摘要
页岩气是一种资源潜力巨大的非常规油气,随着页岩气勘探规模的不断扩大,对页岩气的认识也不断深入。为进一步研究页岩有机质纳米孔隙对CH_4的吸附作用及微观机理,更好地认识页岩气的赋存形式,利用分子模拟软件Material Studio搭建碳纳米管模型表征有机质纳米孔隙,运用蒙特卡洛方法、分子力学、分子动力学方法模拟四川盆地及其周缘早古生代(筇竹寺组、五峰组及龙马溪组)页岩气普遍埋深2~4km条件下,有机质孔隙对CH_4、CO_2的吸附、扩散行为。研究表明,有机质孔隙对CH_4、CO_2的吸附为物理吸附,埋深2km为页岩气最优储存埋深;其混合吸附的数据显示,注入CO_2置换CH_4开采页岩气具有合理性和可行性,埋深约4km时效果较为理想;CH_4与CO_2沿孔隙内壁法线方向的相对密度呈对称分布趋势,并出现明显的吸附分层现象,且第二聚集层及第三聚集层的形成很可能主要受到压力的影响。整体上,随温压的增加,CH_4与CO_2沿Z方向的相对密度呈较小的下降趋势;而CH_4及CO_2的自扩散系数随埋深的增加而增大,与吸附热及吸附量的变化原因一致。
Shale gas is a kind of unconventional oil-gas resource with tremendous potential.For thorough un- derstanding of the methane adsorption and micromechanism in organic-matter nanopores of the shale and better acquaintances of the occurrence form,graphite slit-pores were set up as a representation of organic- matter nanopores by using Material Studio, and the grand canonical Monte Carlo method, molecular me- chanics and molecular dynamics were used for the simulation of adsorption and diffusion behaviors in or- ganic-matter pores on CH4 and CO2 at the shale gas common burial depth of 2-4km in the Upper Yangtze Plate.The results indicated that the adsorptions of CH4 and CO2 were physical and the optimal storage depth was 2km;The mixed adsorption data showed the rationality of exploit shale gas by injecting CO2 to exchange CH4, and the optimal burial depth was 4km;The relative density of CH4 and CO2 along the nor- mal direction of the pore inwall showed a trend of symmetric distribution and apparent adsorption stratifi- cations appeared.As a whole, the self-diffusion coefficient of CH4 and CO2 increased with the increase of burial depth,and it＇s consistent with the reasons for such changes of adsorption amount and adsorption heat.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2017年第1期146-155,共10页
Natural Gas Geoscience
基金
国家自然科学青年基金(编号:41302123)
博士学科点专项科研基金(编号:20125121130001)联合资助
关键词
有机质孔隙
吸附
扩散
碳纳米管
分子模拟
页岩气
Organic-matter pores
Adsorption
Diffusion
Carbon nanotube
Molecular simulation
Shale gas
