Self-powered Wireless System For Communication While Drilling

The LWD(logging while drilling)communication system is that transmits information during drilling.Through the LWD communication system,the downhole information obtained by the drilling sensor network,and the control instructions it relies on form an LWD sensor monitoring system.Common communication methods while drilling includes the mud pulse transmission method,long-wave electromagnetic wave transmission method,and acoustic wave transmission method.The first difficult problem of LWD communication is that transmission of high-frequency electromagnetic waves is limited by the following limitations: the attenuation of electromagnetic waves caused by the mud electrolyte in the drill pipe,and the radius of the pipeline also limit the range of electromagnetic waves available for long distances;The second difficult problem is that the cost of batteries for electromagnetic wave relays cannot be deployed in large quantities during drilling.As a downhole power supply,the mud generator has the limitation of large volume and complex structure,which can only be installed in a certain position in the drill pipe and cannot be distributed for energy supply.Due to the above-mentioned contradiction,the mud-pulse transmission method has been used in practical applications for a long time.Although it can communicate over long distances,its transmission rate is too low,which seriously restricts the intelligence and automation of drilling and the cost of drilling operation cannot be greatly reduced.In this thesis,aiming at the problem that the long-distance transmission of the high-frequency electromagnetic wave in LWD communication system is limited and the mud generator cannot distribute energy supply,using self-powered energy technology and electromagnetic wave for short transmission technology,the prototype of self-energy wireless system for communication while drilling is designed,including the hardware circuit and software design.At the same time,combined with the transmission theory of electromagnetic waves in a circular waveguide,the CST software is used to simulate the transmission of a circular waveguide for commonly used electromagnetic wave bands to determine the frequency used by the self-powered wireless system for communication while drilling.The communication distance of LWD communication self-powered system in salt water is tested experimentally,the system does not need battery to realize high-speed wireless short-transmission communication while drilling.The prototype of the LWD wireless system is verified theoretically and experimentally.The main contents of this thesis are as follows:(1)The first chapter is mainly to investigate the application and research status of LWD communication technology and self-powered technology in the LWD wireless system.This thesis introduces various transmission methods of the LWD communication system,the common self-powered technology,and the application of the existing self-powered technology in the LWD communication,which provides theoretical knowledge for the self-powered wireless system of the LWD communication.(2)The second chapter is based on the theory of electromagnetic wave transmission in a circular waveguide and uses CST software to perform electromagnetic wave communication simulation.Discuss the transmission distance of electromagnetic waves in seawater from the aspect of software simulation,and determine the frequency of electromagnetic waves used in this system.(3)The third chapter discusses the energy consumption characteristics of the self-powered wireless system for LWD,compares and tests the power consumption of mainstream low-power devices,and finally determines the device model of the self-powered system for LWD.(4)The fourth chapter is mainly about the design and experimental verification of the self-powered communication system while drilling,designing the self-powered circuit and software and hardware system for communication while drilling,and testing the distance of brine communication.Completed prototype verification of self-powered wireless system for communication while drilling.