天然气运移速率的微观物理模拟及其相似性分析——以库车坳陷为例

利用真实砂岩分析评价系统,直接观察了气体在孔隙、喉道内的运移方式,建立了天然气在砂岩孔隙介质中运移速率的统计模型,然后对其进行了相似性分析,形成了天然气在砂岩储层中运移速率的地质模型。制作了库车坳陷19个砂岩模型,通过微观模型获得氮气在砂岩中的运动方式,进而研究了气体在岩石介质中的渗流特点,综合分析了动力梯度、含气饱和度、渗透率等因素对气体渗流速率的影响。研究结果表明,气体在地下的渗流速率与岩石的渗透率、压力梯度、含气饱和度等因素成正比。对实验材料、几何尺寸、运移速率和动力梯度与实际地质条件之间的相似性进行了分析,建立了适用于描述库车坳陷地下天然气运移的速率模型,为进一步描述天然气的运移、聚集特点奠定了基础。

Microscopic physical experiment on gas migration rate in sandstone model and similarity analysis

The migration patterns of gas in pores and throats were observed directly in microscope by means of the true sandstone analysis and evaluation system. A statistical model for analyzing rate of gas migration in porous media of sandstones was established. The geological models for analyzing rate of gas migration in underground sandstone reservoir were finished. Nineteen sandstone models of Kuche Depression were developed. The pattern of nitrogen gas migration in sandstone was obtained by micromodel experiment. The characteristics of gas osmosis flow in porous rock were analyzed. The factors influencing rate of gas osmosis including dynamic gradient, gas saturation and permeability were comprehensively evaluated. It is pointed that the mean flow rate of gas is in direct proportion to permeability, dynamic gradient and gas saturation. The similarities of experimental materials, geometrical dimensions, migration rate and dynamic gradient with the real geological conditions were analyzed, and the model for describing underground migration rate of natural gas was proposed.