| 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 |
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| 引用本文： | 李燕,邓运华,李友川.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[J].现代地质,2021,35(4):1065-1077. |
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| 作者姓名： | 李燕 邓运华 李友川 |
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| 作者单位： | 1.中国海洋石油国际有限公司,北京 1000282.中海油研究总院,北京 100028 |
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| 基金项目： | 国家科技重大专项(2011ZX0523) |
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| 摘 要： | 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、生烃潜量、氢指数)相结合,提出微相控烃的特点及机理,建立了珠江口盆地恩平组河流-三角洲体系煤系烃源岩的发育模式。珠江口盆地恩平组沉积时期构造稳定,沉积、沉降速率近平衡;气候温暖湿润,植被繁茂,并且河流和三角洲环境的广泛分布为煤系烃源岩的发育提供了有利条件。河流和三角洲环境发育的煤层均呈薄层状产出,纵向上发育层数多,横向连续性差;河流和三角洲环境发育的煤系烃源岩有机质丰度均较高,生烃潜力和氢指数相近,有机质主要来自陆生高等植物。研究区煤系烃源岩非均质性很强,呈现明显的微相控烃的特点,由河道、分流河道向远离河道、分流河道的河漫沼泽、沼泽有机质丰度增高,有机质类型变好,河流的河漫沼泽和三角洲平原沼泽微相是最有利的沉积相带。各微相的古地形、水动力条件、氧化还原条件等古地理条件的不同是造成各微相烃源岩发育差异的重要原因。在上述研究的基础上,建立了反映研究区河流和三角洲环境各微相烃源岩发育差异及煤层展布特征的煤系烃源岩发育模式。
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| 关 键 词： | 河流-三角洲体系 煤系烃源岩 煤层 沉积模式 珠江口盆地 |
| 收稿时间： | 2020-01-15 |
| 修稿时间： | 2020-12-01 |
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 |
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| LI Yan,DENG Yunhua,LI Youchuan.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[J].Geoscience——Journal of Graduate School,China University of Geosciences,2021,35(4):1065-1077. |
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| Authors: | LI Yan DENG Yunhua LI Youchuan |
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| Institution: | 1. CNOOC International limited, Beijing 100028, China2. CNOOC Research Institute, Beijing 100028, China |
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| Abstract: | 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. |
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| Keywords: | river-delta system coal-measure source rock coal seam sedimentary model Pearl River Estuary basin |
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