I'm uncertain about the ability of independent start-ups to gain much traction in the petroleum industry. Much of that has to do with owning/having access to fleets of ships that are capable of bring you and your equipment to/from the right location on time.

That said, the BP oil spill in the Gulf of Mexico has indeed shown some light on potential niche fields that could be accessible to start-ups, e.g. Kevin Costner's Ocean Therapy device.