基于分段涂层TDR探针的含水合物多孔介质电学参数测量仿真研究

Numerical study on electrical parameter measurement of hydrate-bearing porous media based on segmentally-coated TDR probe

摘要:

针对海洋沉积物中天然气水合物饱和度评价需求，提出了基于分段涂层TDR探针的沉积物介电常数和电导率同步测量新方法。针对无涂层探针、全涂层探针以及分段涂层探针分别建立了模拟TDR测量响应的有限元数值模型，仿真研究了涂层参数对介电常数和电导率测量性能的影响规律，继而应用于含水合物多孔介质的测量并对误差进行了分析与校正。研究结果表明：探针涂层的厚度和介电常数直接影响采集电压信号的衰减程度，因此需根据被测介质的电学性质对其进行优化设计；在涂层厚度和介电常数已确定的条件下，通过改变涂层间隙长度可以调节探针所适用的电导率测量范围；当测量非均匀介质时，可以通过增加涂层间隙的个数来提高电导率测量的准确度；采用分段涂层探针测量含水合物多孔介质的介电常数和电导率时，需要对涂层引起的误差进行校正。

Abstract:

To meet the requirement of evaluating the saturation of natural gas hydrate in marine sediments, a new method based on segmentally-coated TDR probe was proposed for simultaneous measurement of the dielectric constant and conductivity of sediments. Finite element models were established for uncoated probe, fully-coated probe and segmentally-coated probe, respectively, to simulate the TDR measurement responses. The influences of coating parameters on the measurement performance of dielectric constant and conductivity were investigated numerically. The segmentally-coated TDR probe was then applied to the measurement of hydrate-bearing porous media and the measurement errors were analyzed and corrected. It has been shown that: the thickness and dielectric constant of the probe coating directly affect the attenuation of the collected voltage signal, thus it is necessary to optimize the design according to the electrical properties of the measured medium; under the condition that the coating thickness and dielectric constant are determined, the conductivity measurement range of the probe can be adjusted by varying the gap length of segmented coatings; for the measurement of inhomogeneous media, the accuracy of conductivity measurement can be improved by increasing the number of coating gaps; for the measurement of porous media containing hydrates with segmentally-coated TDR probe, it is necessary to correct the errors induced by the coating.