Blockage of flowlines due to hydrate or paraffin plugging is an on-going issue for the offshore industry. The problem seems to be exacerbated with the higher pressures and colder ambient temperatures as developments progress into deeper and deeper waters. There are many blockage prevention equipment and techniques available to the system designers, but in spite of this, blockages are still occurring.
This paper presents a novel approach for remediating hydrate or paraffin blockages of wet insulated flowlines with the application of heat directly to the steel OD of the pipe instead of the OD of the wet insulation, which is less efficient.
The herein proposed solution offers two possible configurations for the same base design, one for near-riser cooldown time extension, and one for “as-needed” intervention when hydrate or paraffin plug(s) have formed.
The proposed method establishes a new paradigm, since it utilizes an unbonded layer of external insulation with a gap between the insulation and the flowline steel OD. The gap will be used to circulate hot media, with heat being transferred through the steel wall, while being insulated from the environment through the insulation.
Rebello, A., Alexander, L.W., “Long Tiebacks for Life Extension of Existing Offshore Facilities – A Novel Solution for Flowline Wet Insulation,” Proceedings of the Offshore Technology Conference Brasil 2017 (OTC-28054-MS), Rio de Janeiro, Brazil, October 24 – 26, 2017.