have an even carbon predominance at nC20 and nC22 in the normal alkane series,the(nC20+nC22)(/nC19+nC21)ratios are more than 1.0.In C13-20 regular isoprenoids,phytane is very abundant,the Pr/Ph ratios are less than 0.60,but the Ph/nC_(18)ratios are higher than 1.30.Moreover,the content of gammacerane indicating the salinity of depositional environment is relatively high,and the gammacerane index are between 0.90 and 1.36.These characteristics are consistent with the geological background of saline depositional environment during the Paleogene in the western Qaidam Basin.Based on the distribution and relative abundance of extended tricyclic terpanes and other biomarkers in different crude oils in the study area,they could be classified into two types.One of them from well Shi 62 and Shixi 58-1 has unusually abundant C_(19-49)tricyclic terpanes,the C_(19-30)T/C_(27-35)H and C_(23)T/C_(30)H ratios are more than 1.60 and 1.40,respectively.In addition,they have higher sterane/hopane(>4.50)andβ-carotane/nC_(37) ratios(>3.20)and lower nC_(37)/nC36 ratios(<1.0),suggesting that algae are their main biological input.The other one from well Shi 57 and Shi 61 has the moderate content of extended C_(19-30) tricyclic terpanes,the C_(19-30)T/C_(27-35)H and C_(23)T/C_(30)H ratios are less than 0.50 and 0.55,respectively.In this king of crude oils,the sterane/hopane andβ-carotane/nC_(37) ratios are less than 2.0 and 1.50,respectively,but the nC_(37)/nC36 ratios are more than 1.0,demonstrating that the algae biological input is relatively low compared to the first one.In the study crude oils,the sterane mat

关 键 词：藿烷系列 C_(19-49)长链三环萜烷系列 伽马蜡烷 β-胡萝卜烷 甾藿比 原油 英西地区 柴达木盆地西部 

分 类 号：P618.13[天文地球—矿床学]