Managed pressure drilling from floaters: feasibility studies for applying managed pressure drilling from a floater on the Skarv/Idun field on the Norwegian Continental Shelf by PGNiG Norway AS

Abstract

Managed Pressure Drilling (MPD) is a relatively young technology that has improved some old ideas of Underbalanced Drilling (UBD). According to the IADC, MPD is an “adaptive process used to precisely control the annular pressure profile throughout the wellbore. The goal is to ascertain the downhole pressure environment limits and to manage the annular pressure profile accordingly”. In other words the main aim of MPD is to avoid continuous influx of formation fluids to the surface by maintaining a state of effective overbalance. It’s done by applying surface backpressure during drilling ahead or shut-in to make a connection of jointed pipe. Basic tools required to conduct MPD are: a rotating control device (RCD), drillstring non-return valves and dedicated choke manifold. MPD allows drilling through the un-drillable in conventional way formations, helps to reduce non productive time (NPT) and to overcome several drilling problems like: drilling with narrow “pressure window” and kick-loss scenarios caused by narrow margins, excessive casing program, low ROP, excessive mud cost caused by the loss of circulation, failure to reach TD with large enough hole diameter and shallow geohazards both with drilling riserless and with casing or marine riser. This technology enables manage pressures through the wellbore in more precise way than conventional drilling and there are several strong indicators that MPD in marine environments will be a breakthrough technology in offshore industry in the next years. It’s a big chance for MPD to be best solution for drilling in reservoirs with narrow pressure window, drilling with troublesome zones, depleted reservoirs, HP/HT reservoirs and to overcome almost all offshore drilling-related challenges. Therefore the main objective of this Master’s Thesis is to evaluate both technical and economical feasibility of using Managed Pressure Drilling technology from a floating drilling rig on the Skarv/Idun field on the NCS. Furthermore to show which MPD variation is most suitable on this field, equipment needed to conduct MPD operations, evaluates reservoir and drilling related benefits and assess which drilling problems can be avoided using Managed Pressure Drilling technology.