烃源岩有机碳含量与生排油效率动态评价

Dynamic assessment of organic carbon content and hydrocarbon generation and expulsion efficiency in source rocks

选择海相典型烃源岩样品和人工配制烃源岩样品进行热压模拟实验,对比分析了海相烃源岩的生油量、生排油效率与烃源岩有机碳含量的关系,模拟结果表明:(1)烃源岩的生排油量与烃源岩有机碳含量呈线性正相关关系,生排油效率与有机碳含量呈曲线(非线性)正相关关系,相关系数的大小与烃源岩的干酪根类型、岩性及演化史等有关;(2)在整个生烃演化过程中,高有机质含量的优质烃源岩(TOC一般大于2%)的生排油量和效率都高于中等有机质丰度的中等烃源岩(TOC一般在0.5%~2.0%之间)和低有机质丰度的差烃源岩(TOC一般小于0.5%),只有高有机质丰度的优质烃源岩才能够大量生排出油并形成大油田,差烃源岩即使很厚也难以形成大量的油气聚集;(3)在地质演化过程中,烃源岩TOC含量及其生排油气能力始终都是动态变化的,因此需要在确定演化阶段的基础上,结合有机碳含量和生排油效率进行烃源岩和资源量动态评价。

The relationship of the yields and efficiencies of oil generation and expulsion with total organic carbon content （TOC） was analyzed based on thermal simulations of typical natural marine source rocks and artificial source rocks. （1） The simulation results show a positive linear correlation between the yields of oil generation and expulsion and TOC, and a nonlinear correlation between the efficiencies of oil generation and expulsion and TOC. The correlation coefficients are related to kerogen type, lithology and thermal maturity. （2） Source rocks with high TOC contents （generally over 2.0%） always have higher yields and efficiencies of oil generation and expulsion throughout the simulation experiments, when compared to source rocks with middle （0.5%-2.0%） and low （less than 0.5%） TOC contents, which indicates that only source rocks with high TOC contents have the capacity to form large oil fields. Source rocks with low TOC content do not generate large hydrocarbon accumulations even if they are very thick. （3） In the process of geological evolution, the TOC content and the capability of hydrocarbon generation and expulsion for source rocks are changing continuously. Correspondingly, the evaluations of source rock and resources should be dynamic.