Muglad盆地Kaikang槽西斜坡沉积演化及其油气地质意义

Sedimentary evolution and its significances for petroleum exploration in the west slope of Kaikang trough,Muglad Basin,Sudan-South Sudan

Muglad盆地Kaikang槽西斜坡为富油气区带,但一直未获得重大勘探发现。为研究其油气成藏条件和多期构造运动的控藏机理,开展了精细地震解释、沉积相分析和沉积演化研究。结果表明:①研究区经历了3期重要的构造运动,形成了2套主力含油气系统,分别为上部的Nayil组上段湖相泥岩盖层-Nayil组下段三角洲相砂岩储层组合和下部的Aradeiba组湖相泥岩盖层-Bentiu组河流相砂岩储层组合;②早白垩世第Ⅰ裂陷-坳陷期控制了斜坡区AG组烃源岩的展布范围,晚白垩世第Ⅱ裂陷-坳陷期控制了下部储盖组合的圈闭形成,古近纪第Ⅲ裂陷-坳陷期对应于研究区的主力生排烃期。上述3期构造运动造就了研究区"断层-盖层控藏、多层系差异聚集"的油气富集模式。

The west slope of Kaikang trough in Muglad Basin has been proven as a hydrocarbon-enriched belt.However,no significant exploration breakthrough has been gained. In order to study hydrocarbon accumulation conditions and reservoir-controlling mechanism of multi-stage tectonic movements,fine seismic interpretation,sedimentary facies analysis and sedimentary evolution were analyzed. The results show that:(1)The study area underwent three stages of tectonic movement and formed two sets of major petroleum systems,the upper play(lacustrine mudstone seal of upper Nayil Formation and delta sandstone reservoir of lower Nayil Formation)and the lower play(lacustrine mudstone seal of Aradeiba Formation and fluvial sandstone reservoir of Bentiu Formation);(2)The stage Ⅰ rifting-depression of Early Cretaceous controlled the distribution of in-place source rock of AG Formation in the slope area,stage Ⅱ rifting-depression of Late Cretaceous controlled the development of traps in the lower play,and stage Ⅲ rifting-depression of Paleogene controlled the major period of hydrocarbon generation and expulsion that matched with the rifting. The three stages of tectonic-sedimentary evolution worked together to gain the hydrocarbon enrichment model of'fault-seal control the accumulation together,differential accumulation in multi layers'in the west slope of Kaikang trough.