Content of nickel and vanadium in more than 120 crudes as function of specific gravity@15°C/60°F.
The figure is based on information from more than 120 crude oil assays from BP, ExxonMobile and Statoil (2008 - 2017). The crudes are produced all over the world. Each datapoint reperesents one specific oil. Each oil contains both nickel and vanadium.
See also Crude oil viscosity as function of gravity.