By Steve Gelsi – Energy stocks traded mixed Thursday as investors weighed another sector acquisition against lower expectations for natural-gas prices down the road.

The NYSE Arca Oil Index rose 0.1% to 1,130, as the benchmark again approached its 52-week high of 1,132 on higher oil prices.

The NYSE Arca Natural Gas Index dipped 0.1% to 566.

The Philadelphia Oil Service Index also fell, off 0.2% to 215.

Shares of Mariner Energy Inc. (ME) jumped 39% to $25.15 after independent oil and gas producer Apache Corp. (APA) said it would buy the exploration firm. Including assumed debt, the deal carries a price tag of about $4 billion.

Also in the spotlight, Seadrill Ltd. (SDRL) shares jumped 6% to $26.58 in their debut on the New York Stock Exchange. The operator of drill ships and offshore platforms has been trading on the Oslo exchange.

Shares of Valero Energy Corp. (VLO) fell 17 cents to $20.19. Credit Suisse initiated coverage of the refining giant with an outperform rating.

In the energy pits, crude-oil prices rose 19 cents to $86.03 a barrel.

S&P Equity Research on Thursday increased its 2010 price target for West Texas Intermediate crude by $4.11 to $83.19 a barrel, after reviewing forecasts from IHS, the Energy Information Administration and Bloomberg. And for 2011, S&P Equity now expects oil prices of about $86.10, up from its earlier view by $4.10 a barrel.

S&P also cut its target price for natural gas in 2010 by 9 cents to $4.04 per British thermal unit. Its 2011 target price was reduced by $2.36 to $3.93 per British thermal unit.

-By Steve Gelsi; 415-439-6400; AskNewswires@dowjones.com

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