摘要
深部煤层封存CO_(2)过程中,注入的超临界CO_(2)随着运移距离的增加压力逐渐降低而转变为气态CO_(2),这种在煤体中发生相态变化的CO_(2)被称为复合相态CO_(2)。复合相态CO_(2)在煤中的压力分布特征及渗透率是影响煤层封存效果的重要因素。传统的达西渗透率以假设气体压力是线性分布为前提。然而,复合相态CO_(2)物理性质复杂,煤体内孔隙压力线性分布的假设可能不再适用。在?100 mm×200 mm的圆柱形无烟煤试件上,研究了不同温度(40、55、70、85℃)和轴压/围压(25、35、45 MPa)条件下,复合相态CO_(2)压力分布特征及渗透率演化规律。结果表明:(1)煤体内部复合相态CO_(2)压力呈先缓后急的非线性降低趋势。实际平均孔隙压力为注入压力的0.6~0.7倍,高于传统的达西渗透率的线性平均假设值。(2)基于修正的平均孔隙压力计算得到的复合相态CO_(2)渗透率值与传统达西定律计算值之间的差值随着轴压/围压和温度的升高逐渐减小至20%以下。(3)在煤体热膨胀、CO_(2)解吸及黏度的综合影响下,复合相态CO_(2)渗透率随着温度呈先降低后增大的变化趋势。(4)当超临界CO_(2)注入时,随着孔隙压力的降低,内部渗透率呈U形变化,最小值出现在CO_(2)相变区。气态CO_(2)渗透率随着孔隙压力的升高而降低,而超临界CO_(2)渗透率随着孔隙压力的升高而增大,这是吸附膨胀与有效应力共同作用的结果。
In the process of CO_(2) sequestration in deep coal seam,the pressure of injected supercritical CO_(2) gradually decreases with the increase of migration distance,and it turns into gaseous state.This kind of CO_(2) with phase change in coal is called mixed-phase CO_(2).The pressure distribution characteristics and permeability of mixed-phase CO_(2) in coal are important factors affecting the sealing effect.The traditional gas permeability is based on the assumption of linear distribution of gas pressure.However,the physical properties of CO_(2) in complex phase state are complicated,and the assumption of linear distribution of pore pressure may no longer be applicable.In this paper,the pressure evolution characteristics of mixed-phase CO_(2) were studied onø100 mm×200 mm anthracite raw coal sample at different temperatures(40,55,70,85℃)and confining pressures(25,35,45 MPa).The results showed as follows:①the mixed-phase CO_(2) pressure in coal showed a nonlinear decreasing trend of first slow and then sharp.The actual average pore pressure is about 0.6-0.7 times of the injection pressure.②The difference between the permeability of mixed-phase CO_(2) calculated based on the modi-fied average pore pressure and that calculated by the traditional Darcy’s law gradually decreases to below 20%with the in-crease of confining pressure and temperature.③Under the comprehensive influence of coal thermal expansion,CO_(2) de-sorption and viscosity,the mixed-phase CO_(2) permeability decreases first and then increases with temperature.④When su-percritical CO_(2) is injected,with the decrease of pore pressure,the internal permeability changes in a U shape,and the min-imum value appears in the CO_(2) phase transition zone.The permeability of gaseous CO_(2) decreases with the increase of pore pressure,while the permeability of supercritical CO_(2) increases with the increase of pore pressure,which is the result of ad-sorption expansion and effective stress.
作者
姚宏波
梁卫国
韦婕
YAO Hongbo;LIANG Weiguo;WEI Jie(College of Energy Engineering,Shanxi College of Technology,Shuozhou 036000,China;Key Laboratory of In-situ Property-improving Mining of Ministry of Education,Taiyuan University of Technology,Taiyuan 030024,China)
出处
《煤炭学报》
北大核心
2025年第7期3566-3578,共13页
Journal of China Coal Society
基金
国家自然科学基金面上资助项目(51874206)
山西工学院高层次人才科研启动费资助项目。
作者简介
姚宏波(1992-),男,山西朔州人,讲师,博士。E-mail:1965614705@qq.com;通讯作者:梁卫国(1972-),男,山西盂县人,教授,博士生导师。E-mail:liangweiguo@tyut.edu.cn。
