四川盆地高石梯—磨溪地区下寒武统筇竹寺组生烃增压定量评价
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摘要
生烃增压是油气运移的主要动力,目前对其机制的研究逐渐向定量化方向发展。四川盆地中部高石梯—磨溪地区下寒武统筇竹寺组烃源岩经历了晚二叠世末到中侏罗世末的生油阶段、中侏罗世末到早白垩世初的原油裂解生气阶段和后期干酪根生气阶段。考虑到岩石的整体压缩系数和原油组分特征,建立了适用于腐泥型干酪根连续生烃的增压模型。由生油增压模型计算,筇竹寺组晚二叠世末到三叠纪末,生油初期阶段,超压缓慢增大;早侏罗世初到中侏罗世初期,进入生油窗阶段,超压快速累积,压力系数最大约为2.4;中侏罗世初期到中侏罗世末期,生油作用结束,超压程度略有降低。由原油裂解生气增压模型计算,中侏罗世末期到早白垩世初期,在原油裂解生气过程中,筇竹寺组烃源岩发生幕式排烃,超压程度先增大后减小,最终保持平衡,压力系数约为2.2。除有机质类型、有机质丰度和热史背景外,烃源岩的封闭条件和原油组分是影响生烃增压的主要因素。封闭性越好,烃源岩生油阶段产生的超压越大,烃源岩内的含油饱和度越高。生成的原油含硫量越低,油气转化率越高,压力增大程度越大。
The overpressure caused by hydrocarbon generation is the main driving force of hydrocarbon migration, the research on its mechanism is gradually becoming quantitative. The source rocks of the Cambrian Qiongzhusi Formation in the Gaoshiti-Moxi area of the Sichuan Basin have experienced the oil generation phase from the end of the late-Permian to the end of the mid-Jurassic, the oil cracking phase from the end of the Jurassic to the early-Cretaceous and the kerogen gas phase later. Considering the overall compressibility of the source rock and the oil component, a quantitative model for the overpressure caused by the continuous process of hydrocarbon generation from sapropel kerogen was established. The pressure evolution calculated by the model for the oil production showed that, from the end of the Permian to the end of the Triassic, the initial stage of oil generation, the excess pressure increased slowly. From the early-Jurassic to the beginning of the mid-Jurassic, the oil window stage, the excess pressure accumulated rapidly with a pressure coefficient up to 2.4. From the beginning of the mid-Jurassic to the end of mid-Jurassic when the oil generation ended, the overpressure reduced slightly. Calculated by the model for oil cracking, from the end of the mid-Jurassic to the beginning of the early-Cretaceous, the overpressure increased first and then decreased subsequently. In the process of oil cracking, the episodic hydrocarbon-expulsion developed in the Qiongzhusi Formation until the pressure balance was reached with a pressure coefficient of about 2.2. In addition to the types and abundance of organic matter and the thermal history, the sealing ability of the source rock and the components of cured oil are also the main factors that affect the calculation accuracy of the quantitative model. The better the closure of source rock, the greater the overpressure accumulated during the oil generation, and the higher the oil saturation retained in the source rock. The lower the sulfur content contained in the oil, the higher the conversion rate of oil to gas was and the greater the pressure formed.
The overpressure caused by hydrocarbon generation is the main driving force of hydrocarbon migration, the research on its mechanism is gradually becoming quantitative. The source rocks of the Cambrian Qiongzhusi Formation in the Gaoshiti-Moxi area of the Sichuan Basin have experienced the oil generation phase from the end of the late-Permian to the end of the mid-Jurassic, the oil cracking phase from the end of the Jurassic to the early-Cretaceous and the kerogen gas phase later. Considering the overall compressibility of the source rock and the oil component, a quantitative model for the overpressure caused by the continuous process of hydrocarbon generation from sapropel kerogen was established. The pressure evolution calculated by the model for the oil production showed that, from the end of the Permian to the end of the Triassic, the initial stage of oil generation, the excess pressure increased slowly. From the early-Jurassic to the beginning of the mid-Jurassic, the oil window stage, the excess pressure accumulated rapidly with a pressure coefficient up to 2.4. From the beginning of the mid-Jurassic to the end of mid-Jurassic when the oil generation ended, the overpressure reduced slightly. Calculated by the model for oil cracking, from the end of the mid-Jurassic to the beginning of the early-Cretaceous, the overpressure increased first and then decreased subsequently. In the process of oil cracking, the episodic hydrocarbon-expulsion developed in the Qiongzhusi Formation until the pressure balance was reached with a pressure coefficient of about 2.2. In addition to the types and abundance of organic matter and the thermal history, the sealing ability of the source rock and the components of cured oil are also the main factors that affect the calculation accuracy of the quantitative model. The better the closure of source rock, the greater the overpressure accumulated during the oil generation, and the higher the oil saturation retained in the source rock. The lower the sulfur content contained in the oil, the higher the conversion rate of oil to gas was and the greater the pressure formed.
引文
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[11]GUO X W, HE S, LIU K Y, et al. Quantitative estimation of overpressure caused by oil generation in petroliferous basins[J]. Organic Geochemistry, 2011,(42):1343-1350.
[12]GUO X W, LIU K Y, HE S, et al. Petroleum generation and charge history of the northern Dongying Depression, Bohai Bay Basin,China:Insight from integrated fluid inclusion analysis and basin modelling[J]. Marine and Petroleum Geology, 2012,(32):1-35.
[13]GUO X W, LIU K Y, JIA C Z, et al. Constraining tectonic compression process by reservoir pressure evolution:Overpressure generation and evolution in the Kelasu Thrust Belt of Kuqa Foreland Basin, NW China[J]. Marine and Petroleum Geology, 2016, 72:30-44.
[14]马卫,王东良,李志生,等.湖湘烃源岩生烃增压模拟实验[J].石油学报, 2013, 34(S.1):65-69.[MA W, WANG D L, LI Z S, et al.A simulation experiment of pressurization during hydrocarbon generation from lacustrine source rocks[J]. Acta Petrolei Sinica, 2013,34(S.1):65-69.]
[15]ZOUCN, WEIGQ,XUCC,etal.GeochemistryoftheSinian-CambriangassystemintheSichuanBasin,China[J].Organic Geochemistry, 2014, 74:13-21.
[16]江强,朱传庆,邱楠生,等.川南地区热史及下寒武统筇竹寺组页岩热演化特征[J].天然气地球科学, 2015, 26(8):1563-1570.[JIANG Q, ZHU C Q, QIU N S, et al. Paleo-heat flow and thermal evolution of the Lower Cambrian Qiongzhusi shale in the southern Sichuan Basin, SW China[J]. Natural Gas Geoscience, 2015, 26(8):1563-1570.]
[17]魏国齐,杜金虎,徐春春,等.四川盆地高石梯—磨溪地区震旦系—寒武系大型气藏特征与聚集模式[J].石油学报, 2015, 36(1):1-12.[WEIGQ,DUJH,XUCC,etal.Characteristics and accumulation modes of largegas reservoirs in Sinian-Cambrian of Gaoshiti-Moxi region, Sichuan Basin[J]. Acta Petrolei Sinica, 2015, 36(1):1-12.]
[18]谢龙,郭绪强,陈光进,等.计算原油体积系数的状态方程法[J].中国石油大学学报(自然科学版), 2007, 31(3):137-139.[XIE L, GUO X Q, CHEN G J, et al. A new method predicting volume factor of formation crude oil[J]. Journal of China University of Petroleum, 2007, 31(3):137-139.]
[19]ZHU C Q, HU S B, QIU N S, et al. Thermal history of the Sichuan Basin, SW China:Evidence from deep boreholes[J]. Science China:Earth Science, 2016, 56(1):70-80.
[20]何丽娟,许鹤华,汪集旸.早二叠世—中三叠世四川盆地热演化及其动力学机制[J].中国科学:地球科学, 2011,41(12):1884-1891.[HE L, XU H H, WANG J Y. Thermal evolution and dynamic mechanism of the Sichuan Basin during the Early Permian-Middle Triassic[J]. Science China:Earth Science, 2011, 41(12):1884-1891.]
[21]WAPLES D W. The kinetics of in-reservoir oil destruction and gas formation:constraints from experimental and empirical data, and from thermodynamics[J]. Organic Geochemistry, 2000, 31(6):553-575.
[22]熊镭,张超谟,张冲,等. A地区页岩气储层总有机碳含量测井评价方法研究[J].岩性油气藏, 2014, 26(3):74-78.[XIONG L,ZHANG C M, ZHANG C, et al. Research on logging evaluation method of TOC content of shale gas reservoir in A area[J]. Lithologic Reservoirs, 2014, 26(3):74-48.]
[23]ROUCHET J. Stress field:A key to oil migration[J]. AAPG Bulletin, 1981, 65:74-85.
[24]解习农,刘晓峰,胡祥云,等.超压盆地中泥岩的流体压裂与幕式排烃作用[J].地质科技情报, 1998, 17(4):59-63.[XIE X N, LIU X F, HU X Y, et al. Hydrofracturing and associated episodic hydrocarbon-expulsion of mudstones in overpressured basin[J]. Geological Science and Technology Information, 1998, 17(4):59-63.]
[25]陈中红,张守春,查明.不同压力体系下原油裂解的地球化学演化特征[J].中国科学:地球科学, 2013, 43(11):1807-1818.[CHEN ZH,ZHANGSC,ZHAM.Geochemical evolution during the cracking of crudeoilin to gas under different pressure systems[J].Science China:Earth Sciences, 2013, 43(11):1807-1818.]
[26]胡国艺,李志生,罗霞,等.两种热模拟体系下有机质生气特征对比[J].沉积学报, 2004, 22(4):718-723.[HU G Y, LI Z S, LUO X,et al. The comparison of gas generation potential and model between two different thermal simulation systems[J]. Acta Sedimentologica Sinica, 2004, 22(4):718-723.]
[2]赵喆,钟宁宁,黄志龙.碳酸盐岩烃源岩生烃增压规律及其含义[J].石油与天然气地质, 2005, 26(3):344-348.[ZHAO Z, ZHONGN N, HUANG Z L. Pattern of pressurization from hydrocarbon generation in carbonate source rocks and its significance[J]. Oil&Gas Geology, 2005, 26(3):344-348.]
[3]MEISSNER F F. Abnormal electric resistivity and fluid pressure in Bakken Formation, Williston Basin, and its relation to petroleum generation, migration and accumulation[J]. AAPG Bulletin, 1976, 60:1403-1404.
[4]UNGERER P, BEHAR E, DISCAMPS D. Tentative calculation of the overall volume expansion of organic matter during hydrocarbon genesis from geochemistry data:Implications for primary migration[G]//BJOROY M. Advances in organic geochemistry. Chichester:John Eiley, 1983, 129-135.
[5]BARKER C. Calculated volume and pressure changes during the thermal cracking of oil to gas in reservoirs[J]. AAPG Bulletin, 1990,74:1254-1261.
[6]CARCIONE J M, GANGI A F. Gas generation and overpressure:Effects on seismic attributes[J]. Geopysics, 2000, 65(6):1769-1779.
[7]郭小文,何生,刘可禹,等.烃源岩生气增压定量评价模型及影响因素[J].地球科学-中国地质大学学报, 2013, 38(6), 1263-1270.[GUO X W, HE S, LIU K Y, et al. A quantitative estimation model for the overpressure caused by natural gas generation and its influential factors[J]. Earth Science-Journal of China University of Geosciences, 2013, 38(6):1263-1270.]
[8]BREDEHOEFT J D, WESLEY J B, FOUCH T D. Simulations of the origin of fluid-pressure fracture generation, and movement of fluids in the Uinta basin, Utah[J]. AAPG Bulletin, 1994, 78:1729-1747.
[9]ROBERT R B, ANTHONY F G. Primary migration by oil-generation microfracturing in low-permeability source rocks:Application to the Austin Chalk, Texas[J]. AAPG Bulletin, 1999, 83(5):727-756.
[10]MUDFORD B S, BEST M E. Venture gas field, offshore Nova Scotia, case study of overpressuring in region of low sedimentation rate[J]. AAPG Bulletin, 1989, 73:1383-1396.
[11]GUO X W, HE S, LIU K Y, et al. Quantitative estimation of overpressure caused by oil generation in petroliferous basins[J]. Organic Geochemistry, 2011,(42):1343-1350.
[12]GUO X W, LIU K Y, HE S, et al. Petroleum generation and charge history of the northern Dongying Depression, Bohai Bay Basin,China:Insight from integrated fluid inclusion analysis and basin modelling[J]. Marine and Petroleum Geology, 2012,(32):1-35.
[13]GUO X W, LIU K Y, JIA C Z, et al. Constraining tectonic compression process by reservoir pressure evolution:Overpressure generation and evolution in the Kelasu Thrust Belt of Kuqa Foreland Basin, NW China[J]. Marine and Petroleum Geology, 2016, 72:30-44.
[14]马卫,王东良,李志生,等.湖湘烃源岩生烃增压模拟实验[J].石油学报, 2013, 34(S.1):65-69.[MA W, WANG D L, LI Z S, et al.A simulation experiment of pressurization during hydrocarbon generation from lacustrine source rocks[J]. Acta Petrolei Sinica, 2013,34(S.1):65-69.]
[15]ZOUCN, WEIGQ,XUCC,etal.GeochemistryoftheSinian-CambriangassystemintheSichuanBasin,China[J].Organic Geochemistry, 2014, 74:13-21.
[16]江强,朱传庆,邱楠生,等.川南地区热史及下寒武统筇竹寺组页岩热演化特征[J].天然气地球科学, 2015, 26(8):1563-1570.[JIANG Q, ZHU C Q, QIU N S, et al. Paleo-heat flow and thermal evolution of the Lower Cambrian Qiongzhusi shale in the southern Sichuan Basin, SW China[J]. Natural Gas Geoscience, 2015, 26(8):1563-1570.]
[17]魏国齐,杜金虎,徐春春,等.四川盆地高石梯—磨溪地区震旦系—寒武系大型气藏特征与聚集模式[J].石油学报, 2015, 36(1):1-12.[WEIGQ,DUJH,XUCC,etal.Characteristics and accumulation modes of largegas reservoirs in Sinian-Cambrian of Gaoshiti-Moxi region, Sichuan Basin[J]. Acta Petrolei Sinica, 2015, 36(1):1-12.]
[18]谢龙,郭绪强,陈光进,等.计算原油体积系数的状态方程法[J].中国石油大学学报(自然科学版), 2007, 31(3):137-139.[XIE L, GUO X Q, CHEN G J, et al. A new method predicting volume factor of formation crude oil[J]. Journal of China University of Petroleum, 2007, 31(3):137-139.]
[19]ZHU C Q, HU S B, QIU N S, et al. Thermal history of the Sichuan Basin, SW China:Evidence from deep boreholes[J]. Science China:Earth Science, 2016, 56(1):70-80.
[20]何丽娟,许鹤华,汪集旸.早二叠世—中三叠世四川盆地热演化及其动力学机制[J].中国科学:地球科学, 2011,41(12):1884-1891.[HE L, XU H H, WANG J Y. Thermal evolution and dynamic mechanism of the Sichuan Basin during the Early Permian-Middle Triassic[J]. Science China:Earth Science, 2011, 41(12):1884-1891.]
[21]WAPLES D W. The kinetics of in-reservoir oil destruction and gas formation:constraints from experimental and empirical data, and from thermodynamics[J]. Organic Geochemistry, 2000, 31(6):553-575.
[22]熊镭,张超谟,张冲,等. A地区页岩气储层总有机碳含量测井评价方法研究[J].岩性油气藏, 2014, 26(3):74-78.[XIONG L,ZHANG C M, ZHANG C, et al. Research on logging evaluation method of TOC content of shale gas reservoir in A area[J]. Lithologic Reservoirs, 2014, 26(3):74-48.]
[23]ROUCHET J. Stress field:A key to oil migration[J]. AAPG Bulletin, 1981, 65:74-85.
[24]解习农,刘晓峰,胡祥云,等.超压盆地中泥岩的流体压裂与幕式排烃作用[J].地质科技情报, 1998, 17(4):59-63.[XIE X N, LIU X F, HU X Y, et al. Hydrofracturing and associated episodic hydrocarbon-expulsion of mudstones in overpressured basin[J]. Geological Science and Technology Information, 1998, 17(4):59-63.]
[25]陈中红,张守春,查明.不同压力体系下原油裂解的地球化学演化特征[J].中国科学:地球科学, 2013, 43(11):1807-1818.[CHEN ZH,ZHANGSC,ZHAM.Geochemical evolution during the cracking of crudeoilin to gas under different pressure systems[J].Science China:Earth Sciences, 2013, 43(11):1807-1818.]
[26]胡国艺,李志生,罗霞,等.两种热模拟体系下有机质生气特征对比[J].沉积学报, 2004, 22(4):718-723.[HU G Y, LI Z S, LUO X,et al. The comparison of gas generation potential and model between two different thermal simulation systems[J]. Acta Sedimentologica Sinica, 2004, 22(4):718-723.]