...
The difference between Oil Crude and Oil Composition is that Oil Composition recovered from petroleum reservoir may not fit the commercial standards and require preliminary processing before becoming an Oil Crude ready for sale.
The difference between Oil Composition and Oil Phase is that apart from typical Oil Composition the Oil Phase may contain non-oil components (like dissolved gas and water) and express a specific dynamic behavior of a fluid fluid phase.
See Also
...
Natural Science / Physics / Chemistry / Chemical Substance
...