LAUSR

Abstract The study is paying attention to the variation of the comparative abundance of naphthalenes, phenanthrenes of aromatic fractions separated from seven different Egyptian crude oils, and were studied by GC–MS to assess the thermal maturity and recognize the organic matter input. Tetramethylnaphthalenes (TeMN), Trimethylnaphthalenes (TMN), Dimethylnaphthalenes (DMN), Methylnaphthalenes (MN) and Naphthalene (N), in addition to Phenanthrene (P), and their mono, di and tri -methyl substituted isomers (MP, DMP and TMP) have been identified. Ratios depending on the differences in the thermal stability of the isomers were studied (MPI, MPr, MNr, DMNr, TMNr). The ratios of β- to α-substituted isomers of both methylnaphthalenes and methylphenanthrenes imply higher thermal maturity of WD1 from Faghur and ND1 from Nile Delta basin compared to the rest samples. WD2 crude oil sample from Faghur basin was found to has high amount of 1,3,7- and 2,3,7-trimethylnaphthalenes (TMN) with (TMNr = 2.16) and high Pristan/Phytane ratio (Pr/Ph = 3.49) compared to WD1 from the same basin suggesting in-reservoir oil mixing.