The grades of nine 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.

This week, Chesapeake Midstream Partners (CHKM) is showing significant improvement as the company’s rating hops from a C (“hold”) to a B (“buy”). 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, Diamondback Energy, Inc. (FANG) is showing good progress as the company’s rating jumps from a B (“buy”) last week to an A (“strong buy”). The share price is in range of the 52-week high of $68.90, currently positioned at $68.04. For more information, get Portfolio Grader’s complete analysis of FANG stock.

U.S. Energy Corp. (USEG) earns a B this week, jumping up from last week’s grade of C. U. S. Energy explores for oil and natural gas. For more information, get Portfolio Grader’s complete analysis of USEG 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. The stock has a dividend yield of 2.2%. For more information, get Portfolio Grader’s complete analysis of PVR stock.

Carrizo Oil & Gas, Inc. (CRZO) is seeing ratings go up from a B last week to an A this week. Carrizo Oil & Gas is engaged in the exploration, development, production and transportation of natural gas and oil, mainly in the United States. Shares of CRZO have increased 6.3% over the past month, better than the 1.3% decrease the Nasdaq has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of CRZO stock.

Frontline (FRO) improves from a C to a B rating this week. Frontline owns a fleet of very large crude carriers and Suezmax tankers that transport crude oil and oil products between ports. For more information, get Portfolio Grader’s complete analysis of FRO stock.

Niska Gas Storage Partners (NKA) boosts its rating from a C to a B this week. Niska Gas Storage is an independent owner and operator of natural gas storage assets in North America. Despite the upgrade, the stock’s price has not seen any measurable improvement over the past week. For more information, get Portfolio Grader’s complete analysis of NKA stock.

The rating of Advantage Oil & Gas (AAV) moves up this week, rising from a C to a B. Advantage Oil & Gas is actively engaged in the business of oil and gas exploitation, development, acquisition and production. The stock’s price of $4.67 is nearing the 52-week high of $4.67. Shares of the stock have been changing hands at an unusually rapid pace, four times the rate of the week prior. For more information, get Portfolio Grader’s complete analysis of AAV stock.

This is a strong week for Cross Timbers Royalty (CRT). The company’s rating climbs to A from the previous week’s B. Cross Timbers Royalty is an express trust in the United States. At present, the stock has a dividend yield of 3.1%. For more information, get Portfolio Grader’s complete analysis of CRT 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.