烃源岩抽提物中藿烷分子碳同位素分析新方法及指示意义

An improved method and indications for the compound specific isotopic analysis of hopanes in source rock extracts

鲁中灯 刘岩 陈祖林 樊云鹏 文志刚 徐耀辉 牛金 田永晶 柳波 谢小敏 谢巍

LU Zhongdeng LIU Yan CHEN Zulin FAN Yunpeng WEN Zhigang XU Yaohui NIU Jin TIAN Yongjing LIU Bo XIE Xiaomin XIE Wei

油气与环境地球化学湖北省重点实验室(长江大学 资源与环境学院), 武汉 430100 山东省地质矿产勘查开发局 第五地质大队, 山东 泰安 250013 东北石油大学 非常规油气研究院, 黑龙江 大庆 163000 中国石油 塔里木油田分公司 实验检测研究院, 新疆 库尔勒 841000

Hubei Key Laboratory of Petroleum and Environmental Geochemistry (School of Resources and Environment, Yangtze University), Wuhan, Hubei 430100, China No.5 Geological Brigade, Shandong Bureau of Geology and Mineral Exploration and Development, Taian, Shandong 250013, China Institute of Unconventional Oil and Gas, Northeast Petroleum University, Daqing, Heilongjiang 163000, China Research Institute of Experimental Detection, Tarim Oilfield Company, PetroChina, Korla, Xinjiang 841000, China

以5Å分子筛/氧化铝混合填料的层析柱对烃源岩抽提物进行了分离，成功获取了以藿烷类化合物为主的亚组分，可直接用于单化合物碳同位素分析。通过对典型海、陆相烃源岩中的藿烷碳同位素特征进行对比研究，结果表明准噶尔盆地二叠系芦草沟组湖相页岩中藿烷系列单体化合物的碳同位素值(δ13C)分布在-40.7‰~-62.7‰，且呈现出随着碳数的增加同位素值变轻的特点；而川西北二叠系海相页岩中藿烷化合物δ13C则相对较重，分布在-20.5‰~-45.4‰，具有随碳数增加先变轻再变重的趋势。两类页岩中藿烷类化合物的碳同位素变化幅度可达±20‰以上，尤其是川西北二叠系海相页岩中藿烷类化合物单体碳同位素的差异可达到±24.9‰，表明藿烷类化合物具有明显的多源特征。藿烷类化合物的分子碳同位素受到原始沉积环境、母质来源与演化过程的影响而可能具有较大的差异，但这并不影响其有望成为新的油源对比指标。

With a mixed stationary phase of 5Å molecular sieve/alumina, extracts of various kinds of source rocks are separated by column and sub-fractions dominated by hopanoid compounds were successfully obtained. The sub-fractions are suitable for the direct analysis on GC-IRMS to obtain compound specific isotopic values of hopanes. Comparison is carried out on isotopic signatures of specific hopanes in a lacustrine oil shale (Permian Lucaogou shale, Junggar Basin, NW China) and another Permian marine shale (NW of Sichuan Basin). Results show that the Permian Lucaogou shale had the δ13C values of hopanes distributed between -40.7‰ and -62.7‰, and decrease with the increasing of carbon number. The δ13C values of hopanes in marine shale of Sichuan Basin are apparently heavier, distribute between -20.5‰ and -45.4‰, and they appeared to be firstly decreased and then increased as carbon number increases. In both of the shales analyzed, the variation range of carbon isotopes of hopanes can be more than ±20‰ (±24.9‰ for the Sichuan Basin shale), which indicates multiple contribution to these compounds. The isotopic signatures of hopanes may be constrained by paleoenvironment, sources as well as maturation, however, compound specific isotope of hopanes is still a useful indicator for oil-source correlation.

国家自然科学基金项目 41503034;国家自然科学基金项目 41972122;国家科技重大专项 2017ZX05001005;中国地质调查局项目 20190085

https://doi.org/10.11781/sysydz202202288