This week, the overall grades of three Energy Services stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Newpark Resources‘ (NYSE:NR) rating falls this week to a F (“strong sell”), down from last week’s D (“sell”). Newpark Resources provides environmental services to the oil and gas exploration and production industry, primarily in the Gulf Coast market. In Portfolio Grader’s specific subcategory of Earnings Momentum, NR also gets an F. The stock price has fallen 18.5% over the past month, worse than the 3.3% decrease the S&P 500 has seen over the same period of time. As of Oct. 25, 2012, 10.2% of outstanding Newpark Resources shares were held short. To get an in-depth look at NR, get Portfolio Grader’s complete analysis of NR stock.

Helix Energy Solutions Group (NYSE:HLX) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Helix Energy Solutions Group is a marine contractor and operator of offshore oil and gas properties and production facilities. The stock also rates an F in Earnings Momentum. The stock price has fallen 11.2% over the past month. For a full analysis of HLX stock, visit Portfolio Grader.

The rating of Bristow Group (NYSE:BRS) slips from a C to a D. Bristow Group provides helicopter services to the worldwide offshore energy industry. The stock gets F’s in Cash Flow and Margin Growth. The stock’s trailing PE Ratio is 27.40. To get an in-depth look at BRS, get Portfolio Grader’s complete analysis of BRS 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.