Unlocking the economic viability of many of these offshore prospects today is a rapidly growing application of Managed Pressure Drilling (MPD) technology. MPD is based upon tools and methods developed for the safe practice of underbalanced drilling. However, in MPD the intent is not to invite hydrocarbon influx into the wellbore and to the surface as in true underbalanced drilling, but to more precisely manage/control/contain annulus fluids downhole and at the surface when drilling overbalanced. MPD applies to near-balanced, balanced, three variations of dual gradient deep water drilling and a zero discharge method of riserless drilling of top holes.

Because MPD relies upon a closed and pressurizable mud returns system and does not intend to produce hydrocarbons when drilling ahead, the technique offers a very positive influence upon environmental considerations and well control in general.

This paper discusses the MPD methods currently underway that are a major step towards zero discharge offshore drilling and specifically identifies the positive environmental ramifications of several MPD applications.