This week, six energy services stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

Exterran Partners, L.P. (EXLP) is bumping up its rating from a C (“hold”) to a B (“buy”) this week. Exterran Partners offers natural gas compression services. In Portfolio Grader’s specific subcategory of Margin Growth, EXLP also gets an A. The stock has a dividend yield of 2.1%. For more information, get Portfolio Grader’s complete analysis of EXLP stock.

Synthesis Energy Systems, Inc. (SYMX) gets a higher grade this week, advancing from a C last week to a B. Synthesis Energy Systems designs, invests in, builds, owns, and operates utility plants for industrial customers. 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 SYMX stock.

This week, Parker Drilling Company (PKD) pushes up from a C to a B rating. Parker Drilling provides contract drilling and related services. For more information, get Portfolio Grader’s complete analysis of PKD stock.

This is a strong week for Forbes Energy Services Ltd. (FES). The company’s rating climbs to B from the previous week’s C. Forbes Energy Services is an independent oilfield services contractor. For more information, get Portfolio Grader’s complete analysis of FES stock.

CARBO Ceramics (CRR) boosts its rating from a C to a B this week. CARBO Ceramics manufactures and supplies resin-coated ceramic and resin-coated sand proppants primarily used in the hydraulic fracturing of natural gas and oil wells in the United States and internationally. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. For more information, get Portfolio Grader’s complete analysis of CRR stock.

This is a strong week for Helmerich & Payne, Inc. (HP). The company’s rating climbs to B from the previous week’s C. Helmerich & Payne provides contract drilling of oil and gas wells in the Gulf of Mexico and South America. The current dividend yield is 2.8%. For more information, get Portfolio Grader’s complete analysis of HP 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.