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.