NEW YORK (TheStreet) - In the energy sector, SM Energy (SM - Get Report), Petrobras Argentina (PZE) advanced last week, whereas Frontline (FRO - Get Report), CGG Veritas (CGV), Transatlantic Petroleum (TAT - Get Report), 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.

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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 - Get Report) fell 21%, Cobalt International Energy ( CIE) lost 20%, Helmerich & Payne ( HP - Get Report) shed 20%, while Nabors Industries ( NBR - Get Report) declined 18%.

Marathon Oil ( MRO - Get Report) 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 - Get Report) shed 18% as the company lowered production guidance for the full year. Tudor Pickering cut the stock to accumulate from buy.

Continental Resources ( CLR - Get Report) erased 18% after a cut to hold at Tudor Pickering.

CARBO Ceramics ( CRR - Get Report) and Patterson-UTI Energy ( PTEN - Get Report) relinquished 17% and 16.7%, respectively.

RPC Inc ( RES - Get Report) and Energy XXI (Bermuda) ( EXXI) trimmed 16.5% and 16.4%, respectively.