BP isn’t just replacing transit lines at Prudhoe Bay, where leaks last year resulted in a partial field shutdown in August. The company is rebuilding the entire transit line system, a process that will take until the end of 2008 to complete and includes 20 new modules and a pilot leak-detection system.
BP Exploration (Alaska)’s new senior vice president for Greater Prudhoe Bay operations, Mike Utsler, and Tony Brock, vice president and technical director, briefed Senate Resources Feb. 14 on the status of the cleanup and replacement following transit line leaks last year.
Utsler told the committee he’s been in this role for six weeks after spending the last five years working in BP’s North Sea operations; after 22 years with Amoco he joined BP at the merger eight years ago. He said his work has been largely in operations, “particularly focusing on our mature operations around the globe. I’ve spent many years working the aspects of how to optimize and improve the performances of mature, declining fields — very much like the Prudhoe Bay environment,” he said.
In reviewing what has been accomplished since August, Utsler said that in addition to installing five bypasses to move current oil, “we have other bypasses that we’ve also installed but aren’t currently using.” Those bypasses, he said, would allow the company a short response time to any future event that would require shutting down a section of the transit system, allowing a quicker return to full production.
The planned maintenance-repair budget for the Greater Prudhoe Bay area is $195 million for 2007, Utsler said, roughly four times what was spent in 2004. He said maintenance strategies are being revised at Prudhoe, and the expectation is that the maintenance spend could potentially increase “to ensure ourselves that we absolutely can keep this product in the pipelines.”
Maintenance pigs now being run weekly
Brock, appointed technical director for BP Alaska in August, told the committee he’s been with BP for 20 years.
In reviewing progress since the spill he said BP is still working to determine “the actual root cause, the actual mechanism that caused these leaks.” There are three causal factors involved: water in the system; sediment buildup in the lines; and bacteria. Velocity in the lines is also an issue, as these are predominantly 30- and 34-inch lines which were “designed for much greater flow rates” than Prudhoe has today, he said.
Brock said the strategy is to change the environment in the pipe with continuous corrosion inhibitor added directly to the transit lines and with water or sediment buildup addressed with weekly maintenance pig runs. Any solids from the weekly runs are analyzed for bacteria growth and sediment buildup, he said.
Solids were recovered initially, but that recovery has dropped off.
“What I can tell you to date is we have had little or no solids returned on these weekly pigging operations, but they are beneficial because they do actually clean the inside of the pipe; they do remove any residual water; and they actually give us a clean surface for the biocide inhibitors to actually interface with the pipe body itself.”
With weekly cleaning pigs and continuous analysis, Brock said they can look for any changes in the pipeline system and make changes as needed in operations or inspections.
Replacement pipe keyed to future production
Replacement transit lines range in size from 12 inches to 28 inches, based on projected production, “to give us optimal production and … management of the transit line flow conditions,” Brock said. “In this we’ve actually addressed a number of issues that we identified through these leaks.”
Asked about optimal flow rate by Resources Chair Charlie Huggins, R-Wasilla, Brock said optimum velocity in the line is about three feet per second, so the pipe is being sized based on forecasted projection rates “that they’re expected to see for the majority of their life” and based on that targeted flow rate.
Pig launchers and receivers are being incorporated in all segments of the transit lines, he said, giving BP the capability to regularly run maintenance and smart pigs in all segments of the transit lines.
There will also be continuous corrosion inhibitor chemical injection points on all the lines, “and we’re changing our corrosion monitoring techniques to update them to allow us to have continuous corrosion monitoring in all these segments.”
There will be 20 new modules and skids, he said.
A new leak detection system is also being pilot tested. “It will be more sensitive, repeatable and more reliable,” he said, allowing BP “to identify small leaks in the system similar to the ones that occurred during the summer.”
The pipelines will be built to Department of Transportation standards, he said, and have an external coating with a 30-year life.
And the system will be redesigned to eliminate some of the characteristics that BP believes contributed to corrosion, such as caribou crossings that cause dips in the line. The new line will be elevated to four feet.
Work this winter and next
In addition to replacing the pipe, “we’re actually providing new modules to support the management of the pipe, the maintenance of the pipe, for future field life,” Brock said. The modules will be built in Anchorage and transported to the slope for installation this winter and next.
Two segments of the transit system will be replaced this year, Brock said, and two in the winter of 2008. He said the module work is expected to take a little longer, “but our current goal is that we’ll actually install and commission the entire system by the end of 2008.”
There are 250 people in the pipeline installation crew and Brock said BP added a 150-person camp and secured 100 extra beds in Deadhorse to accommodate the workers, who are currently replacing a line at Milne Point. He said the Milne Point line replacement is simpler, although it is being done in arctic winter conditions, “and we wanted to actually allow the team to cut their teeth on this project before they moved to the more congested and complex operating environment of Greater Prudhoe Bay.”
