黄骅坳陷中生代构造运动对上古生界煤系烃源岩生烃演化的控制

近期,渤海湾盆地黄骅坳陷港北、乌马营和歧北等古潜山内幕与上古生界煤系有关的原生气藏勘探取得重大发现,揭示其巨大的油气资源潜力。为了深入认识该坳陷中生代构造运动对上古生界煤系烃源岩生烃演化的控制作用,采用构造解析、埋藏—热史分析、岩心薄片观察以及盆地生烃模拟等手段,综合分析了中生代构造体制与演化、盆地迁移过程、煤系烃源岩地球化学特征和生烃史,研究了中生代盆地沉降、迁移及岩浆活动对煤系烃源岩生烃的影响。研究结果表明:①黄骅坳陷中生代发生了多期、多类型的构造运动,构造事件主要有三叠纪克拉通抬升—沉降运动、侏罗纪差异压陷—压扭运动、白垩纪火山活动和伸展抬升运动;②盆地迁移过程为由南向北,孔店隆起为南、北迁移的重要界限;③黄骅坳陷上古生界煤系烃源岩经历两次生烃过程,存在着早期油气藏;④沧东凹陷上古生界煤系晚侏罗世末进入有效生烃门限,歧口凹陷上古生界煤系烃源岩早白垩世末进入生烃门限;⑤中生代构造运动对烃源岩一次生烃演化的控制主要体现在中生代各时期盆地迁移事件控制烃源岩一次生烃序列、岩浆岩局部加热事件促使烃源岩中有机质加速生烃和异常成熟等两个方面。结论认为,该研究成果明确了中生代构造运动对上古生界煤系烃源岩一次生烃演化的控制作用,对华北地区中生代构造运动、原型盆地恢复、煤系生烃演化研究以及油气勘探等都具有参考价值。

Control of the Mesozoic tectonic movement on the hydrocarbon generation and evolution of Upper Paleozoic coal-measure source rocks in the Huanghua Depression,Bohai Bay Basin

Recently, great discoveries have been made on the primary gas reservoirs related to the Upper Paleozoic coal measure in the inner buried hills of Gangbei, Wumaying and Qibei in the Huanghua Depression of the Bohai Bay Basin, which reveals a huge oil and gas resource potential in this depression. In order to deepen the understanding of the controlling factors of the Mesozoic tectonic movement in the Huanghua Depression on the hydrocarbon generation of Upper Paleozoic coal-measure source rocks, we analyzed the Mesozoic tectonic system and evolution, the basin migration process and the geochemical characteristics and hydrocarbon generation history of coal-measure source rocks by means of structural analysis, burial–thermal history analysis, core slice observation and basin hydrocarbon generation simulation. In addition, the influences of the subsidence, migration and magmatic activity of Mesozoic basins on the hydrocarbon generation of coal-measure source rocks were studied. And the following research results were obtained. First, in the Huanghua Depression, there were multi-stage and multi-type tectonic movements in the Mesozoic, and the main tectonic events include Triassic craton uplift-subsidence movement, Jurassic differential depression-compression–torsion movement, Cretaceous volcanic activity and extensional uplift movement. Second, the basin migration process is from south to north, and the Kongdian uplift is an important boundary of South and North migration. Third, the Upper Paleozoic coal-measure source rocks in the Huanghua Depression experience two hydrocarbon generation processes, and there are early hydrocarbon reservoirs. Fourth, the Upper Paleozoic coal measure in the Cangdong Sag reached the effective hydrocarbon generation threshold at the end of Late Jurassic, and the Upper Paleozoic coal-measure source rocks in the Qikou Sag reached the hydrocarbon generation threshold at the end of Early Cretaceous. Fifth, the control of the Mesozoic tectonic movement on the primary hydrocarbon generation and evolution of source rocks is mainly embodied in two aspects. On the one hand, basin migration events in the Mesozoic dominate the primary hydrocarbon generation sequence of source rocks. And on the other hand, local heating events of magmatic rocks accelerate the hydrocarbon generation and abnormal maturation of organic matter in source rocks. In conclusion, the research results define the control factors of the Mesozoic tectonic movement on the primary hydrocarbon generation and evolution of Upper Paleozoic coal-measure source rocks, and can be used as reference for researching the Mesozoic tectonic movement and the hydrocarbon generation and evolution of coal measure, restoring the protobasins and conducting oil and gas exploration in North China.