有机质氮同位素与蛋白质含量在生物气源岩评价中的应用——以柴达木盆地涩北一号构造带为例

Application of Organic Nitrogen Isotopes and Protein Content in Evaluating Biological Gas Source Rocks

按照有机质丰度、类型和成熟度为评价思路的传统石油地球化学评价方法,不能满足和适应具有早期微生物化学成因为关键要素的低成熟生物气资源勘探。尝试从生物气早期营养母源出发,以柴达木盆地涩北一号构造带源岩样品为例,通过生物大分子蛋白质含量、氮同位素以及C/N比值,结合常规岩石热解数据分析生物气沉积有机质特征。地质分布追踪表明:δ15N、蛋白质含量以及传统地球化学指标(有机碳含量TOC、氢指数IH等)高丰度层位与探井主要产气层段相对应。因此,生物大分子蛋白质含量能够表征微生物营养底物的丰富程度,δ15N可以反映生物气母源环境特征和微生物活动强度,可以利用δ15N、蛋白质含量以及C/N比结合传统有机地球化学指标来评价生物气源岩。

The methods of traditional petroleum geochemical evaluation in accordance with the organic matter abundance,its type and maturity could not meet the demands of chemical and biological causation of early micro-organisms,which was the key element for low maturity biogas exploration.Therefore,it needed to re-establish a biogas source rock evaluation system.Starting from the early headstream of biogas,based on the protein content of biological macromolecules,nitrogen isotopes and C/N ratio,the characteristics of biogas sedimentary organic matter were analyzed in combination with traditional rock pyrolysis data.Through analysis of the production gas wells,the δ15N,protein content and the traditional geochemical indicators are corresponding to the major gas producing intervals,δ15N can reflect the characteristics of biogas maternal environment,the protein content of biological macromolecules can be characterized the abundance of the microbial nutrient and the degree of the intensity of microbial activity.Therefore δ15N and the protein content combined with the traditional geochemical indicators can be used to evaluate the biogas source rocks.