Cleary Gottlieb Steen & Hamilton is advising Mexican state oil company Petroleos Mexicanos on a $5.5 billion debt securities offering.

The offering, which is scheduled to close Dec. 13, comes on the heels of Mexico’s largest auction of oil rights. At that auction, held Monday, the country awarded eight of 10 deep-water oil blocks to some of the world’s top oil companies. Mexico ended Petroleos Mexicanos’ monopoly in the energy sector three years ago to permit foreign investment in hopes of increasing the country’s oil production capacity. Years of losses have left the company in difficult financial standing.