I think the large cluster to the left is easiest to understand driven by price. When prices dropped, traders take the opportunity to build inventories and vice versa - when prices rise traders sell into the rise and inventories fall.

There seems to be a target inventory range (that hasn't changed much with demand over time). At some point a few years ago when inventories hit the 260 mmb low point we might normally have expected OPEC to open the spigot and to see prices fall back - but on this occasion that never happened and we have the price migration from 40 to 70 $. It is curious that with rising price, inventories built back towards 350 mmb - presumably this was related to the anticipation of future prices being higher and it therefore making sense to own more oil today - a shift to contango?

The final leg of rising price and falling inventory looks like traders selling into the strong price rally - presumably with the expectation that they can refill their tanks at lower price at some future date. The $100 question - what happens next? We've just seen an uptick in demand to 86 mmbpd with record high prices.

I suspect this chart is worth keeping an eye on. If prices fall then I think we can bet on inventories rising and we head back towards $70 and 360 mmb. If prices rise then we may see another $50 sprint.

The constellation of record demand, record price and low inventories seems fairly bullish to me.