东非海域深水区油气形成地质背景、成藏条件与勘探潜力  

Geological settings,hydrocarbon accumulation conditions and exploration prospects of deep-water oil and gas in East Africa

作　　者：秦雁群[1] 张光亚[1] 刘计国[1] 陈忠民[1] 肖高杰[1] Qin Yanqun;Zhang Guangya;Liu Jiguo;Chen Zhongmin;Xiao Gaojie(PetroChina Research Institute of Petroleum Exploration&Development)

机构地区：[1]中国石油勘探开发研究院

出　　处：《中国石油勘探》2022年第6期110-121,共12页China Petroleum Exploration

基　　金：中国石油天然气股份有限公司科学研究与技术开发项目“海外重点领域油气勘探关键技术研究”(2021DJ3103);中油锐思研发项目“中西非裂谷盆地中深层油气勘探关键技术研究”(2022-FW-022)。

摘　　要：被动大陆边缘深水油气勘探是近年来全球油气勘探热点领域,新发现的大油气田中海域特别是深水区已占主导地位。将同一大陆边缘盆地群进行统一的构造演化与地层充填分析,统计已发现油气田的地质特征,明确其成藏条件和成藏模式,对于区域级别油气区带优选和新项目的获取具有重要指导意义。文章通过IHS、Wood Mackenzie等油气田数据库资料,结合油气勘探新发现和部分内部新项目评价资料等,系统分析东非海域9个盆地深水区油气形成的地质背景及油气成藏条件,指出深水油气有利区带分布。研究表明,东非海域盆地群经历了早石炭世—三叠纪卡鲁裂谷、侏罗纪马达加斯加裂谷和白垩纪至今的被动大陆边缘3个演化阶段,基底断裂受印度洋转换断层、大陆边缘伸展断裂系统和东非裂谷系断裂系统联合控制,由北往南可划分为4个构造段,不同构造段盆地剖面结构和地层充填差异明显。东非海域共发育下侏罗统、中上侏罗统—白垩系和古近系3套烃源岩;形成了海相浊积砂岩和三角洲砂岩两种类型优质储层和海相厚层页岩区域性盖层,储盖组合良好;可划分为证实的新生界和白垩系及推测的上二叠统—侏罗系3套深水成藏组合;形成了漂移早—中期供源、漂移期成藏,裂谷期与漂移早期供源、裂谷期—漂移期成藏,以及裂谷期供源、漂移期成藏3种深水油气成藏模式。东非海域被动大陆边缘时期,形成了大型三角洲及深水重力流沉积物混合的扇复合体和无大型古河流供给、以滑塌形成为主的近岸叠置小型扇朵叶体两种类型的深水扇体;白垩系和古近系深水油气有利区带具有一定的继承性,主要位于坦桑尼亚盆地南部、鲁伍马盆地北部等地区,勘探目标以天然气勘探和碎屑岩勘探为主。In recent years,the deep-water area in the passive continental margin has become a hotspot of global petroleum exploration,and the large-scale new oil and gas fields are mostly discovered in sea area,especially the deep-water area.Therefore,a unified analysis of tectonic evolution and sediments filling of a group of basins at the same continental margin,and the geological characteristics study of the discovered oil and gas fields,as well as the defined hydrocarbon accumulation conditions and patterns will provide important guidance to screen regionallevel favorable oil and gas plays and acquire new projects.By using oil and gas field data base,such as IHS and Wood Mackenzie,and integrating with the new discoveries and internal evaluation data of new venture projects,the geological settings and hydrocarbon accumulation conditions of nine basins in the deep-water area in East Africa are systematically analyzed,and the favorable oil and gas plays in deep-water area are proposed.The study results show that the basin group in East African sea area experienced three stages of tectonic evolution,i.e.,Karoo rift in the Early Carboniferous-Triassic,Madagascar rift in the Jurassic,and passive continental margin since the Cretaceous.Jointly controlled by transfer faults in the Indian Ocean,extensional fault system at the continental margin,and fault system in the East African rift system,the basement faults are divided into four tectonic segments from north to south,and significantly different section structure and sediment filling characteristics show in various basin segments.Three sets of source rocks were developed in East African sea area,including the Lower Jurassic,Middle-Upper Jurassic to Cretaceous and Paleogene.Two types of superior reservoirs of marine turbidite sandstone and delta sandstone were deposited,which formed a good reservoir and cap rock assemblage associated with the regional massive marine shale.Three sets of deep-water hydrocarbon accumulation assemblages are identified,including two proven assembla

关 键 词：被动大陆边缘 深水 东非 大气田 坦桑尼亚盆地 鲁伍马盆地 

分 类 号：TE111.1[石油与天然气工程—油气勘探]