热成因煤层气组成与演化模拟

通过封闭体系条件下对成煤原始物质泥炭的热解实验,获取了甲烷、重烃(C2～C5)和二氧化碳在不同成熟度阶段的产率和固体产物镜质体反射率(Ro)数据,分析了模拟煤层气主要组分的相对百分含量及在有机质成熟度演化过程中的变化情况,并探讨了模拟煤层气的组成研究的地质意义。结果发现:随着Ro的增大,煤层气甲烷相对含量呈现上升的趋势,CO2则呈现单向降低的趋势,重烃气体呈先增后降趋势。同时建立了煤从一定成熟度,分别达到最高演化阶段情况下的3种煤层气组分构成模式,尝试应用此模式恢复现今阶段煤层气藏的原始煤层气组分构成情况,并且推测CO2是重要的原始煤层气组分,其产量和后期保存条件的好坏直接影响到对煤层气成熟度的评价。

A simulation study on the composition and evolution of thermogenic coalbed gas

Through a pyrolysis experiment performed on the coal forming peat under a closed system, we obtained the data of vitrinite reflectance (Ro) and the yield rates of gaseous products including methane, carbon dioxide and heavy carbons (C2 C5) at different maturing periods, analyzed the relative percentage of main components in the simulated coalbed methane gas and how they change in the evolution process of organic matter maturity, and discussed the geological value of component analysis of the simulated coalbed methane gas. This simulation study discovered that with the increase of Ro, the relative percentage of the methane presents the increasing trend, that of the CO2 is in one way decreasing trend, and that of the heavy carbon gases first increases and then declines. Meanwhile, three formation models were built of coalbed methane components from certain maturity to the maximum mature stage respectively, by use of these models, we tried to regain the original composition of coalbed methane gas in coalbed methane gas reservoirs at present stage, and assume that CO2 is one of the most important original components in coalbed methane gas, the yield volume and the later period preservation condition of which have a direct effect on the evaluation of coalbed methane gas mature degree.