Fluids trapped under supercritical conditions are potential geothermal resources yielding high well-productivity. These supercritical fluids may be imaged as deep conductors (> 2km depth) using the magnetotelluric (MT) method. However, MT imaging of a deep conductor is strongly dependent on the conductor geometries and the overlying clay layers. The ability of the MT method to image a deep conductor needs clarification to understand the usefulness of MT for exploring supercritical fluids and accurately relate the imaged conductor to supercritical fluids. In this study, we investigated MT imaging of a deep conductor of supercritical fluids using numerical tests, based on a conceptual resistivity model for a supercritical geothermal system in the Kakkonda area, northeast Japan. The test result showed that the MT method was able to image the deep conductor of supercritical fluids. However, we found that the shape and resistivity value of the imaged deep conductor might significantly differ from those of the true conductor. Specifically, if a deep vertically elongated conductor is imaged by MT inversion, it is necessary to be aware that the actual bottom part may be much wider in the horizontal directions than the imaged size.

在超临界条件下捕获的流体是潜在的地热资源，可产生高产能。可以使用大地电磁 (MT) 方法将这些超临界流体成像为深导体（> 2km 深度）。然而，深导体的 MT 成像强烈依赖于导体几何形状和覆盖的粘土层。MT 方法对深导体成像的能力需要澄清，以了解 MT 在探索超临界流体方面的用途，并将成像的导体与超临界流体准确关联。在这项研究中，我们基于日本东北部 Kakkonda 地区超临界地热系统的概念电阻率模型，使用数值测试研究了超临界流体深层导体的 MT 成像。测试结果表明，MT方法能够对超临界流体的深层导体进行成像。然而，我们发现成像的深导体的形状和电阻率值可能与真实导体的形状和电阻率值显着不同。具体而言，如果通过 MT 反演对深垂直细长导体进行成像，则需要注意实际底部在水平方向上可能比成像尺寸宽得多。