On Aug. 16, the State Pipeline Coordinator’s Office, an agency within the Alaska Department of Natural Resources, released its annual report for the fiscal year ending June 30, 2006. The report includes an assessment of the condition and surveillance of the common carrier pipelines on the North Slope, including the Alpine, Badami, Endicott, Kuparuk, Milne Point and Northstar oil pipelines.
SPCO does not oversee field gathering lines, such as the Prudhoe Bay transit lines where BP has found severe corrosion problems.
Overall the agency has found the common carrier pipelines to be in good shape. SPCO said the ConocoPhillips and BP affiliates that operate the pipelines have run smart pigs through the lines in the past three years. However, only some portions of the Kuparuk pipeline can be tested with smart pigs — ConocoPhillips uses other techniques such as ultrasonic testing to monitor sections of the pipeline that cannot be pigged, SPCO said. ConocoPhillips also cleans the piggable sections of the Kuparuk line monthly with a maintenance pig.
All of the pipeline operators perform regular external checks of the condition of the pipelines. The operators also use corrosion coupons, small pieces of metal place in the pipeline fluid flow to assess internal pipeline corrosion, the agency said.
ConocoPhillips uses an airborne infrared detector to regularly monitor the Alpine and Kuparuk lines for leaks. All pipelines have leak detection systems.
Of the older oil pipelines, the ConocoPhillips-operated Kuparuk pipeline and the BP-operated Milne Point pipeline exhibited some corrosion issues. The Kuparuk line appears in good condition internally but is suffering some external corrosion at wells packs, SPCO said.
A 2005 smart pig run in the Milne Point pipeline showed an increase over a four year period from one internal corrosion anomaly to more than 1,000 anomalies, 144 of which “were identified as being in the 40 percent to 50 percent and 50 percent to 60 percent depth range.”
An Aug. 4 SPCO report on recent surveillance of the BP common carrier lines said that BP is increasing the frequency of maintenance pigging for cleaning the Milne Point line and that BP’s common carrier pipeline corrosion surveillance and monitoring programs are satisfactory.