页岩纳米孔隙气体流动的分子扩散效应研究

Molecular diffusion effect of shale gas flow in nanoscale pores

页岩气多赋存于纳米级的致密页岩孔隙中,孔隙结构大小复杂,具有多尺度的特点。其中,尺度大小由Kn值的大小来评判。当Kn≥10时,孔隙内进行着分子自由扩散运动。分子扩散流主要基于Langmuir等温吸附理论方程,其渗透能力主要由地层压力和孔道共同影响,且随温度、压力、孔隙直径的变化发生动态变化。虽然国内对页岩气成藏机理和资源潜力等方面研究的比较深入,但关于页岩气流动机制和产能递减分析等还有待了解。本文通过研究页岩气的分子扩散效应,可选择更有利的开采方式和增产手段,为页岩气开发和产能评估奠定一定的理论基础。

Shale gas occurs in nanoscale tight shale pore, pore structure size has the charac- teristics of multi-scale.Among them, the scale is evaluated by the value of a Kn.When Kn≥ 10,the molecules free diffuse freely in the pores.Molecular diffusion flow is mainly based on the theory of Langmuir isothermal adsorption equation,its permeability is mainly composed of formation pressure and pore effect,along with the change of temperature,pressure, pore diam- eter change dynamically.Although the domestic research on shale gas accumulation mecha- nism and resource potential and other aspects are in deep,and the shale gas flow mechanism and production decline analysis have yet to be understood.In this paper, through the research of shale gas molecular diffusion effect,we can choose better mining ways and means of pro-duction and lay a certain theoretical basis for shale gas development and capacity assess- ment.