Realizing U.S. President Donald Trump’s plan to lead a revival of Venezuela’s beleaguered oil industry could be a yearslong and challenging process costing upwards of $100 billion.

Years of corruption, underinvestment, fires and thefts have left the nation’s crude infrastructure in tatters. Rebuilding it enough to lift Venezuela’s output back to its peak levels of the 1970s would require companies that could include Chevron, Exxon Mobil and ConocoPhillips to invest about $10 billion per year over the next decade, said Francisco Monaldi, director of Latin American energy policy at Rice University’s Baker Institute for Public Policy.

“A faster recovery would require even more investment,” Monaldi said.