For substantial cost savings, Husky is considering starting up our subsea production wells to the FPSO with overbalanced brine in the wells as the suspension fluid. Eliminating the need to displace to underbalanced base oil would allow us to land the completion with the tubing hanger crown plug pre-installed, and would significantly reduce surface rig-up requirements.
The brine would be overbalanced NaCl or CaCl2 in the density range of 1070 to 1250 kg/m3, depending on the well/field. We would kick off the wells by N2 unloading the annulus through the gas lift valve, N2 being supplied via subsea intervention vessel.
Our initial concerns were hydrate formation, chemical compatibilities, and discharge approvals. We are looking into the addition of MEG to the brine for hydrate inhibition, which appears achievable for our predicted pressures.
Does anyone have any similar experiences to share kicking off wells with overbalanced brines, and flowing brines back through the subsea and topsides production system? Any concerns?
Thanks in advance for your insight!
Sr Completions Engineer
Husky Energy; Atlantic Region