ABSTRACT: One of the main factors in achieving safety management and safety objectives is designing in addition, applying specific risk evaluation techniques. The present study takes this approach to manage the risks related to nonroutine activities and hazardous work in Operation and Maintenance (O&M) project in an oilfield. This semiquantitative and descriptive study was conducted at the Sarvak Azar oil field in Iran in 2023. A combination of the Hazard and Effect Management Process (HEMP) and the Hazard and Risk Prioritization Index (HARPI) are used to assess the risk of activities. Then, to simplify managers' decisions to implement control measures, final risk scores reported based on the Pareto principle. The results show that based on the conventional use of RPN, T11 (Desalters bypassing; 850), has the highest risk, and T1 (PSV installation on the off spec tank; 30) activity has the lowest calculated risk. However, based on the HEMI, T12 (Electrical substation commissioning; 749.7) has the highest calculated risk, and the lowest estimated risk score is associated with T7 (Loading chemical barrels and collecting pallets and empty barrels; 25.5). Furthermore, a survey of the standard deviation of the data shows that among the factors added to the risk assessment, involved people number (Pi), is more influential than other factors. The study showed we could optimize the conventional use of the risk priority number (RPN) with slight modifications. Changes made while maintaining the simplicity and applicability of the method can improve the accuracy of the priority set by the RPN