This week, four oil and gas stocks are improving their overall ratings on Portfolio Grader. Each of these stocks is rated an “A” (“strong buy”) or “B” overall (“buy”).

Chesapeake Midstream Partners’ (CHKM) grade is moving up to a B (“buy”) this week from last week’s C (“hold”). 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, PVR Partners, L.P. (PVR) pushes up from a C to a B rating. PVR Partners owns and operates a network of natural gas pipelines and processing plants that provide gathering, transportation, compression, processing, dehydration and related services to natural gas producers. At present, the stock has a dividend yield of 2.2%. For more information, get Portfolio Grader’s complete analysis of PVR stock.

This week, PrimeEnergy Corporation (PNRG) is showing good progress as the company’s rating jumps from a B (“buy”) last week to an A (“strong buy”). PrimeEnergy is engaged in the oil and gas business through the acquisition, exploration, development, and production of crude oil and natural gas. Shares of the stock have been trading at an exceptionally rapid pace, up 543.5% from the week prior. For more information, get Portfolio Grader’s complete analysis of PNRG stock.

U.S. Energy Corp. (USEG) shows solid improvement this week. The company’s rating rises from a C to a B. U. S. Energy explores for oil and natural gas. For more information, get Portfolio Grader’s complete analysis of USEG 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.