海相成熟干酪根生气潜力评价方法研究

高成熟阶段干酪根热解氢指数（HI）非常低，在热成熟度指标镜质组反射率Ro为2.0%以上的Ⅰ或Ⅱ型有机质，一般都在20 mg/gTOC以下，甚至接近0 mg/gTOC，因此，一般认为这种干酪根生烃能力极低。本文通过对不同成熟阶段的干酪根采用元素分析和热解模拟实验相结合的方法，发现HI指数很低的高过成熟阶段干酪根仍然具有一定的生气能力，生气潜力是HI指数的数倍，如HI指数为12 mg/gTOC的样品，H/C原子比为046，生气能力仍然为65 mg/gTOC，占总生烃能力的15%左右，说明成熟—过成熟有机质HI指数不适合衡量生气潜力。同时发现，干酪根生气能力与H/C原子比具有极好相关性，相关系数达到096，通过回归公式所获得有效生气干酪根H/C原子比下限为026。

Methods of Evaluating the Gas Potential of Marine Mature Kerogen

Kerogen in source rock at the high mature stage usually has a very low hydrogen index (HI),and its Ro value is often more than 2.0% or above,suggesting that it belongs to type I or type II organic matter,which usually contain less than 20 mg/g TOC,even 0 mg/g TOC. Therefore,kerogen of this kind is often regarded as sterile for gas-generating. This paper analyzes kerogens from various mature stages of kerogens by using elemental analysis and pyrolysis simulation test,finding that gas-generating potential is multiple of HI. For example,the sample with TOC of 12 mg/g and H/C atomic ratio of 0.46 still has a gas generating of 65 mg/gTOC,which accounts for 15% of total gas generation in a close system. This fact indicates that the HI of mature or over-matured orangic matters can not be used to evaluate gas-generating potential. Meanwhile,gas generation of kerogen has a good correlation to H/C atomic ratio,with a correlation factor up to 0.96. Calculation by the regression function shows that the minimum H/C atomic ratio for a gas-generating kerogen is 0.26.