柴达木盆地三湖坳陷气钾1井烃源岩地球化学特征分析

对烃源岩的地球化学特性的研究有助于油气的勘测。柴达木盆地三湖坳陷有丰厚的天然气资源,沉积范围广,厚度较大其厚度整体约2 000~3 200 m。选取三湖地区达布逊湖东部气钾1井的烃源岩样品,通过分析生物标志化合物,研究烃源岩的地球化学特征。实验结果表明:饱和烃的中低碳数分子无明显偶奇碳数优势,反映出微生物的降解作用明显改变了常规生物标志物的分布特征;有机质母质,植烷含量丰富,其碳数值接近于主峰碳数值,呈现弱还原的沉积环境特征;气钾1井中天然气有机母质主要来源于以陆生高等植物为主要母源的湖相沉积环境;伽马蜡烷也出峰明显,说明其沉积的水环境主要为高盐特征;正构烷烃C_(31)/C_(29)的比值表明这一期间的气候条件为寒冷干燥。

Geochemical Characteristics of the Source Rocks of Qijia 1 Well in Sanhu Depression in the Qaidam basin

Geochemical characteristics of hydrocarbon source rocks are of great significance to oil and gas exploration. The Sanhu depression area in Qaidam basin has abundant natural gas resources. Sanhu Depression has the largest and thickness sedimentary area, the general thickness is 2000 ~ 3200m. In this paper, the source rocks of the Qijia 1 well in the east of Dabson Lake in Sanhu area were selected, and by analyzing the biomarker compounds to know the geochemical characteristics of the source rocks. Experimental results show that the low-carbon molecules of saturated hydrocarbon has no obvious odd carbon number advantage, suggesting that the degradation of microorganisms significantly changed the distribution of conventional biomarkers; Biological gas source rocks are rich in phytane series compounds, the phytane is even close to the main peak carbon; The natural gas organic parent material in Qijia 1 well is mainly derived from the lake sedimentary environment with aquatic plants as the main source; gammacerane is also evident in the fact that its deposition medium is characterized by salt water; The ratio of n-alkanes C31/C29 partly reflects the relative cold and dry conditions of the climate in this period.