Geochemical Characterization of Two Niger Delta Crude Oils and Their Mixtures I: Bulk Properties and Aliphatic Hydrocarbon Distributions

Two crude oils from Rivers and Delta States, Niger Delta Nigeria, samples A and F respectively, and their binary mixtures at different compositions, samples B, C, D, and E, were geochemically characterized using bulk properties and aliphatic hydrocarbon distributions. Results of density and API gravity, which classified samples A, B, C, D as light oils and samples E, F as medium oils, were observed to increase and decrease with increase in the composition of oil sample F respectively. The composition of the saturates, from 68.00 to 71.10%, suggest high maturity of the oil samples which did not show a relationship to the compositional mix of the two Niger Delta crude oils. Bimodal distribution of n-alkanes in samples A and B with a slight prominence of the short chain suggest marine source with significant terrestrial input, while the prominence of the long chain n-alkanes in sample F, which suggest a terrestrial source, progressively increased in samples C, D, and E. Pr/Ph ratios from 2.37 to 2.70 suggest source rocks deposited in an oxic environment. Ratios of Pr/nC17, from 0.94 to 1.20, and Ph/nC18, from 0.39 to 0.53, suggest shale source rocks with terrestrial higher plant input. From these results, the geochemical characteristics of the individual Niger Delta crude oils were exhibited by their binary mixtures. However, density, API gravity, n-alkane distribution, Pr/nC17 and Ph/nC18 ratios were expressed relative to the compositional mix of the two Niger Delta crude oils