Feasibility of drilling with supercritical carbon dioxide to serve the needs of deep underbalanced drilling operations has been analyzed. A case study involving underbalanced drilling to access a depleted gas reservoir is used to illustrate the need for such a research. For this well, nitrogen was initially considered as the drilling fluid. Dry nitrogen, due to its low density, was unable to ge...

We give a detailed view of estimation and control problems raised by the drilling process where the distributed nature of the system cannot be ignored. In particular, we focus on the transport phenomena in Managed Pressure Drilling (MPD) and UnderBalanced Operations (UBO), as well as the time-delay mechanisms of the mechanical stick-slip vibrations. These industrial challenges raise increasingl...

Good flow and pressure control is essential for successful Underbalanced Drilling (UBD) operations. This work evaluates the use of Model Predictive Control (MPC) for integrated control of well conditions and the topside separation system during UBD. The downhole well pressure, separator liquid levels, and the separator pressure are controlled by manipulation of the rig pump, the choke, and the ...