Nation biggest oil field of United States was shutdown after an indication of severe pipeline corrosion. The Trans-Alaskan Pipeline is one of the world largest oil pipeline. The line that is known for it zig-zag pattern to allow thermal expansion and earthquake movement. The pipeline was designed to allow 5 feet of vertical movement and up to 20 feet laterally. The pipeline which cost about USD 8 billion to build sits on top of 78,000 aboveground supports spaced 60 feet apart.
Figure 1 - Prudhoe Bay Pipeline Network (Source: USA Today, BP, EIA, CSI)
The sections aboveground are insulated and covered. Build in the 1970s after oil discovery at Prudhoe Bay in 1968. The pipeline is 48-inch diameter, 800 mile of line links Prudhoe Bay on the Arctic Ocean with a terminal at Valdes, the ice-freeport within the area. This pipeline serves Californian and some US West Coast Refineries, which accounts for roughly 20 percent of US oil annual production or 2,6% US national supply or about 400,000 barrels per day.
Figure 2. Trans-Alaskan Pipeline
Oil spill was reported in March 2, 2006. US Department of Transportation ordered smart pig inspections responding the leaking report. The inspection record noted that the steel had corroded in 12 places on the eastern side of Prudhoe Bay up to 70-81% orginal thickness which was less than company standard. According to the company corrosion authority, the pipeline was designed for 25 year and at the time of leaking the pipeline was 29 years lasted. Company spent to fight corrosion USD 72 million at the year of leaking and USD 60 million previous year. The effort, according to the company man including corrosion inhibition, X-Ray runs, and ultrasonic tests.
Reference
1. BP: Pipeline shutdown could last weeks or months (USA Today)
2. BP to Shutdown Prudhoe Bay Oilfield (BP Global Press)
3. BP's Prudhoe Bay Pipeline Shutdown Could Continue into Next Year (Guardian UK)
4. Oversight Hearing on BP Pipeline Failure (PHMSA DOT US)
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