海洋直流电阻率法电测深装置响应分析

Response analysis of marine DC resistivity electrical sounding with different configurations

海洋直流电阻率法是海洋电磁勘探的重要方法之一,已经在许多海底资源探测中得到实践.本文推导了供电电极位于海底时四层水平层状介质电位表达式和视电阻率计算公式.根据快速汉克尔滤波法,计算含有贝塞尔函数的积分,编写MATLAB程序计算水平层海洋地电模型电位和视电阻率,探究海水深度和沉积层厚度对于视电阻率曲线的影响.研究表明海水越深,海平面对视电阻率曲线影响越小;沉积层厚度越薄,视电阻率异常响应越明显.建立了各种地电模型,并用二极装置、三极装置、偶极装置进行探测,对不同装置获得的视电阻率曲线进行分析,得出偶极装置对于滨海低阻层和高阻层异常反应能力较强.分析了低阻环境下不同装置在不同供电电流下接收端的电位信号强度,研究发现供电电流强度仅在收发距较小时对接收端电位信号强度影响较大,且供电电流越大电位信号强度越高.本文的结果为深入研究海洋直流电阻率法装置类型应用于海底资源探测奠定了基础.

The marine DC resistivity method is one of the important methods of marine electromagnetic exploration and has been applied in many seabed resource explorations. In this paper, the expression of potential and the apparent resistivity of the four-layer horizontal layered medium are derived when the power supply electrodes are located in seawater. According to the fast Hankel filtering method, the integral containing the Bessel function is calculated. The potential and apparent resistivity of horizontal layer marine geoelectric models are calculated through MATLAB codes, and the influence of seawater depth and sediment layer thickness on the apparent resistivity curve are studied. Research results show that the deeper the seawater, the smaller the effect of sea level on the apparent resistivity curves;the thinner the sediment layer, the more obvious the abnormal response of apparent resistivity. Various geoelectric models have been established, which are detected with configurations of pole-pole, pole-dipole and dipole-dipole, analysis of the apparent resistivity curve of different configurations shows that the dipole-dipole configuration has the strongest abnormal response to offshore low-resistance and high-resistance layers. The potential signal strength of different configurations under different supply currents in a low-resistance environment was analyzed, and it was found that the supply current strength only has a greater impact on the potential signal strength at the receiver when the transceiver distance is small, and the higher the supply current is, the higher the potential signal strength is.The results of this paper lay a foundation for further research on the application of marine DC resistivity devices to seabed resource detection.