Probably nearly 100% of their oil derived industry -- but I don't much care about the expropriation vs nationalization problem. Once Maduro is gone, his and Chavez' family members should not live to count all the money they've grifted. That response would work much better for investors, both now and in the future, in and out of Venezuela.
I expect the very companies with the nationalized assets will be called in to clean up the mess and get it all back on track again.
The thought occurred to me that Venezuelan crude is heavy. One wonders if the basin were fracked, lighter oil might be found further down. Chavez/Maduro lacked the expertise to make that determination