I found this interesting. There are currently 720 large oil tankers. They have to be recertified every so often, kind of like scuba tanks I guess. They have to be recertified at 15 years old and 20 years old, and it runs about $2 million.
Shipping rates are super cheap right now, at $6000/day as opposed to $25,000/day which is break even level for a lot of shipping companies. Rates are down with the US importing less oil. But, recycled metals are higher. So, many shipping companies are selling off their oil tankers, especially as the time for recertification nears.
All this to say, if there is a sudden spike in need, or maybe a supply disruption, if it requires shipping it might take a while for companies to take delivery of new oil tankers and meet the need.
https://www.wsj.com/articles/shipowners-on-pace-to-scrap-1-billion-in-oil-tankers-this-year-1531054800ETA a final paragraph in the article discusses the scrapping of deep sea rigs. Guess that's not going to come back soon either.