From what I've read that can't really happen again. In the prehistoric past, plants could die and would build up into massive layers. Over time those wound up in various geologic processes that caused them to become oil. Nowadays the Earth has plenty of microbes that will quickly decompose the plants into something that is not oil and that's the end of the process.

Until fungi discovered ligninase enzymes, when a tree fell in the forest, it just… sat there. For eons. Got covered up. Got smushed. Became coal.

Now we got these fungi chewing things all up. Thanks a lot, fungi.