NEW YORK ( TheStreet) -- Pride International ( PDE), Lufkin Industries ( LUFK) and Frontier Oil ( FTO) were the top gainers, while Petrobras Argentina ( PZE), Nexen ( NXY) and Southwestern Energy ( SWN) headed the losers' list last week.Pride International gained 16.5%, topping energy gainers, after Ensco ( ESV) announced to buy Pride for $41.60 per share, representing a 21% premium to Prideâ¿¿s Feb. 04 closing price. On Friday, the stock closed at $40.08. Later, Wells Fargo raised the stock to outperform from market perform and its valuation for Pride to $45-$46 from $34-$36. However Macquarie Research, BMO Capital Markets, Barclays, Tudor Pickering, Howard Weil and Capital One Southcoast downgraded the stock preventing a further upside in the stock price last week. Lufkin Industries swung 14.1% higher after the company guided 2011 earnings per share at $2.5-$3.0 vs. consensus $2.67 and revenues at $800-$850 million vs. consensus $820.5 million. During the week, Johnson Rice initiated coverage on the stock with an overweight rating, while Howard Weil raised the stock to market outperform from market perform. Frontier oil gained 9.9% after BofA Merrill Lynch upgraded the stock to buy from neutral. Oil States International ( OIS) rose 9.0% after receiving a three-year contract valued $14 million to supply offshore marine cranes to PTT Exploration and Production. JA Solar Holdings ( JASO) climbed 6.6% last week, leading the pack of solar gainers. Other solar stocks such as First Solar International ( FSLR), Yingli Green Energy Holdings ( YGE), Trina Solar ( TSL), ReneSola ( SOL), GT Solar International ( SOLR) and LDK Solar ( LDK) advanced around 5.2%, 2.6%, 1.9%, 1.7%, 0.9% and 0.7%, respectively. BG Group (OTC: BRGYY) surged 6.5% after reporting a 13% increase in fourth-quarter profit to $1.06 billion, as revenue and other income grew 1.2% to $4.36 billion on improved realized prices. Meanwhile, the company has revised production estimates in Brazilâ¿¿s Santos Basin and the forecast for U.S. Shale gas production. Precision Drilling ( PDS) rose 6.4% last week. For 2010 fourth quarter, the company reported diluted earnings per share of 2 cents vs. a loss per share of 9 cents a year-ago. Revenues came in at C$435.5 million vs. consensus C$369.3 million, up from C$286.1 million reported for 2009 fourth quarter. Meanwhile, Raymond James has upgraded the stock to outperform from market perform. Core Laboratories ( CLB) advanced 6.0% after reporting 2010 fourth quarter earnings per share ex-items at 84 cents vs. estimates of 81 cents, while revenues came in $208.2 million vs. estimates of $206.7 million. Atwood Oceanics ( ATW) climbed 5.6% after Morgan Stanley upgraded the stock to overweight from underweight. Among major movers, Chesapeake Energy ( CHK) gained 2.6% last week. Argus Research upgraded the stock to hold from sell, while Ticonderoga Securities and Global Hunter Securities raised the rating to buy from hold. Meanwhile, Apache ( APA) added around 2.5% after tension eased in Egypt. Other winners include Atlas Pipeline Partners ( APL), SandRidge Energy ( SD), Brigham Exploration ( BEXP) and CARBO Ceramics ( CRR), up 9.8%, 9.5%, 9.2% and 5.7%, respectively. Petrobras Argentina was the top loser, erasing 8.1% value and continuing its losing streak from the penultimate week. Nexen edged 7.0% lower after Cormark Securities cut its rating on the stock to market perform from buy. CNOOC ( CEO) declined around 5.9% despite BNP Paribas raising the stock to buy from hold on attractive valuations. Premier Oil (OTC: PMOIY) dipped around 5.4% after evolution Securities downgraded the stock to add from buy. Similarly, Statoil ( STO) shed 5.3% after Macquarie Research downgraded the stock to neutral. Newfield Exploration ( NFX) was down 5.1% after Jefferies downgraded the stock to hold from buy, citing valuations and lowered price target to $70 from $76. Among others, FMC Technologies ( FTI), PetroChina ( PTR), Petroleo Brasileiro ( PBR) and Exterran Holdings ( EXH) dipped 5.9%, 5.6%, 4.9% and 4.4%, respectively.