高温及三轴应力条件下抚顺油页岩渗透规律试验研究

Experimental Study on the Law with Permeability of Fushun Oil Shale Under High Temperature and Triaxial Stresses

利用自主研发的WYF-I型高温高压热解反应装置及基于岩芯柱脉冲衰减法研制的Smart perm Ⅲ型气体渗透率测量仪,对抚顺西露天矿油页岩试件进行20～600℃范围内的热解试验,研究不同热解温度和应力条件下的油页岩渗透率变化规律。试验结果表明,油页岩热解过程呈明显阶段性变化。第一阶段:20～300℃,油页岩失重率和孔隙率变化较小,渗透率随热解温度变化不明显,体积应力对渗透率影响较小。第二阶段:300～400℃,油页岩失重率和孔隙率迅速增加,试件渗透率增加了24.3～92.4倍;体积应力对渗透率影响明显,当体积应力由13MPa增加至39MPa后,孔隙压力1MPa下的渗透率降低了22.23%.第三阶段:400～600℃,失重率和孔隙率进一步增加,但增速减缓,温度对渗透率影响减弱,400℃增加至600℃时油页岩渗透率仅增加了1.69～2.49倍;体积应力对渗透率影响增强,体积应力增加导致渗透率下降了32.84%～41.79%.研究结果对原位热解开采油页岩时热解温度的合理选取有一定的参考价值。

With the independently developed WYF-I high-temperature and high-pressure pyrolysis reaction device and the Smart perm Ⅲ gas permeability measurement instrument which is developed based on the core column pulse attenuation method, the pyrolysis process and permeability of oil shale samples from Fushun West Open-pit were investigated at a temperature of 20~600 ℃. According to the change of oil shale permeability, the pyrolysis process of the oil shale shows significant phase changes. Stage Ⅰ: 20~300 ℃, the weight loss rate and porosity change of the oil shale are rare, the variation of the permeability with the pyrolysis temperature is not obvious, and the volume stress has little effect on permeability. Stage Ⅱ: 300~400 ℃, the weight loss rate and porosity of the oil shale increase rapidly, and the permeability of the sample increases by 24.3~92.4 times;the effect of the volumetric stress on the permeability is obvious,when the volumetric stress increases from 13 MPa to 39 MPa, the permeability of the sample at pore pressure 1 MPa decreases by 22.23%. Stage Ⅲ: 400~600 ℃, the weight loss rate and porosity further increase, but the growth rate slows down, the effect of temperature on permeability is weakened, when the pyrolysis temperature increases from 400 ℃ to 600 ℃, the permeability of oil shale increases only by 1.69~2.49 times;the effect of volume stress on permeability increases,with the volume stress increases, the permeability decreases by 32.84~41.79%. This study is expected to provide some guidelines for the selection of a reasonable pyrolysis temperature in the process of in situ pyrolysis of oil shale.