羌塘盆地塞仁地区古油藏地球化学特征及意义

【研究目的】羌塘盆地是青藏高原北部的大型海相含油气盆地,研究区塞仁地区位于南羌塘坳陷,该区油气地球化学研究成果较少、研究程度较低。【研究方法】本文对古油藏含油层样品的族组成、及甾萜烷等地球化学特征进行总结,并结合多种生标参数得出结论。【研究结果】该地区古油藏整体处于低成熟-成熟阶段,C27甾烷较C29甾烷占优势,并且三环萜烷类化合物以C23三环萜烷为主峰,也表明母质来源以海相有机质为主,并有一定的陆源有机质贡献。油藏样品具有较低的姥植比(Pr/Ph<1),非藿烷中检测出一定丰度的伽马蜡烷以及较高的C35/C34升藿烷值特征,这些参数指示古油藏形成于沉积水体较深、还原性相对较强并具有一定盐度的沉积环境。【结论】该地区古油藏地球化学特征分析为油气成藏研究与油气富集规律认识奠定基础,确定了该地区古油藏的沉积环境和母质来源。古油藏母质来源以海相为主,沉积环境为较还原环境。

Li Run-yu1, Ji Chang-jun2*,Tang You-jun1, Kang Shao-wei3, Song Jia-yu1

[Objective]:Qiangtang Basin is a large marine petroliferous basin in the northern part of Qinghai-Tibet Plateau. The study area, Sairen area, is located in the south Qiangtang depression, and the research results of oil and gas geochemistry in this area are few and the research degree is low. [Method]:This paper summarizes the ethnic composition and geochemical characteristics of oil-bearing layer samples in ancient oil reservoirs, and draws a conclusion by combining various biomarker parameters. [Results]:The ancient oil reservoirs in this area are in the low-mature stage, C27 sterane is dominant over C29 sterane, and the tricyclic terpanes are mainly C23 tricyclic terpanes, which also indicates that the parent material is mainly marine organic matter, and some terrestrial organic matter contributes. The oil reservoir has a low ratio of vegetation (Pr/Ph<1), and a certain abundance of gamma paraffin and a high C35/C34 liter hopane value are detected in non-hopane. These parameters indicate that the ancient oil reservoir was formed in a sedimentary environment with deep sedimentary water, relatively strong reducibility and certain salinity. [Conclusion]: The analysis of geochemical characteristics of ancient reservoirs in this area lays the foundation for the study of oil and gas accumulation and the understanding of oil and gas enrichment law, and determines the sedimentary environment and parent material source of ancient