NEW YORK ( TheStreet) -- DryShips ( DRYS) won't stay out of the news.

The controversial Greek shipping concern announced Tuesday morning that it had "entered into" another set of charter contracts for three of its oil-exploration rigs, known as "drillships" in the maritime trade. All told, the contracts are worth $590 million over their multiyear lifespans, DryShips said.

The company's shares continued their roller-coaster ride. In morning trading Tuesday, the stock was changing hands at $5.33, up 2.7%, after earlier popping by as much as 4.8%. Those gains come after losing about 5% in the previous session, when Morgan Stanley ( MS) downgraded DryShips' stock.

>>Where Will DryShips Stock Trade in 2011

Four drillships in the company's nascent oil-exploration fleet are in the process of being completed at a South Korean shipyard. The biggest of the charter contracts announced Tuesday was for one of those newbuildings -- a drillship called the Poseidon, hired out by Brazilian energy giant Petrobras ( PBR) for use off the coast of Tanzania. The charter period is 600 days.

As part of the deal, one of DryShips' operating rigs, the Leiv Eiriksson, will be released from its current Petrobas contract. But DryShips also announced that Scotland's Cairn Energy will hire out the Eiriksson and another DryShips newbuilding, the Corcovado, for six months apiece. Those fixtures are for $95 million and $142 million, respectively.

Only one of its four newbuildings remains without a charter contract. DryShips had been working all of last year to hire out these ships, thus guaranteeing that it would be able to pay for them. It had struggled to find charterers, however, until late last year. The last of the newbuildings, the Mykonos, is scheduled for delivery in the fourth quarter of 2011.

DryShips also recently announced a deal to acquire 12 oil-tanker newbuildings for $780 million, which has garnered some criticism for its riskiness and a potential related-party transaction, as alleged by Morgan Stanley in its downgrade Monday.

-- Written by Scott Eden in New York

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