The ratings of 15 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”).

Crescent Point Energy Corp. (CPG) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). The stock also earns F’s in Portfolio Grader’s specific subcategories of Earnings Revisions, Earnings Surprise, Cash Flow and Margin Growth. Shares of the stock have been changing hands at an unusually rapid pace, twice the rate of the week prior. The stock has a trailing PE Ratio of 87.10. To get an in-depth look at CPG, get Portfolio Grader’s complete analysis of CPG stock.

This week, Golar LNG Partners (GMLP) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Golar LNG Partners owns floating storage and regasification units and liquefied natural gas carriers. For more information, get Portfolio Grader’s complete analysis of GMLP stock.

Cosan Limited Class A (CZZ) earns an F this week, moving down from last week’s grade of D. Cosan is a fully integrated company in the renewable energy and infrastructure segments in Brazil. The stock gets F’s in Cash Flow and Margin Growth. Shares of the stock are changing hands at twice the rate they were a week ago. To get an in-depth look at CZZ, get Portfolio Grader’s complete analysis of CZZ stock.

Goodrich Petroleum Corporation (GDP) experiences a ratings drop this week, going from last week’s C to a D. Goodrich Petroleum explores, develops, produces and acquires oil and natural gas properties. In Earnings Growth, Earnings Revisions, Equity and Cash Flow the stock gets F’s. As of Oct. 3, 2014, 32.5% of outstanding Goodrich Petroleum Corporation shares were held short. Shares of the stock have been trading at an exceptionally rapid pace, up threefold from the week prior. For more information, get Portfolio Grader’s complete analysis of GDP stock.

This is a rough week for EXCO Resources, Inc. (XCO). The company’s rating falls to F from the previous week’s D. 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. The stock gets F’s in Earnings Surprise, Equity and Cash Flow. As of Oct. 3, 2014, 13.3% of outstanding EXCO Resources, Inc. shares were held short. Shares of the stock are being traded at a very rapid pace, up 408.7% from the week prior. To get an in-depth look at XCO, get Portfolio Grader’s complete analysis of XCO stock.

This week, Calumet Specialty Products Partners, L.P. (CLMT) drops from a D to an F rating. Calumet Specialty Products produces hydrocarbon products in North America. The stock gets F’s in Earnings Growth, Earnings Momentum and Earnings Revisions. Cash Flow and Margin Growth also get F’s. Shares of the stock have been changing hands at an unusually rapid pace, three times the rate of the week prior. For more information, get Portfolio Grader’s complete analysis of CLMT stock.

Plains All American Pipeline, L.P.’s (PAA) rating weakens this week, dropping to a D versus last week’s C. Plains All American Pipeline is involved in interstate and intrastate crude oil pipeline transportation and crude oil terminalling storage activities. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. The trailing PE Ratio for the stock is 27.20. To get an in-depth look at PAA, get Portfolio Grader’s complete analysis of PAA stock.

This week, TransCanada Corporation’s (TRP) rating worsens to an F from the company’s D rating a week ago. TransCanada develops and operates energy infrastructures, including natural gas pipelines. For more information, get Portfolio Grader’s complete analysis of TRP stock.

The rating of Enbridge (ENB) slips from a D to an F. Enbridge is in the business of transportation and distribution of crude oil and natural gas primarily in Canada and the United States. The stock gets F’s in Earnings Growth, Earnings Momentum and Cash Flow. Shares of the stock have been exchanging at an usually rapid pace, twice the rate of the week prior. The stock’s trailing PE Ratio is 32.30. To get an in-depth look at ENB, get Portfolio Grader’s complete analysis of ENB stock.

StealthGas (GASS) gets weaker ratings this week as last week’s C drops to a D. StealthGas offers marine transport services for liquefied petroleum gas producers and users. The stock receives F’s in Earnings Growth, Earnings Revisions, Earnings Surprise and Cash Flow. For more information, get Portfolio Grader’s complete analysis of GASS stock.

Ultrapar Participacoes S.A. Sponsored ADR (UGP) earns an F this week, moving down from last week’s grade of D. Ultrapar Participacoes is engaged in the fuel distribution and chemical businesses in Brazil. To get an in-depth look at UGP, get Portfolio Grader’s complete analysis of UGP stock.

The rating of Gevo (GEVO) declines this week from a D to an F. Gevo operates as a technology development company for biobutanol. The stock gets F’s in Equity, Cash Flow and Sales Growth. For more information, get Portfolio Grader’s complete analysis of GEVO stock.

PDC Energy’s (PETD) rating weakens this week, dropping to a D versus last week’s C. PDC Energy 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. To get an in-depth look at PETD, get Portfolio Grader’s complete analysis of PETD stock.

Chevron Corporation (CVX) earns an F this week, falling from last week’s grade of D. Chevron is an integrated energy company with operations in countries located around the world. For more information, get Portfolio Grader’s complete analysis of CVX stock.

This week, Kinder Morgan, Inc. Class P’s (KMI) rating worsens to an F from the company’s D rating a week ago. Kinder Morgan is a pipeline transportation and energy storage company. Shares of the stock are changing hands at twice the rate they were a week ago. The stock currently has a trailing PE Ratio of 33.60. To get an in-depth look at KMI, get Portfolio Grader’s complete analysis of KMI 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.