Dutch supermajor Shell said it was spending $350 million to increase its holdings over two companies with strong positions in the U.S. Gulf of Mexico.

Shell pays out to take in another 20 percent stake in the Mars Oil Pipeline Co. and a 49 percent interest in Odyssey Pipeline, two companies with networks tied to the Gulf of Mexico.

"Both Mars and Odyssey build on our key corridor pipeline strategy in the Gulf of Mexico and are advantageously positioned to continue to capture growth of offshore volumes along our footprint of assets," John Hollowell, the CEO in charge of Shell's pipeline business, said in a statement.

Closing on Oct. 3, Shell said the deal, which adds a combined 880,000 barrels of carrying capacity per day to its portfolio, should immediately pay off for its shareholders.

Shell in August sold its entire stake in three blocks known collectively as the Brutus/Glider assets in the Gulf of Mexico in a deal that included $425 million in cash. A few weeks later, the company said it started production from the Stones development in the Gulf of Mexico using a floating production, storage and offloading vessel, the 13th such facility in its portfolio and, tapping a basin beneath 1.8 miles of water, the world's deepest such development.

By the end of next year, the company said Stones should be producing around 50,000 barrels of oil equivalent per day.

The Gulf of Mexico accounts for about 16 percent of the total oil and 4.5 percent of the total natural gas produced in the United States.

Shell this year has moved away from other North American projects apart from the Gulf of Mexico, saying capital constraints were in part behind a decision to delay a final investment decision for a gas export facility in Canada.

Moving through the year after its mega-merger with British energy company BG Group, the company reported its net income during the second quarter fell more than 70 percent to $1.18 billion.