石油科学通报2025，Vol.10Issue(6)：1099-1113,15.DOI:10.3969/j.issn.2096-1693.2025.01.028
四川盆地安岳气田烃源层-储层有机质的碳同位素分布特征研究
Carbon isotopic distribution characteristics and genetic analysis of organic matter in the source-reservoir systems of the Anyue Gas Field,Sichuan Basin
摘要
Abstract
The distribution characteristics of carbon isotopes in sedimentary organic matter are often used as indicators for oil-source correlation,determination of organic matter origins,and paleoenvironmental analysis.However,when organic matter reaches the over-mature stage,cracking processes can lead to isotopic fractionation,resulting in anomalies such as carbon isotope reversal.This phenomenon,particularly in deep and ultra-deep petroleum systems,has long been a key and challenging issue in hydrocarbon geology research.This study examines the carbon isotopic distributionsof various solid and liquid organic materials from source rocks and reservoirs in the Anyue Gas Field,the central Sichuan Uplift,Sichuan Basin,based on existing data and relevant research.The findings indicate that paleo-oil reservoirs experienced thermal alteration,causing the early-formed liquid hydrocarbons in both source and reservoir layers to crack into gaseous hydrocarbons,residual liquid hydrocarbons,and pyrobi-tumen.The pyrobitumen can be categorized into in-situ pyrobitumen in source rocks and reservoir pyrobitumen.In present-day source and reservoir layers,an overall inversion is observed where kerogen has lower δ¹³C values than liquid hydrocarbons,along with a localized inversion in which saturated and aromatic hydrocarbons show higher δ¹³C values than non-hydrocarbon components and asphaltenes.Additionally,the δ¹³C values of reservoir pyrobitumen are lower than those of both kerogen and liquid hydrocarbons.Comprehensive analysis of relevant data and simulation experiments indicates that carbon isotopic enrich-ment during hydrocarbon cracking is the primary cause of the observed isotopic inversions in both source and reservoir samples.After high-temperature cracking,the residual liquid hydrocarbons derived from original liquid hydrocarbons in source rocks and paleo-reservoirs exhibit an overall increase in δ¹³C values of approximately 4‰.Due to varying thermal exposure in source rocks and paleo-reservoirs,the extent of δ¹³C increase differs among various group components of the residual liquid hydrocarbons.Although reservoir pyrobitumen largely inherits the isotopic signature of the original crude oil,thermochemical sulfate reduction(TSR)during its formation may also contribute to its anomalously light carbon isotopic values.In summary,the carbon isotopic inversions observed in the source and reservoir layers of the study area are primarily attributed to carbon isotopic fractionation during liquid hydrocarbon cracking—a phenomenon that may be common in deep and ultra-deep petroleum reservoirs that have experienced high temperatures.关键词
碳同位素/碳同位素倒转/有机质/古油藏/安岳气田Key words
carbon isotope/carbon isotopic reversal/organic matter/paleo-oil reservoir/Anyue Gas Field分类
天文与地球科学引用本文复制引用
YANG Chengyu,WANG Tieguan,QI Xuening,LI Meijun,ZHANG Jianfeng..四川盆地安岳气田烃源层-储层有机质的碳同位素分布特征研究[J].石油科学通报,2025,10(6):1099-1113,15.基金项目
中央高校基本科研业务费专项资金(2462023YJRC011)和国家自然科学基金青年基金项目(41903059)联合资助 （2462023YJRC011）
