| With the continuous increase in the depth of oil and gas well exploration and development of geological guided drilling technology,the requirements for precise control of wellbore trajectory in modern drilling technology are constantly improving.In order to ensure more timely and accurate acquisition of near drill bit formation information parameters such as well deviation,azimuth angle,tool surface,etc.,this paper focuses on theoretical research and experimental verification,and analyzes the impact of key component parameters of the system on the quality of signal transmission.A short transmission system that can achieve wireless transmission of near drill bit information across screws is studied and designed,which has significant theoretical and practical significance for achieving high-precision logging.The main research content includes:(1)In response to the problem of rapid attenuation of signals in the underground geological environment of the cross screw wireless electromagnetic short transmission system,an equivalent current field model of the cross screw wireless electromagnetic short transmission system is established.Based on the coupling characteristics of the transmitting and receiving coils in the current field channel,the attenuation factors during the short transmission signal transmission process and the near and far field characteristics of the short transmission electromagnetic field are analyzed,providing a theoretical basis for subsequent coil parameter design and model simulation.(2)In response to the design issues of key component parameters for the cross screw wireless electromagnetic short transmission system,the design parameters of the transmitting and receiving coils were derived and calculated,including 17 turns of the transmitting coil,63 turns of the receiving coil,and a coil winding diameter of 0.2mm.Iron nickel alloy with high magnetic permeability and easy magnetization characteristics was selected as the magnetic core material to ensure stable and reliable communication in the short transmission system.(3)A COMSOL simulation model for the transmission channel of cross screw wireless electromagnetic short transmission signals was established to address the attenuation characteristics of short transmission signals and the impact of magnetic core coils on signal transmission.The simulation results show that the optimal transmission frequency of short transmission signals is 10-15 k Hz;The received signal strength decreases significantly as the conductivity of the transmission medium increases;Properly increasing the coil radius and the distance between the screw and the receiving and transmitting coil can effectively improve the quality of the received signal;The thickness of the magnetic core has a small impact on the quality of the received signal;When designing the coil,a magnetic core permeability greater than 1000 is sufficient,providing simulation support for optimizing the design of key parameters in the short transmission system.(4)A cross screw wireless electromagnetic short signal transmission circuit was designed to address the issue of 10-20 m error between the measurement point and the drill bit position of conventional while drilling measurement devices.STM32F103 was used to control AD9833 to complete FSK signal modulation.The demodulation circuit of the short signal was designed using the phase-locked loop demodulation chip NE564,and the modulation and demodulation circuit designed was used to achieve FSK modulation and demodulation.(5)In response to the feasibility verification issue of the cross screw wireless electromagnetic short transmission system,a short transmission ground simulation experiment was conducted,and the wireless transmission of the short signal at a distance of 5m was successfully achieved.The optimal transmission frequency band for the short signal was determined to be 10-20 k Hz,which is basically consistent with the COMSOL simulation results. |
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