عنوان مقاله [English]
The risks inherent in drilling operations play a significant role, so, their anticipation and mitigation would prevent much loss of time and extra cost. In this paper, a general, hierarchical, structured and flexible drilling operation risk assessment system (DORA) is presented. The model, which is presented in this paper, is generated from the operator's point of view and is applicable for different wells, ranging from wild cat to re-entry types. The methods used for generating the system, include: interviewing the experts, studying the historical data (the drilling information of phases 6, 7 and 8 of the South Pars gas field), examining questionnaires filled by experts from different oil companies (client, operator, service) and studying 15 general and specialized risk assessment systems (PMBOK, BP Amoco, Schlumberger, US Army, American Bureau of Shipping, Health Safety Executive and Stat Oil). In order to completely define the risk assessment system, its operation model is developed, the tools and methods for each phase are specified and the inputs and outputs are determined. The developed model has four main phases at the beginning, including preliminary risk analysis, secondary risk analysis and support. The inter-related position of these phases and their sub-phases, with respect to the drilling operation steps, are also specified. The other main aspects of this system include: identifying secondary, as well as primary, risks, holding workshops with the drilling team to check the results of the system and foreseeing databases (Risk register and Lesson learned).