US rigs drilling for crude oil dropped by the most in 20 years, although the shift might have been affected by producers listing rigs as seeking natural gas.

One analyst said that oil rigs were down 41 to 1,340, while rigs seeking gas jumped 13 to 429, the highest in 11 weeks.

According to Baker Hughes, the overall rig count was down 25 to 1,774, the lowest in 20 months.

In the Barnett Shale, active rigs rose by two to 38. Montague and Wise counties were the busiest, with eight each, followed by Tarrant with seven and Parker and Denton counties with four each.