Several years after corrosion caused pipeline leaks and spills near Prudhoe Bay, corrosion remains the No. 1 threat to Alaska’s flow lines—“aging infrastructure” that “warrants heightened monitoring,” according to a new draft of the state's Alaska Risk Assessment.
Flow lines that carry a combination of oil, gas and produced water “pose the greatest risk of large spills and warrant the highest-priority attention,” according to the “North Slope Spills Analysis” just released by the Alaska Department of Environmental Conservation.
2 Spills, 5 Months
The purpose of the ARA analysis is to reduce the number and severity of spills on the North Slope.
The ARA project followed a 212,252-gallon oil spill in March 2006 between Gathering Center 2 and GC1 in the Prudhoe Bay oilfield, operated by BP Inc. The leak was traced to internal corrosion—a quarter-inch hole in the 6 o’clock position in an above-ground 34-inch-diameter crude-oil transit pipeline.
Five months later, a leak was discovered near Flow Station 2 in the oilfield. Investigators discovered 16 anomalies in 12 locations along the section—anomalies that were traced to corrosion-related pipeline wall thinning. The oilfield was temporarily shut down.
Spill Increase Noted
The new report cites “a slight increase in spills over 1,000 gallons from flow lines,” but it did not quantify the increase.
Most spills of more than 10,000 gallons are from flow lines, which make up the majority of the North Slope’s 800+ pipeline miles, the report said. Flow line spills are eight times more frequent than oil transmission pipeline spills (4.9 spills per year) and tend to be larger.
And the No. 1 cause of those spills? “Corrosion is the most frequent cause of failure for flow lines and the most frequent cause of spills over 1,000 gallons,” the report said
Call for ‘Increased Vigilance’
The report said that the petroleum infrastructure was not nearing its “end of life” and that investigators had found “no significant change” in spill trends.
However, it also urged “increased vigilance, corrective actions and oversight” of the flow lines, saying, “Older infrastructure warrants special attention; evidence suggests the probability of North Slope spills is linked to age.”
The report suggested “incremental improvements in current operations and regulatory oversight,” rather than “a completely different risk management structure.”
The assessment makes seven major recommendations:
• Standardize and improve spill data collection in order to better assess trends and common causes of spills.
• Oversee implementation of corrective or preventive measures to evaluate their impact and effectiveness.
• Utilize existing and emerging technologies to reduce the time required to detect pipeline leaks.
• Establish a system of escalated enforcement to enhance and increase regulator attention on operators that have spills on the North Slope.
• Adopt or model Integrity Management Program components for flow lines and require documentation of IMP-like activities for flow lines.
• Move to an integrated IMP that focuses on leading indicators, including aggressive monitoring and control of Corrosion Under Insulation (CUI).
• Conduct regular proactive risk analyses to maintain systems at a prescribed level of safety.