UPDATE 3-U.S. releases 500,000 barrels of oil from strategic reserve

(Adds details of the exchange in paragraph 3)

WASHINGTON, Aug 31 (Reuters) - The U.S. Energy Department said on Thursday it would release 500,000 barrels of crude oil from the Strategic Petroleum Reserve as Tropical Storm Harvey's disruption of the petroleum industry has spiked motor fuel prices.

The oil will be delivered to the Phillips 66 refinery in Lake Charles, Louisiana, according to a department statement. That plant has not been affected by the storm, which has hammered the Gulf Coast for several days.

The release, the first emergency release from the reserve since 2012, includes 200,000 barrels of sweet crude and 300,000 barrels of sour crude oil, the statement said. It was an exchange agreement, meaning the government will loan crude to Phillips 66, which is required to replace the reserve's oil at a later date.

The reserve, established in the early 1970s after the Arab oil embargo caused panics over fuel supply, currently contains 679 million barrels of oil. It is a small release of crude for a country that uses nearly 20 million barrels of petroleum daily.

Harvey shut down about a quarter of the country's refining output after it lashed Houston with record floods before it spread to the Louisiana coast, another refining hub.

U.S. gasoline prices surged anew in morning trade after the Colonial Pipeline Co, which operates the biggest U.S. fuel transport system, said it would shut its main lines to the Northeast amid outages at pumping points and lack of supply from refiners.

The Energy Department "will continue to provide assistance as deemed necessary, and will continue to review incoming requests for SPR crude oil," spokeswoman Jess Szymanski said.

Senator Edward Markey, a Democrat, urged the department this week to also release gasoline from the country's emergency gasoline reserve, which holds a total of 1 million barrels of oil in three locations in the Northeast: New York Harbor, Boston and Maine. (Reporting by Timothy Gardner; Editing by Bernadette Baum)