By Brendan Conway Of DOW JONES NEWSWIRES NEW YORK (Dow Jones)--Traders made bets that no big negatives would afflict Transocean Ltd. shares in the few hours before June options' Friday expiry, while others signaled hope that Continental Airlines Inc.'s stock will stay aloft. Shares in Transocean, the rig operator at the center of the Gulf oil spill, surged 8.7% to $53.72, compounding a week of gains for the battered stock. Options traders executed what appeared to be sizable sales of the company's June $50 put contracts. A put conveys the right to sell shares, and selling a put signals confidence that a stock won't drop beneath certain levels. But, in this case, the contracts were set to expire Friday evening, when all the month's options contracts expire. For the day, traders picked up 81,000 call options granting the right to buy stock, compared to 52,000 puts, according to Track Data. Pocketing a small premium, traders effectively bet that Transocean's stock wouldn't drop below $50 in the few hours remaining before expiration. The contract traded for 5 cents by late morning but was down to a penny apiece as expiration drew near. "It's a low-reward, relatively high-risk strategy -- for if the stock sinks on bad news, they're on the hook to buy it at $50," WhatsTrading.com analyst Frederic Ruffy said. Fortunately for the investor, it appeared as though the day's notable gains in Transocean's stock would help it finish above $50. In Continental, an investor arrived midday to carry out what traders identified as a bullish "put spread" in the airline's July contracts. This trader appeared to sell 20,000 of the $20 put contracts while buying the same number of $17 contracts, at a net credit of 15 cents, Ruffy said. Investors carrying out this strategy often look for both contracts to expire worthless, in which case the investor keeps the proceeds. The trader may also be comfortable buying the stock at a price of $20. The stock was off 5 cents recently, to $24.73. The move brings some risk. The trader could lose as much as $2.85 per contract if Continental's stock falls under $17 before expiration next month. But as long as Continental stays above $20, he will be able to keep 15 cents per contract in what amounts to a cheap vote of confidence in the stock. Continental reports quarterly earnings on July 22. Elsewhere, traders executed what looked like another sale of puts in refinery operator Valero Energy Corp. Here, a few thousand July $16 put contracts changed hands that appeared to be sold, according to ONN.tv. Like the Transocean strategy, a trader selling puts collects a small premium and expects Valero shares to remain above the $16 level, in this case hoping the contracts expire worthless by the middle of next month. Valero shares rose 0.6% to $18.04 for the day. -By Brendan Conway, Dow Jones Newswires; (212) 416-2670; brendan.conway@dowjones.com (END) Dow Jones Newswires June 18, 2010 15:30 ET (19:30 GMT)