The majority of overbalanced drilling operations are still performed using conventional drilling. The trend indicates that managed pressure drilling systems are increasingly being introduced in regions where the operational pressure window of formations is restricted. DNV has during the last years noticed a considerable demand for third party evaluation of new upcoming managed pressure drilling systems. This paper discusses some of the challenges and advantages for managed pressure drilling compared with conventional drilling.

Many managed pressure drilling systems introduce critical equipment with the intention to enhance operational effectiveness and safety. At the same time the respective equipment is used to adapt the hydraulic pressure profile throughout the wellbore to manage the annular bottom-hole pressure within the formation pressure limits. A general description of the connection between safety critical equipment and the well barriers is discussed in this paper.

Safety barrier analysis and structured hazard identification of critical managed pressure drilling equipment related to well control have been performed. Well-known risk identification methods have been used to analyze common aspects related to Managed Pressure Drilling. Hopefully the analysis introduced in this paper will help the industry to decide when critical drilling equipment should be regarded as well barrier elements or not.

The results indicate that while managed pressure drilling systems have significant advantages both in terms of safety and productivity, risks related to implementation of safety critical equipment need to be managed through reliable and efficient control systems.

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