Transmission model and analysis of characteristics of downhole wireless RFID signal based on FSK modulation

Abstract

Radio frequency identification (RFID) technology is a new type of intelligent drilling and completion technology that can be used for remote control of downhole tools. In RF modulation, frequency shift keying (FSK) has stronger anti-interference ability compared to amplitude shift keying (ASK), but its transmission characteristics for downhole RF signal are not yet clear, which cannot provide theoretical support for designing downhole RFID systems. In this paper, a transmission model for downhole wireless RF signals based on FSK modulation is established by combining Maxwell's equations, Biot-Savart's law, and the proposed model was verified through the simulation results and the experimental results, and the influence of the excitation intensity, the transmission distance, and the conductivity of drilling fluid on transmission attenuation was deeply studied. This study highlights the influence of conductivity on drilling or completion fluids by integrating 2FSK modulation, excitation, propagation, and induction reception of downhole electromagnetic waves into the proposed model. The mathematical model proposed in this study has been proven to predict transmission characteristic values close to experimental results with an average accuracy of over 90%. The results show that the excitation voltage, the transmission distance and conductivity of drilling and completion fluids have a significant impact on the propagation and reception of downhole RF signals. These analysis results can provide effective guidance and inspiration for the design and application of digital drilling and completion instruments.