FACTBOX: Enbridge Canada-U.S. oil pipeline world's biggest

(Reuters) - The Enbridge pipeline system that ships nearly 2 million barrels per day (bpd) of Canadian crude and fuel from Alberta to the U.S. Midwest and some Canadian refineries is the world's longest and most sophisticated, the company says.

An explosion and fire on the pipeline three miles southeast of the Clearbrook, Minnesota, oil terminal occurred on Wednesday at approximately 3:45 p.m. CST, killing two employees and halting shipments that make up nearly a tenth of U.S. imports.

All Enbridge pipelines in the vicinity -- Lines 1, 2, 3 and 4 -- were immediately shut down and isolated and Enbridge emergency crews were dispatched to the site, it said. Those lines pumped some 1.5 million barrels per day (bpd) in the third quarter.

Find additional details about the lines affected, the types of crude oil involved and refineries below:

THE FOUR AFFECTED LINES:

The fire broke out on line 3, which had been shut down for maintenance on Wednesday in order to investigate a small leak, Enbridge spokesman Larry Springer told Reuters.

He said all four lines of the pipeline will be shut down until the fire dies down enough to allow for inspections of lines 1 and 2, which are located several hundred feet away from the source of the fire and explosion. Springer warned that larger Lines 3 and 4 were likely to remain shut for some time.

Details of the four lines, according to the Enbridge Web site:

LINE 1: capacity 237,000 bpd.

Carries natural gas liquids and refined oil products. Needs to be investigated by company before restarted; investigations to begin once the fire burns down sufficiently.

LINE 2: capacity 409,000 bpd.

Carries condensates, synthetics, light and medium crudes. Needs to be investigated by company before restarted; investigations to begin once the fire burns down sufficiently.

"There is nothing from any other sources that would make us think there is any damage (to Lines 1 and 2), but as prudent operators we have to inspect them before we start them back up."

LINE 3: capacity 447,000 bpd.

Carries light, medium and heavy crudes. Will require repairs and inspection by the company and by regulatory agencies before being restarted. "(Line 3) will be the one that take the most work, it will need repairs plus the investigations."

LINE 4: capacity 669,000 bpd.

Carries heavy crudes. "It's not likely line 4 will start up anytime soon," Springer said.

MINNESOTA REFINERIES THAT COULD BE AFFECTED:

* Flint Hills Resources' 280,000 bpd refinery in Rosmount, Minnesota. A spokeswoman for Flint Hills said she did not have information immediately available on Wednesday night about the impact of the pipeline shutdown on refinery operations.

Flint Hills is a wholly-owned subsidiary of Koch Industries Inc, which also operates Koch Pipeline Co.

* Marathon Petroleum Co LLC's 70,000 bpd at St. Paul Park, Minnesota. Receives Canadian crude via the Minnesota Pipe Line operated by Koch Pipeline Co LP, which receives crude from the Enbridge Pipeline at the Clearbrook station.

REFINERIES FROM OTHER MIDWEST STATES:

* Illinois -ExxonMobil, Joliet, 239,000 bpd

-Marathon Petroleum, Robinson, 192,000 bpd

-PDV Midwest Refining Lemont, Chicago, 167,000 bpd

-WRB, Wood River, 306,000 bpd

* Michigan -Marathon Petroleum, Detroit, 100,000 bpd

* Wisconsin-Murphy Oil, Superior, 34,000 bpd

* Ohio:-BP's 131,000 bpd Toledo refinery

-Marathon's 73,000 bpd Canton refinery

-Premcor's 146,000 bpd Lima refinery

-Sunoco's 160,000 bpd Toledo refinery

ABOUT THE LAKEHEAD PIPELINE SYSTEM:

* The Lakehead System, the U.S. portion of the giant pipeline, consists of nearly 3,300 miles of pipe ranging from 12 to 48 inches in diameter, most of which is underground.

* The original Enbridge pipeline was built to carry oil from the Leduc, Alberta oil fields to Regina, Saskatchewan, and then extended from Regina to Superior, Wisconsin. It was put into full operation in 1950 and extended to Sarnia, Ontario, in 1953.

* The Lakehead System's tank storage capacity is approximately 10 million barrels of crude oil in 58 crude oil storage tanks located at three terminals. It takes almost 14 million barrels of liquid petroleum to fill the system.

* In 1994, the Capacity Expansion program added a new line to the system between Hardisty, Alberta and Clearbrook, Minnesota.

* The Lakehead System employs over 400 employees.

(Sources: Reuters reports, Enbridge Web site www.enbridge.com)

(Reporting by Maryelle Demongeot and Luke Pachymuthu)