"The increase in the rig count as prices near the $50/bbl range is clearly indicative of the elasticity of U.S. production and speaks to the tremendous efficiency gains reaped by the U.S. producer community over recent years," said Michael Tran, director of energy strategy at RBC Capital Markets in New York.
Oil traders view falling U.S. output as key to reducing a global glut of crude that has pressured prices during a steep two-year slump.
Brent crude futures fell 30 cents to $49.74 per barrel, but were still almost double January lows and on track for an eighth weekly gain in nine weeks.
U.S. West Texas Intermediate (WTI) crude futures settled 55 cents lower, or 1.1 percent, at $48.62 a barrel.
Oil prices have rallied from this winter's lows due largely to supply disruptions, particularly in Nigeria, Venezuela, Libya and Canada. On Friday, militants in the restive Niger Delta region that produces more than half of Nigeria's oil claimed three new attacks on oil infrastructure, promising to bring the country's oil production to "zero."
Still, news that ExxonMobil lifted its force majeure on exports of Nigeria's Qua Iboe crude oil, looked likely to bring barrels back to the market.