Standard & Poor's Ratings Services downgraded the outlook for Chesapeake Energy Corp. and two related businesses Monday, citing a potential impact from persistently weak natural gas prices.

S&P lowered the outlook to negative from stable for Chesapeake Energy, Chesapeake Oilfield Operating LLC and Chesapeake Midstream Partners LP. It affirmed its BB+ corporate credit rating and senior unsecured debt issue rating for the Oklahoma City producer and its affiliates. The BB+ rating is considered non-investment grade or "junk."

The outlook depends on Chesapeake continuing to expand its crude oil and natural gas liquids reserves and production, S&P credit analyst Scott Sprinzen said in a news release. Another factor will be Chesapeake's ability to fund the gap between operating cash flow and capital expenditures while avoiding an increase in financial leverage.

Natural gas futures prices declined to a decade-low of $2.32 per 1,000 cubic feet last month. A year ago it was close to $5 per 1,000 cubic feet. The nation's supplies have remained well above the five-year range for this time of year, according to the Energy Information Administration.

Natural gas rose 5 cents to finish Monday at $2.55 per 1,000 cubic feet on the commodities market.

Chesapeake, the nation's second largest natural gas producer, said last month that it planned to cut its current daily production by 8 percent. It said low gas prices have made some drilling operations unprofitable. Over a year, that means the company would produce the same or slightly less natural gas in 2012 than it did in 2011. Chesapeake produces about 9 percent of the natural gas in the U.S.

Chesapeake expects crude oil and natural gas liquids production to account for 25 percent of total production in 2012 and 30 percent in 2013. S&P said. That compares with about 16 percent in 2011.

Shares of Chesapeake rose 34 cents to finish at $22.65. Chesapeake Midstream Partners fell 14 cents to close at $28.13.