毛塞几比盆地南部三角洲-深水扇沉积特征及勘探前景  

Sedimentary characteristics and exploration potential of the delta-deep water fan in the southern M.S.G.B.C Basin

作　　者：田立新 赵红岩 逄林安 TIAN Lixin;ZHAO Hongyan;PANG Lin’an(CNOOC International Limited,Beijing 100028,China)

机构地区：[1]中国海洋石油国际有限公司,北京100028

出　　处：《中国海上油气》2022年第3期1-11,共11页China Offshore Oil and Gas

基　　金：中国海洋石油有限公司“十四五”重大科技项目“‘两岸一带’重点盆地油气富集规律和成藏差异性研究(编号:KJGG2022-0901)”;“十三五”国家科技重大专项“非洲重点区油气勘探潜力综合评价(编号:2017ZX05032-002)”部分研究成果。

摘　　要：毛塞几比盆地是近年来西非油气勘探热点盆地之一,下白垩统阿尔布阶三角洲-深水扇领域是盆地的重要勘探领域,已发现了大量油气。在“源-汇”理论的指导下,利用地震、测井、岩心薄片等资料,对毛塞几比盆地南部阿尔布期冈比亚河和热巴河三角洲的沉积特征、物源、古沟谷和深水扇沉积特征开展对比研究,探讨陡台缘背景下三角洲-深水扇的沉积特征与发育规律。研究结果表明,冈比亚河和热巴河阿尔布期三角洲均为退积型三角洲,整体呈现“下粗上细”的沉积旋回,但二者物源区不同,导致同一时期发育的热巴河三角洲无论是规模还是含砂率均大于冈比亚河三角洲。根据古斜坡长度和高程差及古沟谷平面组合样式,将古沟谷划分为4种12类,其中北部冈比亚河陆架边缘斜坡主要为离散式矮近型,主要发育近岸斜坡扇;南部热巴河陆架边缘古沟谷为汇聚式高远型,可向深水区提供大量能量强、沉积分异好的陆源碎屑,更有利于形成高能富砂盆底扇。通过源和渠的比较分析,明确指出盆地南部三角洲和深水扇是勘探新领域和主攻方向,可为中国石油公司的海外油气勘探提供技术指导。M.S.G.B.C Basin is one of the hotspots for oil and gas exploration in West Africa in recent years.The Lower Cretaceous Albian delta-deep water fan area where a large amount of oil and gas has been discovered is an important exploration region in this basin.Under the guidance of“source-sink”theory,this paper uses data such as seismic,logging,core thin section,etc,to carry out the comparative study in the delta sedimentary characteristics and provenance,ancient valleys and deep-water fan sedimentary characteristics of the Albian Gambia and Geba rivers in the southern M.S.G.B.C basin,and to explore the sedimentary characteristics and development laws of delta-deep water fan under the background of steep platform margin.The study results show that both the Gambia river delta and the Geba river delta are regressive deltas with a sedimentary cycle of“coarse at the bottom and fine at the top”,whereas,the different provenance areas of those two result in that the Geba river delta developed contemporarily is larger than the Gambia River delta in terms of size and sand content.According to the Paleoslope length,elevation difference and the paleo-valleys planar combination styles,the paleo-valleys could be divided into 4 classes and12 sub-classes.Among them,the northern Gambia River continental shelf margin slope is dominated by discrete dwarf type,and mainly developed nearshore slope fans;the ancient valleys at the margin of the southern Geba River continental shelf are of converging high-distance type,which can provide a large amount of terrigenous debris with strong energy and good sedimentary differentiation to the deep water area,conducive to the formation of high-energy sand-rich basin floor fan.Through the comparative analysis of source and channel,it is clearly pointed out that the delta and deep water fan in the southern basin are the new fields and main directions for exploration,which can provide technical guidance for the overseas oil and gas exploration of Chinese oil companies.

关 键 词：毛塞几比盆地 沉积特征 三角洲 古沟谷 深水扇 

分 类 号：TE121.1[石油与天然气工程—油气勘探]