珠江口盆地白云凹陷东北部原油运移聚集特征

珠江口盆地白云凹陷是中国南海北部深水区最大的富烃凹陷,近年来在白云凹陷东北部获得了多个商业性轻质油气藏,勘探前景良好,但对其原油运移、聚集成藏的研究还处于探索阶段。基于三维地震资料解释、油气地球化学资料分析以及油气成藏综合研究,探讨白云凹陷东北部油气藏分布特征,研究了原油的输导体系及其运移和聚集特征,建立了原油成藏模式。结果表明:油源断裂是原油垂向运移的主要通道,顺源型油源断裂和向源型油源断裂都具有良好的输导性能,由物性较好的珠江组下段砂体组成的构造脊1和2为原油侧向运移的优势路径; 原油主要聚集在反向断裂控制的翘倾半背斜圈闭中,具有“内气外油”的差异聚集特征; 原油成藏具有“断-脊输导、断-盖控聚、差异聚集”的特征。白云凹陷东北部展现了以断裂为依托,沿构造脊找油的良好勘探方向,对白云凹陷及其邻区的深水油气勘探具有一定的指导意义。

Characteristics of Crude Oil Migration and Accumulation in the Northeastern Baiyun Sag of Pearl River Mouth Basin,China

Baiyun sag of Pearl River Mouth Basin is the biggest hydrocarbon-rich sag in the deep water area of the northern South China Sea. In recent years, a series of commercial light hydrocarbon reservoirs are discovered in the northeastern Baiyun Sag, showing good exploration prospects, but there is no deep understanding on migration and accumulation patterns of crude oil. The 3D seismic interpretation, geochemical analysis and hydrocarbon accumulation research were deployed to comprehensively evaluate the distribution of hydrocarbon reserviors, the migration pathway system, the migration and accumulation characteristics of crude oil in the northeastern Baiyun sag, so the accumulation pattern was established. The results show that the main passages of the vertical migration of crude oil are oil-source faults, among which the migration ability of follow-source and forward-source faults is favorable, meanwhile, it is noteworthy that the sandbodies with good physical properties in Lower Zhujiang Formation can constitute the structure ridges 1 and 2, and these two ridges provide dominant migration pathways for crude oil; crude oil mainly accumulates in semi-anticlinal traps controlled by reverse faults, and the hydrocarbon has the characteristics of differential accumulation, which are oil in the inner and gas in the outer; migrated through oil-source faults and structure ridges, accumulated under the control of faults and cap rock, as well as the differential accumulation of hydrocarbon, are the three accumulation characteristics of crude oil. The northeastern Baiyun sag shows good exploration direction for finding petroleum along the structure ridges, as well as based on the recognition of faults, that is of certain guiding significance for hydrocarbon exploration of deep water area in Baiyun sag and adjacent areas.