AbstractsEarth & Environmental Science

This thesis aims to identify the potential and limitations of using Managed Pressure Drilling (MPD) in deepwater fields where narrow and unpredictable mud weight windows are encountered. A significant effort has been done to understand the methods used to estimate and verify the underground pressure and stress environment.Some of the worlds largest conventional oil fields are located in the deep waters beyond the continental shelves. As the industry engage in these highly productive and promising deepwater fields, major obstacles are encountered during drilling which leads to high amounts of costly Non-Productive Time (NPT). With unique challenges such as lost circulation, narrow drilling windows and vast amounts of salt, there is a need for innovative techniques to develop these fields in a safe and effective manner. MPD is presented as a favourable solution to overcome challenges associated with uncertain and narrow mud windows. Being able to control the annular pressure profile throughout the wellbore and react to pressure fluctuations within seconds allows drilling to proceed safely and uninterrupted, while keeping the operational problems to a bare minimum. In addition to increased operational flexibility, MPD has shown positive effects on lost circulation, which is a major well cost driver in conventional drilling. A case study is conducted for a deepwater exploration well in the Gulf of Mexico. Based on estimations of the pore and fracture pressure gradients, drilling programs are designed for respectively conventional drilling, and the two MPD variants: Constant Bottom-Hole Pressure (CBHP) and Controlled Mud Level (CML). Where the latter is a Dual Gradient Drilling (DGD) approach. The deepwater well is then drilled with the planned drilling programs and real pore and fracture pressure gradients. This case study shows the unique flexibility MPD entails when deviations from the plan are encountered.