井间ERT电极阵列优化及监测实验系统设计与开发

Optimization of Electrode Array for Cross-hole ERT and development of Monitoring Experimental System

摘要:

为了开发用于地层中CO2运移监测的井间ERT系统，研究了ERT电极阵列和工作模式优化设计方法并研制了井间ERT监测模拟实验系统。基于COMSOL平台构建了模拟井间ERT测量响应的有限元数值模型，利用数值模型分析了电极间距和宽度等参数对监测区域电场灵敏度的影响规律以及不同电极阵列工作模式下场域灵敏度的分布特征，确定了井间ERT实验系统中最优的电极参数，即电极间距、宽度与监测范围的比值分别为0.200、0.025，电极阵列的工作模式为AM-BN。在对实验系统进行功能需求分析、总体设计以及上述优化设计的基础上，分别对系统硬件部分和软件部分进行了开发，采用多路切换开关并配合精密电桥仪实现了对电阻抗参数的测量，利用以LabVIEW为平台开发的测控软件实现了对实验系统的自动化控制。以埋放绝缘物体来模拟注入地层CO2的方式开展了实验测试，结果显示测量到的电阻抗数据可以灵敏地反映出监测区域电参数的变化且能够用于定位绝缘物体的位置，从而验证了所开发系统的可用性。所建立的电极阵列优化设计方法以及开发的井间ERT监测模拟实验系统为下一步深入研究基于复电导率参数的CO2饱和度评价模型和开发现场适用的井间ERT监测系统提供了实验平台。

Abstract:

To develop a cross-hole ERT system for monitoring CO2 migration in the formation, an optimization design method of ERT electrode array and working mode was studied, and an experimental system for cross-hole ERT was developed. Based on the COMSOL platform, a finite-element numerical model for simulating the responses of cross-hole ERT measurement was built. The impact of the spacing and axial width of electrodes and the operating mode of electrode arrays on the electric-field sensitivity in the monitoring area were investigated through the numerical model. The optimized parameters of the electrodes were derived. The ratios of the electrode spacing and width to the monitoring range were determined as 0.200 and 0.025, respectively. The AM-BN configuration was chosen as the best operating mode of the electrode array. Based on the functional requirements analysis, overall design and the above optimization design of the experimental system, the hardware and software parts of the system were developed respectively. The measurement of electrical impedance parameters was realized by using a multiplexer switch and precise bridge instrument. The automatic control of the experimental system was realized by using the measurement and control software developed on the platform of LabVIEW. Experimental tests were carried out by embedding insulating objects to simulate the injection of CO2 into formation. The results have shown that the measured electrical impedance data can reflect the changes in electrical parameters in the monitoring area sensitively and can be used to locate the position of the insulating objects. The validity of the developed system was verified through an analysis of the test data. The design method for optimizing the electrode array and cross-hole ERT experimental system provide an experimental platform for an in-depth study of the CO2 saturation-evaluation model based on complex-conductivity parameters and development of cross-hole ERT monitoring systems for field applications.