Some people like me like to play with low resource settings. Normal resources are usually generated, but with oil is a serious problem. I can not generate oil in such a way that the number of deposits was 1-6 and no more.
Here are some examples.
Low frequency, high size.

Low frequency, normal size.

Low frequency, low size.

Low frequency, very low size.

As you can see there is no difference between these settings.
Sometimes the generation breaks down so that the oil is very difficult to find.
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PS
Does oil depend on biome? Logically, there should be more oil in the deserts.