The Obama administration today announced it has completed its first unannounced oil spill response drill since the overhaul of the former Minerals Management Service last October.

Last week's surprise drill, which was jointly led by the Bureau of Safety and Environmental Enforcement, U.S. Coast Guard and state of Louisiana, tested Stone Energy Corp.'s ability to assess a subsea well control situation and swiftly mobilize the appropriate containment and intervention equipment, Interior said.

Interior said it will issue a final evaluation of the drill as soon as all documentation is complete.

"The unannounced spill drill Program provides an effective tool that helps us ensure operators are appropriately trained in effective containment deployment and that the necessary equipment and resources are truly in place to implement the approved response plan," said BSEE Director James Watson in a statement. "This program is one of many diverse activities we employ within our agency to ensure operators are able to fully execute their oil spill response plans."

Since 1989, Interior has selected operators for unannounced "tabletop" drills based on factors including the number of production facilities, total oil production and proximity to sensitive areas.

The agency selects a location, spill scenario and simulated weather conditions to produce a hypothetical spill trajectory. Operators are graded on their ability to notify appropriate contacts and personnel, including government officials and response contractors, and take appropriate action to implement approved response plans.

Last week's drill tasked Stone Energy with responding to a theoretical blowout of one of its deepwater exploratory wells.

Interior's unannounced spill drill last September on Petrobras America Inc.'s operation was the agency's first to test a subsea-containment response since the devices were required in response to the BP PLC Deepwater Horizon spill in the Gulf of Mexico.