The Mishrif reservoir (Cenomanian - Turonian) in the Z, H, B and N oilfields in southern Iraq was investigated to clarify how nickel, vanadium, asphaltene, NSO and sulfur content affect the crude oil quality. The GC-Mass and ICP-MS analyses were used to provide fruitful hydrocarbon results. Classification of crude oil based on API gravity broadly indicates the oil's density and general properties. Typically, lighter crude oils are easier to refine, yield higher percentages of valuable products such as gasoline and diesel, and have a higher market value. Heavier crude oils require more processing and may yield more residual products, such as heavy fuel oil and asphalt. The Mishrif crude oil was classified as a medium sour crude oil containing high sulfur content (%) in Z oilfield (5.22), H oilfield (5.1), and B (5.12); more significant than those in N crude oil, which is classified a sweet based on less than 5% sulfur. The content of asphaltene, nickel, NSO, and vanadium affects the quality of crude oil and the market price because of its negative impact on refining processes, susceptibility to corrosion, and environmental damage later after fuel consumption and burning.
