摘要
从轻烃分子及其稳定碳同位素组成两方面刻画了塔中4石炭系油藏原油轻烃地球化学特征,同时结合高分子量烃类生物标志化合物指标初步厘定了蒸发分馏、水溶分馏、有机质熟化、热蚀变等次生作用对石炭系原油的影响程度,并探讨了其地质意义。石炭系不同油组(CⅠ、CⅡ、CⅢ)原油轻烃地球化学特征显示,CⅠ和CⅡ—CⅢ可分别视为两个相互独立的成藏体系。CⅠ原油主要是早期形成的低熟原油,该类原油轻烃富含正构烷烃,贫环烷烃和芳烃,链烷烃/环烷烃比值偏高,稳定碳同位素组成富含12C,高分子量芳烃成熟度指标偏低;CⅠ原油保存相对较好,可能只遭受了程度较弱的水溶分馏等次生改造。CⅡ与CⅢ原油大多是晚期形成的高熟原油,这类原油轻烃富含轻质环烷烃和芳烃,贫正构烷烃,链烷烃/环烷烃比值偏低,稳定碳同位素组成富含13C,高分子量芳烃成熟度指标偏高;热蚀变和蒸发分馏次生作用对CⅡ与CⅢ原油轻烃地球化学特征有重要影响,不同期次及成因原油在CⅡ与CⅢ油组内相互混合的现象也较为普遍;CⅡ与CⅢ部分遭受热蚀变改造的原油可能是寒武系—下奥陶统古油藏内的原油热裂解后通过断层运移到石炭系聚集成藏,原油热裂解对该区晚期天然气形成可能具有重要意义。
The influences of thermal alteration,evaporation fractionation and water washing on the Carboniferous oils were evaluated by using chemical and isotopic compositions of light hydrocarbons（C6—C8） in Carboniferous crude oils from the Tz4 Oilfield,NW China.The results suggest that hydrocarbons in the CI Fm and CII and CIII Fms have distinct accumulation processes.Compared with C6—C8 in the CII and CIII Fms,C6—C8 in the CI Fm contain more normal alkanes,but less cycloalkanes and aromatics resulting in greater ratios of normal（branched） alkanes to cycloalkanes,and are comparatively depleted in 13C.These results indicate that hydrocarbons entrapped in the CI Fm are derived from a relatively less matured kerogen,which is consistent with the conclusion based on the biomarkers in the aromatic fraction of these oils.Water washing during petroleum secondary migration along carrier bed has a relatively minor influence on oils in the CI Fm,while oil cracking and evaporation fractionation have important role in regulating the chemical and isotopic compositions of light hydrocarbons in the CII and CIII Fms.Therefore,it is commonplace that different generative oils mix together within the CII and CIII Fms.Oil cracking probably occurred in the deeply-buried Lower Ordovician and Cambrian paleo-reservoirs through geological time scale,these thermally altered oils migrated upward along faults and finally accumulated in the Carboniferous;natural gases from hydrocarbon secondary cracking should have a critical implication in forming gas accumulations in this region recently.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2011年第2期206-211,共6页
Acta Petrolei Sinica
基金
国家自然科学基金项目(No.40672084)
国家重点基础研究发展规划(973)项目(2006CB202303)
中国科学院广州地球化学研究所有机地球化学国家重点实验室开放基金课题(OGL-200916)联合资助
关键词
轻烃
稳定碳同位素
蒸发分馏
原油热裂解
塔里木盆地
light hydrocarbons
stable carbon isotope
evaporation fractionation
oil cracking
Tarim Basin
