In this work, the object of research was the long-term deposits of liquid hydrocarbons located within the boundaries of fields with high geological heterogeneity, the proportion of which is actively increasing every year due to the selection of a significant part of the “light” oil reserves. Based on the generalization of the results of direct and indirect research on the topic of the work, the key causes of well flooding were identified and their primary sources were identified, which made it possible to successfully describe the mechanisms of formation of the transition zone of the oil-water system, depending on the stage of development. The conclusion is made about the importance of applying relevant and reliable scientific and methodological approaches in interpreting the results of geophysical research to solve various problems of oil field development.