Managed pressure drilling from floaters

Abstract

Drilling in challenging environments with different drilling hazards cause a lot of non-productive time (NPT), ie time where the rig is not drilling. Much of the challenging environments are in water depth demanding the use of floating drilling facilities. The result of NPT and high rig costs is a lot of money spent on nothing productive. To solve the challenges associated with challenging environments and high percentage of non-productive time, there is in particular one drilling method many operators have been looking at for the last decade, and that is managed pressure drilling (MPD), with its different variations. Even though there are several challenges associated with combining MPD and floaters and bringing them in to some geological areas, the involved parties in the industry seem to be determined to solve the challenges and take the technology into the future. Due to its experience with MPD from jack-ups and platforms, the operator BG Group is now looking towards utilizing MPD from floaters in several of their assets around the globe. The scope of this thesis is to look into the technology existing today and the experience gained up to date with MPD from floaters in various locations, which then could be useful for BG Group. The specific challenges for MPD from floaters, such as variations in drilling fluid temperature, surge and swab due to heave motions and riser margin, should be analyzed from a risk perspective. The proven benefits of performing MPD which gives a more accurate pressure control during the drilling operation and earlier detection of influx and losses suggests that MPD from floaters should be taken into use. The risks for bad weather conditions and possibilities of riser disconnect should be included in an overall risk analysis. Looking at the operations performed up to date on floaters, it is clear that a thorough planning process is crucial for a successful operation. Close collaboration in the planning process between operator, service companies and rig contractor with regard to equipment, procedures, HSE and last, but not least personnel training is of great importance.