Royal Dutch Shell Plc announced on Thursday the sale of onshore U.S. shale gas assets as the energy company restructures its North America production and reins in costs.

Shell said it had agreed to sell its relatively mature natural gas-producing properties in Wyoming's Pinedale field and Louisiana's Haynesville field for about $2.1 billion in cash.

The Anglo-Dutch company is selling the Pinedale asset to Ultra Petroleum in exchange for $925 million in cash and acreage in the Marcellus and Utica oil and gas shale fields in Pennsylvania.

It will sell the Haynesville asset to Vine Oil & Gas LP and its partner Blackstone for $1.2 billion.

"We continue to restructure and focus our North America shale oil and gas portfolio to deliver the most value in the longer term," said Marvin Odum, Shell's Upstream Americas Director.

In the second quarter of 2014, Shell produced 190 million cubic feet per day (mcf/d) of natural gas from Pinedale. The Haynesville gas production reached 700 mcf/d as of July 1, Shell said.

Shell, like many other global oil companies, is carrying out a broad cost-cutting drive aimed at boosting profits. Its Chief Executive Ben van Beurden is seeking to offload $15 billion-worth of assets by the end of 2015.

The company has focused on selling gas assets where development costs are high while revenues are relatively low compared with the oil sector, especially as natural gas prices around the world have dropped sharply this year.

Shell's shares were trading up 0.24 percent at 29.635 pence per share at 1313 GMT. (Additional reporting by Henning Gloystein in London and Swetha Gopinath in Bangalore; Editing by Pravin Char)