The first edition of the textbook was published in 2011. The second edition includes corrections and additions based on the studies conducted recently in the field of environmental monitoring. The textbook is devoted the basic aspects of the ecological monitoring in the process of oil&gas fields exploitation, as well as the main aspects of background assessment of the state of the environment prior to the development of the hydrocarbon deposits. The textbook is intended for undergraduate students enrolled in the Joint Norwegian-Russian Master of Science program “Geoecological monitoring and rational use of natural resources in the Northern oil and gas production regions”.