东非裂谷系盆地群石油地质特征及勘探潜力
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摘要
东非裂谷系属于形成地质时期比较新的陆内裂谷盆地群,阿尔伯特裂谷位于东非裂谷系西支北段,自2006年至今相继发现了16个油气田,累计发现可采储量11.27×108bbl。通过对阿尔伯特裂谷盆地的解剖,指出东非裂谷系为中生代与新生代两期叠合裂谷盆地,其中、新生代为主裂谷期,全部为陆相河流、湖泊沉积充填。湖盆周缘发育沉积速度快、相带变化快的冲积扇—扇(辫状河)三角洲—浊积砂体沉积体系组合。钻探结果证实具备很好的含油气条件好,发育新近系中新统湖相优质烃源岩,储层物性好,以辫状河三角洲和扇三角洲前缘亚相河道沉积为主,已发现油气全部富集于断块和断鼻圈闭之中,地震显示具备浊积砂体成藏可能。通过类比分析,东非裂谷系西支阿尔伯特裂谷至少具有(40～50)×108bbl的资源潜力,向南的系列裂谷也同样勘探潜力巨大,而东支虽然火山岩比较发育,但同样值得关注。
East African rift system belongs to comparatively new intracontinental rift basin group. Albert rift is located in the north of the west branch of East African rift system. Since 2006, 16 oil and gas fields have been discovered here, with total recoverable reserves being 1.127 billion bbl. Through dissection of Albert rift basin, it is pointed out that East African rift system is a rift basin Mesozoic and Caenozoic era overlay. Among this, Caenozoic era is the main rift phase and filled with continental river and lacustrine deposit. Combination of alluvial fan---fan (braid river) delta---turbidite sand deposit system developed in peripheral lake basins, featuring in rapid deposition and change of facies and belts. Drilling results proved that the rift system had favorable petroliferous conditions, with development of high-quality Neocene Miocene lake source rock and good reservoir property. It is dominated by braid river delta and fan delta front subfacies channel deposit. All oil and gas discovered concentrate in faulted blocks and faulted-nose traps. It is seismically indicated that turbidite sand reservoir might be formed here. Analogy analysis showed that Albert rift has 4～5billion bbl resources at least, and the rifts southward have huge exploration potential. The east branch of the rift system deserves attention, even though volcanic rock developed here.
East African rift system belongs to comparatively new intracontinental rift basin group. Albert rift is located in the north of the west branch of East African rift system. Since 2006, 16 oil and gas fields have been discovered here, with total recoverable reserves being 1.127 billion bbl. Through dissection of Albert rift basin, it is pointed out that East African rift system is a rift basin Mesozoic and Caenozoic era overlay. Among this, Caenozoic era is the main rift phase and filled with continental river and lacustrine deposit. Combination of alluvial fan---fan (braid river) delta---turbidite sand deposit system developed in peripheral lake basins, featuring in rapid deposition and change of facies and belts. Drilling results proved that the rift system had favorable petroliferous conditions, with development of high-quality Neocene Miocene lake source rock and good reservoir property. It is dominated by braid river delta and fan delta front subfacies channel deposit. All oil and gas discovered concentrate in faulted blocks and faulted-nose traps. It is seismically indicated that turbidite sand reservoir might be formed here. Analogy analysis showed that Albert rift has 4～5billion bbl resources at least, and the rifts southward have huge exploration potential. The east branch of the rift system deserves attention, even though volcanic rock developed here.
引文
1张亮成,世界沉积盆地与油气分布,1996:12～19。
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[1]Bosworth W,Huchon P,McClay K.The Red Sea and Gulf of Aden Basins.Journal of African Earth Sciences43,2005:334～378.
[2]张兴,童晓光.艾伯特裂谷盆地含油气远景评价[J].石油勘探与开发,2001,28(2):102～106.
[3]Karner G D,Byamungu B R,Ebinger C J,et al.Distribution of crustal extension and regional basin architecture of the Albertine rift system,East Africa.Marine and Petroleum Geology17,2000:1131～1150.
[4]窦立荣,王建君,等.乌干达Albertine地堑石油地质条件与油气勘探潜力[J].地质学报,2004,32(3):51～53.
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