Investigation on the Multiparameter of Hydrate-Bearing Sands Using Nano-Focus X-Ray Computed Tomography
Investigation on the Multiparameter of Hydrate-Bearing Sands Using Nano-Focus X-Ray Computed Tomography
复制标题
利用纳米焦点 X 射线计算机断层扫描研究含水合物砂的多参数
DOI：
10.1029/2018jb015849
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发表时间：
2019-03-01
影响因子：
3.9
通讯作者：
Meng, Qingguo
中科院分区：
文献类型：
--
作者：
Li, Chengfeng;Liu, Changling;Meng, Qingguo
在这项研究中，利用纳米焦点X射线计算机层析成像(X-CT)在孔隙尺度上观察了甲烷水合物在砂岩中的形成，并量化了含水合物砂岩的水合物饱和度、孔隙结构参数和渗透率。发展了一种新的分析技术，以提高水合物边界的识别能力。在孔隙中观察到三种水合物聚集习性(即漂浮、接触和胶结)。在没有甲烷气泡的情况下，随着水合物饱和度的增加，水合物分布从漂浮到接触再到胶结。相反，在有甲烷气泡的孔隙中只出现接触和胶结的分布模式。在三维图像表面提取和缺陷检测的基础上，研究了气水水合物的分布和孔隙结构特征。结果表明，随着水合物在孔隙中的积累，孔隙率、最大孔体积和最大直径减小。而最大孔面、总孔数和大孔数(>；100体素)逐渐增加，直至水合物饱和度达到35%，然后迅速下降。孔隙结构参数反映了水合物和水在孔隙尺度上的详细变化。基于X射线CT数字图像，采用不可压缩的Navier-Stokes方程计算了含水合物砂岩的绝对渗透率。结果表明，水合物的微观分布对渗透率计算有很大影响。通过模拟得到的流体流线用于跟踪输水路径。
In this study, a nano-focus X-ray computed tomography (X-CT) is used to observe the formation of methane hydrate in sands on pore scale and to quantify hydrate saturation, pore structure parameters, and permeability of hydrate-bearing sands. A new analytical technique is developed to improve the identification of water-hydrate boundary. Three hydrate accumulation habits (i.e., floating, contacting, and cementing) in pore spaces are observed. When there is no methane bubble, hydrate distribution evolves from floating to contacting and then to cementing as hydrate saturation increases. In contrast, only contacting and cementing distribution patterns appear in the pores with methane bubbles. Based on the surface extraction and defect detection from 3-D images, both the gas/water/hydrate distributions and the pore structure characteristics are investigated. The results show that the porosity, the maximal pore volume, and maximal diameter decrease as hydrates accumulate in the pores. However, the maximal pore surface, the total pore number, and the large pores (>100 voxels) number increase gradually until the hydrate saturation reaches 35%, when they turn to decrease rapidly. The pore structure parameters show detailed changes of hydrate and water on pore scale. The incompressible Navier-Stokes equations are used to calculate absolute permeability of hydrate-bearing sands based on X-ray computed tomography digital images. It indicates that the microdistribution of the hydrate has a significant effect on the permeability calculation. The fluid streamlines obtained through simulation are used to track the water transport paths.