There are three major references to oil depending on the context:

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 Oil Phase may contain non-Dead Oil components (like dissolved gas and water) and express a specific dynamic behavior of a fluid phase. The word "oil" in Oil Phase simply means that Oil Composition is dominant in a given fluid phase.

See Also

Natural Science / Physics / Chemistry / Chemical Substance

Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology / Petroleum fluids