The ratings of 17 Oil and Gas stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, SandRidge Permian Trust (NYSE:PER) falls to a D (“sell”), worse than last week’s grade of C (“hold”). The stock price has dropped 7.9% over the past month, worse than the 1.4% increase the S&P 500 has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of PER stock.

Saratoga Resources (AMEX:SARA) earns a D this week, falling from last week’s grade of C. Saratoga Resources is an independent oil and natural gas company engaged in the production, development, acquisition and exploitation of natural gas and crude oil properties. The stock gets F’s in Earnings Growth, Earnings Momentum, and Earnings Revisions. Cash Flow and Sales Growth also get F’s. For a full analysis of SARA stock, visit Portfolio Grader.

Gevo (NASDAQ:GEVO) ratings are on the decline this week as the company earns an F (“strong sell”). Last week, it received a D (“sell”). Gevo operates as a technology development company for biobutanol. The stock gets F’s in Equity, Cash Flow, and Sales Growth. Wall Street appears to agree with the stock downgrade, with share prices dropping 25.1% over the past month. As of Dec. 7, 2012, 15.8% of outstanding Gevo shares were held short. To get an in-depth look at GEVO, get Portfolio Grader’s complete analysis of GEVO stock.

This week, VOC Energy’s (NYSE:VOC) rating worsens to an F from the company’s D rating a week ago. VOC Energy Trust is a Delaware statutory trust. The stock also gets an F in Sales Growth. For a full analysis of VOC stock, visit Portfolio Grader.

Clean Energy Fuels (NASDAQ:CLNE) is having a tough week. The company’s rating falls from C to a D. Clean Energy Fuels sells natural gas fueling solutions to its customers mainly in the United States and Canada. The stock gets F’s in Equity and Cash Flow. As of Dec. 7, 2012, 22.2% of outstanding Clean Energy Fuels shares were held short. For more information, get Portfolio Grader’s complete analysis of CLNE stock.

The rating of Murphy Oil (NYSE:MUR) slips from C to a D. Murphy Oil is a worldwide oil and gas exploration and production company with refining and marketing operations in the United States and the United Kingdom. To get an in-depth look at MUR, get Portfolio Grader’s complete analysis of MUR stock.

This week, McMoRan Exploration (NYSE:MMR) drops from a D to an F rating. McMoran Exploration explores for and produces oil and gas offshore in the Gulf of Mexico and onshore in the Gulf Coast area. The stock gets F’s in Earnings Momentum, Equity, Cash Flow, and Sales Growth. As of Dec. 7, 2012, 14.5% of outstanding McMoRan Exploration shares were held short. For a full analysis of MMR stock, visit Portfolio Grader.

The rating of Noble Energy (NYSE:NBL) declines this week from a D to an F. Noble Energy is an independent company engaged in the acquisition, exploration, development, production and marketing of crude oil, natural gas, and natural gas liquids. The stock receives F’s in Earnings Growth, Earnings Surprise, Cash Flow, and Margin Growth. For more information, get Portfolio Grader’s complete analysis of NBL stock.

This is a rough week for PDC Energy (NASDAQ:PETD). The company’s rating falls to D from the previous week’s C. PDC is an oil and gas company with drilling and production operations in the Rocky Mountains, the Appalachian Basin, and Michigan. The stock gets F’s in Earnings Revisions and Cash Flow. As of Dec. 7, 2012, 19.1% of outstanding PDC Energy shares were held short. To get an in-depth look at PETD, get Portfolio Grader’s complete analysis of PETD stock.

QEP Resources’ (NYSE:QEP) rating weakens this week, dropping to an F versus last week’s D. QEP Resources is an independent natural gas and oil exploration and production company. The stock rates an F in Earnings Growth, Earnings Momentum, and Earnings Revisions. Earnings Surprise, Cash Flow, and Sales Growth also get F’s. The trailing PE Ratio for the stock is 34.80. For a full analysis of QEP stock, visit Portfolio Grader.

Bellatrix Exploration Ltd. (AMEX:BXE) experiences a ratings drop this week, going from last week’s D to an F. The stock gets F’s in Earnings Growth, Cash Flow, and Sales Growth. The stock has a trailing PE Ratio of 122.80. To get an in-depth look at BXE, get Portfolio Grader’s complete analysis of BXE stock.

Suncor Energy (NYSE:SU) earns a D this week, moving down from last week’s grade of C. Suncor Energy is an integrated energy company in Canada. For more information, get Portfolio Grader’s complete analysis of SU stock.

Cloud Peak Energy (NYSE:CLD) gets weaker ratings this week as last week’s C drops to a D. Cloud Peak Energy engages in the coal mining operations in the Powder River Basin and the United States. To get an in-depth look at CLD, get Portfolio Grader’s complete analysis of CLD stock.

Slipping from C to a D rating, Hallador Energy (NASDAQ:HNRG) takes a hit this week. Hallador Energy processes, mines and sells coal to producers of electric power. Share prices fell 11.5% over the past month. For a full analysis of HNRG stock, visit Portfolio Grader.

This week, EXCO Resources (NYSE:XCO) drops from a D to an F rating. EXCO Resources is an oil and natural gas company involved in the exploration, exploitation, development and production of onshore North American oil and natural gas properties. As of Dec. 7, 2012, 10.1% of outstanding EXCO Resources shares were held short. For more information, get Portfolio Grader’s complete analysis of XCO stock.

Eagle Rock Energy (NASDAQ:EROC) is having a tough week. The company’s rating falls from a D to an F. Eagle Rock Energy engages in gathering, compressing, treating, processing, transporting, marketing, and trading natural gas, as well as fractionating and transporting natural gas liquids. For a full analysis of EROC stock, visit Portfolio Grader.

BPZ Resources (NYSE:BPZ) experiences a ratings drop this week, going from last week’s D to an F. BPZ Resources is an independent oil and gas company focused on the exploration, development and production of oil and natural gas in Peru and Ecuador. The stock receives F’s in Earnings Growth, Earnings Revisions, and Equity. Cash Flow and Sales Growth also get F’s. The stock price has fallen 9% over the past month. As of Dec. 7, 2012, 15.4% of outstanding BPZ Resources shares were held short. To get an in-depth look at BPZ, get Portfolio Grader’s complete analysis of BPZ stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.