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通常超临界页岩气密度具有一定特殊性,对研究页岩气分子数量与吸附量间的关系具有重要意义,但目前针对超临界页岩气密度特征鲜有研究。因此,通过建立吸附量与密度间的数学关系,设计超临界页岩气密度测试实验与等温吸附实验,来研究超临界页岩气在自由态和吸附态时的密度特征。结果表明:等温时超临界页岩气自由态密度曲线呈“先凹后凸”形态,增幅先快(<10 MPa)后慢(>10 MPa),增幅拐点压力随温度的增加而增大;等压时密度随温度的升高而减小,高压下(>20 MPa)密度受温度影响较大。超临界页岩气吸附态密度随温度的增大而增大,利用数学方法获取整个测试压力范围内吸附态密度变化特征可知,其密度在低压下较小,高压下远大于同条件时自由态密度。
Generally, the supercritical shale gas density has some particularities. It is of great significance to study the relationship between shale gas molecules and adsorption capacity. However, there are few studies on the gas density characteristics of supercritical shale gas. Therefore, by establishing the mathematical relationship between the adsorption capacity and the density, the density test of supercritical shale gas and the isothermal adsorption experiment are designed to study the density characteristics of supercritical shale gas in free and adsorbed states. The results show that the free-state density curve of supercritical shale gas is in the form of “kyphotic kyphosis” when the isothermal temperature increases rapidly (<10 MPa) and then slows down (> 10 MPa), and the increase inflection point pressure increases with the increase of temperature The density decreases with increasing temperature under isobaric pressure. The density under high pressure (> 20 MPa) is greatly affected by temperature. The density of supercritical shale gas adsorption increases with the increase of temperature. Using the mathematical method to get the characteristics of the adsorption density in the whole test pressure range, the density is lower under low pressure and much higher than the free state at high pressure density.