Research on the Relay Transmission Characteristics of Irregular Grid-Based Electromagnetic Wireless Repeater While Drilling

In order to solve the difficulty in predicting the transmission distance and installation location of downhole electromagnetic (EM) wireless repeater in engineering application, one model of downhole EM relay transmission is established by building a finite element (FEM) irregular grid refinement strategy that can eliminate the influence of suspension nodes. It can obtain the relationship between the transmission depth and signal attenuation rate of EM wireless repeater system, and the parameters like well depth, formation resistivity and carrier frequency, and establish the prediction method for the installation position and transmission depth of the repeater. Finally, field tests in several wells of Jiangsu Oilfield verified the correctness of this algorithm, and the accuracy rate of transmission depth prediction exceeds 85%. The results show that such transmission model can effectively eliminate the influence of suspension nodes on calculation accuracy and convergence speed, accurately predict repeater installation position, and ensure the continuous downhole transmission of EM signals. This paper provides theoretical reference for the field application of EM Measurement While Drilling (MWD) measurement technology..