Based on experiences with the Controlled Mud Level (CML) system ECD-Management (ECD-M) in the Gulf of Mexico (GoM) in 2014 and 2015, this paper outlines how the reduced riser level was applied to improve kick detection and to reduce drilling risks associated with downhole pressure constraints. CML is a Managed Pressure Drilling (MPD) technology, but it is not only about Constant Bottom Hole Pressure (CBHP). The paper will cover the authors' learning curve from the first to the 4th well. The main focus during the first well was to make everything work and to train the personnel on the rig. The riser level was only reduced by about 150 feet and the ECD-M system was mainly used for improved kick detection by using the riser as a trip tank. Several kick drills were performed with good results showing how the drill crew was able to detect influxes even earlier with the new CML parameters. The use in the second well was extended by mitigating salt creep in the salt section, CBHP during salt exit and reducing hydrostatic head during a cement operation. Further experiences were gained during the last two wells, even though one major new component failed during commissioning. Other potential applications will also be described. The paper will describe the planning of riser levels and controller modes together with the usual drilling parameters mud weight, flow rate, ROP, etc. using hydraulic simulations and pore and fracture gradients taking the different constraints and risk into consideration.

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