Layered water injection runs through the entire life cycle of oil and gas field development. Wellbore communication serves as the bridge between the surface and reservoirs. In recent years, the scale of oil and gas production has gradually expanded, imposing higher demands on wellbore control technology. Efficient transmission of wellbore data has become pivotal for achieving precise reservoir layer control and facilitating digital and intelligent development. Continuously strengthening fundamental wellbore communication technology research holds significant importance for the construction of smart oil fields. Extremely low frequency electromagnetic waves have advantages such as long communication distance and strong penetration capability, holding broad application prospects in wellbore wireless communication. However, their wellbore communication model and propagation characteristics remain undetermined. This research establishes a polygonal complex network communication model for wellbore wireless communication of extremely low frequency electromagnetic waves in N-layers media, based on the concept of network splitting. The propagation, reflection, transmission, and attenuation characteristics of extremely low frequency electromagnetic waves in irregular layered geological conditions are determined, and special factors such as casing threads are comprehensively considered. Through finite element simulation and field experiments, it is confirmed that wellbore wireless communication without relays can achieve distances exceeding 1500 m and the transmitting frequency cannot be blindly reduced to improve communication efficiency. The distribution patterns and characteristics of electromagnetic fields in layered media are analyzed, and the optimal transmitting frequency range under typical operational conditions is derived as 5–20 Hz. This research also quantitatively expresses the structural parameters and placement positions of the transmitter and receiver solenoid, verifying the stability and reliability of wellbore wireless communication of extremely low frequency electromagnetic waves through theoretical analysis and field experiments. This research provides a crucial theoretical basis and experimental support for the subsequent advancement of efficient wellbore wireless communication and the development of intelligent well networks.