Statoil has increased the effort to maximize the recovery from oil and gas fields. The development of gas fields and long tie-backs is gaining higher priority. Lean development poses technical challenges within flow assurance and system design. A large production pressure envelope and high production rates require optimisation of the system design related to the pressure drop, production velocities, fluid content, sand erosion, vibrations and acoustic fatigue. Risks such as formation water break-through and hydrate management raise additional requirements for the subsea equipment for the long tie-back projects.
Those issues are addressed in the common studies between Statoil projects Troll phase 3 (gas off-take to Troll A) and Askeladd (gas export to Hammefest LNG via Snøhvit, world’s longest tie-back) performed in cooperation with Aker Solutions, TFMC and OneSubsea. A high rate 7” subsea production system (SPS) has been developed based on an updated Vertical Xmas Tree (VXT) where the wing section and piping is increased from 5’’ to 7’’ and a Choke Bridge Module (CBM) is implemented. The CBM also includes functionality for fluid control, water monitoring and erosion monitoring.
This paper will address how the new SPS design enables 10% production recovery increase, delayed investments for the next phases, lower CO2 intensity at the processing facilities, reduced production velocities and increased robustness with regards to vibration and erosion potential in the subsea equipment.