CNSOPB Releases Marathon Crimson F-81 Incident Report

The Canada-Nova Scotia Offshore Petroleum Board released its report into the discharge of synthetic based drilling mud (SBM) at the Crimson F-81 well on August 26, 2004.

The cause of the discharge has been identified as a flaw in a rubber compound seal ring inside of a flex joint, which is part of the riser mechanism connecting the drillship to the well on the seafloor. The failure was due to inherent flaws in the rubber, and could not have been identified without dismantling the entire mechanism and performing specific tests – which is beyond any legislated requirements or industry standards.

During drilling the flex joint is located 17.6 meters above the seafloor, and the riser is filled with SBM from the drillship to the seafloor. SBM is specialized fluid used to lubricate and maintain pressure on the well during drilling, as well as to return drill cuttings to the surface. The seal ring flaw caused 354 cubic meters of SBM to be discharged onto the ocean floor at a depth of over 2 kilometers.

The Board will not be pursuing charges against Marathon Canada ULC, operators of the Crimson F-81 project, as the discharge was due to an unforeseeable and unpreventable mechanical defect. All equipment on the project was properly procured, inspected and approved for use, and Marathon did not violate any regulations during operations.

Due to its density no SBM could have flowed to the surface, and therefore any environmental impact was confined to the seafloor. Although scientific knowledge of the effects of such discharges on the seafloor environment is limited, SBM is designed for low toxicity and any such impact is expected to be localized and short term.

The Board's goals for all such investigations are to identify the cause and circumstances of the incident and determine if any regulations were contravened. Then, the Board seeks to learn as much as possible to help prevent similar occurrences in the future.

Following this investigation, the Board is making recommendations that regulations regarding flex joint testing be improved. These changes will make inspections and documentation requirements more rigorous, in an attempt to ensure any manufacturing flaws can be identified before the equipment is approved for use. As well, the Board is recommending governments develop standards specifically addressing potential discharges of SBM and other substances.