It used to be that oil would just seep to the surface. That generally stopped once we figured out we could usefully burn it and began draining the easily access sources. I wonder which is "worse" what there was prior to petroleum becoming a commodity or the pipeline leaks that happen now.

There are well known ocean seeps that have been ongoing for tens or hundreds of thousands of years[1]:

>Researchers have found that natural offshore seeps near Goleta, California, alone have leaked up to 25 tons of oil each day – for the last several hundred thousand years.

1. http://aoghs.org/offshore-history/california-oil-seeps/