摘要
库车坳陷南斜坡牙哈地区是塔里木盆地重要的油气富集区,然而其原油来源仍不明确。选取了牙哈地区13个原油样品对其进行了有机地球化学分析,并采用端元油模拟混合的方法揭示了混源油中海陆相油混源贡献。依据原油生物标志化合物特征,牙哈地区原油可以大致分为3类:陆相油、海相油以及混合油。陆相油主要来自陆相源岩,姥鲛烷和植烷比值(Pr/Ph)介于1.20~2.35,平均值为1.74,三环萜烷(TT)以C_(20)TT和C_(21)TT为主峰,存在高丰度的C_(30)早洗脱重排藿烷(X化合物)等重排类化合物,正构烷烃碳同位素值介于−28‰~−32‰。海相油是多期海相油的混合,Pr/Ph介于0.74~0.92,平均值为0.81,三环萜烷以C_(23)TT和C_(24)TT为主峰,存在高丰度的长链三环萜烷,正构烷烃碳同位素值均轻于−32‰。此外,海相油中均检测到25-降藿烷类化合物,指示海相原油早期遭受了强烈的生物降解。混合油兼具海相和陆相油的生物标志化合物和碳同位素特征。除牙哈401和牙哈3井计算的原油绝对成熟度值偏低外(牙哈401井镜质体反射率R_(c)为0.54%,牙哈3井R_(c)为0.57%),研究区内其他原油的成熟度总体分布比较均匀,R_(c)介于0.86%~1.11%,平均值为0.97%。二端元混合贡献计算结果表明,研究区混合油中海相油占比均超过60%,其中桥古1井海相油占比可达到90%以上。油源分析表明研究区的陆相油主要来源于三叠系黄山街组,海相油来源于寒武系玉尔吐斯组。研究成果表明库车坳陷南斜坡传统陆相油区依然存在发现海相油气的潜力,对拓展南斜坡下一步油气勘探领域具有重要指导意义。
[Objective]The Yaha area on the southern slope of the Kuqa sub-basin is a significant hydrocarbon-rich region in the Tarim Basin;however,the origin of its crude oil remains unclear.[Methods]This study analyzed 13 crude oil samples from the Yaha area using organic geochemical techniques and employed an end-member oil mixing model to quantify the contributions of marine and terrestrial sources in the mixed oils.[Results]Biomarker characteristics indicate that the crude oils in the Yaha area can be broadly classified into three types:Terrestrial oils,marine oils,and mixed oils.Terrestrial oils primarily derive from lacustrine source rocks,with pristane/phytane(Pr/Ph)values ranging from 1.20 to 2.35(averaging 1.74).The tricyclic terpanes(TT)are dominated by C_(20)TT and C_(21)TT,with a high abundance of rearranged compounds such as C_(30) early-eluting rearranged hopanes(compound X).The n-alkane carbon isotope values range from−28‰to 32‰.Marine oils are a mixture of multi-stage marine source rock contributions,exhibiting Pr/Ph values between 0.74 and 0.92(average of 0.81),with peak C_(23)TT and C_(24)TT compounds and a high abundance of long-chain tricyclic terpanes.Their n-alkane carbon isotope values are generally lighter than−32‰.Additionally,the presence of 25-norhopane compounds in the marine oils indicates significant early-stage biodegradation..Mixed oils display biomarker and isotopic features characteristic of both marine and terrestrial oils.Except for the lower absolute maturity values observed in wells Yaha5,Yaha 401,and Yaha 3(Well Yaha 3:0.57% R_(c);Well Yaha 401:0.54% R_(c)),the overall maturity distribution across the study area is relatively uniform,ranging from 0.86 to 1.11% R_(c),with an average of 0.97% R_(c).Two-end-member mixing calculation suggests that marine oils account for over 60%of the mixed oils in the study area,with marine the contribution in Well Qiaogu 1 exceeding 90%.Source analysis indicates that the terrestrial oils primarily originate from the Triassic Huangshanjie Formation,while the marine oils are derived from the Cambrian Yuertusi Formation.[Conclusion]These findings demonstrate that the continental oil prospects on the southern slope of the Kuqa subbasin remain promising for discovering marine oil and gas resources.This has significant implications for expanding future oil and gas exploration in the southern slope of the Kuqa Depression.
作者
蒋俊
平宏伟
吴少军
赵凤全
王晓雪
袁瑞
鲁中灯
邓晓睿
宋煜
JIANG Jun;PING Hongwei;WU Shaojun;ZHAO Fengquan;WANG Xiaoxue;YUAN Rui;LU Zhongdeng;DENG Xiaorui;SONG Yu(Tarim Oilfield Company,PetroChina,Korla Xinjiang 841000,China;R&D Center for Ultra-Deep Complex Reservoir Exploration and Development,CNPC,Korla Xinjiang 841000,China;Department of Petroleum Geology,School of Earth Resources,China University of Geosciences(Wuhan),Wuhan 430074,China)
出处
《地质科技通报》
北大核心
2025年第4期201-216,共16页
Bulletin of Geological Science and Technology
基金
国家自然科学基金项目(42072176,42272169)。
关键词
牙哈地区
生物标志化合物
碳同位素
混源贡献
玉尔吐斯组
源油识别
库车坳陷
Yaha area
biomarker
carbon isotope
mixed source contribution
Yuertusi Formation
oil source identification
Kuqa Depression
