College of Safety Science and Engineering, Xi’an University of Science and Technology
Key Laboratory of Western Mine Exploitation and Hazard Prevention, Ministry of Education

基于巨正则系综蒙特卡洛(GCMC)和分子动力学(MD)方法，构建了固(煤)−气(CH4)−液(表面活性剂)三相作用的体系模型，从吸附构型、吸附量、相互作用能、相对浓度分布和扩散系数等方面，探讨了纳米颗粒分别复合阳离子表面活性剂CTAB、阴离子表面活性剂SDBS和非离子表面活性剂VAEO8对CH4吸附/解吸及扩散的影响规律。结果表明：表面活性剂和纳米颗粒在润湿效应及静电力作用下渗吸进入孔隙中占据煤表面CH4的吸附位点，造成煤基质处CH4相对浓度降低，而孔隙中游离态CH4增多。无纳米颗粒时，阴离子表面活性剂SDBS增强煤体亲水性，促进CH4解吸效果最好；而阳离子表面活性剂CTAB和非离子表面活性剂VAEO8增强煤体疏水性，导致CH4解吸能力变弱。纳米颗粒和表面活性剂具有协同降低固−液界面张力的作用，纳米颗粒复合表面活性剂促进CH4的解吸效果优于无纳米颗粒时相应的表面活性剂促进CH4的解吸效果。加入纳米颗粒后，煤体系中静电力及相互作用能均升高。原煤体系中CH4扩散系数 > 表面活性剂煤体系中CH4扩散系数 > 纳米颗粒复合表面活性剂煤体系中CH4扩散系数。从微观角度阐明了纳米颗粒复合不同类型表面活性剂对煤中CH4吸附和扩散的影响机制，研究为优化压裂液体系提高煤层气采收率提供了一定的理论依据。

A solid (coal) - gas (CH4) - liquid (surfactant) three-phase interaction system model is established based on the Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) methods. The effects of the nanoparticle composite cationic surfactant CTAB, anionic surfactant SDBS and nonionic surfactant VAEO8 on CH4 adsorption/desorption and diffusion in coal are investigated from the aspects of adsorption configuration, adsorption amount, interaction energy, relative concentration distribution and diffusion coefficient. The results show that the surfactants and nanoparticles are imbibed into coal pores, occupying the adsorption sites of CH4 on the coal surface under the wetting effect and electrostatic action. In the absence of nanoparticles, the anionic surfactant SDBS enhances the hydrophilicity of coal and has the best effect on promoting CH4 desorption. Whereas the cationic surfactant CTAB and nonionic surfactant VAEO8 enhance the hydrophobicity of coal, resulting in a weaker CH4 desorption capacity. Nanoparticles and surfactants act synergistically in reducing solid-liquid interfacial tension, so nanoparticle composite surfactants are better than surfactants without nanoparticles in promoting CH4 desorption. After adding nanoparticles, the electrostatic force and interaction energy of the system are all increased. The CH4 diffusion coefficient in the raw coal system > the CH4 diffusion coefficient in surfactant coal system > the CH4 diffusion coefficient in coal system with nanoparticles composite surfactant. Overall, the mechanism of the influence of nanoparticle composite different types of surfactants on CH4 adsorption and diffusion is clarified from the microscopic point of view, and the study provides a theoretical basis for optimizing fracturing fluid system to improve coalbed methane recovery.

国家自然科学基金资助项目(11802231，51974239，52174205)

石钰，阳梦，李树刚，等. 纳米颗粒复合表面活性剂对煤中CH4吸附/解吸和扩散的影响[J]. 煤炭学报，2023，48(8)：3116−3127.

SHI Yu，YANG Meng，LI Shugang，et al. Effects of nanoparticle composite surfactants on the adsorption/desorption and diffusion of ch4 in coal[J]. Journal of China Coal Society，2023，48(8)：3116−3127.