Offshore drilling blowout risk model: an integration of basic causes, safety barriers, risk influencing factors and operational performance indicators

Offshore drilling is an activity inherent to the oil and gas industry as it is essential for confirming the economic feasibility of hydrocarbon reservoirs. However, operational uncertainties and risks inherent to typical major accident hazards are associated with the performance of this activity, where blowouts are assumed to be one of the major contributors to risk in offshore drilling. This paper presents an accident precursor risk model for offshore drilling blowouts that integrates the blowout basic causes, safety critical barriers & elements, Risk Influencing Factors (RIF) including Human and Organizational Factors (HOF), and Operational Performance Indicators (OPI). The method, which was adopted to design the model and allow its customization for reflecting the characteristics of any drilling rig, well and operation is also described and demonstrated using a theoretical example. The model is hybrid, as it combines bow-tie diagram (fault tree and event tree) with directed acyclic graphs (DAG), to account for the effect of the RIF on the performance of safety barriers through the direct observation of pre-defined OPI.