涠西南凹陷南部斜坡次生油藏成藏模式及启示

Accumulation Model of the Secondary Oil Reservoir in Southern Slope,Weixi’nan Sag and the Implications for Future Exploration

为揭示涠西南凹陷南部斜坡次生油藏的成藏规律及成藏模式,通过油气来源对比、油藏特征及构造演化过程研究,对南部斜坡次生油藏初次聚集及晚期改造调整过程进行分析。研究认为,南部斜坡晚中新世之前为西高东低形态,在西部披覆背斜圈闭中形成油气初次成藏,油水界面附近碎屑岩水化作用与有机质脱羧基作用共同形成的"底钙层"为确定古油藏含油范围的有效标志。晚中新世晚期东沙运动使南部斜坡西部古油藏受到破坏,溢出油气向东部上倾方向挤压反转背斜构造中再次聚集形成次生油藏,南部斜坡东部角尾组、下洋组低幅背斜圈闭为下一步油气勘探重点。

In order to reveal the oil and gas accumulation rule and accumulation model of the secondary reservoir in the southern slope of Weixi’nan Sag,the study of oil-source correlation,oil reservoir characteristics,tectonic evolution,the accumulation model of secondary oil reservoirs were analyzed.The results show that before late Miocene the structure shape of southern slope was high in west and low in east,and primary hydrocarbon accumulation was formed in the western anticline trap.The"bottom calcium layer"formed by the hydration of clastic rocks and the decarboxylation of organic matter near the oil-water interface was an effective indicator to determine the oil-bearing range of paleo-reservoirs.Dongsha movement in late Miocene destroyed paleo-reservoir in the western anticline trap and leaded to the redistribution of oil and gas,and formed secondary oil reservoirs in the eastern reversal anticlines.The main exploration objects of the southern slope should be the low-rising anticlines in the eastern part.