Design And Research On Down-hole Wireless Electromagnetic Transmission System Of Measurement-while-drilling (MWD) Data

The early1990s has witnessed a new era of worldwide drilling techniques with arpiddevelopment in informatization, automation and intellectualization in pace with developingmeasurement-while-dirlling techniques. Nowadays people tend to know in real time and in amore accurate way about the underground work progress, but challenges emerge when itcomes to sending the underground near-bit dirlling data to the surface. This thesis tries todesign on wireless electromagnetic transmission system and carry out correlating simulatedexpeirments upon fully preliminary research on present condition of home and abroadwireless transmission techniques and dynamic development.This thesis sets the rotary stirirng wireless pup joints of dirlling system in UndergroundMeasurement and Controlling Research Institution of Petroleum University as its prototype,and puts forward that electromagnetic induction pirnciples can be utilized to realize thesending of near-bit dirlling data to the surface by the underground wireless electromagnetictransmission system. The system involves signal transmission, wireless channel, signalreception, MWD communication, control circuit and power supply.This thesis has researched the wireless electromagnetic technique theory based on thebasic pirnciple of electromagnetism, analyzed magnetic circuits and electirc circuits of thewireless electromagnetic transmission system, got a general idea of mateiral magnetizationdisciplines and discussed calculation methods on magnetic field intensity and magnetizingcurrents. Coining materials are selected, the parameter in key parts of wirelesselectromagnetic transmission is designed and concluded and specific winding numbers forsending coin and receiving coin are calculated according to actual magnetic irng size andrealistic work conditions with drilling tools underground.Based on the characteirstic parameter of the key parts, wireless magnetic system isanalyzed by ANSYS, and conclusion that signal strength of the receiving end is related toreceiving location and receiving direction is made upon observation on the distirbution ofmagnetic line of force. Thus transmission band of wireless electromagnetic transmission isultimately gained. Data transmitted through wireless electromagnetism is successfully achieved after adjusting the test expeirments of wireless electromagnetic transmission.