Research And Implementation Of Channel Estimation And Channel Quality Assessment Method For Communication While Drilling

With the development of economy and society,the significance of oil as a strategic resource is becoming more and more obvious.MWD technology is an important technical means in the field of petroleum exploration.It can obtain the formation parameters required by logging in real time during drilling.At present,mud continuous wave pulse transmission mode has become the most widely used data transmission technology in MWD.It controls the area of mud flow through through the relative movement of stator and rotor inside the downhole signal generator to generate pressure wave,The pressure wave propagates from the underground to the ground,and then the signal is collected by the pressure sensor on the ground to realize the transmission of the signal.Finally,the data is transmitted through the demodulation system on the ground.However,in the process of data transmission,due to the particularity of mud channel,the bad environment of drilling platform and the uniqueness of signal generation mode,the signal modulation and demodulation technology will usually face great challenges.Although the self-developed mud wave pulse transmission system in China has a variety of modulation and demodulation methods,when setting communication parameters,field engineers do not know the channel information,resulting in blind and wrong parameter setting in most cases,which always limits the transmission performance of the system.At present,in the field of wireless communication,link adaptive technology has been widely used in many communication systems.By acquiring the current channel quality information,it can adjust the transmission parameters such as modulation and coding mode,working frequency point,working bit rate and transmission power,so as to effectively improve the transmission speed,spectral efficiency and transmission reliability of data in the system.In order to improve the transmission performance of the system,this thesis will study a channel quality evaluation scheme for the mud while drilling continuous wave pulse transmission system from the perspective of link adaptation.The scheme can guide the transmission frequency of the system,To solve the current problems faced by field engineers,this scheme may also become the basis for realizing link adaptation of MWD mud wave pulse transmission system in China in the future.Based on this,this thesis mainly does the following three aspects:(1)The system structure,signal generation mechanism,data frame format,channel and noise characteristics of mud while drilling continuous wave pulse transmission system are studied and analyzed,and the system transmission model is established.(2)According to the characteristics of mud channel,when the traditional channel estimation methods have been basically unable to work,a channel estimation method using deep learning technology is innovatively proposed.Compared with the traditional channel estimation methods and the current advanced deep learning methods,this scheme shows significant performance advantages.(3)Combined with the noise characteristics of the system,this thesis studies and implements three commonly used pump impulse interference cancellation algorithms,and designs a new channel quality evaluation index on this basis.Finally,a BPSK modulation and demodulation simulation platform is built to verify the feasibility and effectiveness of the proposed channel quality evaluation scheme.