The oil seeps are the migration of oil up from the depths that is not trapped and pooled by geological formations. This is happening around the world. The same is true of the outgassing of methane and helium. It’s going on everywhere but it’s in places that are cold enough and with enough water pressure that methane hydrates are formed. Remember, many extremely large oil fields are directly upon basement rock. That oil didn’t sink down from a higher source.
The only fields that I am aware of that lie on basement such as in the Texas Panhandle have had lateral migration from the Woodford Shale out of the Anadarko Basin. There is some production from the underlying granite wash that sits on fresh granite basement but the production is out of fractures as granite has no porosity. I believe there is a small amount of Precambrian oil in Australia that has been sourced from stromatalites but it is a rarity. Most people stop drilling in basement as they know they have hit a dead end. The rest are just pouring good money down a bad hole.