珠三拗陷优质烃源岩地震相特征及分布预测

Characteristics of Seismic Facies of High-quality Source Rocks and Prediction of Their Distributions in the Zhu III Depression, Pearl River Mouth Basin

游君君 雷明珠 刘亿 翟亚楠 江黎

YOUJunjun LEIMingzhu LIUYi ZHAIYanan JIANGLi

中海石油(中国)有限公司湛江分公司, 广东 湛江 524057 中海石油(中国)有限公司海南分公司, 海南 海口 570312

CNOOC China Limited, Zhanjiang Branch, Zhangjiang, Guangdong 524057, China CNOOC China Limited, Hainan Branch, Haikou, Hainan 570312, China

珠三拗陷不同沉积环境发育的烃源岩地球化学特征及成藏贡献差异较大，各相带烃源岩的空间分布尚不明确，制约了下一步油气勘探工作。通过综合分析岩屑、测井、地球化学和地震资料，对珠三拗陷优质烃源岩分布开展了系统研究。研究结果表明： 1）文昌B凹陷文昌组中深湖相烃源岩、滨浅湖相烃源岩和文昌A凹陷恩平组浅湖相烃源岩地震相特征分别为强振幅-低频-平行-中连续反射、弱振幅-低频-平行-弱连续反射（或空白反射）和中弱振幅-低频-平行-中连续反射（或杂乱反射）。2）文昌B凹陷中深湖相优质源岩广泛分布于凹陷中心和陡坡带，滨浅湖相烃源岩分布于中心边缘和缓坡带。但文昌A凹陷中深湖相烃源岩仅分布于凹陷中心，滨浅湖相烃源岩大面积分布于凹陷周缘。因此，文昌B凹陷文昌组中深湖相和浅湖相烃源岩以及文昌A凹陷滨浅湖相烃源岩为主力烃源岩。

The source rocks developed in different sedimentary environments have different geochemical characteristics and contributions to petroleum accumulation. However, the spatial distribution of the source rocks of different facies is unknow, which restricts the following petroleum exploration. Based on the comprehensive analysis of rock debris, well logging, geochemistry and seismic data, the characteristics of seismic facies of high-quality sources within the Enping Formation and Wenchang Formation as well as their distribution modes are systematically investigated. The results demonstrate that: 1) the seismic facies of the source rocks of the Wenchang Formation deposited in the semi-deep and shallow lake in the Wenchang B Sag as well as the source rocks of Enping Formation deposited in the shallow lake are featured by strong amplitude-low frequency-parallel-moderately continuous reflection, weak amplitude-low frequency-parallel-weakly continuous reflection, and moderate and weak amplitude-low frequency-parallel-moderately continuous reflection (or chaotic reflection). 2) the highquality source rocks deposited in the semi-deep lake in the Wenchang B Sag are widely distributed in the sag center and steep slope zone, whereas the source rocks deposited in shallow lake are primarily distributed in the sag center and gentle slope; however, the source rocks deposited in the semi-deep lake are only located in the sag center in the Wenchang A Sag, and the source rocks deposited in the shallow lake are well developed around the sag. Thus, source rocks deposited in the semi-deep lake and shallow lake within the Wenchang Formation in the Wenchang B Sag and that deposited in the shallow lake in the Wenchang A Sag are the primary source rocks.

10.11885/j.issn.1674-5086.2022.03.11.03