NEW YORK ( TheStreet) -- Duncan Energy Partners ( DEP), Chesapeake Energy ( CHK) and SandRidge Energy ( SD) were the top gainers, while Seacor Holdings ( CKH), JA Solar Holdings ( JASO), and ReneSola ( SOL) headed the losers' list last week.Duncan Energy Partners gained 24.5%, topping energy gainers, after Enterprise Products Partners ( EPD) made an offer to acquire the company. Enterprise offered 0.9545 shares for each Duncan share, representing a 30% premium based on Feb. 18 closing price. Citigroup upgraded Duncan Energy to buy from hold, while RBC capital downgraded the stock to sector perform from outperform. Chesapeake Energy rose 16% on multiple events that happened during the week. BHP Billiton ( BHP) agreed to buy the company's Arkansas shale gas assets for $4.75 in cash that will help Chesapeake reduce its debt. Additionally, Chesapeake reported robust 2010 fourth quarter earnings per share at 70 cents ahead of analysts' estimates of 64 cents. Later in the week, Citigroup raised its target price for the stock to $35 from $28, maintaining hold rating. The bank estimates Chesapeake's 2011 EPS at $2.97 vs. consensus $2.70 and 2012 EPS at $3.64 vs. consensus $2.70. Meanwhile, BMO capital raised its target to $39 from $30, reflecting the company's increased production of oil and liquids. Separately, Oppenheimer raised its target to $40 from $28, maintaining outperform rating, on attractive valuation compared with its peers. Lastly, Canaccord Genuity upgraded the stock to buy from hold. SandRidge Energy surged 13.5%, after reporting 2010 fourth quarter adjusted earnings per share at 7 cents vs. consensus loss of 8 cents per share. During the week, the company signed an agreement to sell certain New Mexico properties for $200 million. Cabot Oil & Gas ( COG) rose 12.3% last week, after reporting stronger-than-expected 2010 fourth quarter revenue at $216.9 million vs. estimates of $212.4 million. UBS raised its target price for the stock to $44 from $38, while maintaining its neutral rating, after Cabot Oil & Gas issued production growth guidance of 33% for 2011, in comparison to bank's estimate of 25%. Wells Fargo upgraded its valuation range on Cabot Oil & Gas to $52-$53 from $47-$50, while maintaining an outperform rating. The bank raised its 2011 EPS estimate to 89 cents from 40 cents. Meanwhile, Tudor Pickering upgraded the stock to buy from accumulate. Raymond James upgraded the stock to market perform from underperform.