In the drilling process real-time downhole engineering parameters and geological parameters can be obtained by the MWD technology which has greatly promoted the development of drilling technology. Electromagnetic MWD technology has unique advantages, but it is vulnerable to formation resistivity restriction and results in a smaller depth of electromagnetic signal transmission. Therefore, the transmitted depth of electromagnetic signal is the greatest constraint in the development and application of EM-MWD. The relay transmission technology is the best way to improve the transmission depth of electromagnetic signal. For this reason, in this paper theoretical research of electromagnetic signal transmission characteristics is conducted, and the electromagnetic excitation mode of repeater and the antenna structure are determined. Then an electromagnetic signal relay transmission model and a repeater development program are established. On this basis, the repeater and application experiments are developed. Experimental results show that the downhole electromagnetic relay transmission technology can improve the depth of EM-MWD. The transmission depth can be increased more than 70 percent by each repeater. Therefore, the use of EM-MWD is greatly expanded.

EM-MWD  /  relay transmission  /  repeater