基于TDR的多孔介质中含水/水合物饱和度测量方法仿真研究

Simulation Study on Measurement Method of Water/Hydrate Saturation in Porous Media Based on TDR

为了优化设计时域反射技术(TDR)中的探针结构,建立基于TDR响应的含水/水合物测量模型,利用有限元数值模拟方法建立了TDR测量过程数值仿真模型;分别以空气、不同浓度氯化钠溶液以及不同水合物含量的石英砂为被测介质验证了模型的正确性、研究了被测介质电导率和介电常数对反射波形的影响规律;通过改变被测介质的介电常数来模拟含水/水合物饱和度不同的石英砂,随着石英砂中水合物含量的增加,含水量逐渐降低,表观介电常数随之减小,电磁波传播速度随之以非线性形式增加;与理论值相比较,仿真计算所得到的传播速度最大误差处于5%以内;下一步需要在数值模型中的被测区域中填充各向异性材料来更加真实地模拟含水合物沉积物被测介质。

To optimize the probe structure in time domain reflectometry(TDR)and establish a water/hydrate saturation measurement model based on TDR response,a numerical simulation model of TDR measurement process was established by using the finite element numerical simulation method.The numerical model was verified by using air as the measured medium first.Then the sodium chloride solution of different concentration and quartz sand with different hydrate saturation were used as the measured media,and the influence of the conductivity and dielectric constant of the measured medium on the reflection waveform was studied.The quartz sand with different water/hydrate saturation was simulated by changing the dielectric constant of the measured medium.It has been shown by the numerical data that the apparent dielectric constant decreases with the increase of hydrate saturation in quartz sand,thus propagation speed of electromagnetic wave increases in a nonlinear form,and the maximum error of the propagation speed obtained is within 5% compared with the theoretical values.Filling the tested area with anisotropic materials in the numerical model to simulate the hydrate-bearing sediment more realistically will be the future work.