That's the question. How much makes it to the surface? Oil used to pop up everywhere before humans sucked up all the easy to reach surface sources. There's still a little that comes up from the ocean floor without any human help.

https://response.restoration.noaa.gov/oil-and-chemical-spill...

Why would it be different for other things created by the same processes? And do the pipes let less leak out than if we just left it in the ground?