穆格莱德盆地A区块构造特征对油气分布的影响

Influence of structural characteristics on oil and gas distribution in block A of the Muglad Basin

由于穆格莱德盆地A区块构造位置特殊、断裂特征复杂、构造样式多,现有的研究成果不能满足A区块勘探、开发需求。为此,对研究区重新划分构造分区、深入研究断裂活动期次、对比不同构造单元之间活动差异性、恢复构造演化史,并分析构造演化与油气成藏的关系。结果表明:(1)A区块构造演化过程经历前裂谷期、同裂谷期和后裂谷期,同裂谷期又进一步划分为三个构造阶段,即早白垩世—晚白垩世、晚白垩世—古新世、始新世—上新世,分别控制烃源岩、构造圈闭、油气分布。(2)A区块从东向西可以划分为继承稳定型和持续活动型两种构造分区。前者以凯康东部斜坡和凯康西部斜坡为典型,在演化阶段构造活动强度具有"强—强—弱"的特征;后者以凯康槽为典型,在演化阶段构造活动强度具有"强—强—最强"的特征。(3)A区块存在"断裂活动减弱型深层"和"断裂活动持续型的晚期调整多层系"两种油气成藏模式。前者多见于凯康东部斜坡和凯康西部斜坡,后者常见于凯康槽。上述认识对类似地质条件盆地的油气勘探具有参考价值。

Existing research results cannot fully support the exploration and development of block A in the Muglad Basin due to the special tectonic positions,complex faults and diversified structural patterns in this area.In this regard,structural zoning is redivided to study the active periods of faults in depth.In addition,the activity differences among structural units are compared and the tectonic evolution history is restored to clarify the relationship between tectonic evolution and hydrocarbon accumulation.Results demonstrate the following points:(1)The tectonic evolution of block A has experienced pre-rift,syn-rift and post-rift periods.Then the syn-rift period was further divided into three tectonic stages,namely the Early Cretaceous to the Late Cretaceous,the Late Cretaceous to the Paleocene and the Eocene to the Pliocene,controlling source rocks,structural traps and hydrocarbon distribution,respectively.(2)Block A,from east to west,can be divided into two tectonic zones:an inheritably stable zone and a continuously active zone.The former is typical of the east and west slopes of the Kaikang trough,with a"strongstrong-weak"fault pattern during evolution,while the latter is typical of the Kaikang trough,with a"strong-strong-the strongest"pattern.(3)Two patterns of hydrocarbon migration and accumulation in block A are presented,namely the deep play and the late-adjustment play.They are common in the east and west slopes of the Kaikang trough with a low level of fault activities and the Kaikang trough with multi-layer reservoirs and continuous fault activities,respectively.The above research can support oil and gas exploration in basins with similar geological settings.