含甲烷水合物沉积物电–声响应特性联合探测:装置开发与实验研究

Joint Detection of the Electrical and Acoustic Response Characteristics of Methane Hydrate Bearing Sediments: Apparatus Development and Experimental Study

为了满足开展天然气水合物模拟实验、测试电学和声学特性参数以及建立特性参数与含水合物饱和度之间关系的需求,开发了一套电–声响应特性联合探测实验装置,以海沙模拟松散沉积物开展了甲烷水合物生成和分解模拟实验,联合探测了电学和声学参数,分析了被测体系的电学和声学响应特性。研究表明:(1)通过电–声响应联合探测实验装置能够同步获取宽频率范围电学阻抗谱和超声波接收信号波形;(2)通过设计电声复合传感器及其阵列式排布方式和"分时轮流"工作模式能够获取电学和声学参数的空间分布信息;(3)基于所提出的波动百分比和相关系数指标对不同频率阻抗模值进行评价所获得的100 k Hz阻抗模值随含水合物饱和度的增加先减小后增大,经过有效压力校正后的超声波接收信号波动幅度值随含水合物饱和度的增加而升高;(4)上述两者分别可以作为分析和建立与含水合物饱和度之间关系的电学和声学有效特征参数。所开发的实验装置为将来开展含水合物复杂沉积物的模拟实验与测试工作提供了必要条件,所得到的电学和声学有效特征参数为含水合物饱和度计算模型的建立奠定了基础。

To meet the needs of conducting natural gas hydrate simulation experiments,detecting electrical and acoustic parameters and establishing the relationship between the parameters and hydrate saturation,a joint electrical-acoustic detection apparatus was developed.A series of methane hydrate formation and decomposition simulation experiments was carried out with electrical and acoustic parameters detected,and the electrical and acoustic response characteristics were analyzed and discussed.It has been demonstrated that:(1)the electrical impedance spectra with a wide range of frequencies and ultrasonic signal waveforms can be obtained synchronously by utilizing the joint electrical-acoustic detection apparatus;(2)the space distribution information of electrical and acoustic parameters can be obtained through the designed electrical-acoustic compound sensors,array-arrangement scheme and the‘time-sharing and rotating’working mode of sensors;(3)the impedance modulus with a frequency of 100 kHz selected based on the proposed evaluation specifications,i.e.the fluctuation percentage and correlation coefficient,decreases first and then increases with an increasing hydrate saturation,and the fluctuation amplitude of the received ultrasonic signal corrected by effective pressure increases with the increase of hydrate saturation;(4)the 100 kHz impedance modulus and corrected fluctuation amplitude of ultrasonic signal can be treated as effective electrical and acoustic characteristic parameters,respectively,for analyzing and establishing the relationships between the hydrate saturation and them.The apparatus developed in this work provides a necessary condition for future simulation experiments and parameter detection of hydrate-bearing complex sediments,and the proposed effective electrical and acoustic characteristic parameters provide a basis for establishing hydrate saturation calculation models.