BP shuts in 137 Alaska wells for production casing inspection

Sept. 4, 2002
A technical team of BP Exploration Inc. and outside experts are investigating the integrity of subsurface casings on 137 North Slope oil wells that the company shut in following an explosion and fire.

By OGJ editors

HOUSTON, Sept. 4 -- A technical team of BP Exploration (Alaska) Inc. and outside experts are investigating the integrity of subsurface casings on 137 North Slope oil wells that the company shut in following an explosion and fire at one unit that seriously injured a well pad operator in mid-August.

"We hope to get a recommendation from the technical team in the next week or so, but we won't bring the wells back on line until we're sure they're safe," a BP Exploration spokesman Wednesday told OGJ Online. The shut-in wells normally produce an aggregate 45,000 b/d, representing 5% of total North Slope production, he said.

The accident occurred Aug. 16 at Prudhoe Bay well A-22. That well earlier had been shut in because of high pressure in the outer annulus of its production casing, but was brought back on line "4-5 hours" prior to the accident. The pad operator had taken a gauge reading of the well's pressure and had started to his truck for tools to "bleed off" pressure when a casing apparently burst, the BP Exploration spokesman said. The worker remains hospitalized in Seattle, Wash., with broken bones and severe burns.

One of the issues being investigated by the technical team is why the outer annulus casing of the A-22 well failed. Pressures in excess of 2,000 psi were recorded at that well prior to the accident, "significantly lower" than the casing's official rating of more than 5,000 psi, BP Exploration reported.

Meanwhile, the investigating team recommended that BP Exploration shut in wells that had outer annulus pressures greater than 1,000 psi. The company began taking the wells off production Aug. 24.

At first, 150 oil wells were targeted, with a combined production of 60,000 b/d. But some of those wells were already off line, and a "handful" had annulus pressures below the 1,000 psi cutoff, the company said.

Natural gas produced in association with the oil contributes to the annulus pressure on those wells, said the company spokesman