煤岩生气热模拟及其对煤层气形成的示踪意义

THERMAL SIMULATION OF GAS GENERATION OF COAL ROCKS AND ITS SIGNIFICANCE TRACING COALBED METHANE FORMATION

煤岩热解模拟实验为认识含煤盆地的成烃演化、煤层气地球化学特征的成因及其资源预测提供了科 学依据。文章在336.8～600℃温度和50MPa压力及20℃/h和2℃/h升温速率条件下,对沁水盆地上古生界煤 岩进行了热解生气模拟实验。结果表明,煤岩热模拟气体产物主要由甲烷(CH4)、C2-5烃类气体和二氧化碳(CO2) 非烃气体组成,氢气(H2)和硫化氢(H2S)含量极低;随着模拟温度的增加,气体产物中甲烷和大部分氢气(H2)的 相对百分含量呈单向增加,二氧化碳表现为单向降低,C2-5烃类气体和硫化氢(H2S)气体先增加后降低;低温速率 有利于甲烷、C2-5气体、氢气和二氧化碳气体的生成,并且它们的形成表现为多阶段性;相同升温速率下二氧化碳 和氢气的相对产率与甲烷的相对产率变化表现为正相关,反映了它们与甲烷同是煤岩热解过程中同步进行的平行 反应产物;相同模拟温度和温速条件下,山西组煤岩比太原组煤岩具有较高的产甲烷和C2-5烃类气体能力,这意味 着在实际的地质环境中,山西组煤岩更有利于煤层气的形成。并且对煤岩生气热模拟实验结果在煤层气形成方面 的示踪意义进行了探讨。

The thermal simulation experiment of coal rock can provide a scientific basis for understanding the evolution of hydrocarbon generation in coal-bearing basin and the geochemical characteristics of coalbed methane and its resource prediction. The thermal simulation experiments of gas generation of the upper Paleozoic coal rock samples collected from Qinshui Basin were carried out at the temperatures of 336. 8 - 600°C, the pressure of 50 MPa and the, temperature-rising rates of 20°C/h and 2°C/h. The results indicated that the gaseous products (relative percent content) were mainly composed of methane, C2-5 hydrocarbon gases and carbon dioxide, the hydrogen content and hydrogen sulfide content being extremely low; along with the increase in simulation temperature, the methane and hydrogen increased but carbon dioxide decreased, and the C2-5 hydrocarbon gases and hydrogen sulfide increased first and decreased after-wards; the low temperature-rising rate was favourable to the generation of methane, C 2-5 hydrocarbon gases, hydrogen and carbon dioxide, their formation being stage; the relative productivity of carbon dioxide or hydrogen was positively correlated with that of methane at the same temperature-rising rate, which reflects that they and the methane were the products of simultaneous parallel reaction in the process of the pyrolysis of coal rockst and the ability of generating methane and C2-5 hydrocarbon gases of Shanxi Formation coal rocks was higher than that of Taiyuan Formation coal rocks at the same simulation temperature and temperaturerising rate, which means that the Shanxi Formation coal rocks were more beneficial to coalbed methane formation in natural conditions. Finally, the significance tracing coalbed methane formation is discussed in the paper according to the experimental results.