Houston-based Marathon Oil Corporation announced Wednesday that it has entered into definitive agreements to sell the majority of its “Minnesota downstream assets” for $900 million.

The company first announced plans to sell its Minnesota assets in May, when it signed a non-binding letter of intent with Washington, D.C.-based Acon Investments, LLC, and Fort Worth, Texas-based TPG Capital, LP.

Marathon expects the deal to close by the end of the year, subject to Acon and TPG meeting the conditions of their financing arrangements and other customary closing conditions.

Included in the transaction is Marathon's 74,000 barrel-per-day St. Paul Park refinery; 166 SuperAmerica convenience stores (including six stores in Wisconsin); SuperMom's, LLC, a distributor of bakery products and sandwiches; SuperAmerica Franchising, LLC, a franchising and licensing company; interests in pipeline assets in Minnesota; and associated store inventories.

The sale will also include a supply contract to 90 SuperAmerica stores in Minnesota that are independently owned.

Marathon spokeswoman Angelia Graves said that the sale affects about 3,100 workers, most of whom are SuperAmerica employees. Graves said that the new owners agreed to make job offers to all active employees.

ACON and TPG have formed Northern Tier Energy, LLC, to operate the Minnesota assets as a stand-alone company.

Marathon is the fourth-largest integrated oil company in the country and the fifth-largest refiner, according to the company, which reported $53.5 billion in 2009 revenue.

-Melissa Loth