中文摘要：

泥页岩以孔隙丰富、孔径细小为特征,纳米孔隙对孔隙流体的局限效应决定了泥页岩中页岩气的赋存形式和扩散性质以及潜在的CO_2处置能力。本文在总结泥质岩石纳米孔隙表征结果的基础上,使用淬火固体密度泛函理论（QSDFT）和分子动力学方法（MD）,研究了泥质岩石中纳米孔隙内流体的密度分布、赋存形式以及活动性。结果表明,孔径较小（如1.0nm）时,因孔壁的束缚效应纳米孔隙内甲烷成单层分布,而当孔径增大至2.0nm时,除孔壁表面多层吸附的甲烷外还出现自由态甲烷。相同条件下,孔径较小的孔内吸附态甲烷密度高于孔径较大的孔内吸附态甲烷密度,有机孔内吸附态甲烷的密度高于无机孔内吸附态甲烷的密度。随着温度、压力（深度）的增大,孔隙表面的局限效应减弱,表面束缚的吸附态甲烷比例减小,自由态甲烷相对增加。

英文摘要：

It has been well known that mudstones and shales are characterized with abundant tiny pores. The occurrence state and diffusion feature of shale gas as well as the CO_2 storage capacity are commonly controlled by confining effects of nano-sized pores in shales. Based on the summary of nano-pore structure characteristics of shales,a study on the density variation,occurrence state,and mobility of pore fluids in nano-pores in shales has been carried out in this paper by using methods of the quenched solid density functional theory（ QSDFT） calculation and molecular dynamics（ MD） simulation. Results show that the methane is distributed as a monolayer or bilayer in nano-pores which are less than 1. 0 nm in size.However,the pore methane occurs as multiple adsorption layers and even free methane in 2. 0 nm sized pores. Under the same conditions,the calculated density of the methane in small nano-pores is higher than that of the methane in relatively big nano-pores,and the density of the methane in the organic pore is higher than that of the methane in the inorganic one.With the increase of temperature and pressure（ i.e.,buried depth）,the confining effects of nano-pores are decreased. This resulted in the decrease of the proportion of confining methane and the increase of the free methane increases in nanopores.