Geophysical research: article

Аnnotation: Following the materials of publicly available foreign and Russian scientific literature, we have carried out an analytical review of applying toroidal coils - unconventional for oil and gas well logging transmitters and receivers of electromagnetic signals. The performed analysis indicates a variety of problems to be solved with toroidal coils in sections of vertical and highly deviated wells. Among these issues are resistivity measurement during drilling at high electrical contrasts between the well and formation, resistivity-at-the-bit determination, while-drilling appraisal of the filtration-volumetric properties of thin interlayers, electrical imaging, quantitative characterization of hydraulic fracturing parameters, and resistivity anisotropy evaluation for realistic fluid saturation estimation. The idea of applying toroidal coils is embodied in the Russian practice in a new electromagnetic tool with toroidal coils of the Trofimuk Institute of Petroleum Geology and Geophysics SB RAS and the ‘Looch’ Scientific Production Enterprise of Geophysical Equipment, aimed at logging in oil and gas wells with assessing the resistivity anisotropy coefficient of thin-layered sand-shale deposits. The electromagnetic tool with toroidal coils, devised in Novosibirsk, is characterized by a high spatial resolution and is a worthy alternative to multicomponent induction logging tools.