I lived in Santa Barbara, oil would just bubble up out of cracks in the ocean floor. I would bet that natural releases of oil exceed that from oil spills, if you take into account all the oceans, not just local areas where man made influences may dominate.
I have seen that in Texas, Saudi Arabia and Kuwait on land.
Recent articles about the infamous, earth-shaking, paradigm-changing 1969 Santa Barbara Well No. 21, Platform A spill point out that small oil slicks and patches are still found in the area and blamed on the remnants of the long-ago disaster but are in fact natural seeps from the ocean floor.