If some 90% of production shut down, it would certainly take care of any glut.
For some wells here in the US, it is still economically feasible to pump at even $10 a barrel, but even the Saudi oil fields would be struggling at those prices.
Everybody else in the world will be closing up shop. Russia for sure.
And Russia without oil to export is essentially bankrupt, even more than the US now is.
The Saudis can produce oil cheaply but still need a price of over $100 a barrel to pay for their government spending.
Their high production play is temporary as their cash reserves will be gone in less than 5 years at these prices. I think they underestimate the ability of the USA to quickly shrink and grow its energy industry depending on conditions.
The Saudis have no economy without oil. The USA is much more diversified.