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已有的油气勘探成果表明,南海北部陆缘东部与西部的油气运聚特征具有很大的差异。通过总结前人对东、西部油气运聚规律的成果和认识,以东部的珠江口盆地与西部的莺—琼盆地为例,分析对比了东、西部油气运聚模式的差异性。东部表现为:油气垂向运移与侧向运移相互配合,动力为水动力及浮力,后期断层的活动性对油气运聚成藏起关键作用;西部表现为:底辟带作为油气垂向运移的主要通道,不整合面以及砂岩疏导层作为油气侧向运移通道,主要驱动力为高压活动流体;流体底辟和后期断层的活动性分别对天然气的聚集和保存起关键作用。通过油气运聚差异性的对比分析,结合南海北部陆缘的沉积特征以及构造运动背景分析,结论认为:这种差异性实质就是运聚过程中环境的差异,即东部为常压环境,西部为超压环境,形成原因是北部陆缘东部珠江口盆地受东沙运动影响,发育的一系列张扭性NW向断裂对超压层系起卸压作用,西部受东沙运动影响弱而容易形成超压环境。
The existing oil and gas exploration results show that the characteristics of hydrocarbon migration and accumulation in the eastern and western parts of the northern South China Sea margin are quite different. By summarizing the achievements and understanding of previous studies on the laws of hydrocarbon migration and accumulation in the east and west regions, taking the Pearl River Mouth Basin in the east and Ying-Qiong Basin in the west as an example, the differences between the modes of petroleum migration and accumulation in the east and west regions are analyzed. In the eastern part, the vertical migration and lateral migration of oil and gas interact with each other, the motive force is hydrodynamic force and buoyancy, and the activity of the later faults plays a key role in hydrocarbon migration and accumulation. In the west, the diapir belt is regarded as the vertical The main channel of migration, unconformity and sandstone drainage layer are the lateral migration channels of oil and gas. The main driving force is high pressure active fluid. The activities of fluid diapirs and later faults play a key role in the accumulation and preservation of natural gas respectively. Based on the comparative analysis of the differences in hydrocarbon migration and accumulation and the sedimentary characteristics of the continental margin in the northern South China Sea and the tectonic movement background analysis, the conclusion is that the difference is essentially the difference in the environment during the migration and accumulation process, ie, the atmospheric pressure in the east and the The overpressure environment is mainly due to the influence of the Dongsha movement in the Pearl River Mouth Basin to the east of the northern continental margin. A series of tensile NW NW faults play an important role in the relief of the overpressured layer, and the overpressure is easily formed in the western part due to the weak influence of the Dongsha movement surroundings.