石英砂中甲烷水合物渗透率实验与模型验证

多孔介质渗透率是影响天然气水合物开采的重要物理参数,目前研究该参数所采用的测试手段和多孔介质差别很大,没有形成较为公认的实验手段和测量结果。为此,研制了含甲烷水合物多孔介质渗透率一维测试装置,利用该装置合成甲烷水合物,并在稳定流态条件下测量流入液态水的流体流量和压差;基于达西定律的基本原理,采用稳态法注水计算了30~40目石英砂中甲烷水合物体系的渗透率。结果表明:(1)该装置可以在稳定压力、温度的条件下,获得稳定流体流量和压差,满足达西定律的基本条件,进而计算出渗透率;(2)该装置可在渗透率试验中有效控制甲烷水合物饱和度,保证了含甲烷水合物石英砂渗透率测量的可靠性和可重复性;(3)甲烷水合物晶体在孔隙中心形成并逐渐生长,占据孔隙空间并阻碍流动通道,液相有效渗透率随甲烷水合物饱和度的增加而迅速降低;(4)Masuda模型、Dai模型和Li模型渗透率参数值分别为13.0、7.0和4.0时,其计算的渗透率与实验结果吻合良好。结论认为,该研究成果为含甲烷水合物的多孔介质中流体渗透率的量化,提供了实验数据和理论计算依据。

The permeability experiment on the methane hydrate in quartz sands and its model verification

The permeability of porous media is an important physical parameter that affects the exploitation of natural gas hydrate. At present, however, the measurement methods and porous media used for investigating the permeability are so different that neither well-recognized experiment methods nor measurement results are available yet. In this paper, a one-dimensional test apparatus was developed to measure the permeability of porous media with methane hydrate. By virtue of this apparatus, methane hydrate was generated and the flow rate and pressure difference of inflow liquid water were measured in a stable flow pattern. Then, based on the basic principle of the Darcy's Law, the permeability of 30–40 mesh quartz sands with a methane hydrate system was calculated using steady-state water injection. And the experimental results were obtained. First, this apparatus can provide the flow rates and pressure differences of stable fluid under constant pressures and temperatures, so it satisfies the basic conditions of the Darcy's Law and consequently the permeability is calculated. Second, with this apparatus, the methane hydrate saturation in permeability experiments can be controlled effectively, so that the reliability and repeatability of permeability measurement of methane hydrate bearing quartz sands are ensured. Third, methane hydrate crystals are formed and gradually grow in the pore center, occupying the pore space and blocking the flow channel. And the liquid effective permeability decreases sharply with the increase of methane hydrate saturation. Fourth, the permeability calculated by the Masuda, Dai and Li models is 13.0, 7.0 and 4.0, respectively and the calculated values are in accordance with the experimental results. These research results provide experimental data and a theoretical calculation basis for the quantification of fluid permeability of methane hydrate bearing porous media.