Oil prices rocketed more than 8 percent higher on Friday, their biggest one-day gain in two and a half years, after data showed U.S. drillers were slamming the brakes on the shale drilling boom. In a rally that may spur speculation that a seven-month price collapse has ended, global benchmark Brent crude shot up to more than $53 (35 pounds) per barrel, its highest in more than three weeks, after Baker Hughes data showed the number of rigs drilling for oil in the United States fell by 94 – or 7 percent – this week.