| 内蒙古西乌旗地区下二叠统寿山沟组泥页岩有机地球化学特征——以MXD1井为例 |
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| 引用本文：崔新宇,施立志,张永生,张晓凯,汪彪,罗立艳.2021.内蒙古西乌旗地区下二叠统寿山沟组泥页岩有机地球化学特征——以MXD1井为例[J].地球学报,42(5):663-676. |
| DOI：10.3975/cagsb.2021.051101 |
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| 基金项目:中国地质调查局项目“二连盆地及外围石炭-二叠系油气地质调查”(编号: DD20190099);国家自然科学基金项目(编号: 41572098) |
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| 中文摘要:本文采用岩石热解、饱和烃色质、芳烃色质等测试方法, 首次对内蒙二连盆地西乌旗地区MXD1井钻遇的二叠统寿山沟组二段深灰色、灰黑色泥页岩样品进行了系统的有机地球化学分析, 对烃源岩的沉积环境、母质来源及有机质类型和有机质成熟度等科学问题进行了深入研究。样品的正构烷烃特征表明该段的有机质受到生物降解作用的影响较小。规则甾烷相对含量、碳优势指数(CPI)、三环萜烷/17α-藿烷值特征表明该段的沉积环境为咸水、还原环境, 生源以水生藻类与浮游生物为主, 有少量的陆源植物贡献, 为该段为海相沉积环境提供了证据。正构烷烃的峰型峰态、Pr/nC17值与Ph/nC18值相对关系和规则甾烷相对含量共同表明有机质类型主要为II型。芳烃中三甲基萘、菲、三芳甾特征和饱和烃中藿烷、甾烷、正构烷烃的分布特征和指标共同表明烃源岩成熟度高, 镜质体反射率Ro平均为2.93%, 可以判断有机质成熟度为高成熟-过成熟, 有利于天然气的形成。样品残余有机碳含量为0.10%~0.85%, 经过原始有机碳恢复可以得到原始总有机碳含量为0.17%~1.46%, 表明MXD1井寿山沟组二段的部分泥页岩层段可达到中等到较好烃源岩的水平。综合评价认为内蒙古西乌旗地区寿山沟组二段烃源岩具有中等的生烃潜力。以上研究成果表明该区上古生界具备油气成藏的烃源条件, 为西乌旗地区的新层系油气勘探提供了重要的有机地球化学依据, 对二连盆地及外围地区的石炭二叠系新领域油气勘探工作具有一定的借鉴意义, 对于我国北方石炭二叠系的油气勘探的战略接替及可持续发展也有一定的参考价值。 |
| 中文关键词:有机质丰度 成熟度 有机质类型 有机质来源 沉积环境 原始有机碳恢复 |
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| Organic Geochemical Characteristics of the Mud or Shale in the Lower Permian Shoushangou Formation of West Ujimqin Banner, Inner Mongolia: A Case Study of Well MXD1 |
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| Abstract:To evaluate such problems as the hydrocarbon potential of the thick mud shale and the hydrocarbon generation potential of depositional environment, the origin of parent materials and the maturity, the authors carried out for the first time systematic organic geochemical research on the dark mud shale in Shoushangou Formation of Well MXD1 in West Ujimqin Banner, Inner Mongolia. The n-alkane peak form and the main peak in the second member indicate that the organic matter on the whole has not been affected by biodegradation. The relative content of regular steranes, the Carbon Preference Index and tricyclic terpanes/17α-hophane features show that this member was deposited in saline water facies of the reducing environment, and its source was mainly aquatic and partly terrigenous; and it is also proved that the sedimentary environment was mainly of marine facies. The peak shape of positive alkanes, the relationship between Pr/nC17 value and Ph/nC18 value and the relative content of the normal sterane suggest that the parental materials of organic matter is mainly of Type II. The characteristics of aromatic organic chromatin can reflect the maturity of the source rock, which is highly mature-over-mature. The characteristics of aromatic organic chromatin materials such as Trimethylnaphthalene, Phenanthrene, triaromatic steroid and the characteristics of saturated hydrocarbon chromatography such as hopane series, sterane and Methylphenanthrene all show that its hydrocarbon source rock has high maturity, and the average of vitrinite reflectance is 2.93%, which implies that the maturity of organic matter is mature-over mature, beneficial to the formation of natural gas. The residual organic carbon content of the samples is 0.10% to 0.85%, and the original total organic carbon content recovered is 0.17%~1.46%, with an average of 0.51%, so part of the shales or mudstones in Well MXD1 can reach the level of medium hydrocarbon source rocks. The comprehensive evaluation suggests that the hydrocarbon source rock of Well MXD1 is of medium hydrocarbon potential. The research results show that the upper Paleozoic strata in the study area have hydrocarbon source conditions for oil and gas reservoirs, and provide an important basis of organic geochemistry for oil and gas exploration in the Paleozoic strata of West Ujimqin Banner. The results obtained by the authors have certain reference significance for the new-area gas exploration in Carboniferous–Permian strata of Erlian Basin, and also provide useful materials for the oil-gas exploration strategic succession and sustainable development of North China. |
| keywords:organic matter abundance maturity organic matter type source of organic matter sedimentary environment original organic carbon recovery |
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