铀对(Ⅱ型)低熟烃源岩生烃演化的影响

摘要

在油、气、煤、铀多种能源矿产形成演化富集成藏(矿)过程中,有机-无机相互作用是普遍存在的,在有机质的强大吸附作用及其所提供的还原环境为铀的富集成矿起促进作用的同时,铀也改变了烃源岩的生烃演化进程.本文在Ⅱ型低熟烃源岩中加入碳酸铀酰溶液的条件下进行了生烃模拟实验,对比无铀-加铀样品生烃模拟实验产物的相关参数,以探讨油气生成过程中无机铀所起的作用.从实验结果可以看出,铀可以使产物中不饱和烃向饱和烃转化;促进长链烃的裂解,促进低分子量烃类的产生,从而使CH4的含量提高,使生成的烃类的干气化程度增加.铀可以在低温阶段促进有机质的成熟度,降低烃源岩的生烃门限,使低熟烃源岩早期生成烃类;同时在高温阶段阻止有机质过度成熟,利于所生成烃的保存.因而铀可能是未熟—低熟油气生成可能的无机促进因素之一.%Organic-inorganic interaction is ubiquitous in the process of formation, evolution, concentration and accumulation of multi-energy resources of oil, gas, coal and uranium. Uranium also alters the process of hydrocarbon generation and evolution of hydrocarbon source rocks while that organic matter accelerates concentration and mineralization of uranium by the strong adsorption and reduction environment from the organic matter. The study carried out simulation experiment of hydrocarbon generation by adding uranium (UO2CO3 solution) into hydrocarbon source rock containing kerogen type II, and compared the relevant parameters obtained from experiments, thus exploring the effect of inorganic uranium over the hydrocarbon generation. Experiment results show that uranium can facilitate the conversion of unsaturated hydrocarbons into saturated hydrocarbons, promote the breaking of long-chain hydrocarbons and generation of the low molecular weight hydrocarbons,resulting in increase of CH4 content and improvement of dry gasification degree. Uranium can promote the maturity of organic matters and reduce the threshold values of hydrocarbon generation, thus speeding up the hydrocarbon generation from immature hydrocarbon source rocks at low temperature. Meanwhile, it can delay the over mature of organic matters, which is conducive to preservation of hydrocarbons under the condition of high temperature. Therefore, uranium is likely the inorganic factor which accelerates generation of immature hydrocarbon.