New Orleans ? In the chaotic days after the oil rig explosion, BP engineers and federal regulators desperate to plug the blown-out well scrambled to complete plans for a pair of deepwater relief wells that represent the best chance to end the disastrous spill in the Gulf of Mexico.

But BP didn’t begin drilling the relief well until 12 days after the start of the disaster as the company and government rushed through environmental reviews, permits and other plans. The government does not require oil companies to have relief well plans in place ahead of time, and the lack of planning cost the company valuable time to get the spill under control.

And the plan ultimately approved by the government offers virtually no details outlining the relief well effort or what dangers might lurk in the depths as the company drills 18,000 feet below the surface. Experts say the relief effort could be exposed to the same risks that caused the original well to blow out in catastrophic fashion, while potentially creating a worse spill if engineers were to accidentally damage the existing well or tear a hole in the undersea oil reservoir.