Both the spring maintenance period in the US (creating a 'glut' of WTI), Seaway pipeline, and tensions in the Middle East are exaggerating the Brent-WTI spread which traded back to two-month highs. In the last week or so the differential has surged from around $16 to over $22 as WTI fell and Brent prices surged. There is a great degree of seasonality in this shift (and typically the Spring maintenance period has ended within the next week) but Iranian sanctions remain at the forefront (as does the belief that Germany's growth will be the engine of European demand - especially if EUR drops). This year was 'different' in so much as WTI outperformed for the first few weeks - potentially on the back of the global rise in risk-assets thanks to global central bank largesse. It appears the oil market is hinting at some slowdown.
The Brent-WTI spread is highly seasonal (with Spring maintenance creating a buildup pre-refinery)... and is close to its typical seasonal peak..
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but the divergence is dramatic (after a few weeks of Central bank largesse pumped assets up everywhere)...
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Chart: Bloomberg