The success of the Trump administration's blockbuster Venezuela oil deal hinges on fields that are aging, degraded, or expensive to access. The agreement with Alejandro Betancourt, an energy mogul with a controversial history, includes 17 fields and gives the U.S. majority control of a huge amount of Venezuela's oil wealth. Betancourt's North American Blue Energy Partners aims to more than double crude production, adding about 300,000 barrels a day in just over two years.

However, conversations with more than a dozen industry executives and analysts suggest the company will struggle to reach that goal. The names of the 17 fields were identified by Bloomberg News but haven't been officially listed.