| 火山活动与海侵影响下的典型湖相页岩有机质保存差异分析 |
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| 引用本文： | 李鹏,刘全有,毕赫,孟庆强.火山活动与海侵影响下的典型湖相页岩有机质保存差异分析[J].地质学报,2021,95(3):632-642. |
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| 作者姓名： | 李鹏 刘全有 毕赫 孟庆强 |
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| 作者单位： | 页岩油气富集机理与有效开发国家重点实验室,北京,100083;中国石油化工股份有限公司石油勘探开发研究院,北京,100083;中国石油勘探开发研究院,北京,100083 |
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| 基金项目： | 本文为国家自然科学基金项目（编号41872164、41625009和42002139）和中国科学院先导A项目（编号XDA14010404）联合资助的成果。 |
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| 摘 要： | 黑色富有机质页岩是页岩油气生成和赋存的主要母体,是强还原环境水体的沉积产物,在其形成过程中,细菌硫酸盐还原作用(BSR)对水体环境影响明显,但BSR强度如何影响有机质的保存尚未得到关注。我国陆相湖盆富有机质泥页岩广泛发育,形成过程中常常伴随有火山活动或者海侵等事件,大量硫酸盐进入湖盆,改变水体的沉积环境,不同环境下BSR对黑色页岩有机质保存的影响明显不同。本次研究选取鄂尔多斯盆地延长组长7段页岩、松辽盆地青山口组和嫩江组页岩作为对象,同时与现代沉积物进行对比。研究表明,TOC与TS之间关系复杂,但细菌硫酸盐还原强度指数(SRI)与TOC呈现幂指数变化,且表现出两阶段变化的特征。当SRI大于1.375时,TOC整体偏低,指示了强硫酸盐还原作用消耗大量有机质;当SRI小于1.375时,TOC明显较高,指示了弱硫酸盐还原作用对有机质消耗相对较少,更有利于有机质保存。火山活动和海侵作用均向水体提供了大量硫酸盐,但对陆相湖盆页岩中有机质的保存影响不同。火山活动影响的长7段页岩SRI普遍小于1.375,BSR对有机质消耗相对弱,页岩TOC高。而受海侵影响的青山口组一段底部和嫩江组一段底部页岩SRI大于1.375,BSR过度消耗了大量有机质,使得页岩TOC偏低。嫩江组一段下部SRI指数更高,海侵强度更大,BSR反应更强,更不利于有机质保存。
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| 关 键 词： | 富有机质页岩 火山活动 海侵 硫酸盐还原指数(SRI) |
| 收稿时间： | 2020/9/24 0:00:00 |
| 修稿时间： | 2020/12/23 0:00:00 |
Analysis of the difference in organic matter preservation in typical lacustrine shale under the influence of volcanism and transgression |
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| LI Peng,LIU Quanyou,BI He,MENG Qingqiang.Analysis of the difference in organic matter preservation in typical lacustrine shale under the influence of volcanism and transgression[J].Acta Geologica Sinica,2021,95(3):632-642. |
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| Authors: | LI Peng LIU Quanyou BI He MENG Qingqiang |
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| Institution: | (Slate Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing,100083;Petroleum Exploration and Production Research Instiute,SINOPEC,Beijing,100083;Research Institure of Petroleum Exploration and Derelopment,PetroChina,Beijing,100083) |
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| Abstract: | Black organic- rich shale is the main source of shale oil and gas generation. It is the sedimentary product of reduced environment. During its formation, bacterial sulfate reduction (BSR) has an obvious effect on the water environment, but how BSR intensity affects the preservation of organic matter has not received much attention.Organic rich shale is widely developed in lacustrine basins in China, and the formation process is often accompanied by volcanic activities or transgression. A large amount of sulfates enter the lacustrine basin and change the sedimentary environment of the water body. Under different environments, BSR has significantly different effects on the preservation of organic matter in black shale.In this study, the shale of the Chang 7 member of Yanchang Formation in the Ordos Basin, the Qingshankou and the Nenjiang Formationsin the Songliao Basin were selected for study and compared with modern sediments.Studies have shown that the relationship between TOC and TS is complex, but the sulfate reduction index
(SRI) and TOC show power exponential relation and two- stage changes.When SRI was greater than 1. 375, TOC as a whole was low, indicating that strong sulfate reduction consumed a large amount of organic matter.When SRI was less than 1. 375, TOC was significantly higher, indicating that the consumption of organic matter by weak sulfate reduction was relatively low, which was more conducive to the preservation of organic matter. Both volcanism and transgression provide a large amount of sulfate to water bodies, but there are significantly different results of the enrichment of organic matter in the lacustrine shale. The SRI of Chang 7 shale affected by volcanic activity was generally less than 1. 375, BSR had relatively weak organic matter consumption, and the TOC was high.However, the SRI of the bottom of 1st Member of the Qingshankou Formation and the bottom of 1st Member of the Nenjiang Formation was greater than 1. 375 under the influence of transgression, BSR overconsumed a large amount of organic matter, thus lowering the TOC. In the bottom of 1st Member of the Nenjiang Formation, the SRI was higher, indicating that the higher the transgression intensity is, the stronger the BSR reaction will be, which is not conducive to the preservation of organic matter. |
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| Keywords: | organic- rich shale volcanic activity transgression sulfate reduction index (SRI) |
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