Gulf of Mexico natural gas rig blew while completing 'sidetrack well'

The blowout that occurred on a natural gas well in the Gulf of Mexico Tuesday morning happened as Walter Oil & Gas Corp., of Houston, was completing work on a "sidetrack well" to prepare that well for new production, according to the Bureau of Safety and Environmental Enforcement. A sidetrack well uses the same hole as the original well but then spreads to a new location at the same depth.

From: http://www.nola.com/traffic/index.ssf/2013/07/gulf_of_mexico_natural_gas_rig.html#incart_river