The 2/4-22 S Romeo and the 2/4-23 S Julius exploration wells were drilled on the Norwegian continental shelf in 2014-2015, with a jack-up rig, utilizing Managed Pressure Drilling (MPD) and a hydrostatically underbalanced mud column. Both were High Pressure High Temperature (HPHT) wells with an expected Total Depth (TD) of 5500 m true vertical depth (TVD), expected reservoir pressures up to 2.14 SG and expected temperatures of 185 °C.
The 2/4 block is known for its challenging pressure and temperature regimes, and the underground blowout that occurred on the 2/4-14 well in 1989. The 2/4-21 King Lear well was drilled on the same structure as the 2/4-14 in 2012. Wellbore breathing, in combination with having a smaller drilling window than prognosed, caused drilling difficulties and endangered the likelihood of reaching TD and achieving the objectives of the well. For the two next well in the area, it was decided to utilize MPD to mitigate the expected drilling issues.
Both the 2/4-22 S Romeo and the 2/4-23 S Julius well encountered challenging drilling conditions that caused narrow drilling windows and the MPD technology was key for achieving the objectives for both wells. However, a serious well control incident occurred drilling the second well, when several barriers failed, following a sensor failure on the MPD equipment.
The purpose of the paper is to describe how the MPD operations were planned and executed, with focus on lessons learned.