The grades of four Oil and Gas stocks are better this week, according to the Portfolio Grader database. Every one of these stocks has an “A” (“strong buy”) or “B” overall (“buy”) rating.

Chesapeake Midstream Partners (NYSE:CHKM) is bumping up its rating from a C (“hold”) to a B (“buy”) this week. Chesapeake Midstream Partners owns, operates, develops, and acquires natural gas, natural gas liquids, and oil gathering systems, as well as other midstream energy assets in the United States. For more information, get Portfolio Grader’s complete analysis of CHKM stock.

This week, Oiltanking Partners LP (NYSE:OILT) is showing good progress as the company’s rating jumps from a B (“buy”) last week to an A (“strong buy”). Oiltanking Partners LP engages in the terminaling, storage and transportation of crude oil, refined petroleum products and liquefied petroleum gas. Shares of OILT have increased 6.6% over the past month, better than the 4.1% increase the S&P 500 has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of OILT stock.

This week, Vermilion Energy Inc.’s (NYSE:VET) ratings are up from a C last week to a B. The stock has a dividend yield of 2.4%. For more information, get Portfolio Grader’s complete analysis of VET stock.

Cabot Oil & Gas’ (NYSE:COG) ratings are looking better this week, moving up to an A from last week’s B. Cabot Oil & Gas is an independent company that develops, explores, produces and markets natural gas, and transports, stores, and gathers it for resale. For more information, get Portfolio Grader’s complete analysis of COG 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.