柴达木盆地西南地区天然气C_5—C_7轻烃地球化学特征
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摘要
以天然气中C_5—C_7轻烃组分为研究重点,结合天然气组分、碳同位素特征,对柴达木盆地西南地区英东、乌南和扎哈泉油田天然气母质类型、成熟度、油气生成温度和油气次生改造作用进行了研究。研究表明,英东、乌南和扎哈泉油田天然气C_7化合物整体表现出正庚烷含量高的特征,乌南油田C_7化合物中甲基环己烷含量较高,结合天然气碳同位素分析,认为英东、乌南和扎哈泉油田天然气主要为油型气,在乌南和扎哈泉油田有煤型气和混合气。庚烷值和异庚烷值指示天然气多处于成熟—高成熟演化阶段,甲烷碳同位素值计算获得天然气成熟度为0.8%～1.5%,平均为1.2%,说明天然气主要为成熟阶段产物。利用C_7化合物计算得到天然气生成温度,生成温度能大致反映现今油气藏主体部分油气的形成温度;英东、乌南和扎哈泉油田油气生成温度(124～129℃)高于七个泉和狮子沟油田(108～109℃),表明在柴西南地区英东、乌南和扎哈泉油田天然气成熟度更高。通过轻烃研究识别出个别油气藏遭受了生物降解、蒸发分馏和水洗的次生改造作用。
Focusing on the C_5～C_7 light hydrocarbons in natural gas, combined with natural gas components and carbon isotopes, the paper studies the organic precursor type and maturity, hydrocarbon generation temperature and secondary hydrocarbon reconstruction in Yingdong, Wunan and Zhahaquan oilfields in southwestern Qaidam basin. The results show that the C_7 compounds in the natural gas of the 3 oilfields exhibit high n-heptane contents and the C_7 compounds in Wunan oilfield have relatively high methylcyclohexane content. Based on the carbon isotope analysis, it is considered that the natural gas from Yingdong, Wunan and Zhahaquan oilfields mainly belong to oil-type gas, and coal-type gas and mixed gas are found in Wunan and Zhahaquan oilfields. The heptane and isoheptane values indicate that the natural gas are mostly in the mature-highly mature stage, based on the δ~(13)C_(1-Ro)% relationships, the calculated natural gas maturity is 0.8%～1.5% with the average value of 1.2%, indicating these gases were mainly generated in the mature stage. The calculated natural gas generation temperatures can roughly reflect petroleum forming temperatures of the main part of the modern reservoir. The petroleum generation temperatures in Yingdong, Wunan and Zhahaquan oilfields(124～129 ℃) are higher than those in Qigequan and Shizigou oilfields(108～109 ℃), showing that the natural gas maturity in Yingdong, Wunan and Zhahaquan oilfields are even higher. Through light hydrocarbon analysis, several oil and gas reservoirs suffered from biodegradation, evaporative fractionation and water washing have been identified.
Focusing on the C_5～C_7 light hydrocarbons in natural gas, combined with natural gas components and carbon isotopes, the paper studies the organic precursor type and maturity, hydrocarbon generation temperature and secondary hydrocarbon reconstruction in Yingdong, Wunan and Zhahaquan oilfields in southwestern Qaidam basin. The results show that the C_7 compounds in the natural gas of the 3 oilfields exhibit high n-heptane contents and the C_7 compounds in Wunan oilfield have relatively high methylcyclohexane content. Based on the carbon isotope analysis, it is considered that the natural gas from Yingdong, Wunan and Zhahaquan oilfields mainly belong to oil-type gas, and coal-type gas and mixed gas are found in Wunan and Zhahaquan oilfields. The heptane and isoheptane values indicate that the natural gas are mostly in the mature-highly mature stage, based on the δ~(13)C_(1-Ro)% relationships, the calculated natural gas maturity is 0.8%～1.5% with the average value of 1.2%, indicating these gases were mainly generated in the mature stage. The calculated natural gas generation temperatures can roughly reflect petroleum forming temperatures of the main part of the modern reservoir. The petroleum generation temperatures in Yingdong, Wunan and Zhahaquan oilfields(124～129 ℃) are higher than those in Qigequan and Shizigou oilfields(108～109 ℃), showing that the natural gas maturity in Yingdong, Wunan and Zhahaquan oilfields are even higher. Through light hydrocarbon analysis, several oil and gas reservoirs suffered from biodegradation, evaporative fractionation and water washing have been identified.
引文
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[15]郭泽清,马寅生,易士威,等.柴西地区古近系-新近系含气系统模拟及勘探方向[J].天然气地球科学,2017,28(1):82-92.GUO Zeqing,MA Yinsheng,YI Shiwei,et al.Simulation and exploration direction of Paleogene-Neogene gas systemin the western Qaidam basin[J].Natural Gas Geoscience,2017,28(1):82-92.
[16]杨帆.柴西第三系咸水湖相烃源岩特征分析[D].北京:中国地质大学,2009.YANG Fan.Characteristics analysis of Tertiary saline lacustrine source rocks in the western Qaidam basin[D].Beijing:China University of Geosciences,2009.
[17]戴金星,裴锡古,戚厚发,等.中国天然气地质学,卷1[M].北京:石油工业出版社,1992.DAI Jinxing,PEI Xigu,QI Houfa,et al.China natural gas geology,volume 1[M].Beijing:Petroleum Industry Press,1992.
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[19]程克明,金伟明,何忠华,等.陆相原油及凝析油的轻烃单体烃组成特征及地质意义[J].石油勘探与开发,1987,14(1):34-43.CHENG Keming,JIN Weiming,HE Zhonghua,et al.Composoitioncharacetristics of light hydrocarbons in continental oil and condensate and their geological significance[J].Petroleum Exploration and Development,1987,14(1):34-43.
[20]BEMENT W O,LEVEY R A,MANGO F D.The temperature of oil generation as defined with C7chemistry maturity parameter(2,4-DMP/2,3-DMP ratio)[C]//GRIMALT J O,DORRONSORO C.Organic geochemistry:developments and applications to energy,climate,environment and human history.Donostia,San Sebastian,Spain,1995:505-507.
[21]李海,汤达祯,许浩,等.柴达木盆地狮子沟油田古近系油气成藏期次[J].油气地质与采收率,2013,20(3):30-32.LI Hai,TANG Dazhen,XU Hao,et al.Analysis of hydrocarbon accumulation period in Paleogene reservoirs,Shizigou oilfield of Qaidam basin[J].Petroleum Geology and Recovery Efficiency,2013,20(3):30-32.
[22]ZHU Yangming,WENG Huanxin,SU Aiguo,et al.Geochemical characteristics of Tertiary saline lacustrine oils in the western Qaidam basin,northwest China[J].Applied Geochemistry,2005,20:1 875-1 889.
[23]付锁堂,袁剑英,汪立群,等.柴达木盆地油气地质成藏条件研究[M].北京:科学出版社,2014.FU Suotang,YUAN Jianying,WANG Liqun,et al.Study on conditions of hydrocarbon geology accumulation in Qaidam basin[M].Beijing:Science Press,2014.(编辑杨新玲)
[2]王琳,吴海,王科,等.柴达木盆地西部扎哈泉地区油气成藏过程[J].科学技术与工程,2017,17(34):202-209.WANG Lin,WU Hai,WANG Ke,et al.Hydrocarbon charge history of Zhahaquan area,western Qaidam basin[J].Science Technology and Engineering,2017,17(34):202-209.
[3]路俊刚,姚宜同,王力,等.柴达木盆地跃进斜坡区油源判识与原油勘探方向[J].吉林大学学报(地球科学版),2014,44(3):730-740.LU Jungang,YAO Yitong,WANG Li,et al.Oil source and mature oil exploration potential of Yuejin slope area in Qaidam basin[J].Journal of Jilin University(Earth Science Edition),2014,44(3):730-740.
[4]朱扬明,苏爱国,梁狄刚,等.柴达木盆地原油地球化学特征及其源岩时代判识[J].地质学报,2003,77(2):212-279.ZHU Yangming,SU Aiguo,LIANG Digang,et al.Geochemical characteristic and source rock age identification of crude oils in the Qaidam basin,northwest China[J].Acta Geologica Sinca,2003,77(2):212-279.
[5]张晓宝,胡勇,马立元,等.柴达木盆地西部第三系盐湖相天然气碳同位素特征、成因与分布[J].中国科学D辑:地球科学,2002,32(7):598-608.ZHANG Xiaobao,HU Yong,MA Liyuan,et al.Carbon isotopic characteristics,genesis and distribution of the natural gas of the Tertiary saline lake in the western part of Qaidam basin[J].Science in China Series D:Earth Sciences,2002,32(7):598-608.
[6]LIU Chenglin,LIU Jun,SUN Ping,et al.Geochemical features of natural gas in the Qaidam basin,NW China[J].Journal of Petroleum Science and Engineering,2013,110:58-93.
[7]胡国艺,李剑,谢增业,等.天然气轻烃地球化学[M].北京:石油工业出版社,2018.HU Guoyi,LI Jian,XIE Zengye,et al.Light hydrocarbons geochemistry in natural gas[M].Beijing:Petroleum Industry Press,2018.
[8]MANGO F D.An invariance in the isoheptanes of petroleum[J].Science,1987,273:514-517.
[9]MANGO F D.The light hydrocarbons in petroleum:a critical review[J].Organic Geochemistry,1997,26:417-440.
[10]王培荣,徐冠军,肖廷荣,等.用C7轻烃参数判识烃源岩沉积环境的探索[J].石油勘探与开发,2007,34(2):156-159.WANG Peirong,XU Guanjun,XIAO Tingrong,et al.Application of C7light hydrocarbon parameters in identifying source rock depositional environment[J].Petroleum Exploration and Development,2007,34(2):156-159.
[11]段毅,赵阳,姚泾利,等.轻烃地球化学研究进展及发展趋势[J].天然气地球科学,2014,25(12):1 875-1 887.DUAN Yi,ZHAO Yang,YAO Jingli,et al.Research advance and tendency of light hydrocarbon geochemistry[J].Natural Gas Geoscience,2014,25(12):1 875-1 887.
[12]陈世悦,徐凤银,彭德华.柴达木盆地基底构造特征及其控油意义[J].新疆石油地质,2000,21(3):175-179.CHEN Shiyue,XU Fengyin,PENG Dehua.Characteristics of basement structures and their controls on hydrocarbon in Qaidam basin[J].Xinjiang Petroleum Geology,2000,21(3):175-179.
[13]孙平,郭泽清,刘卫红,等.柴达木盆地英东一号油气田成藏机理[J].石油勘探与开发,2013,40(4):429-435.SUN Ping,GUO Zeqing,LIU Weihong,et al.Accumulation mechanism of the Yingdong I field in the Qaidam basin,NW China[J].Petroleum Exploration and Development,2013,40(4):429-435.
[14]彭德华.柴达木盆地西部第三系咸化湖泊烃源岩地质地球化学特征与生烃机理[D].广州:中国科学院广州地球化学研究所,2004.PENG Dehua.Geology,geochemical characteristics and mechanism of hydrocarbon-generating for source rocks from the Tertiary salty lacustrine facies in the west region of the Qaidam basin[D].Guangzhou:Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,2004.
[15]郭泽清,马寅生,易士威,等.柴西地区古近系-新近系含气系统模拟及勘探方向[J].天然气地球科学,2017,28(1):82-92.GUO Zeqing,MA Yinsheng,YI Shiwei,et al.Simulation and exploration direction of Paleogene-Neogene gas systemin the western Qaidam basin[J].Natural Gas Geoscience,2017,28(1):82-92.
[16]杨帆.柴西第三系咸水湖相烃源岩特征分析[D].北京:中国地质大学,2009.YANG Fan.Characteristics analysis of Tertiary saline lacustrine source rocks in the western Qaidam basin[D].Beijing:China University of Geosciences,2009.
[17]戴金星,裴锡古,戚厚发,等.中国天然气地质学,卷1[M].北京:石油工业出版社,1992.DAI Jinxing,PEI Xigu,QI Houfa,et al.China natural gas geology,volume 1[M].Beijing:Petroleum Industry Press,1992.
[18]胡国艺,李健,李谨,等.判识天然气成因的轻烃指标探讨[J].中国科学D辑:地球科学,2007,37(增刊Ⅱ):111-117.HU Guoyi,LI Jian,LI Jin,et al.A study on the light hydrocarbon index of identifying the origin of natural gas[J].Science in China Series D:Earth Science,2007,37(Supp.Ⅱ):111-117.
[19]程克明,金伟明,何忠华,等.陆相原油及凝析油的轻烃单体烃组成特征及地质意义[J].石油勘探与开发,1987,14(1):34-43.CHENG Keming,JIN Weiming,HE Zhonghua,et al.Composoitioncharacetristics of light hydrocarbons in continental oil and condensate and their geological significance[J].Petroleum Exploration and Development,1987,14(1):34-43.
[20]BEMENT W O,LEVEY R A,MANGO F D.The temperature of oil generation as defined with C7chemistry maturity parameter(2,4-DMP/2,3-DMP ratio)[C]//GRIMALT J O,DORRONSORO C.Organic geochemistry:developments and applications to energy,climate,environment and human history.Donostia,San Sebastian,Spain,1995:505-507.
[21]李海,汤达祯,许浩,等.柴达木盆地狮子沟油田古近系油气成藏期次[J].油气地质与采收率,2013,20(3):30-32.LI Hai,TANG Dazhen,XU Hao,et al.Analysis of hydrocarbon accumulation period in Paleogene reservoirs,Shizigou oilfield of Qaidam basin[J].Petroleum Geology and Recovery Efficiency,2013,20(3):30-32.
[22]ZHU Yangming,WENG Huanxin,SU Aiguo,et al.Geochemical characteristics of Tertiary saline lacustrine oils in the western Qaidam basin,northwest China[J].Applied Geochemistry,2005,20:1 875-1 889.
[23]付锁堂,袁剑英,汪立群,等.柴达木盆地油气地质成藏条件研究[M].北京:科学出版社,2014.FU Suotang,YUAN Jianying,WANG Liqun,et al.Study on conditions of hydrocarbon geology accumulation in Qaidam basin[M].Beijing:Science Press,2014.(编辑杨新玲)