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MAJOR CUSTOMERS
12 Months Ended
Dec. 31, 2012
MAJOR CUSTOMERS

12.    MAJOR CUSTOMERS

In 2012, 2011, and 2010, purchases by Royal Dutch Shell plc and its subsidiaries accounted for 20 percent, 11 percent, and 15 percent, respectively, of the Company’s worldwide oil and gas production revenues. In 2011, purchases by the Vitol Group accounted for 13 percent of the Company’s worldwide oil and gas production revenues.