Safety and risk analysis of managed pressure drilling operation using Bayesian network

The exploration and development of oil and gas resources located in extreme and harsh offshore environments are characterized with high safety risk and drilling cost. Some of these resources would be either uneconomical if extracted using conventional overbalanced drilling due to increased drilling problems and prolonged non-productive time, or too risky to adopt underbalanced drilling technique. Seeking new ways to reduce drilling cost and minimize risks has led to the development of managed pressure drilling techniques. Managed pressure drilling methods address the drawbacks of conventional overbalanced and underbalanced drilling techniques. As managed pressure drilling techniques are evolving, there are many unanswered questions related to safety and operating pressure regime. This study investigates the safety and operational issues of constant bottom-hole pressure drilling technique which is used in managed pressure drilling compared to conventional overbalanced drilling. The study first uses bow-tie models to map safety challenges and operating pressure regimes in constant bottom-hole pressure drilling technique. Due to the difficulties in modeling dependencies and updating the belief on the operational data, the bow-ties are mapped into Bayesian networks. The Bayesian networks are thoroughly analyzed to assess the safety critical elements of constant bottom-hole pressure drilling techniques and their safe operating pressure regime.