Abstract
The objective of this paper is to describe howApplied Surface Back Pressure -Managed Pressure Drilling (ASBP-MPD) can be used to augment the limitations of conventionaldeepwater well control. This paper will discuss equipment design and operating philosophy as well as expand on what actions can be taken to respond to an influx while remaining within the primary well barrier.
A critical evaluation of deepwater well control has been performed uncovering several limitations which can be mitigated with anASBP-MPD system. As such, this paper will describe the disadvantages of shutting in the Subsea Blowout Preventer(SSBOP) such as the risk ofnon-productive time associated with stuck-pipe and the total influx volume increase associated with the process. Additional items discussed in this paper include managing an influx in the riser and inaccurate conventional kick detection methods.
The paper will explain howdeepwater well control can be augmented with anASBP-MPD system by sealing the wellbore with either an MPD annular preventer or an MPD riser seal. Closing the MPD annularforms a wellbore seal on drill pipebefore the mud pumps are shutdown enabling a closed system flow check and the ability to add back pressure with the MPD choke to reduce influx volume. The activation of an MPD riser sealing system provides an even faster influx response time, as drilling operations are executedin a closed system with a continuous wellbore sealwhile diverting flow through an MPD choke. Additionally, since the riser is already sealed, an MPD sealing system serves as reliable protection from a sudden riser gas unloading event which can occur in seconds. By redefining the primary well barrier in the above context, ASBP-MPD equipment can be used to circulate a small influx out of the wellbore without closing the SSBOP while remaining within the limits of the primary well barrier. Finally, accurate flowmetering of flow out and flow in provides a level of advanced down hole event detection that reduces influx volumes and further eliminates the need for a conventional flow check prior to confirming that an influx event has occurred.
