苏丹穆格莱德盆地福拉凹陷油气成藏特征及勘探启示

Hydrocarbon Accumulation Characteristics of Reservoir in Fula Depression and Their Implication for Petroleum Exploration,Muglad Basin,Sudan

福拉凹陷下白垩统Abu Gabra组发育有湖相好—极好烃源岩,但热演化程度低、成藏主控因素不确定,勘探潜力不明。通过地层层序划分、构造分析、沉积相分析,认为张剪性区域构造背景控制福拉凹陷的构造与沉积发育,下白垩统Abu Gabra组发育有一定规模有效生烃凹陷,可形成Abu Gabra组烃源岩层,Abu Gabra组自储自盖,Bentiu组储、Aradeiba组盖及Aradeiba组自储自盖等3套生储盖组合,其中第二套储盖组合为该凹陷不同于六区其他凹陷的良好储盖组合。紧邻生烃凹陷、继承性发育的构造带,如中部滚动背斜—断鼻、南部次凹西缘断鼻、南部断阶带断鼻、北部次凹东缘断鼻等构造带是有利的成藏带。继承性发育的Fula1号滚动背斜、Fula2号断鼻构造具有多套储盖组合,勘探风险低,为有利的勘探目标。这些认识为福拉凹陷油气勘探提供了科学依据,且其研究方法及思路也为新区油气勘探提供良好的借鉴。

Before the discovery of Fula oilfield,previous studies consider that there developed source rock of semi-deep to deep lacustrine in Abu Gabra Formation,Fula depression,which were comprehensively evaluated to be good to very good source rocks but with lower thermal evolution degree,and the other main factors controlling the formation of oil pools were uncertainty,so Fula depression were considered lack of the oil and gas exploration potential.Based on detailed study of gravity data,seismic data and well data,analysis stratigraphic sequence,structure development and evolution,sedimentary facies combined with lithofacies,log-facies and seismic facies,this study reveals that the development of structure and deposition in Fula depression were controlled by shear-extensional regional tectonism.There developed a certain and effective hydrocarbon generation sag of the Abu Gabra Formation in Lower Cretaceous.Three favorable source-reservoir-seal assemblages and 4 reservoir-forming zones are identified.The rollover anticline-faulted nose zone in the middle structure belt,the faulted noses zones in west margin of south sub-depression,in the south faulted step belt and in east margin of the north sub-depression are evaluated prospect reservoir plays.Fula 1 rollover anticline and Fula 2 faulted nose are regarded as the best of prospect targets.These study results play an important role on oil and gas exploration and development in Fula depression.This research methods and exploration strategy can provide references for early petroleum exploration and basin analysis.