As U.S. companies return to Venezuela's oilfields, one Canadian driller has a head start. Calgary's Ensign Energy Services has quietly kept rigs running in the volatile oil-rich nation for more than two decades. But here's where it gets controversial: While the Trump administration has issued a general license enabling U.S. oilfield service companies to work in Venezuela, Ensign Energy Services has been quietly maintaining a foothold in the politically volatile country, despite years of upheaval and sanctions that drove competitors away. This Canadian driller is widely understood to be working with Chevron Corp., the only U.S. oil major currently authorized to produce and export Venezuelan crude under a restricted license from Washington. And this is the part most people miss: Drilling in Venezuela requires far more advance planning than in Canada or the U.S., where parts and services can be delivered within hours. Newcomers are likely to struggle to get equipment through ports and to staff rigs and run them safely and efficiently, he said. So, is the Trump administration's intervention a catalyst for large-scale foreign investment in Venezuela's oilfields? Or is it just a temporary boost for Ensign Energy Services? The answer may lie in the spending plans of oil producers, not U.S. government policy.