苏丹Muglad盆地区域盖层对油藏特征的控制作用
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摘要
苏丹Muglad盆地是在中非剪切带右行走滑背景上发育起来的中-新生代陆内裂谷盆地。盆地的主力产层为下白垩统的Bentiu组,上覆的区域盖层是Darfur群,尤其是Aradeiba组的大套泥岩。盆地70%以上的探明石油可采储量分布在Bentiu-Darfur成藏组合中。通过地震反演预测了区域盖层的宏观分布,通过对20口探井测井资料的处理确定了盖层的封闭性。对部分井壁取芯样品的扫描电镜观察发现,存在宽度达10~30μm的微裂缝,且这些微裂缝被伊利石或绿泥石等自生矿物充填。原油地球化学分析表明,Bentiu组油藏近中非剪切带原油密度大,生物降解严重;远离中非剪切带处的原油密度正常,生物降解程度降低直至消失。这说明后期的构造活动对油气藏的保存有明显的控制作用。
Muglad Basin is a continental rift basin developed during the Mesozoic-Cenozoic time under the dextral shears of the Central African Shear Zone(CASZ).The Lower Cretaceous Bentiu Formation is the major pay zone,It is covered by the Darfur Group,especially the massive mudstones of the Aradeiba Formation.More than 70% of recoverable proven oil reserves are located in the BentiuDarfur Play.The regional seal distribution was predicted by using seismic inversion.The sealing capacity of overlying formations in 20 wells was calculated by using log data processing.The scanning electron microscopy(SEM) analysis of well-side cores shows that there are micro-fractures of 10μm to 30μm in width,and those micro-fractures are filled by autogenetic ilite and chlorate.The geochemical analysis of oils indicate that the oil biodegradation decreases,and oil API increase away from CASZ.It is concluded that the late tectonic movement of CASZ obviously controls the preservation of oil accumulation.
Muglad Basin is a continental rift basin developed during the Mesozoic-Cenozoic time under the dextral shears of the Central African Shear Zone(CASZ).The Lower Cretaceous Bentiu Formation is the major pay zone,It is covered by the Darfur Group,especially the massive mudstones of the Aradeiba Formation.More than 70% of recoverable proven oil reserves are located in the BentiuDarfur Play.The regional seal distribution was predicted by using seismic inversion.The sealing capacity of overlying formations in 20 wells was calculated by using log data processing.The scanning electron microscopy(SEM) analysis of well-side cores shows that there are micro-fractures of 10μm to 30μm in width,and those micro-fractures are filled by autogenetic ilite and chlorate.The geochemical analysis of oils indicate that the oil biodegradation decreases,and oil API increase away from CASZ.It is concluded that the late tectonic movement of CASZ obviously controls the preservation of oil accumulation.
引文
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[2]窦立荣.油气藏地质学概论[M].北京:石油工业出版社,2001:1-194.
[3]Downey M W.Evaluating seals for hydrocarbon accumulations[J].AAPG Bulletin,1984,68(12):1752-1763.
[4]McHargue T R,Heidrick T L,Livingston J K.Tectonostrati-graphic development of the interior Sudan rifts,Central Africa[J].Tectonophysics,1992,213(1/2):187-202.
[5]Genik G J.Petroleum geology of Cretaceous-Tertiary rift basinsin Niger,Chad,and Central African Republic[J].AAPG Bulle-tin,1993,77(8):1405-1434.
[6]Schull T J.Rift basins of interior Sudan:Petroleum explorationand discovery[J].AAPG Bulletin,1988,72(10):1128-1142.
[7]王秀林,汪望泉,李素珍,等.M盆地的构造特征及与油气的关系[J].石油与天然气地质,2000,21(1):76-79.
[8]张亚敏,陈发景.穆格莱德盆地形成特点与勘探潜力[J].石油与天然气地质,2002,23(3):236-240.
[9]童晓光,窦立荣,田作基,等.苏丹穆格莱德盆地的地质模式和成藏模式[J].石油学报,2004,25(1):19-24.
[10]窦立荣.苏丹迈努特盆地油气成藏机理和成藏模式[J].矿物岩石地球化学通报,2005,24(1):50-57.
[11]窦立荣,程顶胜,张志伟.利用油藏地质地球化学特征综合划分含油气系统[J].地质科学,2002,37(4):495-501.
[12]李国平,郑德文,欧阳永林,等.天然气封盖层研究与评价[M].北京:石油工业出版社,1996:1-133.
[13]Peters K E,Moldowan J M.The biomarker guide:Interpretingmolecular fossils in petroleum and ancient sediments[M].Engle-wood Cliffs,N J:Prentice Hall Inc.,1993:252-265.
[14]窦立荣,程顶胜,李志.苏丹Muglad盆地FN油田沥青垫的确认及成因分析[J].地球化学,2004,33(3):309-316.
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