四川盆地震旦—寒武系高演化烃源岩无机地球化学特征与评价

Inorganic geochemical characteristics and evaluation of Sinian-Cambrian post-mature source rocks in Sichuan Basin

施春华 山述娇 郝靖 罗冰 曹剑

SHI Chunhua SHAN Shujiao HAO Jing LUO Bing CAO Jian

贵州大学 资源与环境工程学院, 贵阳 550025 贵州大学 喀斯特地质资源与环境教育部重点实验室, 贵阳 550025 南京大学 地球科学与工程学院, 南京 210023 中国石油 西南油气田分公司 勘探开发研究院, 成都 610041 中国石油 西南油气田分公司 重庆气矿, 重庆 401120

College of Resources and Environmental Engineering, Guizhou University, Guiyang, Guizhou 550025, China Key Laboratory of Karst Georesources and Environment, Ministry of Education, Guizhou University, Guiyang, Guizhou 550025, China School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu 210023, China Exploration and Development Research Institute, PetroChina Southwest Oil and Gas Field Company, Chengdu, Sichuan 610041, China Chongqing Gas Mine, PetroChina Southwest Oil and Gas Field Company, Chongqing 401120, China

高演化烃源岩评价因有机质的损耗而使得传统有机地球化学参数逐渐失效，而烃源岩中的无机元素不易受成熟度的影响。为探索无机地球化学方法在高演化烃源岩评价中的应用，以四川盆地震旦—寒武系为例，基于无机(主量、微量和稀土元素)地球化学方法，从烃源岩发育的三大控制因素(古生产力、沉积环境和沉积速率)分析入手，开展了烃源岩无机地球化学研究。结果表明，综合运用Ba和Ni元素丰度确定烃源岩古生产力，MoEF、UEF、Ce异常特征确定沉积水体氧化—还原条件，TiO2/Al2O3比值确定沉积速率，揭示研究区烃源岩有机质富集主要受控于沉积环境与古生产力，而受沉积速率的影响相对较小；川中与威远—资阳地区下寒武统筇竹寺组烃源岩古生产力高、沉积环境最为还原，烃源岩质量最好，属于高生产力和好保存模式。无机地球化学方法是高演化烃源岩评价的一种有效途径。

The evaluation of post-mature source rocks gradually invalidates by traditional organic geochemical parameters due to the decreasing of organic matter abundance. However, the inorganic elements in source rocks are not easily affected by thermal evolution. In order to explore the application of inorganic geochemical methods in the evaluation of post-mature source rocks, this paper takes the Sinian-Cambrian source rocks in the Sichuan Basin as an example to conduct an evaluation based on the inorganic (major, trace and rare earth elements) geochemistry method with three controlling factors of source rock development (paleoproductivity, sedimentary environment and sedimentary rate). The concentration of Ba and Ni, MoEF and UEF and Ce anomaly, and TiO2/Al2O3 ratio could be correlated with paleoproducitvity, sedimentary environment and sedimentary rate, respectively. The results showed that the enrichment of organic matter was mainly controlled by sedimentary environment and paleoproductivity, but are barely effected by sedimentary rate. Source rocks in the Lower Cambrian Qiongzhusi Formation in the central Sichuan and Weiyuan-Ziyang areas have high paleoproductivity and the most reduced environment and thus are one of the best quality source rocks. Therefore, inorganic geochemistry method is an effective way to evaluate postmature source rocks.

国家自然科学基金青年项目 41802145;国家自然科学基金面上项目 42172089

https://doi.org/10.11781/sysydz202203505