In a 2018 Energy Economics paper, Professor Dan Scheitrum replicates the 2011 U.S. and European oil price divergence. This 2011 experience informs the 2020 incident where U.S. crude oil prices trade at a negative price meaning producers have to pay to be able to give away their oil. The negative prices are largely a symptom of COVID-19 oil demand reductions, storage capacity constraints, and transport limitations. For further reading, see “US Oil Prices Plummet. What Does it Mean?” by Rosemary Brandt at https://uanews.arizona.edu/.
Tucson's KGUN 9 News, April 20, 2020, interviewed Prof. Scheitrum: