河流-三角洲体系微相控烃及机理研究:以珠江口盆地恩平组煤系烃源岩为例

河流-三角洲体系煤系烃源岩是重要的油气来源,传统的研究方法主要为单井点分析,对研究区的勘探程度和资料情况的依赖性大,而且认识滞后于勘探,很难在油气勘探和有利生烃洼陷的预测中发挥作用.对珠江口盆地恩平组煤系烃源岩进行系统研究,揭示煤系烃源岩发育的特征和有利地质条件,并将沉积微相分析与烃源岩的地球化学指标(有机质丰度、生烃...

Characteristics and Mechanism of Source Rock Development Controlled by Sedimentary Microfacies in River-delta System: Case Study of Coal-measure Source Rock in Enping Formation in Pearl River Estuary Basin

Coal-measure source rocks are important sources of oil and gas. Conventional research of source rocks mainly focuses on single-well analysis, which depends heavily on the degree of exploration and available data. It lags behind exploration, and is thus difficult to predict favorable hydrocarbon-generating sags. The coal-measure source rocks of the Enping Formation in the Pearl River Estuary basin are systematically studied here, in combination with sedimentology and geochemistry. The favorable geological conditions, characteristics, and favorable facies for these coal-measure source rocks are revealed, and the sedimentary model of coal-measure source rock in river-delta system is established. Based on the analysis of sedimentary facies and geochemical indicators (organic matter abundance, hydrocarbon generation potential, hydrogen index), the characteristics and mechanism of source rock controlled by sedimentary microfacies are revealed. There are several favorable geological conditions for the development of coal-measure source rock in river-delta system of the Enping Formation: (1) steady tectonic subsidence, and largely balanced sedimentation and subsidence rates; (2) warm humid climate with flourishing vegetation; (3) widely distributed river and delta. The coal seam has thin single layer, multiple vertical layers, and poor horizontal continuity. Coal-measure source rocks in fluvial and deltaic environment are both rich in organic matter, which may have derived mainly from terrestrial higher plants. The hydrocarbon generation potential and hydrogen index of these coal-measure source rocks are similar in fluvial and deltaic environment. The coal-measure source rocks of river-delta system are highly heterogeneous, and are controlled by sedimentary facies. From channels and distributary channels to fluvial swamps and deltaic plain swamps distal from rivers and distributary channels, the organic matter abundance increases and the organic matter types improves. The fluvial swamp and deltaic plain swamp microfacies are the most favorable sedimentary facies for the formation of coal-measure source rocks in river-delta systems. Paleogeographical conditions such as paleotopography, hydrodynamic and redox conditions are important factors that formed difference source rocks in different microfacies. The sedimentary model of coal-measure source rock formation in different microfacies and the distribution characteristics of coal seams in river-delta systems is newly established.