Abstract: The source rock drilling cuttings from Xu⁵ to Xu¹(2530~3780m)of Upper Triassic were continuously sampled in West Sichuan Basin.The absorbed hydrocarbons in the cuttings were analyzed and studied.The generation and evolution of C₄~C₇ light hydrocarbons derived from terrestrial organic matter in this area were defined as three stages:cycloalkane,alkane and aromatic.The thermal evolution triangle of light hydrocarbons from a large number of experimental data became the important foundation for the correlation of C₄~C₇ light hydrocarbons between terrestrial condensates and terrestral source rocks,as well as the correlation among terrestrial condensates from different reservoirs(different maturity)in the same structure.The modification to Thompson's maturation indexes of condensates was suggested from the discovering of the reversion of heptane and isoheptane values with R_o reaching 1.18%,not increasing with maturity in the profile section.Besides,the hydrocarbon generation model of the terrestrial organic matter in West Sichuan Basin was established based on the light hydrocarbon generation stages and the geological characteristics:gas-cycloalkane condensate stage(R_o=0.55%~1.13%),gas-alkane condensate stage (R_o=1.08%~1.40%)and gas-aromatic condensate or dry gas stage (R_o=1.30%~1.40%).

Key words: Sichuan Basin, Upper Triassic, terrestrial, light hydrocarbon, heptane value, isoheptane value, hydrocarbon generation

摘要： 对川西地区井下上三叠统剖面须五段-须一段(2530～3780m)新鲜生油岩岩屑系统取样,作吸附烃分析、研究,得出了该区陆相有机质C₄-C₇轻烃的生成演化规律,共分为环烷烃、链烷烃和芳香烃等三个发展阶段.以大量实验数据作出的轻烃族组成热演化三角图,为气藏中陆相凝析油与陆相生油岩、以及同一构造不同储层(不同成熟度)之间陆相凝析油的C₄-C₇轻烃对比奠定了重要基础.在井下系统剖面轻烃族组成纵向变化研究中,发现了当R_o达1.18%时,庚烷值和异庚烷值发生倒转这一重要现象,并以此为契机,提出了对Thompson凝析油热演化程度判别标准的修正方案.此外,从轻烃生成阶段出发,结合本区地质特点,建立了川西地区陆相有机质的成烃模式,即气-环烷凝析油阶段,R_o=0.55%～1.13%;气-链烷凝析油阶段,R_o=1.08%～1.40%;气-芳烃凝析油或干气阶段,R_o≥1.30%～1.40%.

关键词: 四川盆地, 上三叠统, 陆相, 轻烃, 庚烷值, 异庚烷值, 油气生成