Methodology of risk assessment of negative environmental impacts during the operation of gas production wells is presented in the paper. The main events that can result in negative environmental impacts are considered. The interrelationships between these events are formalized using the set-theoretic approach. The methodology proposed in this paper allows to determine how likely the occurrence of negative environmental impacts on a certain environment (atmosphere, soil, etc.) is, taking into account verbal and numerical assessments. In addition, the damage from such impacts is determined and a conclusion is made whether this damage is acceptable. This, in turn, allows to effectively reduce the company's risk level and minimize the harmful environmental impact during the operation of gas production wells.