Design And Implementation Of System In Measurement While Drilling Wireless Electromagnetic Transmission

In the geological exploration drilling engineering,timely and accurate monitoring of the well trajectory and accurate adjustment of drilling attitude is one of the key technologies in drilling engineering.At present,the data transmission scheme based on the drilling fluid pulse is generally adopted by the mature MWD at home and abroad,but this transmission method is limited by the drilling fluid and the transmission rate is low.Drilling with the measurement of wireless electromagnetic transmission system is a low-frequency electromagnetic wave as the medium,the signal is properly encoded,and then through the drill pipe-formation channel to the ground.It is very good to overcome the shortcomings of traditional drilling fluid pulse wireless transmission technology,has become the major domestic and foreign companies research hot spots.But the domestic research in this area started late,technology far behind large foreign companies similar to the lack of mature commercial products.Therefore,the research and development of the electromagnetic wave measurement while drilling system with the independent core technology has become a crucial task for the domestic industry companies and the R & D personnel.In this paper,the design and improvement of various problems encountered in the realization of wireless electromagnetic transmission system are studied.The main tasks include:1.According to the technical specifications and the actual engineering situation,the complete system scheme is put forward,and the overall function frame of the system is designed;2.In view of the contradiction between the underground lithium battery power supply and the long time down-hole operation requirements,a special power management module is designed to realize the requirement of long time standby and efficient work of the system;3.In this paper,the SOC system is used to control the modulation and transmission of the signal system,which effectively reduces the area of the transmission system and makes it easy to install the underground circuit.4.Affected by the environment,downhole communication signal attenuation is faster,the carrier frequency is relatively low,low band bandwidth is narrow.In this paper,BPSK modulation scheme is adopted to effectively reduce the bandwidth of the signal.Combined with the problem of low frequency signal carrier synchronization,this paper designs a context-based BPSK demodulation algorithm.The algorithm has high efficiency,fast carrier synchronization,and has good anti-interference ability to noise and power frequency signal,and the algorithm has low requirement for hardware circuit.This paper uses FPGA to achieve the BPSK algorithm demodulation,only FPGA minimum system and ADC can be;Finally,a series of related tests and experiments on the wireless radio transmission system are designed.The experimental results show that the system can work stably for a long time to meet the technical requirements of the design and realize the expected function.