塔北隆起中部原油轻烃地球化学特征及其意义

对塔北隆起中部27个原油样品进行了轻烃地球化学分析，结果表明这些不同区块、不同层位、不同产状原油C₅-C₇与C₇轻烃组成非常接近，原油母质高度相似，均反映典型的海相成因、主要源自藻类和细菌等低等生物。轻烃2-MH/3-MH值和Pr/Ph值具有较好的正相关性，指示其沉积环境介质条件可能存在细微差异。庚烷值和异庚烷值分别介于22.97%～37.37%和1.04～4.06之间，原油生成温度为119.03~130.89℃，表明属于高成熟原油。混有早期生物降解原油的多期充注成藏，使得轻烃组成揭示的仅为晚期正常原油的地质地球化学信息。

Geochemical Characteristics of Light Hydrocarbons from the Central Part of Tabei Uplift and Their Implications

Geochemical characteristics of light hydrocarbons for 27 crude oils from Tabei Uplift were investigated.The results show that the source input was highly similar for their roughly equal compositions ofC₅-C₇ and C₇ light hydrocarbons,despite they were sampled from different horizons of different oilfields with variable occurrence.It is suggested that those oils were of marine origin and mainly sourced from algae and bacteria.The 2-MH/3-MH ratio correlates well with the Pr/Ph ratio,implying the subtly different media conditions of sedimentary environment.Heptane and isoheptane values are 22.97%-37.37% and 1.04-4.06 respectively,indicating a high maturity of oils,associated with the high hydrocarbon-generating temperature (119.03-130.89℃).Due to the severe biodegradation of early charged oil,light hydrocarbons from mixed oils with multi-stage charging only delineate the geochemical implications of late charged fresh oil.