不同饱和度水合物沉积物的三轴加载渗透率试验

水合物沉积层的渗透率是影响天然气水合物开采效率的重要物性参数之一,为了探讨在天然气水合物开发过程中有效体积应力和水合物饱和度变化对含水合物沉积层渗透率的影响规律,选取天然粉砂土作为沉积物骨架,进行了不同饱和度水合物沉积物的三轴加载渗透率试验。结果表明:(1)当水合物饱和度恒定时,水合物沉积物的渗透率与有效体积应力呈负指数曲线变化规律,且曲线的斜率随着有效体积应力的增加由大变小;(2)在一定的有效体积应力条件下,水合物沉积物的渗透率随水合物饱和度亦呈指数递减规律变化;(3)有效体积应力和水合物饱和度变化对水合物沉积物渗透率的影响表现为非独立性,即随着前者的增大,后者对水合物沉积物渗透率的影响减弱,而随着后者的增加,前者对水合物沉积物渗透率的影响也减小。由此提出了有效体积应力和水合物饱和度对水合物沉积物渗透率的影响机理,即前者对渗透率的影响在于其对渗流通道的压缩作用,而后者对渗透率的影响则在于水合物对渗流通道的堵塞作用。

Triaxial loading permeability experiments on hydrate bearing sediments with different saturations

The permeability of a natural gas hydrate (NGH) bearing sedimentary reservoir is one of the important physical property parameters that affect the NGH exploitation efficiency. The influencing laws of effective volume stress and NGH saturation on the permeability of NGH bearing sedimentary layers in the process of NGH exploitation was studied through triaxial loading permeability experiments which were carried out on hydrate bearing sediments in different saturations with natural silty soil as the sediment skeleton. And the following test results were obtained. First, when the hydrate saturation is constant, the relationship between the permeability of NGH bearing sediments and the effective volume stress follows the change law of negative exponential curves, and the slope of the curve reduces with the increase of effective volume stress. Second, at a fixed effective volume stress, the relationship between the permeability of NGH bearing sediments and the NGH saturation follows the change law of exponential decline. And third, the effects of effective volume stress and NGH saturation on the permeability of NGH bearing sediments are not independent. That is to say, with the increase of effective volume stress (NGH saturation), the effect of NGH saturation (effective volume stress) on the permeability of NGH bearing sediments reduces. It is concluded that the effect of effective volume stress on the permeability is mainly presented as a compression effect on the seepage channels, and the effect of NGH saturation on the permeability is mainly embodied as an NGH blocking effect on the seepage channels.