And the inverse ETF is: DUG. Shown below. It does not exactly track the inverse but is good enough for a trade from the buy side.
On the fundamental side, the recent squabble in OPEC over raising output. The Saudis wanted to raise output, but they couldn't get the organization to agree. So the Saudis say they will raise their output. If they happen to be wrong about world demand they may just push oil lower than they intend. That would be the trade.
It is strange for OPEC to be disagreeing about raising output. For many years many of them cheated by producing more than they were supposed to. And they lied about their reserves in order to produce more. Now they want to hold it back. I am fairly sure they know they are going to run out of spare capacity, and see no sense in letting go of it cheaply.
The DUG trade was a fail. Out with a small loss several days ago...