试论火山活动对东非裂谷系油气成藏的作用
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摘要
长期以来,东非裂谷系被认为形成较晚,难以形成大规模成熟烃源岩,且火山活动对油气成藏不利。基于东非裂谷系露头、钻井、测井、地震等资料,结合前人研究成果,采用对比、类比和将今论古方法,对研究区火山活动对油气地质和成藏条件的影响进行了研究,结果表明火山与热点活动为本地区大规模油气藏的形成提供了有利条件:火山热点控制了盆地的构造格局,形成裂谷系东支主动型裂谷和裂谷系西支被动型裂谷,并控制了东、西支盆地不同的构造样式和圈闭类型及其发育位置;火山活动提供的营养物质促使藻类繁盛,火山活动提供的过渡金属元素的催化作用和火山的烘烤作用加速了有机质的热演化,从而形成年轻而优质的成熟烃源岩;火山岩风化为裂谷湖盆提供了充足的侧向物源,形成湖盆陡断带巨厚的优质储层,从而为裂谷东支陡断带的油气富集提供了有利的储集空间;火山活动形成的大面积的致密火成岩还可以作为油气聚集的有效区域盖层。本文研究成果对东非裂谷系下一步油气勘探有指导作用。
For a long time,East African rift system has been considered to be too young to form large-scale mature hydrocarbon source rocks,and volcanic activities were unfavorable for hydrocarbon accumulation. Based on East African rift system outcrop,drilling,logging and seismic data,combining previous research results,the methods of comparison,analogy and uniformitarianism were used to study the effect of volcanic activities in the study area on oil and gas geology and accumulation conditions. The result shows that volcanic activities in the region together with the hot spot of large-scale reservoirs provides favorable conditions: the volcanic hot spots controlled the tectonic framework of the basin,consisting of the active rift valley in the east branch of the rift system and the passive rift in the west branch,and also controlled different tectonic patterns and types of traps and its development location in the east and west branch basins; the volcanic activity provided nutrients which have promoted algal boom,and transition metal elements that accelerated the thermal evolution of organic matter through the catalysis function together with volcanic baking,thus developing a young,high-quality mature hydrocarbon source rock; volcanic rock weathering provided ample lateral provenance to rift lake basin,which developed super-thick high-quality reservoir in lake basin with steep fault belt,hence providing favorable reservoir space for oil and gas enrichment. The large area of dense igneous rocks developed by volcanic activities can also be used as effective regional caprock for hydrocarbon accumulation. This study is of guiding function for further oil and gas exploration in East African rift system.
For a long time,East African rift system has been considered to be too young to form large-scale mature hydrocarbon source rocks,and volcanic activities were unfavorable for hydrocarbon accumulation. Based on East African rift system outcrop,drilling,logging and seismic data,combining previous research results,the methods of comparison,analogy and uniformitarianism were used to study the effect of volcanic activities in the study area on oil and gas geology and accumulation conditions. The result shows that volcanic activities in the region together with the hot spot of large-scale reservoirs provides favorable conditions: the volcanic hot spots controlled the tectonic framework of the basin,consisting of the active rift valley in the east branch of the rift system and the passive rift in the west branch,and also controlled different tectonic patterns and types of traps and its development location in the east and west branch basins; the volcanic activity provided nutrients which have promoted algal boom,and transition metal elements that accelerated the thermal evolution of organic matter through the catalysis function together with volcanic baking,thus developing a young,high-quality mature hydrocarbon source rock; volcanic rock weathering provided ample lateral provenance to rift lake basin,which developed super-thick high-quality reservoir in lake basin with steep fault belt,hence providing favorable reservoir space for oil and gas enrichment. The large area of dense igneous rocks developed by volcanic activities can also be used as effective regional caprock for hydrocarbon accumulation. This study is of guiding function for further oil and gas exploration in East African rift system.
引文
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[14]高福红,高红梅,赵磊.火山喷发活动对烃源岩的影响:以拉布达林盆地上库力组为例[J].岩石学报,2009,25(10):2671-2678.GAO Fuhong,GAO Hongmei,ZHAO Lei.Effects of volcanic eruptions on characteristics of source rocks:taking Shangkuli Formation of Labudalin basin as an example[J].Acta Petrologica Sinica,2009,25(10):2671-2678.
[15]翟庆龙,金强,万从礼.裂谷盆地CO2的一种潜在成因:论火成岩与烃源岩的相互作用[J].天然气工业,2003,23(3):129-130.ZHAI Qinglong,JIN Qiang,WAN Congli.A potential cause of CO2in rift basin:the interaction between igneous rocks and hydrocarbon source rocks[J].Natural Gas Industry,2003,23(3):129-130.
[2]张可宝,史卜庆,徐志强,等.东非地区沉积盆地油气潜力浅析[J].天然气地球科学,2007,18(6):869-874.ZHANG Kebao,SHI Buqing,XU Zhiqiang,et al.A study on petroleum geology and hydrocarbon potential in eastern Africa[J].Natural Gas Geoscience,2007,18(6):869-874.
[3]马君,刘剑平,潘校华.东非大陆边缘地质特征及油气勘探前景[J].世界地质,2008,27(4):400-405.MA Jun,LIU Jianping,PAN Xiaohua.Geological characteristics and prospect on hydrocarbon exploration in East Africa Continental Margin[J].Global Geology,2008,27(4):400-405.
[4]张兴,童晓光.艾伯特裂谷盆地含油气远景评价:极低勘探程度盆地评价实例[J].石油勘探与开发,2001,28(2):102-106.ZAHNG Xing,TONG Xiaoguang.Hydrocarbon prospective evaluation of Albert rift basin:an example of evaluation about least explored basins[J].Petroleum Exploration and Development,2001,28(2):102-106.
[5]DOU Lirong,WANG Jianjun,CHENG Dingsheng,et al.Geological conditions and petroleum exploration potential of the Albertine Graben of Uganda[J].Acta Geologica Sinica,2004,78(4):1002-1010.
[6]CHOROWICZ J,FOURNIER J L,VIDAL G.A model for rift development in Eastern Africa[J].Geological Journal,1987,22(S2):495-513.
[7]曾昭琪,钱峰.盘星藻在湖泊沉积中的成矿作用[J].湖泊科学,2000,12(4):304-310.ZENG Zhaoqi,QIAN Feng.Pediastrum in lake sediment and its mineralization[J].Journal of Lake Sciences,2000,12(4):304-310.
[8]宋国栋,石晓勇,侯继灵,等.铁对浮游植物吸收营养盐的围隔实验初步研究[J].海洋与湖泊,2008,39(3):209-216.SONG Guodong,SHI Xiaoyong,HOU Jiling,et al.Iron impact on phytoplankton nutrients uptake in mesocosm[J].Oceanologia et Limnologia Sinica,2008,39(3):209-216.
[9]许海,秦伯强,朱广伟.太湖不同湖区夏季蓝藻生长的营养盐限制研究[J].中国环境科学,2012,32(12):2230-2236.XU Hai,QIN Boqiang,ZHU Guangwei.Nutrient limitation of cyanobacterial growth in different regions of Lake Taihu in summer.[J].China Environmental Science,2012,32(12):2230-2236.
[10]DELMELLE P,LAMBERT M,DUFRENE Y,et al.Gas/aerosolash interaction in volcanic plumes:new insights from surface analyses of fine ash particles[J].Earth Planet Science Letters,2007,259:159-170.
[11]LIN I I,HU Chuanmin,LI Yuanhui,et al.Fertilization potential of volcanie dust in the low-nutrient low-ehlorophyll western North Pacific subtropical gyre:satellite evidence and laboratory study[J].Global Biogeochemieal Cycles,2011,25(1):1-12.
[12]LANGMANN B,ZAKSEK K,HORT M,et al.Volcanic ash as fertilizer for the surface ocean[J].Atmospheric Chemistry and Physics Discussion,2010,10(8):3891-3899.
[13]DUGGEN S,CROOT P,SCHACHT U,et al.Subduction zone volcanic ash can fertilize the surface ocean and stimulate phytoplankton growth:evidence from biogeochemical experiments and satellite data[J].Geophysical Research Letters,2007,34(1):95-119.
[14]高福红,高红梅,赵磊.火山喷发活动对烃源岩的影响:以拉布达林盆地上库力组为例[J].岩石学报,2009,25(10):2671-2678.GAO Fuhong,GAO Hongmei,ZHAO Lei.Effects of volcanic eruptions on characteristics of source rocks:taking Shangkuli Formation of Labudalin basin as an example[J].Acta Petrologica Sinica,2009,25(10):2671-2678.
[15]翟庆龙,金强,万从礼.裂谷盆地CO2的一种潜在成因:论火成岩与烃源岩的相互作用[J].天然气工业,2003,23(3):129-130.ZHAI Qinglong,JIN Qiang,WAN Congli.A potential cause of CO2in rift basin:the interaction between igneous rocks and hydrocarbon source rocks[J].Natural Gas Industry,2003,23(3):129-130.