摘要
为了厘清复式箕状断陷烃源岩发育模式,本文以丽水凹陷月桂峰组为研究对象,在构造背景、沉积相分析的基础上,挑选不同构造区、不同沉积相带的典型代表井开展烃源岩有机岩石学和地球化学对比研究。结果表明,月桂峰组烃源岩有机质的富集主要受有机质输入量与保存条件控制,区域上发育前三角洲亚相混合输入型和中深湖亚相原地保存型两种富集模式。由于复式箕状断陷内部的不同次凹周缘沉积“源-汇”系统的差异性,导致其富集程度存在差异。前三角洲亚相混合输入型烃源岩在弱氧化环境下有机质的富集程度主要受控于三角洲携带陆源有机质的输入量,干酪根类型以Ⅱ2—Ⅲ型为主,该型烃源岩主要分布在丽水西次凹大型三角洲的前三角洲亚相;中深湖原地保存型在弱还原环境下有机质的富集程度受原地水生生物生长量及保存条件共同控制,干酪根类型以Ⅱ2型为主,该型烃源岩主要分布在同沉积生长大断裂控制的深洼区。西次凹西部为巨大的浙闽隆起,辫状河-三角洲发育,沉积物注入量大,Ⅱ2型烃源岩发育规模小;而东次凹两侧为灵峰低凸起和雁荡凸起,点物源控制的三角洲规模小,Ⅱ2型烃源岩发育规模较大。
To clarify the development model of source rocks in the composite half-graben basins,we studied the Yueguifeng Formation in the Lishui Sag.The tectonic background and sedimentary facies were analyzed,and representative wells were selected from different tectonic units and sedimentary facies zones.The source rocks in organic petrology and geochemistry were compared.Results show that the enrichment of organic matter in the source rocks of Yueguifeng Formation was directly related to the amount of organic matter input and preservation conditions.Two enrichment models were developed,namely,the prodelta mixed input type and the mid-deep lacustrine in-situ preservation type.The enrichment degree of the two types of source rocks in half-graben basins was different in each sub-sag due mainly to the variation of the sedimentary“source-to-sink”systems around different sub-sags.In the mixed input type,the degree of organic matter enrichment under weakly oxidizing environments depended on the amount of terrestrial organic matter in the delta,and the dominant kerogen type wasⅡ2-Ⅲ.This type of source rock is generally distributed in the western Lishui Sag in prodelta facies.In the in-situ preservation type,the accumulation of organic matter in a mildly reduction environment was controlled by the growth of local aquatic organisms and preservation conditions.The kerogen type is mainly typeⅡ2,and the source rock of this type is distributed in the central area of the sag under the control of the growth of syn-rift faults.The western part of the Lishui Sag faced a vast Zhejiang-Fujian uplift to the west,with braided river delta development and large sediment injection,resulting in a small scale of development of typeⅡ2 source rocks,while the eastern part of Lishui Sag was in-between the Lingfeng Low uplift and Yandang uplift,receiving small-scale input from pointsourced rocks,thus the development scale of this type of source rock is relatively large.
作者
王宁
覃军
常文琪
董哲
朱虹浩
WANG Ning;QIN Jun;CHANG Wenqi;DONG Zhe;ZHU Honghao(Shanghai Branch of CNOOC(China)Ltd.,Shanghai 200335,China)
出处
《海洋地质前沿》
北大核心
2025年第12期16-28,共13页
Marine Geology Frontiers
基金
中海石油(中国)有限公司“十四五”重大项目“近海重点潜在富烃洼陷评价技术”(KJGG2022-0301)。
关键词
复式箕状断陷
烃源岩
有机质富集模式
月桂峰组
丽水凹陷
composite half-graben basin
source rock
enrichment model of organic matter
Yueguifeng Formation
Lishui Sag
