One danger is that, as the oil slowly oozes out, it might leak into the ground water before a drilling rig can pump it out.

NPR: Industry Seeks to Extract Oil from Rocky Mountain Shale

When an offshore oil rig is outdated, or can no longer cost-effectively pump oil, most countries require that the oil rigs be wholly decommissioned.

FORBES: Environmental Scientists Urge That Decommissioned Oil Rigs Be Transformed Into Artificial Reefs

This is what this data is supposed to monitor, but the well flow evidence would appear to have been ignored, because at this point the BP rig supervisors should have gone to a well kill operation and started to pump heavy mud back into the well bore to restore the primary control mechanism.

WSJ: The Oil Disaster Is About Human, Not System, Failure