高价Mn氧化物介导下轻烃热化学氧化的模拟实验研究

Simulated experimental study on thermochemical oxidation of light hydrocarbons mediated by high-valent Mn oxides

研究烃类的热化学氧化对分析油气保存条件和探讨深部碳循环机制都具有重要意义。本文以轻烃-MnO2-水体系为例,基于熔融石英毛细硅管和拉曼光谱分析技术的在线观测热液实验技术,对油气藏中常见的轻烃热化学氧化反应的发生温度和变化规律进行了研究。结果表明,轻烃热化学氧化温度随烃类碳数的增大而降低,从丁烷到十三烷,其反应发生温度从125℃降到约100℃,与热化学氧化反应的吉布斯自由能变化顺序一致。表明烃类热化学氧化需要的温度条件并不苛刻,在3000 m以下埋深且含有氧化性地层的沉积盆地中即可发生。实验结果与准噶尔盆地地质实例基本相符,油气充注中心区优先氧化高碳数烃类,远离充注中心缺乏液态烃的井区发生甲烷等轻烃氧化,烃类的热氧化过程受烃类氧化顺序和油气充注时空差异性两大因素制约。

Studying the thermochemical oxidation of hydrocarbons is of great significance for analyzing the hydrocarbon preservation condition and exploring the deep carbon cycle mechanism.This study took the light hydrocarbon-manganese dioxide-water system as an example to investigate the initiation temperature of common thermochemical oxidation reactions of light hydrocarbons in oil and gas reservoirs and its changing rule by using the on-line observational hydrothermal experimental technique based on fused silica capillary silica tubes and Raman spectroscopy analysis technology.Results showed that the initiation temperature of thermochemical oxidation of light hydrocarbons decreases with increasing carbon number of hydrocarbons,from butane to tridecane,the reaction occurring temperature of which decreases from 125℃to about 100℃,which is consistent with the change order of Gibbs free energy in thermochemical oxidation reactions.We also found that the thermochemical oxidation of hydrocarbons requires moderate temperature conditions and can occur in sedimentary basins as deep as 3000 m.These experimental findings are consistent with the geological examples observed in the Junggar Basin.High-carbon hydrocarbons are preferentially oxidized in the center of oil and gas charging area,whereas light hydrocarbons such as methane are oxidized in wells that lack liquid hydrocarbons t and are far away from charge centers.This suggests that the oxidation sequence of hydrocarbons and the spatiotemporal difference are two factors that influence the actual process and constrain oil and gas charging.