苏丹穆格莱特盆地的地质模式和成藏模式

Geological mode and hydrocarbon accumulation mode in Muglad passive rift basin of Sudan

苏丹穆格莱特盆地是在中非剪切带的右旋剪切应力场背景下拉张形成的一种被动裂谷盆地 ,不同于地幔对流上涌产生的主动裂谷。裂谷多期断坳旋回明显 ,纵向上三期裂谷作用表现为强—弱—强。其盆地地温梯度比主动裂谷盆地低 ,而比克拉通盆地高。盆地坳陷带与隆起相间排列 ,具有东、西分带的特点。半地堑是最主要的构造组合形式。盆地发育多套生油岩 ,其中第一裂谷期AbuGabra组是盆地的主力生油层。以Bentiu组为储层、Aradeiba组为区域盖层的组合是盆地内的主要成藏组合 ,反向正断层翘倾断块为主要圈闭类型 ,断距和断层对盘的地层岩性决定了油藏的封闭性和油柱高度。研究结果表明 ,盆地具有优越的油气成藏条件和较好的勘探前景。

Muglad Basin in Sudan is a passive rift basin.It was resulted from the extensional tectonics of the dextral shear stress field in the shear zone of middle Africa.It is different from the active rift basin formed by the uplift of mantle convection.The multi-phase rifting and sagging cycles are obvious in the basin.In the vertical direction,there are three phases of rifts with the strong-weak-strong pattern,respectively.The geothermal gradient in Muglad Basin is lower than that in active rift basin and higher than that in cratonic basin.The main structure stale is half graben.In generally,the basin (mainly in Block 1/2/4) can be characterized by an uplift,two depressions and two slopes.The depressions and uplifts arranged in alternative pattern and have different characteristics in the east and the west parts.There developed many sets of oil source rocks.The Abu Gabra Formation generated in the first rift phase is the principle oil source bed in the basin.The assemblage of Bentiu reservoir rock and Aradeiba regional cap rock formed the chief oil-bearing beds.The tilted antithetic normal fault blocks are the main traps,where the enclose ability of the reservoir and the height of oil column were decided by the throw of the fault and lithology in both sides of the fault.The Muglad Basin has predominant hydrocarbon forming conditions and a great exploration potential.