Document Type: Research Paper
Lighthydrocarbons are commonly used to evaluatecrude oils to determine oil families in reservoirs undergone some kind of alteration process. In this study crude oil contentsfromNorthwestern IranDelta (samples A, B and C)were analyzed in order to evaluate the IranDelta petroleum system independent of higher molecular weight markers. Ultra high resolution gas chromatography was used in separation and analysis of the light hydrocarbons.Heptane ratio, invariance, maturity,aromaticity and paraffinicity parameters among the C7 light hydrocarbons discriminated the oils into two families namely marine and terrigenous and also revealed the Northwestern IranDelta oils as supermature. Further confirmation of these two sources for crude oils in the Northwestern IranDeltawas obtained from multivariate plots of each crude oil on a star diagram. Sample B and sample C oils were closely matched by their similar path on the star diagram and grossly different from sample A oil which followed a different pattern.