Theory and Analysis of Influencing Factors of Electromagnetic Wave Wireless Transmission in Cased Wells

Low-frequency electromagnetic telemetry technology has been widely used in the oil and gas industry. It can realize the collection of downhole data and transmit it to the ground in real time, so that ground workers can obtain formation parameters in a timely manner. However, the application of this technology in cased wells has long been limited by the high magnetic permeability and low resistivity of metal casings. This makes the casing absorb most of the electromagnetic waves transmitted by the downhole transmitter, resulting in the electromagnetic signal received on the ground being much weaker than the signal transmitted by open hole wells. Based on the finite element method, this paper constructs a theoretical model of downhole electromagnetic wave transmission, and through simulation, deeply studies the influence of various factors such as casing conductivity on the attenuation law of electromagnetic waves. We propose a method of double helical loop antenna based on electromagnetic induction to solve the shielding problem of metal casing, and the calculation results are relatively ideal.