The negative price on WTI crude is an anomaly. It has very little to do with the physical price that producers will realize at the wellhead. WTI futures delivery point is at Cushing Oklahoma. Today was the expiration date for WTI contracts for May. Anyone on the long side of a WTI future has two choices. They can close the future out financially by selling it, or they can take receipt of the oil at Cushing.
Today there were a lot of long oil contracts outstanding and no buyers. Traders with long contracts had to sell at any price or take delivery at Cushing. But there is no space at Cushing. It is all sold out at least until the end of 2020.