天然气生成过程中的碳同位素分馏作用研究
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摘要
天然气是一种以轻烃为主的混合物,由于缺少大分子指纹化石,许多重要的成因信息难以单纯依靠组分获得。同位素效应的存在弥补了这一缺憾,同位素分馏是同位素效应的集中体现。
影响天然气碳同位素值的主要因素为母质类型和成熟度。受“结构效应”的影响,相同成熟度条件下,由腐殖型有机质生成的煤型气碳同位素值比由腐泥型有机质生成的油型气的重。而对于某种确定成因的天然气,随成熟度的增加其δ13C 值一般是增大的。
生气母质中不同成气官能团具有不同的碳同位素组成和12C-12C 与13C-12C 的活化能差。在描述天然气碳同位素分馏的众多模型中,从早期的静态模型到后来的以Rayleigh 方程为基础的分馏模型,再到现在的动力学模型是一个不断完善过程:静态模型无法动态地再现天然气的演化历程,无法预测天然气形成过程中的各种复杂变化;以Rayleigh 方程为基础的分馏模型把碳同位素的分馏体现在一个恒定的分馏因子上;动力学模型均认识到同位素动力学效应是温度和时间的函数。但是,Cramer1、Cramer2模型却都有缺陷,均认为所有平行反应对应的母质即不同成气官能团具有相同的碳同位素组成,这一假设看来并不合理,而且Cramer1 模型更大胆地假设不同成气官能团的12C-12C 与13C-12C 的键能差相同,这与量子化学理论相背。Cramer3 模型基本摆脱了这些不足,它从实际生成含12C及13C的甲烷量出发,来计算碳同位素动力学效应。建模基础的不同造成了拟合效果的不同:以Rayleigh 方程为基础的模型和Cramer1 模型仅仅能够近似地模拟出碳同位素值随着热解温度的升高而变重的部分,而对低温段和高温段存在的异常变化都模拟不出来;Cramer2 模型能对碳同位素的整体演化趋势进行较好的拟合,但存在波动;Cramer3 模型能完全模拟出碳同位素值的演化趋势,是最为完善的模型。
应用静态模型,直接应用天然气的碳同位素值可以确定天然气成因类型及成熟度。而应用同位素动力学模型结合盆地的热史和埋藏史则可以对气藏的成藏史加以研究。
Nature gas is a kind of mixture in which light hydrocarbons are dominant, it is very difficult to acquire some important origin information because macromolecule fingerprint fossil is absent. Presence of isotope effect fetches up this regret.
Important factors affecting carbon isotope value of nature gas are parent material type and maturity. Under the effect of “structure effect”, carbon isotope value of coaliferous gas generated from humus is greater than that of petroliferous gas generated from sapropelic substance if they have same maturity. Popularly, carbon isotope value of nature gas from certain parent material becomes greater and greater as its maturity increases.
Different functional groups in generating gas parent material have distinct isotope composition and ?Ea between 12C-12C and 13C-12C. The models describing nature gas carbon isotope distillation become more and more perfect from early static models to models based on Rayleigh expression and kinetic models. Static models can not dynamically describe nature gas evolvement course and can not forecast all kinds of complicated variety in the process of natural gas generation; and models based on Rayleigh expression incarnate carbon isotope distillation using a constant distillation gene; but kinetic models realize isotope kinetic domino offect is a function of temperature and time. But models of Cramer1 and Cramer2 have bugs: they consider different generating gas functional groups corresponding with parallel reactions have same carbon isotope constitute, this is not reasonable. In Cramer1 model it is boldly supposed that ?Ea between 12C-12C and 13C-12C of different functional groups is equal which breaches quantum chemistry theory. Cramer3 model casts off these flaws, it calculates isotope kinetic effect using actual genertated quantity of 12C1 and 13C1. Models’fitting effect is different as they are founded on distinct bases: models based on Rayleigh expression and Cramer1 model can only simulate the part in which carbon isotope value become great when temperature increases, for abnormal varieties in parties of low temperature and high temperature they fail. Cramer2 model can simulate carbon isotope value curve preferably, but fluctuate is unavoidable. Only Cramer3 model can simulate it completely, so it is the most perfect.
Genesis type and maturity of nature gas can be confirmed using carbon isotope value by static models. Using kinetic models and combining basin’s thermal history and embedding history we can study gas reservoir form history.
影响天然气碳同位素值的主要因素为母质类型和成熟度。受“结构效应”的影响,相同成熟度条件下,由腐殖型有机质生成的煤型气碳同位素值比由腐泥型有机质生成的油型气的重。而对于某种确定成因的天然气,随成熟度的增加其δ13C 值一般是增大的。
生气母质中不同成气官能团具有不同的碳同位素组成和12C-12C 与13C-12C 的活化能差。在描述天然气碳同位素分馏的众多模型中,从早期的静态模型到后来的以Rayleigh 方程为基础的分馏模型,再到现在的动力学模型是一个不断完善过程:静态模型无法动态地再现天然气的演化历程,无法预测天然气形成过程中的各种复杂变化;以Rayleigh 方程为基础的分馏模型把碳同位素的分馏体现在一个恒定的分馏因子上;动力学模型均认识到同位素动力学效应是温度和时间的函数。但是,Cramer1、Cramer2模型却都有缺陷,均认为所有平行反应对应的母质即不同成气官能团具有相同的碳同位素组成,这一假设看来并不合理,而且Cramer1 模型更大胆地假设不同成气官能团的12C-12C 与13C-12C 的键能差相同,这与量子化学理论相背。Cramer3 模型基本摆脱了这些不足,它从实际生成含12C及13C的甲烷量出发,来计算碳同位素动力学效应。建模基础的不同造成了拟合效果的不同:以Rayleigh 方程为基础的模型和Cramer1 模型仅仅能够近似地模拟出碳同位素值随着热解温度的升高而变重的部分,而对低温段和高温段存在的异常变化都模拟不出来;Cramer2 模型能对碳同位素的整体演化趋势进行较好的拟合,但存在波动;Cramer3 模型能完全模拟出碳同位素值的演化趋势,是最为完善的模型。
应用静态模型,直接应用天然气的碳同位素值可以确定天然气成因类型及成熟度。而应用同位素动力学模型结合盆地的热史和埋藏史则可以对气藏的成藏史加以研究。
Nature gas is a kind of mixture in which light hydrocarbons are dominant, it is very difficult to acquire some important origin information because macromolecule fingerprint fossil is absent. Presence of isotope effect fetches up this regret.
Important factors affecting carbon isotope value of nature gas are parent material type and maturity. Under the effect of “structure effect”, carbon isotope value of coaliferous gas generated from humus is greater than that of petroliferous gas generated from sapropelic substance if they have same maturity. Popularly, carbon isotope value of nature gas from certain parent material becomes greater and greater as its maturity increases.
Different functional groups in generating gas parent material have distinct isotope composition and ?Ea between 12C-12C and 13C-12C. The models describing nature gas carbon isotope distillation become more and more perfect from early static models to models based on Rayleigh expression and kinetic models. Static models can not dynamically describe nature gas evolvement course and can not forecast all kinds of complicated variety in the process of natural gas generation; and models based on Rayleigh expression incarnate carbon isotope distillation using a constant distillation gene; but kinetic models realize isotope kinetic domino offect is a function of temperature and time. But models of Cramer1 and Cramer2 have bugs: they consider different generating gas functional groups corresponding with parallel reactions have same carbon isotope constitute, this is not reasonable. In Cramer1 model it is boldly supposed that ?Ea between 12C-12C and 13C-12C of different functional groups is equal which breaches quantum chemistry theory. Cramer3 model casts off these flaws, it calculates isotope kinetic effect using actual genertated quantity of 12C1 and 13C1. Models’fitting effect is different as they are founded on distinct bases: models based on Rayleigh expression and Cramer1 model can only simulate the part in which carbon isotope value become great when temperature increases, for abnormal varieties in parties of low temperature and high temperature they fail. Cramer2 model can simulate carbon isotope value curve preferably, but fluctuate is unavoidable. Only Cramer3 model can simulate it completely, so it is the most perfect.
Genesis type and maturity of nature gas can be confirmed using carbon isotope value by static models. Using kinetic models and combining basin’s thermal history and embedding history we can study gas reservoir form history.
引文
1 王大锐. 油气稳定同位素地球化学[M]. 北京:石油工业出版社,2000,275~280
2 李钜源. 单分子烃碳同位素分析方法及影响因素探讨[J]. 地球学报,2004,25(2):109～113
3 陈践发,陈振岩等. 辽河盆地天然气中重烃异常富集重碳同位素的成因探讨[J]. 沉积学报,1998,16(2):5～7
4 窦立荣,徐树宝. 松辽盆地天然气的地球化学特征和成因类型[J]. 石油勘探与开发,1991,(3):16～23
5 李赞豪,杨义康等. 甲烷碳同位素在天然气勘探中的应用[J]. 石油与天然气地质,1985,6(4):116～119
6 刚文哲,高岗等. 论乙烷碳同位素在天然气成因类型研究中的应用[J]. 石油实验地质,1997,19(2):164～166
7 R.J.Pallasser. Recognising biodegration in gas/oil accumulations through the δ13C composition of gas components [J]. Organic Geochemistry, 2000, 31: 1363~1373
8 黄第藩,刘宝泉等. 塔里木盆地东部天然气的成因类型及其成熟度识别[J]. 中国科学(D),1996,26(4):365～372
9 Chung H M, Sackett W M. Use of stable carbon isotope compositions of pyrolytically derived methane as maturity indices for carbonaceous materials [J]. Geochimical et Cosmochimica, 1979, 43: 1979~1988
10 黄籍中. 论天然气甲烷碳同位素偏负的基因[J]. 天然气勘探与开发,1998,21(1):27～34
11 Zhang T, Krooss B M. Experimential investigation on the carbon isotope fractionation of methane during gas migration by diffusion through sedimentary rocks at elevated temperature and pressure [J]. Geochimical et Cosmochimica, 2001, 65: 2723~2742
12 蒋助生,罗霞等. 苯、甲苯碳同位素组成作为气源对比新指标的研究[J]. 地球化学,2000,29(4):413
13 黄海平,许晓宏. 天然气同位素特征及作用[J]. 石油与天然气地质,1997,18(2):136～139
14 James A T. Correlation of reservoired gased useing the carbon isotopic compositions of wet gas components [J]. A.A.P.Bull, 1990, 74(9): 1441~1458
15 王顺玉,戴鸿鸣等. 四川盆地海相碳酸盐岩大型气田天然气地球化学特征与气源[J]. 天然气地球科学,2000,11(2):10～17
16 王廷栋,王海清等. 以凝析油轻烃和天然气碳同位素特征判断气源[J]. 西南石油学院学报,1989,11(3):11～14
17 熊永强,耿安松等. 生烃动力学模拟实验结合GC-IRMS 测定在有效气源岩判识中的应用[J]. 地球化学,2002,31(1):21～24
18 郑永飞,陈江峰. 稳定同位素地球化学[M]. 北京:科学出版社,2000
19 Alain A. Prinzhofer, Alain Y. Huc. Genetic and post-genetic molecular and isotope fractionations in matural gases [J]. Chemical Geology, 1995, 126: 281~290
20 Ulrich Berner, Eckhard Faber. Empirical carbon isotope/maturity relationships for gases from algal kerogens and terrigenous organic matter, based on dry, open-system pyrolysis [J]. Org. Geochem, 1996, 24(10-11): 947~955
21 Schoell M. Genetic Characterization of natural gases [J]. The American Association of Petroleum Geologists Bulletin, 1983, 67(12): 2225~2238
22 戴金星. 天然气碳氢同位素特征和各类天然气鉴别[J]. 天然气地球科学. 1993,2(3):2～40
23 石昕,孙冬敏等. 煤成大、中型气田天然气的碳同位素特征[J]. 石油实验地质,2000,22(1):16～21
24 刘文汇,宋岩等. 煤岩及其主显微组份热解气碳同位素组成的演化[J]. 沉积学报,2003,21(1):183～190
25 沈平,徐永昌. 中国陆相成因天然气同位素组成特征[J]. 地球化学,1991,6(2):144～151
26 杨玉峰,任延广等. 松辽盆地汪升地区深层天然气地球化学特征及成因[J]. 石油勘探与开发,1999,26(4):18～21
27 Landais P, Michels R, Elie M. Are time and temperature the only constraints to the simulation of organic maturation? Organic Geochemistry, 1994, 22, 617~630
28 戴金星,夏新宇,秦胜飞等. 中国有机烷烃气碳同位素系列倒转的原因[J]. 石油与天然气地质,2003,24(1):1~6
29 Bjorg Andresen, Torbjorn Throndsen, et al. A comparison of pyrolysis products with models for natural gas generation [J]. Chemical Geology, 1995, 126: 261~280
30 Jianguo Du, Zhijun Jin, et al. Stable carbon isotope compositions of gaseous hydrocarbons produced from high high pressure and high temperature pyrolysis of lignite [J]. Org. Geochem, 2003, 34: 97~104
31 关平,伍天洪. 热成因甲烷碳同位素分布的形成机制. 沉积学报. 2003,21(1):175～180
32 帅燕华,邹艳荣,彭平安. 天然气甲烷碳同位素动力学模型与地质应用新进展. 地球科学进展[J]. 2003,18(3):405～411
33 邹艳荣,帅燕华等. 煤成甲烷碳同位素演化的数学模型与应用. 天然气地球科学[J]. 2003,14(2):92～96
34 Clayton C. Carbon isotope fractionation during natural gas generation from kerogen [J]. Mar.Pet.Geo, 1991, 8: 232~240
35 Bener U, Faber E, Stahl W. Mathematical simulation of the carbon isotopic fractionation between huminitic coals and related methane [J]. Chemical Geology, 1992, 94(4): 315~319
36 Bener U, Faber E, Scheeder G. Primary cracking of algal and landplant kerogens:Kinetic models of isotope variations in methane, ethane and propane [J]. Chemical Geology, 1995, 126: 233~245
37 Lorant F, Prinzhofer A. Carbon isotopic and molecular constraints on the formation and the expulsion of thermogenic hydrocarbon gases [J]. Chemical Geology, 1998, 147: 249~264
38 Lorant F, Behar F, Vandenbroucke M. Methane generation from methylated aromatics:Kinetic study and carbon isotope modeling [J]. Energy&Fuels, 2000, 14: 1143~1155
39 Clayton C. Carbon isotope fractionation during natural gas generation from kerogen [J]. Mar.Pet.Geo, 1991, 8: 232~240
40 周兴熙,王红军. 略论天然气甲烷碳同位素的累积效应[J]. 石油勘探与开发,1999,26(1):10～12
41 Rooney M A. Modeling thermogenic gas generaion using carbon isotope ratios of natural gas hydrocarbons [J]. Chemical Geology, 1995, 126: 219~232
42 Bernhard Cramer, Eckhard Faber, Peter Gerling, et al. Reaction kinetics of stable carbon isotopes in nature gas-Insights from dry, open system pyrolysis experiments [J]. Energy & Fuels, 2001, 15(3): 517~532
43 Cramer B, Krooss B M, Littke R. Modelling isotope fractionation during primary cracking of natural gas: a reaction kinetic approach [J]. Chemical Geology, 1998, 149(3-4): 235~250
44 帅燕华,邹艳荣,彭平安. 塔里木盆地库车坳陷煤成气甲烷碳同位素动力学研究及其成藏意义[J]. 地球化学,2003,32(5):469～475
45 Tang Y, Perry J K, et al. Mathematical modeling of stable carbon isotope ratios in naturan gases [J]. Geochimica et Cosmochimica Acta, 2000, 64(15): 2673~2687
46 卢双舫. 有机质成烃动力学理论及其应用[M]. 北京:石油工业出版社,1996
47 F. Behar, M. Vandenbroucke, et al. Experimental simulation of gas generation from coals and a marine kerogen [J]. Chemical Geology, 1995, 126: 247~260
48 R.Gaschinitz,Bernhard M. Krooss, et al. On-line pyrolysis-GC-IRMS:isotope fractionation of thermally generated gases from coals [J]. Fuel, 2001, 80:2139~2153
49 S.A.Macko, M. Ryan, M.H. Engel. Stable isotopic analysis of individual carbohydrates by gas chromatographic/combustion/isotope ratio mass spectrometry [J]. Chemical Geology, 1998, 152: 205~210
2 李钜源. 单分子烃碳同位素分析方法及影响因素探讨[J]. 地球学报,2004,25(2):109～113
3 陈践发,陈振岩等. 辽河盆地天然气中重烃异常富集重碳同位素的成因探讨[J]. 沉积学报,1998,16(2):5～7
4 窦立荣,徐树宝. 松辽盆地天然气的地球化学特征和成因类型[J]. 石油勘探与开发,1991,(3):16～23
5 李赞豪,杨义康等. 甲烷碳同位素在天然气勘探中的应用[J]. 石油与天然气地质,1985,6(4):116～119
6 刚文哲,高岗等. 论乙烷碳同位素在天然气成因类型研究中的应用[J]. 石油实验地质,1997,19(2):164～166
7 R.J.Pallasser. Recognising biodegration in gas/oil accumulations through the δ13C composition of gas components [J]. Organic Geochemistry, 2000, 31: 1363~1373
8 黄第藩,刘宝泉等. 塔里木盆地东部天然气的成因类型及其成熟度识别[J]. 中国科学(D),1996,26(4):365～372
9 Chung H M, Sackett W M. Use of stable carbon isotope compositions of pyrolytically derived methane as maturity indices for carbonaceous materials [J]. Geochimical et Cosmochimica, 1979, 43: 1979~1988
10 黄籍中. 论天然气甲烷碳同位素偏负的基因[J]. 天然气勘探与开发,1998,21(1):27～34
11 Zhang T, Krooss B M. Experimential investigation on the carbon isotope fractionation of methane during gas migration by diffusion through sedimentary rocks at elevated temperature and pressure [J]. Geochimical et Cosmochimica, 2001, 65: 2723~2742
12 蒋助生,罗霞等. 苯、甲苯碳同位素组成作为气源对比新指标的研究[J]. 地球化学,2000,29(4):413
13 黄海平,许晓宏. 天然气同位素特征及作用[J]. 石油与天然气地质,1997,18(2):136～139
14 James A T. Correlation of reservoired gased useing the carbon isotopic compositions of wet gas components [J]. A.A.P.Bull, 1990, 74(9): 1441~1458
15 王顺玉,戴鸿鸣等. 四川盆地海相碳酸盐岩大型气田天然气地球化学特征与气源[J]. 天然气地球科学,2000,11(2):10～17
16 王廷栋,王海清等. 以凝析油轻烃和天然气碳同位素特征判断气源[J]. 西南石油学院学报,1989,11(3):11～14
17 熊永强,耿安松等. 生烃动力学模拟实验结合GC-IRMS 测定在有效气源岩判识中的应用[J]. 地球化学,2002,31(1):21～24
18 郑永飞,陈江峰. 稳定同位素地球化学[M]. 北京:科学出版社,2000
19 Alain A. Prinzhofer, Alain Y. Huc. Genetic and post-genetic molecular and isotope fractionations in matural gases [J]. Chemical Geology, 1995, 126: 281~290
20 Ulrich Berner, Eckhard Faber. Empirical carbon isotope/maturity relationships for gases from algal kerogens and terrigenous organic matter, based on dry, open-system pyrolysis [J]. Org. Geochem, 1996, 24(10-11): 947~955
21 Schoell M. Genetic Characterization of natural gases [J]. The American Association of Petroleum Geologists Bulletin, 1983, 67(12): 2225~2238
22 戴金星. 天然气碳氢同位素特征和各类天然气鉴别[J]. 天然气地球科学. 1993,2(3):2～40
23 石昕,孙冬敏等. 煤成大、中型气田天然气的碳同位素特征[J]. 石油实验地质,2000,22(1):16～21
24 刘文汇,宋岩等. 煤岩及其主显微组份热解气碳同位素组成的演化[J]. 沉积学报,2003,21(1):183～190
25 沈平,徐永昌. 中国陆相成因天然气同位素组成特征[J]. 地球化学,1991,6(2):144～151
26 杨玉峰,任延广等. 松辽盆地汪升地区深层天然气地球化学特征及成因[J]. 石油勘探与开发,1999,26(4):18～21
27 Landais P, Michels R, Elie M. Are time and temperature the only constraints to the simulation of organic maturation? Organic Geochemistry, 1994, 22, 617~630
28 戴金星,夏新宇,秦胜飞等. 中国有机烷烃气碳同位素系列倒转的原因[J]. 石油与天然气地质,2003,24(1):1~6
29 Bjorg Andresen, Torbjorn Throndsen, et al. A comparison of pyrolysis products with models for natural gas generation [J]. Chemical Geology, 1995, 126: 261~280
30 Jianguo Du, Zhijun Jin, et al. Stable carbon isotope compositions of gaseous hydrocarbons produced from high high pressure and high temperature pyrolysis of lignite [J]. Org. Geochem, 2003, 34: 97~104
31 关平,伍天洪. 热成因甲烷碳同位素分布的形成机制. 沉积学报. 2003,21(1):175～180
32 帅燕华,邹艳荣,彭平安. 天然气甲烷碳同位素动力学模型与地质应用新进展. 地球科学进展[J]. 2003,18(3):405～411
33 邹艳荣,帅燕华等. 煤成甲烷碳同位素演化的数学模型与应用. 天然气地球科学[J]. 2003,14(2):92～96
34 Clayton C. Carbon isotope fractionation during natural gas generation from kerogen [J]. Mar.Pet.Geo, 1991, 8: 232~240
35 Bener U, Faber E, Stahl W. Mathematical simulation of the carbon isotopic fractionation between huminitic coals and related methane [J]. Chemical Geology, 1992, 94(4): 315~319
36 Bener U, Faber E, Scheeder G. Primary cracking of algal and landplant kerogens:Kinetic models of isotope variations in methane, ethane and propane [J]. Chemical Geology, 1995, 126: 233~245
37 Lorant F, Prinzhofer A. Carbon isotopic and molecular constraints on the formation and the expulsion of thermogenic hydrocarbon gases [J]. Chemical Geology, 1998, 147: 249~264
38 Lorant F, Behar F, Vandenbroucke M. Methane generation from methylated aromatics:Kinetic study and carbon isotope modeling [J]. Energy&Fuels, 2000, 14: 1143~1155
39 Clayton C. Carbon isotope fractionation during natural gas generation from kerogen [J]. Mar.Pet.Geo, 1991, 8: 232~240
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