Among the numerous harmful substances of anthropogenicorigin that enter the environment, petroleum products belong to one of the first places. In this paper, changes in the physical and chemical properties of the oil of the Surakhany field of Azerbaijan from the well and from the surface of the water, under the influence of environmental factors, are investigated. The composition and properties of oils after production and prolonged exposure to the surface of the water are compared. Oil samples are isolated according to GOST 11858-66 into three components: oils, resin and asphaltenes. The results of mass spectrometric, chromatographic and IR spectrometric examination of samples of crude and degraded oils are presented. The results of the research showed that under the influence of natural factors on the surface of water bodies in the composition of degraded oil, the content of hydrocarbons decreases, and the content of resins and asphaltenes increases. The content of identified polycyclic aromatic hydrocarbons in both oil and resin fractions increases. The change in the most toxic polycyclic aromatic hydrocarbons (PAHs) in the processes of oil degradation was studied, an increase in toxic effects in PAHs was established. The content of various groups of hydrocarbons in the composition of the oil and resin fractions of freshly extracted and degraded oils on the surface of water is given. It was found that in the resinous fractions of both oils, the presence of the studied groups of PAHs exceeds their values in comparison with the oil fractions. The results of IR spectroscopy of degraded oil samples showed the formation of more condensed aromatic rings in the structure. The results of the studies indicate significant changes in the composition of oil degraded on the water surface. Analysis of the transformation of oil pollution when oil enters the environment is necessary to optimize the choice of remediation technologies.