Analysis of methods for measuring the liquid level in the annular space of an oil wellJuriy Shinyakov, Maxim Sukhorukov, Daria Torgaeva, Andrey Soldatov, Natalia Shalyapina and Dmitriy LiMATEC Web Conf., 158 (2018) 01029DOI: https://doi.org/10.1051/matecconf/201815801029