Development of Sectional Resistivity Image Analysis System and Its Application to Investigation of Fractured Rocks

本研究所开发的仪器由电流发射单元、电压接收单元、电极开关单元和测量单元组成。测量池截面为正方形（11cm × 11cm），周围以1cm的间距布置铂电极。通过数值实验验证了该软件的精度和分辨率。虽然对于大规模的低电阻率异常的结果是令人满意的，它被发现，类似于岩石的导电带被复制为一个更广泛的anomal.The系统首先使用一个合成的样品，模拟与铜板的裂缝进行了测试。该导电目标被明确地定义为低电阻率区，但是如在数值实验中，图像的宽度大于真实宽度。这一结果在一定程度上表明了电位测量固有的分辨率的局限性，但还需要做更多的工作来确定可达到的分辨率。用含裂缝的砂岩进行的实验表明了类似的结果。

The instrument developed in this study consists of the current transmitting unit, the voltage receiving unit, the electrode switch unit, and the measuring cell. The section of the measuring cell is square (11cm by 11cm) and is surrounded by platinum electrodes at a spacing of 1cm.The software developed is based on the finite-element and iterative lest-squares methods. The accuracy and resolution attained by this software was tested through numerical experiment. While the result for a massive low-resistivity anomaly is satisfactory, it is found that the fracture-like conductive zone is reproduced as a broader anomaly.The system was first tested using a synthetic sample which simulates a fracture with a copper plate. This conductive target is clearly defined as a low-resistivity zone, but as in the numerical experiment the width of the image is larger than the true width. This result suggest, to some extent, the limitation of resolution inherent in potential measurement, but more work has to be done to define the attainable resolving power. The experiment using a sandstone with a fracture shows similar result.