南羌塘坳陷古油藏原油生物降解作用及意义  

Biodegradation of Crude Oil in Paleo-oil Reservoirs in South Qiangtang Basin and Its Significance

作　　者：于珺 李娜 胡春桥 黄峰 张洪美 YU Jun;LI Na;HU Chun-qiao;HUANG Feng;ZHANG Hong-mei(Research Institute of Shaanxi Yanchang Petroleum Co.Ltd.,Xi’an,Shaanxi 710075)

机构地区：[1]陕西延长石油(集团)有限责任公司研究院,陕西西安710075

出　　处：《地球学报》2023年第6期1053-1061,共9页Acta Geoscientica Sinica

基　　金：陕西延长石油(集团)有限责任公司“北羌塘坳陷基本石油地质特征与勘探潜力”项目(编号:YJKTS22SFW0001)资助。

摘　　要：对南羌塘坳陷古油藏开展了有机地球化学分析,从生物标志化合物特征和地质条件探讨古油藏生物降解特征及成藏期次。研究表明,古油藏储层样品抽提物的正构烷烃分布完整,但色谱基线发生不同程度抬升,形成“鼓包”现象,指示古油藏遭受了一定程度的生物降解作用;古油藏族组分碳同位素发生“倒转”和普遍检出的25-降藿烷也证实了古油藏经历了中等-严重的生物降解。然而,古油藏储层样品饱和烃色谱图显示出正构烷烃较为完整,指示古油藏储层可能经历两期原油充注,第一次原油遭受了生物降解,第二期原油保留相对完整的正构烷烃。古油藏储层经历了两次原油充注,与南羌塘坳陷富有机质页岩经历了两次生排烃的过程是一致。We conducted organic geochemical analysis of the paleo-oil reservoirs in the south Qiangtang Basin and discussed the biodegradation characteristics and charge timing of these reservoirs in terms of the characteristics of biomarkers and geological conditions.The distribution of n-alkanes in the paleo-oil reservoirs is complete,but the chromatographic baseline rises to different degrees,forming a“bulge”,indicating that the paleo-oil reservoirs have suffered a certain degree of biodegradation.The inversion of the carbon isotopes of the components and the widespread detection of 25-norhopanes also confirmed that the paleo-oil reservoir has experienced moderate to severe biodegradation.However,the saturated hydrocarbon chromatogram of samples from the paleo-oil reservoir show that the normal alkanes are relatively complete,indicating that the reservoir may have experienced two stages of crude oil charging.In the first stage,the crude oil was subject to biodegradation,and in the second stage,the crude oil retained relatively complete normal alkanes.The paleo-oil reservoir has experienced two stages of oil charging,which is consistent with the processes of hydrocarbon generation and expulsion of organic rich shale in the south Qiangtang Basin.

关 键 词：羌塘盆地 油气地球化学 生物降解 25-降藿烷 充注期次 

分 类 号：P618.13[天文地球—矿床学]