Detection performance of the azimuthal electromagnetic wave logging instrument at coal-rock interface in horizontal wells

The advance and accurate identification of coal-rock interfaces is one of the key technologies to realize intelligent mining, improve mining efficiency and reduce cost. Azimuthal electromagnetic wave logging has achieved good results in lithologic interface identification of petroleum logging, but the identification of coal-rock interface is seldom studied. For the purpose of studying the applicability and detection performance of azimuthal electromagnetic wave in the coalfield logging environment, the one-dimensional generalized reflection coefficient method is used to calculate the magnetic field component, and the fast Hankel transform is used to accelerate the integral calculation speed. What is more, the effects of coil system combination mode, frequency, source distance, radius of coil system, resistivity contrast, emission current and resistivity anisotropy on azimuth electromagnetic logging response in the coal field are simulated. The results show that the azimuthal electromagnetic wave logging instrument can distinguish the coal-rock interface and has a great application potential in coal-rock interface recognition. The radius of the coil system and the emission current mainly affect the size of the instrument response signal. In a certain range of resistivity contrast, the amplitude ratio and phase difference near the interface increase with the increase of resistivity contrast, and the resistivity anisotropy has little effect on the amplitude ratio and phase difference in high resistivity formation. The transmitting frequency, source distance and resistivity contrast of the instrument simultaneously affect the maximum edge depth of the azimuth signal.