丽水-椒江凹陷月桂峰组湖相烃源岩的主控因素与分布预测

Main constraining factors and distribution prediction of lacustrine hydrocarbon source rocks in Yueguifeng Formation in Lishui-Jiaojiang Sag

月桂峰组是丽水-椒江凹陷的主力烃源岩层系。丽水-椒江凹陷在月桂峰组沉积时期为强断陷期,构造分割性强,沉积环境相对封闭,内部多个次洼的湖相烃源岩发育特征不清。为明确丽水-椒江凹陷内各富烃次洼中月桂峰组烃源岩发育条件及空间展布规律,进一步指导该区的油气勘探,利用钻井、岩芯、地球物理、地球化学及古生物等资料,基于湖盆演化动态全生命周期过程,提出“早期断层活动速率、中期母岩性质和遮挡条件、晚期火山活动”联合控制丽水-椒江凹陷4个次洼优质烃源岩的发育。在地质认识约束下,基于多属性神经网络深度学习,对中-深湖相烃源岩的空间展布进行了定量刻画。结合优质烃源岩的发育机制和中-深湖相烃源岩分布范围,对4个主要次洼内烃源岩的发育情况进行综合评价。结果表明,椒江A洼为Ⅰ类富烃次洼,丽水A洼和丽水C洼为Ⅱ类次富烃次洼,丽水B洼为Ⅲ类生烃次洼。

The Yueguifeng Formation is the main source rock of Lishui-Jiaojiang Sag that formed in the period of strong fault filling of the Yueguifeng Formation,with strong tectonic segmentation,relatively enclosed sedimentary environment,and unclear development characteristics of lacustrine source rock in mainly four sub-sags.To clarify the development conditions and spatial distribution of the source rocks of the Yueguifeng Formation in each hydrocarbon-rich sub-sag,and further guide the oil and gas exploration in the area,the data of logging and coring in geophysics,geochemistry,and paleontology were used based on the dynamic life cycle process of the lake basin evolution.We proposed that the four factors,in temporal order,of early-stage fault activity rate,middlestage parent rock property and the shielding conditions,and late-stage volcanic activity,jointly constrained the development of high-quality source rock in the four major sub-sags.Under the best geological knowledge,based on multi-attribute neural network deep learning,the spatial distribution of middle-deep lacustrine hydrocarbon source rocks was depicted quantitatively.Based on the development mechanism of high-quality source rocks and the distribution range of medium-deep lacustrine source rocks,the development of high-quality source rocks in the four major sub-sags was evaluated comprehensively.The results indicate that Jiaojiang A Sub-sag is a ClassⅠhydrocarbon rich sub-sag,Lishui A and Lishui C Sub-sags are ClassⅡsub-rich hydrocarbon sub-sags,and Lishui B Sub-sag is ClassⅢhydrocarbon-generating sub-sag.