琼东南盆地深水区烃源岩地球化学特征与天然气潜力
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摘要
琼东南盆地深水区探井地球化学资料和地震信息显示,中央坳陷发育始新统湖相、渐新统海相—海岸平原相2套主力烃源岩,其中渐新统崖城组海岸平原相含煤烃源岩富含陆源有机质,是深水区优质气源岩;崖城组半封闭浅海相烃源岩TOC含量大多介于0.5%～1.5%之间,有机质类型以腐殖型干酪根为主,且该套烃源岩分布广、规模大。针对琼东南盆地深水区钻井资料少的现状,综合应用沉积相—地震相—有机相研究手段对崖城组主力气源岩的分布进行了初步预测,结果显示崖城组烃源岩在中央坳陷分布较广,尤其以宝岛、陵水、乐东、长昌和北礁凹陷更为发育。高温高压环境生气机理模拟实验表明,研究区内高地温场加速了天然气生成,中央坳陷渐新统普遍发育的超压对早期生气有一定的抑制作用,而晚期又促进了天然气生成,从而拓宽了琼东南盆地深水区生气窗的范围和天然气勘探领域;始新统湖相烃源岩因埋深大,可能早期生油,晚期利于裂解气生成。因此,琼东南盆地深水区主要凹陷生气强度较高且生气潜力大,具有良好的勘探前景。
In the deep water area of Qiongdongnan basin,the geochemical data in exploration wells and seismic records show that two sets of source rocks are developed in its central depression,i.e.Eocene lacustrine facies and Oligocene marine-coastal plain facies,in which the coal-bearing source rock of coastal plain facies in Oligocene Yacheng Formation is excellent in gas generation capacity due to its high content of terrigenous organic matter.The source rock of semi-isolated shallow marine facies in Yacheng Formation is mostly between 0.5% and 1.5% in TOC(total organic carbon) and predominated by humic kerogen,with its distribution area and volume quite great.Because of limited drilling data in the deep water area,the tools of depositional facies,seismic facies and organic facies were comprehensively used to predict the distribution of the major gas source rocks in Yacheng Formation,and the results have indicated that the source rocks in Yacheng Formation are more widely developed in the central depression,especially in Baodao,Lingshui,Ledong、Changchang and Beijiao sags.The modeling experiments of gas generation under high temperature and pressure have suggested that the higher geothermal gradient in the central depression could accelerate gas generation,and that the widespread Oligocene overpressure in the depression might restrain early gas generation to a certain degree and promote later gas generation,resulting in the expanding of gas window and gas exploration play.Furthermore,the source rocks of Eocene lacustrine facies could generate oil early and produce oil-cracked gas lately due to their deep burial.Therefore,the main sags in the deep water area are higher in gas generation capacity and good in gas exploration potential.
In the deep water area of Qiongdongnan basin,the geochemical data in exploration wells and seismic records show that two sets of source rocks are developed in its central depression,i.e.Eocene lacustrine facies and Oligocene marine-coastal plain facies,in which the coal-bearing source rock of coastal plain facies in Oligocene Yacheng Formation is excellent in gas generation capacity due to its high content of terrigenous organic matter.The source rock of semi-isolated shallow marine facies in Yacheng Formation is mostly between 0.5% and 1.5% in TOC(total organic carbon) and predominated by humic kerogen,with its distribution area and volume quite great.Because of limited drilling data in the deep water area,the tools of depositional facies,seismic facies and organic facies were comprehensively used to predict the distribution of the major gas source rocks in Yacheng Formation,and the results have indicated that the source rocks in Yacheng Formation are more widely developed in the central depression,especially in Baodao,Lingshui,Ledong、Changchang and Beijiao sags.The modeling experiments of gas generation under high temperature and pressure have suggested that the higher geothermal gradient in the central depression could accelerate gas generation,and that the widespread Oligocene overpressure in the depression might restrain early gas generation to a certain degree and promote later gas generation,resulting in the expanding of gas window and gas exploration play.Furthermore,the source rocks of Eocene lacustrine facies could generate oil early and produce oil-cracked gas lately due to their deep burial.Therefore,the main sags in the deep water area are higher in gas generation capacity and good in gas exploration potential.
引文
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[15]CARR A D.A vitrinite reflectance kinetic model incorporatingoverpressure retardation[J].Marine and Petroleum Geology,1999,16:355-377.
[16]HILL R J,JENDEN P D,TANG Y C,et al.Influence of pres-sure on pylolysis of coals[C]∥Vitrinite Reflectance as a Matu-rity Parameter:Application and Limitation.American ChemicalSociety,ACS Symposium Series,1994:570,161-193.
[17]李友川,张功成,傅宁.南海北部深水区油气生成特性研究[J].中国海上油气,2010,22(6):375-381.
[18]戴金星,王庭斌,宋岩,等.中国大中型天然气田形成与分布规律[M].北京:地质出版社,1997:1-300.
[19]王振峰,李绪深,孙志鹏,等.琼东南盆地深水区油气成藏条件和勘探潜力[J].中国海上油气,2011,23(1):7-13.
[20]张功成,米立军,吴景富,等.凸起及其倾没端——琼东南盆地深水区大中型油气田有利勘探方向[J].中国海上油气,2010,22(6):360-368.
[21]朱伟林,米立军,高阳东,等.领域性突破展现中国近海油气勘探前景——2011年中国近海油气勘探回顾[J].中国海上油气,2012,24(1):1-5.
[2]龚再升,李思田.南海北部大陆边缘盆地分析与油气聚集[M].北京:科学出版社,1997:1-510.
[3]黄保家.琼东南盆地天然气潜力及有利勘探方向[J].天然气工业,1999,19(1):26-32.
[4]董伟良,黄保家.莺-琼盆地煤型气的鉴别标志和气源判识[J].天然气工业,2001,20(1):23-27.
[5]HUANG B J,XIAO X M,LI X X.Geochemistry and originsof natural gases in the Yinggehai and Qiongdongnan basins,Offshore South China Sea[J].Organic Geochemistry,2003,34:1009-1025.
[6]XIAO X M,XIONG M,TIAN H,et al.Determination of thesource area of the Ya13-1 gas pool in the Qiongdongnan ba-sin,South China Sea[J].Organic Geochemistry,2006,37:990-1002.
[7]ZHU Weilin,HUANG Baojia,MI Lijun,et al.Geochemistry,origin and deep-water exploration potential of natural gases inthe Pearl River Mouth and Qiongdongnan basins,South ChinaSea[J].AAPG Bulletin,2009,93:741-761.
[8]HUANG B J,XIAO Xianming,LI Xuxuan.Oil families andtheir source rocks in the Weixinan Sub-basin,Beibuwan ba-sin,South China Sea[J].Organic Geochemistry,2011,42:134-145.
[9]李友川,邓运华,张功成.中国近海海域烃源岩和油气的分带性[J].中国海上油气,2012,24(1):6-12.
[10]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,1993,4(2-3):1-40.
[11]KEVIN B,SUTER J.Sequence straigraphic distribution ofcoaly rocks:fundamental controls and paralic examples.AAPG Bulletin,1997,81:1612-1639.
[12]MOTHINOUX N,LANDAIS P,DURAND B.Comparison be-tween extracts from natural and artificial maturation series ofMahakam delta coals[J].Organic Geochemistry,1986,10:648-650.
[13]PRINCE L C,WENGER L M.The influence of pressure onpetroleum generation and maturation as suggested by aqueouspyrolysis[J].Organic Geochemistry,1992,19:141-159.
[14]HAO Fang,SUN Yongchuan,LI Sitian,et al.Overpressure retar-dation of organic-matter maturation and hydrocarbon generation:acase study from the Yinggehai and Qiongdonnan basins,Off-shore South China Sea[J].AAPG Bulletin,1995,79:551-562.
[15]CARR A D.A vitrinite reflectance kinetic model incorporatingoverpressure retardation[J].Marine and Petroleum Geology,1999,16:355-377.
[16]HILL R J,JENDEN P D,TANG Y C,et al.Influence of pres-sure on pylolysis of coals[C]∥Vitrinite Reflectance as a Matu-rity Parameter:Application and Limitation.American ChemicalSociety,ACS Symposium Series,1994:570,161-193.
[17]李友川,张功成,傅宁.南海北部深水区油气生成特性研究[J].中国海上油气,2010,22(6):375-381.
[18]戴金星,王庭斌,宋岩,等.中国大中型天然气田形成与分布规律[M].北京:地质出版社,1997:1-300.
[19]王振峰,李绪深,孙志鹏,等.琼东南盆地深水区油气成藏条件和勘探潜力[J].中国海上油气,2011,23(1):7-13.
[20]张功成,米立军,吴景富,等.凸起及其倾没端——琼东南盆地深水区大中型油气田有利勘探方向[J].中国海上油气,2010,22(6):360-368.
[21]朱伟林,米立军,高阳东,等.领域性突破展现中国近海油气勘探前景——2011年中国近海油气勘探回顾[J].中国海上油气,2012,24(1):1-5.
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