Yes, earlier this afternoon, very briefly, western Canadian oil was selling for $ -0.15. At least I saw a report of this. The price may have been there for only three seconds, but it is the first time I have ever heard of there being negative oil or energy prices ever. Negative interest rates, which are now quite common are one thing, but negative oil prices?
OTOH, some energy related assets have had negative prices before. I am thinking of abandoned coal mines and some highly polluting energy production facilities in certain locations with strict environmental laws that mandate that the owner of the asset pay for cleaning up the pollution coming out of it. One location and period when and where I heard numerous reports of negative price sales of such asets was in the former East Germany after unification with privatization by the Treuhandstalt.
Addendum, 4:40 PM: So I jusr saw a Reuters story claiming that at some point this afternoon, the price for May West Texas Intermediate crude, one of the world's two main oil benchmarks (Brent crude is the other) hit a price $-36.73 per barrel. If true, this is quite astounding. Apparently they have run out of storage for all the surplus WTI (and west Canadian) crude. I note that at 4 PM the sopt price for WTI was $1.50, just barely positive. Meantime, Brent has held at around $26. Frankly I do not know where this is going, but it is definitely unprecedented.
The only story I have seen is that this is Putin in Russia and MbS in Saudi Arabia working to really thoroughly bust the US fraking industry, which faces much higher variable costs than conventional oil drilling, which tends to have higher fixed costs. This is certainly possible, although I am not sure how they are able to target WTI without it hitting Brent. In any case, this certainlyi makes absud Trump's parading around and bragging about how he cooked up a deal between him and the other two, with AMLO from Mexico on board as well as implicitly the rest of OPEC beyond KSA, to cut world oil production by as much as 20 mbpd to stabilize the price. This deal, if it was ever really there, looks to be in complete tatters like so many other diplomatic initiatives Trump has engaged in and bragged about, only to lead to vacuous if not negative results.