NEW YORK ( TheStreet) - In the energy sector, SM Energy ( SM), Petrobras Argentina ( PZE) advanced last week, whereas Frontline ( FRO), CGG Veritas ( CGV), Transatlantic Petroleum ( TAT), STR Holdings ( STRI) and Exterran Holdings ( EXH) eroded substantial value.Among the week's advancers, SM Energy topped the charts gaining 4.4% as it announced the sale of mineral rights acreage in the Eagle Ford basin in Texas for about $227.4 million. The company also reported positive second-quarter earnings. Jefferies upgraded the stock to buy from hold with a target price of $114 per share. Frontline was the top lagger, shedding 28%. Jefferies equity analyst Douglas Mavrinac downgraded the stock to hold from buy with a 12-month target price of $10 per share. Bloomberg also published an article citing slow demolition rates hurting revenue for tankers. >> Keep the stock market at your fingertips with TheStreet's iPad app. CGG Veritas shed 27% after second-quarter results fell below guidance. Operating income came at $16 million, 60% below consensus estimates. Transatlantic Petroleum plummeted 27% at close last week. STR Holdings plunged 24% as Macquarie Research equity analyst Kelly Dougherty downgraded the stock to underperform from neutral with a 12-month target price of $11.5 per share. Exterran Holdings ( EXH) retreated 23% after Credit Suisse downgraded the stock to neutral from outperform with a target price of $17 per share from $32. Among other losers last week, ReneSola ( SOL) fell 21%, Cobalt International Energy ( CIE) lost 20%, Helmerich & Payne ( HP) shed 20%, while Nabors Industries ( NBR) declined 18%. Marathon Oil ( MRO) erased 19% after the company reported disappointing earnings. The stock was downgraded to neutral from outperform at Credit Suisse with a target price of $36 per share. Climarex Energy ( XEC) shed 18% as the company lowered production guidance for the full year. Tudor Pickering cut the stock to accumulate from buy. Continental Resources ( CLR) erased 18% after a cut to hold at Tudor Pickering. CARBO Ceramics ( CRR) and Patterson-UTI Energy ( PTEN) relinquished 17% and 16.7%, respectively. RPC Inc ( RES) and Energy XXI (Bermuda) ( EXXI) trimmed 16.5% and 16.4%, respectively.