This week, the ratings of 27 Oil and Gas stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, PDC Energy (NASDAQ:PDCE) falls to a D (“sell”), worse than last week’s grade of C (“hold”). PDC Energy is an oil and gas company with drilling and production operations in the Rocky Mountains, the Appalachian Basin, and Michigan. In Portfolio Grader’s specific subcategories of Earnings Momentum, Earnings Revisions, and Cash Flow, PDCE also gets an F. The stock price has fallen 17.4% over the past month, worse than the 7% decrease the Nasdaq has seen over the same period of time. As of Nov. 9, 2012, 18.6% of outstanding PDC Energy shares were held short. For a full analysis of PDCE stock, visit Portfolio Grader.

QEP Resources (NYSE:QEP) ratings are on the decline this week as the company earns a F (“strong sell”). Last week, it received a D (“sell”). QEP Resources is an independent natural gas and oil exploration and production company. The stock gets F’s in Earnings Growth, Earnings Momentum, and Earnings Surprise. Cash Flow and Sales Growth also get F’s. The stock price has fallen 9.1% over the past month. The stock’s trailing PE Ratio is 33.40. To get an in-depth look at QEP, get Portfolio Grader’s complete analysis of QEP stock.

PVR Partners L.P. (NYSE:PVR) is having a tough week. The company’s rating falls from a C to a D rating. Penn Virginia Resource Partners owns and operates a network of natural gas pipelines and processing plants which provide gathering, transportation, compression, processing, dehydration and related services to natural gas producers. The stock receives F’s in Earnings Growth, Equity, and Cash Flow. Margin Growth and Sales Growth also get F’s. Shares of the company have declined 6.5% from a month ago. For more information, get Portfolio Grader’s complete analysis of PVR stock.

This is a rough week for Clayton Williams Energy (NASDAQ:CWEI). The company’s rating falls to F from the previous week’s D. Clayton Williams Energy is an independent oil and gas company engaged in the exploration for and production of oil and natural gas mainly in Texas, Louisiana and New Mexico. The stock gets F’s in Earnings Momentum, Earnings Revisions, and Cash Flow. Wall Street appears to agree with the stock downgrade, with share prices dropping 20.9% over the past month. The stock has a trailing PE Ratio of 27.00. To get an in-depth look at CWEI, get Portfolio Grader’s complete analysis of CWEI stock.

Consol Energy‘s (NYSE:CNX) rating weakens this week, dropping to a F versus last week’s D. Consol Energy is an energy producer and energy services provider that mainly serves the electric power generation industry in the United States. In Earnings Growth, Earnings Momentum, Earnings Revisions, and Sales Growth the stock gets F’s. Investors seem to agree with the downgrade and have pushed down the share price 3.3% over the past month. For more information, get Portfolio Grader’s complete analysis of CNX stock.

This week, Talisman Energy (NYSE:TLM) drops from a D to a F rating. Talisman Energy is a global diversified upstream oil and gas company. Share prices fell 16.5% over the past month. For a full analysis of TLM stock, visit Portfolio Grader.

This week, Cameco‘s (NYSE:CCJ) rating worsens to a F from the company’s D rating a week ago. Cameco produces uranium and supplies conversion services commercially. The stock gets F’s in Earnings Growth, Earnings Surprise, and Sales Growth. Wall Street appears to agree with the stock downgrade, with share prices dropping 11.1% over the past month. For more information, get Portfolio Grader’s complete analysis of CCJ stock.

Chevron (NYSE:CVX) earns a D this week, moving down from last week’s grade of C. Chevron gives management and technological support to international subsidiaries that operate petroleum, chemicals, mining, power generation, and energy services. The stock also rates an F in Sales Growth. Shares of the company are down 9.9% from a month ago. For a full analysis of CVX stock, visit Portfolio Grader.

NuSTAR Energy (NYSE:NS) gets weaker ratings this week as last week’s D drops to a F. Nustar Energy transports and stores crude oil and refined products. The stock receives F’s in Earnings Growth, Earnings Momentum, and Earnings Revisions. Earnings Surprise, Cash Flow, and Margin Growth also get F’s. Share prices fell 15.1% over the past month. To get an in-depth look at NS, get Portfolio Grader’s complete analysis of NS stock.

Slipping from a C to a D rating, Boardwalk Pipeline (NYSE:BWP) takes a hit this week. Boardwalk Pipeline Partners engages in the ownership and operation of integrated natural gas pipelines and storage systems in the United States. The stock price has fallen 7.8% over the past month. For a full analysis of BWP stock, visit Portfolio Grader.

Forest Oil (NYSE:FST) experiences a ratings drop this week, going from last week’s D to a F. Forest Oil is involved in the acquisition, exploration, development, production, and marketing of natural gas and crude oil in North American and international locations. The stock rates an F in Earnings Growth, Earnings Momentum, and Equity. Cash Flow, Margin Growth, and Sales Growth also get F’s. Investors seem to agree with the downgrade and have pushed down the share price 19.9% over the past month. As of Nov. 9, 2012, 17% of outstanding Forest Oil shares were held short. To get an in-depth look at FST, get Portfolio Grader’s complete analysis of FST stock.

The rating of Gevo (NASDAQ:GEVO) slips from a D to a F. Gevo operates as a technology development company for biobutanol. The stock gets F’s in Equity, Cash Flow, and Sales Growth. As of Nov. 9, 2012, 15.3% of outstanding Gevo shares were held short. The price of GEVO has dropped 6.1% since last month. For more information, get Portfolio Grader’s complete analysis of GEVO stock.

The rating of Spectra Energy (NYSE:SE) declines this week from a C to a D. Spectra Energy owns and operates a portfolio of natural gas-related energy assets. The stock also gets an F in Earnings Surprise. Over the past month, the stock price has fallen 7.2%. To get an in-depth look at SE, get Portfolio Grader’s complete analysis of SE stock.

Murphy Oil (NYSE:MUR) earns a D this week, falling from last week’s grade of C. 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. For a full analysis of MUR stock, visit Portfolio Grader.

Berry Petroleum (NYSE:BRY) gets weaker ratings this week as last week’s C drops to a F. Berry Petroleum is an independent energy company engaged in the production, development, acquisition, exploitation of and exploration for crude oil and natural gas. The stock gets F’s in Earnings Surprise, Equity, and Margin Growth. The stock price has fallen 15.6% over the past month. For more information, get Portfolio Grader’s complete analysis of BRY stock.

The rating of Oxford Resource Partners (NYSE:OXF) declines this week from a C to a D. Oxford Resource Partners acquires and produces surface coal reserves in the Northern Appalachia and the Illinois Basin. The stock gets F’s in Equity and Cash Flow. Investors seem to agree with the downgrade and have pushed down the share price 38% over the past month. To get an in-depth look at OXF, get Portfolio Grader’s complete analysis of OXF stock.

Plains Exploration & Production (NYSE:PXP) is having a tough week. The company’s rating falls from a C to a D rating. Plains Exploration & Production is an independent oil and gas company with onshore and offshore operations in California, West Texas, East Texas and the Gulf Coast region. The stock gets F’s in Earnings Revisions, Earnings Surprise, and Cash Flow. The stock currently has a trailing PE Ratio of 26.40. Over the last month, shares of the company have fallen 4.9%. For more information, get Portfolio Grader’s complete analysis of PXP stock.

Gulfport Energy (NASDAQ:GPOR) earns a D this week, falling from last week’s grade of C. Gulfport Energy owns and operates oil and gas properties in the Louisiana Gulf Coast area of the United States. The stock also gets an F in Earnings Revisions. To get an in-depth look at GPOR, get Portfolio Grader’s complete analysis of GPOR stock.

Callon Petroleum (NYSE:CPE) experiences a ratings drop this week, going from last week’s C to a D. Callon Petroleum engages in the acquisition, exploration, development, and production of crude oil and natural gas properties. The stock gets F’s in Earnings Growth, Earnings Momentum, and Sales Growth. Wall Street appears to agree with the stock downgrade, with share prices dropping 25.6% over the past month. For more information, get Portfolio Grader’s complete analysis of CPE stock.

This week, Natural Resource Partners (NYSE:NRP) drops from a D to a F rating. Natural Resource Partners owns and manages coal properties in Appalachia, the Illinois Basin, and the Western United States. The stock gets F’s in Cash Flow and Margin Growth. Share prices fell 9.6% over the past month. The trailing PE Ratio for the stock is 37.40. For a full analysis of NRP stock, visit Portfolio Grader.

Slipping from a C to a D rating, Inergy (NYSE:NRGY) takes a hit this week. Inergy operates a retail and wholesale propane supply, marketing and distribution business. The stock gets F’s in Cash Flow and Margin Growth. NGRY shares have fallen 1.6% over the past month. For more information, get Portfolio Grader’s complete analysis of NRGY stock.

This is a rough week for Northern Oil & Gas (AMEX:NOG). The company’s rating falls to F from the previous week’s D. Northern Oil & Gas is an independent energy company that acquires, explores, exploits and develops oil and natural gas properties. The stock gets F’s in Earnings Momentum and Cash Flow. As of Nov. 9, 2012, 16.3% of outstanding Northern Oil & Gas shares were held short. Shares of the company are down 12.4% from a month ago. To get an in-depth look at NOG, get Portfolio Grader’s complete analysis of NOG stock.

This week, Rhino Resource Partner‘s (NYSE:RNO) rating worsens to a D from the company’s C rating a week ago. Rhino Resource Partners produces, processes and sells high quality coal of various steam and metallurgical grades. The stock also rates an F in Cash Flow. Investors seem to agree with the downgrade and have pushed down the share price 14.7% over the past month. For a full analysis of RNO stock, visit Portfolio Grader.

NuSTAR GP Holdings‘s (NYSE:NSH) rating weakens this week, dropping to a D versus last week’s C. Nustar operates oil pipelines, terminals, and storage facilities. The stock gets F’s in Earnings Growth, Earnings Momentum, Earnings Revisions, and Sales Growth. The stock price has fallen 11.6% over the past month. The stock currently has a trailing PE Ratio of 74.80. To get an in-depth look at NSH, get Portfolio Grader’s complete analysis of NSH stock.

The rating of Eagle Rock Energy (NASDAQ:EROC) slips from a C to a D. Eagle Rock Energy engages in gathering, compressing, treating, processing, transporting, marketing, and trading natural gas, as well as fractionating and transporting natural gas liquids. The stock gets F’s in Earnings Momentum, Earnings Revisions, and Equity. Cash Flow and Sales Growth also get F’s. Wall Street appears to agree with the stock downgrade, with share prices dropping 9.7% over the past month. For more information, get Portfolio Grader’s complete analysis of EROC stock.

Slipping from a C to a D rating, Triangle Petroleum (AMEX:TPLM) takes a hit this week. Triangle Petroleum acquires, explores, and develops mineral properties. The stock gets F’s in Equity and Cash Flow. Over the last month, shares of the company have dropped 18.8%. For a full analysis of TPLM stock, visit Portfolio Grader.

ZaZa Energy (NASDAQ:ZAZA) is having a tough week. The company’s rating falls from a D to a F rating. Toreador Resources is an independent international energy company engaged in the acquisition, development, exploration and production of crude oil. The stock gets F’s in Earnings Revisions and Cash Flow. The trailing PE Ratio for the stock is 64.50. For more information, get Portfolio Grader’s complete analysis of ZAZA 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.