NEW YORK (TheStreet) - Southern Union (SUG), McMoran Exploration (MMR), SunPower (SPWRA) and Cenovus Energy (CVE - Get Report) were top performers the past week, while STR Holdings (STRI), Transatlantic Petroleum (TAT - Get Report) and EXCO Resources (XCO) eroded value.

Among the advancers for the week, Southern Union topped the charts, jumping 17.6%, as Williams Cos. offered to buy Southern Union for $4.86 billion in an all-cash transaction, higher than the bid by Energy Transfer Equity LP.

McMoran Exploration rose 13.7% as CEO James Moffett is optimistic on gas finds in the shallow waters of Gulf of Mexico. He believes that new prospects could be valued at $50 to $65 per share. He further added that gas discoveries could have no liquids, but may produce gas liquids if found.

SunPower gained 11.8%.

Cenovus Energy advanced 8.3% after equity analyst John Mawdsley at Alta Corp Capital maintained a market outperform rating on the stock with a target price of $42.3 per share.

Rosetta Resources ( ROSE - Get Report) rose 11.8% over the week.

FMC Technologies ( FTI - Get Report) moved up 10.9% after the company signed an agreement with Shell Development (Australia) to supply sub-sea production and other related equipment and services used in field development. The company is required to supply seven large-bore sub-sea production trees, riser bases, sub-sea control systems, production manifolds and other related equipment.

Nexen ( NXY) advanced 10.8%.

SM Energy ( SM - Get Report) added 10.7% after the company announced plans to sell 12.5% stake in Eagle Ford shale to a Mitsui & Co. subsidiary for $680 million, as the proceeds could be used to develop assets in the shale play.

Trina Solar ( TSL) advanced 10.5% after analysts at Maxim Group rated a new buy on the stock with a price target of $26 per share. Brigantine Advisors equity analyst Ramesh Misra also rated it a buy with a target price of $35 per share.

Brigham Exploration ( BEXP) increased 10.1% after equity analyst John Selser of IBERIA Capital Partners raised the stock to outperform from sector perform with a target price of $42 per share.

Other winners included Swift Energy ( SFY) up 9.8%, Carbo Ceramics ( CRR - Get Report) rose 9.8%, Bristow Group ( BRS) grew 9.7%, Patterson-UTI Energy ( PTEN - Get Report) added 9.5%, Oasis Petroleum ( OAS) gained 9.4%, InterOil ( IOC) improved 9.3%, National-Oilwell Varco ( NOV - Get Report) piled 8.9% and Oil States International ( OIS - Get Report) added 8.5%.

STR Holdings was the top lagger, shedding 10.8% as the stock was downgraded to accumulate from buy at Craig Hallum's with a target price of $21 per share.

Transatlantic Petroleum lost 9.1% after news that the GRB-1 well could be abandoned.

EXCO Resources declined 7.6% after S&P Rating Services placed the company's RTGS on credit-watch negative.

JA Solar ( JASO) erased 2.1% after Brean Murray, equity analyst at Wayne Chang, downgraded the stock to sell from hold with a target price of $4 per share.

Others on the downside were Energy Transfer Equity ( ETE), Quicksilver Resources ( KWK) and Enbridge Energy Partners ( EEP) with marginal losses.