Keep in mind that the price of natural gas has gone negative in some markets in recent years.  Different animal because it is a byproduct of oil in many fields, and can't be stored, and in some places can't be flared, or there are large costs to flaring, so the price went negative, had to pay to get a place in a pipeline to get rid of it.  
Oil is the primary product, so no one will produce it at a loss, at least not for long.  
The exception being places like Siberia, where supposedly you can't just shut in a well or a pipeline, or the facitilies, because the fluids will freeze solid and wreck the infrastructure, possibly requiring re drilling the well.  Not sure I buy that logic, unless they have never heard of glycol or methanol, and the permafrost extends down for ever.  But if that is true, their prices could well go negative, if they aren't already.
I know oilsands oil prices are now effecively negative to the producer, shipping costs more than the product is worth.  WCS oil is in the ~$4/ barrel range lately.