有机质纳米孔隙吸附页岩气的分子模拟

发布时间：2018-03-28 15:30

本文选题：有机质孔隙　切入点：吸附　出处：《天然气地球科学》2017年01期

【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。
[Abstract]:Shale gas is a kind of unconventional oil and gas with great resource potential. With the expansion of shale gas exploration scale, the understanding of shale gas is also deepening. In order to further study the adsorption and microscopic mechanism of CH_4 by nano-pores of shale organic matter, To better understand the occurrence form of shale gas, to use the molecular simulation software Material Studio to build a carbon nanotube model to characterize the organic nano-pores, and to use Monte Carlo method, molecular mechanics, Molecular dynamics simulation of the early Paleozoic (Qiongzhusi formation, Wufeng formation and Longmaxi formation) shale gas in Sichuan Basin and its periphery under the condition of 2~4km, the adsorption and diffusion behavior of organic matter pores to Ch _ 4 and CO _ 2 are simulated. The adsorption of organic matter to Ch _ 4C _ 2O _ 2 is physical adsorption, and the buried depth 2km is the best storage depth of shale gas. The data of mixed adsorption show that it is reasonable and feasible to inject CO_2 to replace CH_4 to exploit shale gas. The relative density of CHS _ 4 and CO_2 along the normal direction of the inner wall of the pore shows a symmetrical distribution trend when the depth is about 4km, and there is obvious phenomenon of adsorption and stratification. The formation of the second and third aggregates may be mainly affected by the pressure. On the whole, the relative density of CH4 and CO_2 in Z direction decreases with the increase of temperature and pressure. The self-diffusion coefficients of CH_4 and CO_2 increase with the increase of buried depth, which is consistent with the change of adsorption heat and adsorption capacity.
【作者单位】：西南石油大学油气藏地质与开发工程国家重点实验室;西南石油大学地球科学与技术学院;青海油田勘探开发研究院;
【分类号】：TE132.2

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