An oil depot, or fuel farm, is seen from the air over Carson, California, February 16, 2012.

These are good times to be a diversified oil and gas company.

Companies with a strict focus on natural gas production are set to suffer in 2012 as prices remain at very low levels on the back of sustained record output and limited demand growth, ratings company Moody’s said in a report on capital spending by exploration and production companies.

The economic conundrum borne of the shale revolution – that higher oil prices have often meant lower prices for natural gas produced by the same fields – is not a new development. Energy firms have been actively repositioning for nearly a decade to absorb the shocks of low natural gas prices while managing hugely increased opportunities at the same time that oil prices have remained robust; long lead times and large investment requirements have slowed that process and sparked partnerships between companies with the right assets and firms with larger cash piles.

The Moody’s report makes it clear how little oil and natural gas liquid a diversified producer needs to be selling as part of its product mix to support a large-scale natural gas development slate. While E&P spending is bound to fall across the sector, the ratings agency said, it is firms that have focused on dry natural gas drilling that face the biggest risks to their spending and their all-important debt ratings in the coming year.

“Relatively small shift in production from dry natural gas to oil and NGLs [natural gas liquids] can significantly affect economics for the companies that produce these commodities,” the agency said in a report dated February 16, 2012. “While a company’s production may include as little as 20% oil and NGLS, these commodities could bring in more than half of its revenue and cash flow.”

Cash flows at all North American natural gas producers will “undoubtedly” be slashed, Moody’s predicts, but some firms can withstand the “trough pricing” and high ratings will help them manage their options, the firm says.

Moody’s names five gas-focused producers with single-B long-term ratings that it says will be especially vulnerable to gas prices lower than $3.00/thousand cubic feet in the coming year. Those companies include Comstock Resources, EXCO Resources, Penn Virginia, Quicksilver Resources and Carrizo Oil & Gas.