乍得Bongor盆地东、西部构造特征差异及其对油气富集的影响

Different structural characteristics in the east and west parts,Bongor Basin,Chad,and their influence on hydrocarbon accumulation

按照"南、北分带"的原则,在勘探早期开展了区带评价和圈闭优选,认为北部斜坡带是乍得Bongor盆地最有利的含油气构造单元,在此认识指导下在北部斜坡带东段发现了8个油田。然而,近年来在北部斜坡带西段风险钻探区域的探井均失利。为此,本文从盆地东、西部断陷结构、构造样式、构造演化等方面分析了盆地东、西部的构造特征差异及其对烃源岩、储盖组合等石油地质条件的影响,指出盆地在形成过程中受"东、西分段"主导应力机制控制,这一应力机制将Bongor盆地划分为北部隆起、北部坳陷、南部隆起与南部坳陷等4个构造单元,即"东、西分段"是Bongor盆地主体(北部坳陷)的主要构造特征。北部坳陷又可进一步划分为4个箕状断陷,自东向西分别为Moul、Mango、Cola与Annona等断陷。进一步明确了盆地的勘探方向:Mango斜坡带深层K1P组与中浅层K1K组、Mango陡坡带中浅层K1K组是下步勘探主攻领域;Moul斜坡带深层K1P组与中浅层K1K组是下步勘探重点领域;Annona陡坡带K1P组是下步勘探值得探索的新领域。

In the early stage of exploration,structural zone evaluations and prospect optimizations for Bongor Basin were carried out based on the principle of 'structural belt division in the S-N direction',and the northern slope was considered as the most favorable oil-bearing structural units.Latter on 8oil fields are discovered in the east segment of the northern slope on the basis of the above geological understanding. However,a few wildcat wells were dry holes in the western segment of the northern slope in the recent years.Therefore,the thesis studies the different structural characteristics of the eastern and western Bongor Basin from the aspects of fault depression structure,structural styles,structural evolution etc and theirs influence to hydrocarbon conditions such as source rocks and reservoir-seal assemblage.Bongor Basin is controlled by the major stress mechanism of'structural segment division in the E-W direction' and is divided into four structural units of the northern uplift,the northern depression,the southern uplift and the southern depression.'Structural segment division in the E-W direction'is major structural characteristics of the northern depression which is the main part of Bongor Basin.The northern depression is sequentially divided into 4 fault depressions from east to west,such as Moul fault depression,Mango fault depression,Cola fault depression,and Annona fault depression.The direction for further exploration is pointed out.The deep member K_(1P) and the shallow-middle member K_(1K) in Mango slope,and the shallow-middle member K_(1K) in Mango steep slope are the most favorable targets for further exploration.The deep member K_(1P) and the shallow-middle member K_(1K) in Moul slope are the second favorable targets for further exploration.The deep member K1 Pin Annona steep slope is the third favorable target for further exploration.