珠江口盆地白云凹陷始新统不同岩性烃源岩有机质特征及其油气地质意义

Organic matter characteristics of Eocene source rocks with different lithologies in Baiyun Sag of Pearl River Mouth Basin and their geological significance

陈玥 朱晓军 张丽丽 向绪洪 曾翔 朱伟林

CHEN Yue ZHU Xiaojun ZHANG Lili XIANG Xuhong ZENG Xiang ZHU Weilin

同济大学 海洋地质全国重点实验室, 上海 200092 同济大学 海洋资源研究中心, 上海 200092 中海石油(中国)有限公司 深圳分公司, 广东 深圳 518054 中海石油(中国)有限公司 深海开发有限公司, 广东 深圳 518054 中国石化 经纬有限公司 地质测控技术研究院, 山东 青岛 266071

State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China Research Center for Marine Resources, Tongji University, Shanghai 200092, China Shenzhen Branch of CNOOC, Shenzhen, Guangdong 518054, China CNOOC Deepwater Development Ltd., Shenzhen, Guangdong 518054, China Geosteering & Logging Research Institute, SINOPEC Matrix Corporation, Qingdao, Shandong 266071, China

珠江口盆地珠二坳陷深水区白云凹陷发育泥岩、碳质泥岩和煤3类烃源岩。现有研究缺乏充分的实验数据支撑，难以准确评估不同岩性烃源岩生烃潜力差异及区域资源潜力。为厘清白云凹陷始新统烃源岩的岩性特征及生烃潜力，综合运用岩石薄片鉴定、X射线衍射分析、孢粉相识别及有机地球化学分析等手段，系统开展了岩性划分、有机质组成解析和生烃潜力评估。白云凹陷始新统烃源岩矿物成分和有机质组成差异大，沉积构造多样。按照总有机碳含量和矿物成分特征，凹陷内烃源岩可分为富砂泥岩、含砂泥岩、碳质泥岩和煤。不同岩性烃源岩特征差异大：含砂泥岩主要为块状构造，有机质丰度较高，以煤质有机质为主，含有一定量的无定形有机质，为偏腐泥型烃源岩，生烃潜力相对较大，倾向于生油；富砂泥岩主要为含碎屑块状构造，有机质丰度较低，以煤质和孢质为主，为偏腐殖型烃源岩，生烃潜力相对小于含砂泥岩，倾向于生气；碳质泥岩和煤分别以断续纹层状和纹层状构造为主，二者有机质丰度高，以煤质、木质和壳质有机质为主，为偏腐殖型烃源岩，倾向于生气。富砂泥岩主要分布于始新统恩平组和文昌组沉积期的凹陷东部和南部，含砂泥岩主要分布于恩平组和文昌组沉积期的凹陷东部，碳质泥岩和煤主要分布于下文昌组和恩平组沉积期的凹陷南部。

In the deep-water area of the Zhu Ⅱ Depression of the Pearl River Mouth Basin, the Baiyun Sag develops three types of source rocks: mudstone, carbonaceous mudstone, and coal. Existing studies lack experimental data support, making it difficult to accurately assess the differences in hydrocarbon generation potential among source rocks with different lithologies and from different regions. To clarify the lithologies and hydrocarbon generation potential of Eocene source rocks in the Baiyun Sag, comprehensive methods, including thin-section identification, X-ray diffraction analysis, palynofacies identification, and organic geochemical analysis, were used to systematically conduct lithological division, organic matter composition analysis, and hydrocarbon generation potential evaluation. The Eocene source rocks in the Baiyun Sag showed significant differences in mineral composition and organic matter content, with diverse sedimentary structures. Based on the total organic carbon content and mineral composition characteristics, the source rocks in the Baiyun Sag can be classified into sand-rich mudstone, sand-bearing mudstone, carbonaceous mudstone, and coal. The characteristics of these source rocks with different lithologies vary greatly. The sand-bearing mudstone has a massive structure with a relatively high organic matter abundance, mainly coaly organic matter, and contains some amorphous organic matter. Its source rocks are primarily sapropelic with relatively higher hydrocarbon generation potential and tend to generate oil. Sand-rich mudstone is primarily characterized by a clastic massive structure with a relatively low abundance of organic matter, mainly coaly and sporonic organic matter. The source rocks are mainly humic with relatively smaller hydrocarbon generation potential and tend to generate gas. Carbonaceous mudstone and coal are mainly characterized by discontinuous laminated structures and laminated structures, respectively, with high organic matter abundance, predominantly coaly, woody, and shell-type organic matter. Both are humic source rocks and tend to generate gas. The sand-rich mudstone is mainly distributed in the eastern and southern parts of the sag during the sedimentation periods of the Eocene Enping Formation and Wenchang Formation, the sand-bearing mudstone in the eastern part of the sag during the same periods, and the carbonaceous mudstone and coal in the southern part of the sag during the sedimentation periods of the Lower Wenchang Formation and Enping Formation.

中央高校基本科研业务费专项资金 22120220591;上海市自然科学基金 21ZR1468900

https://doi.org/10.11781/sysydz2025040835