超临界CO_2增透煤热流固耦合模型与数值模拟  

Thermo-fluid-solid Coupling Model and Numerical Simulation of Supercritical CO_2 Antireflection Coal

作　　者：郝志勇[1] 岳立新[1] HAO Zhiyong;YUE Lixin(College of Mechanical Eng.,Liaoning Technical Univ.,Fuxin 123000,China)

机构地区：[1]辽宁工程技术大学机械工程学院,辽宁阜新123000

出　　处：《工程科学与技术》2018年第4期228-236,共9页Advanced Engineering Sciences

基　　金：国家自然科学基金资助项目(51404135;51674133)

摘　　要：针对中国绝大多数高瓦斯煤层渗透性低以及低渗透煤层强化抽采瓦斯效果不理想的现状,结合超临界CO_2强扩散和溶解增透孔隙介质等独特优点,依据超临界CO_2作用后煤微观孔裂隙的演化特征,得到煤微观孔隙率和渗透率演化方程,根据孔隙率的变化确定损伤变量,考虑体积应力、温度、孔隙压力及超临界CO_2溶解增透作用的影响,建立超临界CO_2作用后煤的热流固耦合力学模型,利用ABAQUS软件提供的场变量子程序,结合PYTHON脚本和子程序二次开发功能,实现低渗透煤层注超临界CO_2增透规律数值模拟。结果显示:超临界CO_2注入后,注气孔周围煤体内体积应力、温度及孔隙压力变化明显,随着距注气孔距离的增加,影响程度逐渐减弱,并趋于稳定;经超临界CO_2作用后,注气孔周围煤体内不断萌生新的孔裂隙,并与原有的孔裂隙相互贯通,随注气时间的延长各级孔裂隙不断向煤体纵深演化发展,煤微观孔隙率较注气前提高了2个数量级;超临界CO_2的致裂增透作用引起煤体不同程度的损伤,距注气孔越近,损伤程度越大,损伤增加越快,注气时间越长,损伤增加的幅度越大;煤微观孔裂隙的有效发育为煤层气的扩散渗流提供了更多的运移通道,使煤体渗透系数较注气前提高了3个数量级。In view of the situation that the permeability of the most high gas coal seam is poor and the effect of coalbed methane extraction is not ideal by strengthening extraction in low permeability coal seam, which combines the strong diffusion, dissolution-increasing-permeability on pore medium and other unique advantages of super-critical carbon dioxide. According to the evolution features of coal pore fissure after the action of supercritical carbon dioxide, the micro porosity and permeability evolution equation was gained, the damage variable was ascertained according to the change of the porosity. Thermo-fluid-solid coupling model of coal was built after the action of supercritical carbon dioxide, which considered the effects of volume stress, temperature, pore pressure and the dissolution-increasing-permeability action of supercritical carbon dioxide, field variable subroutine supplied by ABAQUS was used, the PYTHON script and the two development function of subprogram were combined, the increasing-permeability law of numerical simulation is realized in the low permeability coal seam injected by supercritical carbon dioxide. The results showed that after the injection of supercritical carbon dioxide, the volume stress, temperature and pore pressure around the injection-gas hole changed obviously, with the increase of the distance from the injection hole, the influence degree gradually weakened and tended to be stable.New pore fissures sprouted constantly and interconnected with the original hole fissures in the coal around the injection hole, the crevice at all levels evolved constantly to the depth of coal, the micro-porosity was increased by two orders of magnitude than that before injecting the gas. The fracturing and increasing permeability action of supercritical CO2, the coal was damaged with different degrees, the closer the injection-gas hole is, the greater the degree of damage is and the faster the damage increases, the longer the gas injection, the greater the increase in damage. Effective development

关 键 词：超临界CO2 渗透系数 孔隙率 增透作用 

分 类 号：TP69[自动化与计算机技术—控制理论与控制工程] TE377[自动化与计算机技术—控制科学与工程]