Numerical simulation of azimuth electromagnetic wave response of complex geological model of horizontal hole in coal mines

The advance and accurate identification of the coal-rock interface is one of the key technologies to realize automatic tunneling and intellectualization of coal mines. Azimuth electromagnetic wave tool has a large detection range and can distinguish the lithologic interface and interface orientation. It has been successfully applied in oilfield logging, but there are few researches on the coal mine measurement environment. In order to study the detection performance of azimuth electromagnetic wave logging in the complex 3D model of coal mines, the finite element numerical simulation method is used to investigate the influence of the drilling fluid in the borehole on azimuth electromagnetic wave logging with different transmission frequency and spacing in the coal mine measuring environment, and the influence of the mined-out area and the stratigraphic boundary on the azimuth electromagnetic wave measurement. The results show that the azimuth electromagnetic wave response is less affected by the borehole when the fluid in the borehole is air. The azimuth electromagnetic wave measurement signal can reflect the fluctuation of the stratum interface, and its detection ability is related to the transmission frequency and spacing. The azimuth electromagnetic wave is sensitive to the low-resistance goaf, but a phase difference signal can be used to detect high-resistance goaf in high-frequency transmission. The azimuth electromagnetic wave method provides a new technical means for the measurement of the coal-rock interface and goaf in the horizontal hole of coal mines, which has great application potential.