The reply from Jean:

Every time that I plot a creaming curve, I am amazed to see how easy it is to model with several hyperbolas, but this doesn't explain why, except that on earth everything is curved. Linear is just a local effect (horizontal with the bubble, vertical with the mead) being the tangent of a curve. I found the same thing with fractals: it is a curve, so I took the simplest second degree curve : the parabola.

For creaming, hyperbola is the simplest with an asymptote. But the most important is to use several curves because exploration is cyclical. But another important point is to define the boundaries of the area. If the area is too big, it may combine apples and oranges making it difficult to find a natural trend. If the area is too small it will have too little data to find a trend. The best is to select a large Petroleum System which is a natural domain. The Arctic area is an artificial boundary and not a geological one.