Advances in technology for electromagnetic measurement while drilling in China

The electromagnetic measurement while drilling（EM-MWD）system is a major technical means for MWD in gasdrilling. It has been one of the popular researching subjects of new technologies abroad in recent years. The Petroleum Exploration Production Research Institute of Sinopec developed the model machine of the EM-MWD system, i.e., CEM-MWD. When theformation resistivity ranges from 2 Ω•m to 3 Ω•m, the effective surveying depth of CEM-MWD will reach 2100m. In this paper, thesystem structure and working principle of CEM-MWD are discussed, and the field test is introduced. The factors influencing the testdata and the electromagnetic signal transmission are analyzed, and the development prospect and trend of the EM-MWD technologyare discussed. The research results can be good reference to the development of the EM-MWD technology in China.