Dec 07 2020
Helix Energy Solutions with SBS Energy set a new offshore Snubbing unit / Hydraulic Workover (HWO) world record
Helix Energy Solutions with SBS Energy set a new offshore Snubbing unit / Hydraulic Workover (HWO) world record onboard the Q4000 after completing a flowline cleanout operation to a length of 28,789’ (actual drill pipe measurement) on the Ozona Garden Banks 515 location in the U.S. Gulf of Mexico.
In 2014, the Ozona well and flowline, located in 3,276’ water depth, were shut-in after becoming plugged with asphaltenes. In 2016 the well was plugged and the subsea tree was recovered and an attempt to clean out the flowline was made using coiled tubing with tractor tooling. The coiled tubing reached a length of 23,059’ but failed to reach the full length of the flowline (28,789’), which was connected at both ends (A&B) with a Pipeline End Termination (or PLET).
In August 2020, Helix recovered PLET A to the Q4000 vessel via a drill string and rigging attached to the PLET hook and lifted through the water column. The flowline and PLET were secured on the vessel floor, and the pressure was bled off from the flowline, which was then cut away from the PLET. Helix installed a slip-on wellhead on the flowline and rigged up surface pressure control equipment along with a 340k snubbing unit from SBS Energy. Helix ran drill pipe into the flowline with the snubbing unit, the treatment fluid was heated with special equipment to +130°F on surface and pumped down the drill pipe to dissolve asphaltenes along the flowline. Helix ran the drill pipe to a final measured depth of 28,789’ while washing and reaming the flowline clean. The flowline was then flushed and displaced to seawater for the final circulation. The drill pipe was recovered from the flowline with the snubbing unit. The surface equipment was rigged down and the flowline was capped with a blind flange.
The highlight of the operation was to successfully clean out the Ozona flowline from the Q4000 rather than cutting the flowline up into sections which has been performed previously on long flowlines such as this one. This significantly reduces the number of critical subsea lifts, the EHS exposure and overall timeline for the flowline abandonment. The flowline was lowered subsea with the deployment rigging and drill string where it was laid back in the original trench on the sea floor. This is another benefit of being able to perform the full cleanout in a single lift and requires the least amount of onshore disposal of flowline components.
This method is an environmentally friendly, cost-efficient solution of performing a flowline cleanout rather than recovering the flowline and disposing it onshore. To date, this is the longest subsea flowline cleanout conducted via this method. The previous snubbing record depth of 23,800’ was set in 2006 by Helix (then Cal Dive) on the Q4000 during the Mariner Energy Pluto pipeline clean out.