Abstract
How much has research on ultra-deep-sea (>1500 m) oil and gas blowout behavior progressed since the Deepwater Horizon (DWH) accident, and what additional key questions remain to be resolved? In this chapter, we summarize at a high level: (1) the state of knowledge of deep blowout behavior and mitigation prior to DWH, (2) essential information that has come to light in the 9+ years since DWH, and (3) important unresolved questions and additional key research bearing on the prevention of similar marine disasters, mitigation of their effects, and understanding their impacts.