Extremely Low-Frequency Electromagnetic Wave Communication Model and Simulation in Wellbore Communication

Abstract In recent years, the scale of oil and gas production has been continuously expanded, and processes such as layered water injection, gas injection, and oil recovery have led to stricter requirements for the precision of layered wellbore control and the distance of bidirectional data transmission. Extremely low frequency (ELF: below 30 Hz) electromagnetic wave wireless wellbore communication technology can achieve high-precision and long-distance bidirectional data transmission and overcome the problems of traditional wired communication technologies' poor pass-ability and load capacity. It does not require the addition of relays and is more cost-effective, making it a wireless wellbore communication technology with broad application prospects. This article is based on the theory of network splitting, establishes a multi-delay and multi-weight complex network model of ELF electromagnetic waves in wellbore communication, and designs a controller. It deduces quantitative expressions for the electromagnetic field in different directions in N-layered media. The article calculates the propagation and attenuation characteristics of ELF electromagnetic waves. Deriving calculation formulas and combining simulations determines the optimal transmitting frequency range to be 5Hz to 20Hz. Field experiments have confirmed that ELF electromagnetic waves can achieve wireless communication without relays over 1600 meters. Numerical simulations are conducted to solve the distribution relationship between electric and magnetic fields in layered media, determine the coupling coefficients between transmitter and receiver, and clarify the transmission channels. Comparing the electrical signal strengths at different frequencies proves that blindly reducing the transmitting frequency is not advisable. Both theoretical analysis and experiments validate the correctness of the model. This article provides a theoretical basis and feasibility for subsequent engineering applications. This method provides a new idea for wellbore wireless communication technology in fields such as rod lifting and separated layered injection.