May 28 (Bloomberg) - By Fred Pals - Royal Dutch Shell Plc, Europe's largest energy producer, agreed to buy most of closely held East Resources Inc. for $4.7 billion in cash, expanding its holdings of U.S. shale gas deposits.

As part of the deal, Shell will obtain new positions in "high potential" U.S. shale gas acreage, in the Marcellus and Eagle Ford plays, according to a statement today. The sale is expected to be completed in two phases starting from the summer.

Shell is catching up with Exxon Mobil Corp. and BP Plc in snapping up unconventional gas reserves in anticipation prices for the cleaner-burning fuel will recover as governments curb carbon dioxide emissions. The Marcellus Shale, which stretches into New York, may hold 262 trillion cubic feet of recoverable gas, making it the biggest known U.S. deposit of the heating and power-plant fuel, the Energy Department estimates.

"They've seen others take material positions in U.S. gas, and this is one way they can also play a part in that business," said Jason Kenney, head of oil and gas research at ING Commercial Banking in Edinburgh.

The acquisition is the second-biggest oil and gas deal this year, after BP's acquisition of deepwater assets from Devon Energy Corp. for $7 billion in March, according to Bloomberg data.

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