石油与天然气地质2025，Vol.46Issue(5)：1430-1445,16.DOI:10.11743/ogg20250504
陆源物质输入对有机质类型的影响
Impacts of terrigenous inputs on organic matter type:A case study of shales in the Chang 73 oil sub-group of the Triassic Yanchang Formation,Ordos Basin
摘要
Abstract
This study aims to explore the impacts of terrigenous inputs on the organic matter type of semi-deep-to deep-lacustrine shales.Focusing on shales in the 3rd sub-group of the 7th oil group of the Triassic Yanchang Formation(also referred to as the Chang 73 oil sub-group)in the Ordos Basin,we conduct comprehensive petrological,sedimentological,and geochemical analyses on core samples from four wells located in the northeastern,northwestern,and southwestern parts of the lacustrine basin during the deposition of the Yanchang Formation.Accordingly,the impacts of terrigenous inputs on the organic matter type are delved into.The results indicate that the samples involved are all rich in organic matter,with maturities ranging from 0.91％to 1.03％,suggesting medium to low maturity.The organic matter comprises types Ⅱ 1 and Ⅱ 2 kerogens,with kerogen macerals dominated by sapropelinite,followed by vitrinite.Notably,maceral types differ greatly across different wells.Shales in the Chang 73 oil sub-group comprise seven lithofacies types:layered shale,shale with discontinuous to continuous laminae,silt-bearing shale with massive-discontinuous laminae,silty shale with massive-discontinuous laminae,layered silty shale,laminated silty shale,and massive silty shale.The layered shale,among others,is the least affected by terrigenous inputs,whereas the last four lithofacies are strongly affected.Shales from well W336 are weakly influenced by terrigenous clastic inputs.Correspondingly,type Ⅱ1 kerogen occurs in this well,with macerals dominated by sapropelinite(with a content of 64％～83％).In contrast,shales from the other three wells are more strongly affected by terrigenous clastic inputs.In these wells,type Ⅱ2 kerogen predominates,with vitrinite content ranging from 15％to 42％.Despite the strong influence of terrigenous inputs,the parent materials of organic matter in the semi-deep to deep lacustrine environment remain dominated by aquatic organisms,producing favorable organic matter types.However,in the anoxic bottom water,higher plant debris accompanied by terrigenous inputs such as quartz and feldspar coexist with algae,leading to the formation of mixed type Ⅱ1-Ⅱ2 kerogen and comparatively less favorable organic matter types.关键词
干酪根类型/显微组分/陆源物质/页岩岩相/富有机质页岩/延长组/三叠系/鄂尔多斯盆地Key words
kerogen type/terrigenous material/maceral/shale lithofacies/organic-rich shale/Yanchang Formation/Triassic/Ordos Basin分类
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耳闯,关宏博,刘伟,程妮,白洁,胡崇..陆源物质输入对有机质类型的影响[J].石油与天然气地质,2025,46(5):1430-1445,16.基金项目
国家自然科学基金项目(41702132). （41702132）
