温度对油页岩热解-力学-渗流特性的影响研究

Study on the Effect of Temperature on the Pyrolysis-Mechanics-Seepage Characteristics of Oil Shale

为了得到油页岩热解化学结构、渗流特性以及力学特征对温度的响应规律,通过傅里叶红外光谱(FTIR)对不同温度作用下油页岩内部官能团的结构演变进行定性描述和定量分析,结合电子万能试验机和高温三轴渗透测试系统分别研究温度对油页岩强度和渗透率的影响规律;同时与其它地区油页岩的热解、渗流与力学特性进行对比研究。结果显示:油页岩内部含有脂肪族化合物、芳香族化合物、含氧官能团和硅酸盐。随着热解温度的升高,脂肪族化合物的C—H键首先发生断裂,高温下C=C也会发生断裂。此外,C—O和Si—O等官能团的特征峰强度也出现了连续的波动。油页岩的抗压强度会逐渐降低,温度从300℃到500℃,抗压强度降低速率很快。当温度处于20℃~400℃之间时,应力约束状态下油页岩渗透率的量级较小,最高仅为10^(-5)μm^(2),当温度高于400℃时,油页岩渗透率较大;同时,渗透率几乎随着孔隙压力的增大而线性减小,归因于气体滑脱效应、吸附效应以及有效应力的共同作用。与其他地区油页岩的热解、渗流与力学特性进行了对比研究,发现不同地区油页岩升温过程中表现出的热解特性演变规律较为一致,而力学强度和渗透率结果差异较大,认为主要是有机质含量以及成熟度的影响。

In order to obtain the response law of pyrolytic chemical structure,seepage characteristics,and mechanical characteristics of oil shale to temperature,the structural evolution of functional groups in oil shale under different temperatures was qualitatively described and quantitatively analyzed by Fourier infrared spectroscopy(FTIR).Electronic universal testing and high-temperature triaxial penetration test were combined to reveal,the influence law of temperature on oil shale strength and permeability.At the same time,the pyrolysis,seepage,and mechanical properties of oil shale in other areas were compared.The results show that:The oil shale contains aliphatic compounds,aromatic compounds,oxygen-containing functional groups,and silicates.With the increase of pyrolysis temperature,the C—H bond of aliphatic compounds breaks first,and C=C breaks at high temperature.In addition,continuous fluctuations were also observed in the characteristic band intensities of functional groups such as C—O and Si—O.The compressive strength of oil shale gradually decreases,especially at a rapid rate from 300℃to 500℃.When the temperature is between 20℃and 400℃,the magnitude of the oil shale permeability in the stress-constrained state is small,and the highest is only 10^(-5)μm^(2).When the temperature is higher than 400℃,the oil shale permeability is larger.At the same time,the permeability decreases almost linearly with the increase of pore pressure,owing to the combined effect of gas slippage effect,adsorption effect,and effective stress.From the comparison with the pyrolysis,percolation,and mechanical properties of oil shale in other areas,it is seen that the evolution law of the pyrolysis characteristic of oil shale in different areas is relatively identical,while the mechanical strength and permeability results are quite different.It is considered that the main factors are organic matter content and maturity.