Marathon Petroleum Corp, the third-largest standalone U.S. refining company, said its quarterly profit rose 44 percent, helped by higher crude refining margins on the Gulf of Mexico coast.

Gulf Coast refiners' profits have shot up as new and expanded pipelines bring them cheaper North American crude, helping them boost margins when exporting refined products.

Marathon's purchase of BP Plc's Texas City refinery in 2012 has raised its exposure to the Gulf Coast, which now accounts for about two-thirds of its refining capacity.

Crack spread - the difference between the price of crude oil and the petroleum products extracted from it - for Light Louisiana sweet on the Gulf Coast rose by $2.55 per barrel in the second quarter from a year earlier, the company said.

Marathon, which is making a big push into pipeline and retail businesses to shield itself from the volatile refining business, said it expects to invest about $295 million in Enbridge Inc's Southern Access Extension pipeline project.

The pipeline will transport crude oil from Flanagan, Illinois, to a crude storage and blending hub in Patoka, Illinois, and is expected to up and running by mid-2015.

Marathon also said that the Federal Trade Commission had concluded its review of the company's purchase of Hess Corp's retail business and that the deal would close by the end of the year.

Marathon bought the business to expand its network of gas stations and convenience stores along the U.S. East Coast. The deal will result in Marathon's retail unit, Speedway, growing to more than 2,700 stores in 23 states, the company said.

Net income attributable to Marathon rose to $855 million, or $2.95 per share, in the quarter ended June 30, from $593 million, or $1.83 per share, a year earlier.

Revenue rose 4.5 percent to $26.84 billion.

Marathon on Wednesday raised its share buyback program by $2 billion.

The company also raised its dividend to 50 cents per share from 42 cents, marking the fourth such increase since it was spun off from Marathon Oil Corp in July 2011.

(Reporting by Swetha Gopinath in Bangalore; Editing by Saumyadeb Chakrabarty and Simon Jennings)