Crude oil futures continued down on Friday, spooked by the dim outlook for the U.S. economy. That’s precisely what makes it likely oil prices will rebound next year.

 A tough run upstream (AP)

Big oil companies are already finding it harder to maintain, let alone increase, production. Chevron doubled its third-quarter net profit, but said production fell 5.7% in the quarter, after ExxonMobil reported an 8% production drop yesterday.

Falling oil prices are only going to accelerate that trend, analysts warn, at a time when OPEC is accelerating output cuts and production declines at oil fields around the world is apparently increasing.

Big oil as a whole needs oil prices of about $82 a barrel next year to fund their plans for new investment in oil exploration and production, Credit Suisse says in a new report. Right now, the consensus forecast of about $75 oil means overall, oil companies will suspend some marginal projects, as Shell has already announced with Canadian tar sands.

If oil stays around $60 a barrel, the funding shortfall for Big Oil will increase to more than $70 billion, CSFB says, as oil companies mothball a range of tricky new projects. That represents about 20% of planned capital expenditure for big oil companies in 2009.

Not everybody would be affected equally. ExxonMobil can weather oil prices at $50 a barrel, the bank says, while big Chinese oil companies are praying oil returns to record levels north of $140.

Oil bears have been betting all month that collapsing global demand is going to keep crude prices low next year. But if supply and demand do mean anything to the oil markets—an open question these days—the specter of a supply crunch next year could send the bulls back into the ring.