NEW YORK ( TheStreet) -- Atlas Pipeline Partners ( APL), Southwestern Energy ( SWN) and Encana ( ECA) were the top gainers, while YPF ( YPF), Oasis Petroleum ( OAS) and Oil States International ( OIS) headed the losers' list last week.

Atlas Pipeline Partners ( APL) and Southwestern Energy ( SWN) grossed highest gains last week, growing 12.1% and 11.4%, respectively.

Encana rose 11.1%, after the company sought to buy a 30% stake in the Kitimat liquefied natural gas terminal. The company has agreed to acquire a 30% interest in the planned Kitimat LNG export terminal -- located on the west coast of central British Columbia -- and the associated natural gas pipeline.

Other prominent winners were Comstock Resources ( CRK), InterOil ( IOC) and EV Energy Partner ( EVEP), up 11.1%, 10.9% and 10.5%, respectively.

Cabot Oil & Gas ( COG) surged 10.1% after the company received an upgrade from a couple of leading brokerages. The BOFA Merrill Lynch revised the stock's investment rating to buy from neutral and increased the price target to $55. Besides, Goldman Sachs also upgraded the stock to buy from neutral, following Marcellus Shale growth, and revised its target price upwards to $60 from $52.

STR Holdings ( STRI) rose 10.1% last week after the company reported 2010 net income of $49.3 million, from $ 23 million in 2009, benefiting from robust sales of its solar products, particularly in Asia.

Solar Stocks Yingli Green Energy Holding ( YGE) and Trina Solar ( TSL) were up 9.8% and 9.6%, respectively.

Other winners Petrohawk Energy ( HK) and Teekay LNG Partners ( TGP) rose 9.2% and 9%, respectively.

Complete Production Services ( CVX) advanced 9% after SunTrust initiated a buy on the stock with a target price of $37.5.

Other solar stocks Rosetta Resources ( ROSE), CARBO Ceramics ( CRR), Ultra Petroleum ( UPL), GT Solar International ( SOLR) and Range Resources ( RRC) advanced around 9%, 8.5%, 8.5%, 8.4% and 7.9%, respectively.

YPF was a major loser, erasing 9% value last week. Oil States International shed 5.2%. Oasis Petroleum lost 5.3% during the week, after brokerage firm Madison Williams downgraded the stock from accumulate to neutral, citing relative valuation.

Among other losers, Enbridge Energy Management ( EEQ), Ecopetrol ( EC), PetroChina ( PTR), China Petroleum & Chemical ( SNP) and Tidewater ( TDW) dropped 4.4%, 4.3%, 4.1%, 4.1% and 3.7%, respectively.

Quicksilver Resources ( KWK) erased 3.5% last week. According to the Wall Street Journal, Dardens, the founding family of Quicksilver Resources holding 26% equity share, abandoned the bid to take the company private. The Darden family and SPO Partners & Company -- QuickSilver's second-largest shareholder -- were given time until March 16 to arrange for the buyout. However, talks between SPO Partners and Dardens failed and the bid was subsequently dropped.