Muglad盆地Sufyan凹陷石油地质特征及勘探潜力分析

Petroleum Geologic Feature and Exploration Potential of Sufyan Depression,Muglad Basin

Sufyan凹陷位于非洲苏丹南部Muglad盆地西北缘,是一个相对独立的凹陷,勘探程度仍很低,对石油地质特征认识仍存在许多分岐。分析认为,Sufyan凹陷是一个在中非剪切带的右旋剪应力场背景下形成的中、新生代内陆断陷湖盆,可划分为4个二级构造带,即南部深次凹、中央构造带、北部斜坡带和西北次凹;自白垩纪到第四纪发育了3个沉积旋回,早白垩世AbuGabra组的湖相暗色泥岩为凹陷主力烃源岩,具很大生烃潜能;凹陷的形成与演化大体上经历了3个阶段,以"3断3坳"为特征,在该构造背景下发育了两套储盖组合,其中以Bentiu砂岩为储层、Aradeiba泥岩为区域盖层是凹陷内最好的成藏组合;圈闭类型以断块圈闭为主,反向翘倾断块最有利于油气的聚集。综合研究表明,Sufyan凹陷拥有丰富的油气资源和优越的成藏条件,具有较大勘探潜力,中部构造带是最有利的油气聚集区,北部斜坡也是较有利的勘探目标区。

Sufyan Depression was a relatively independent depression,located in northwest of Muglad Basin,south of Sudan in Africa.With low exploration degree,there was still some controversy on basic petroleum geologic feature.The analysis shows that Sufyan Depression is a continental rift basin,developed during the Mesozoic-Cenozoic time under the dextral shears of the Central African Shear Zone.It can be divided into four structural units:south deep sag,center structural zone,north slope,northwest sag.Vertically,three sedimentary cycles are developed from Cretaceous to Quaternary.Lacustrine facies dark shale and claystone of Abu Gabra formation of early Cretaceous is main source rock with great oil-generating capacity.The development and evolution underwent three stages characterized by three-time rifting and sagging,which result in the formation of two assemblages of reservoir and seal in Cretaceous formation.Reservoir rock Bentiu sandstone and regional caprock Aradeiba claytone formed the best play in the whole area.Trap types are mainly faulted blocks,of which the tilted antithetic fault block is the most favorable to capture oil.Integrated study indicates that Sufyan Depression is of abundant hydrocarbon resources and has a great exploration potential.Central structural zone is the most favorable area for oil to accumulate and north slope is the second one.