THE GENERATING MECHANISM OF METHYLATED NAPHTHALENE SERIES IN CRUDE OILS AND THE APPLICATION OF THEIR MATURITY PARAMETERS

Naphthalene and methylated naphthalene series in crude oils and sedimentary organic matters are formed through isomerization and disproportionation,which can be interpreted by aromatic electrophilic substitution process.The relative concentrations of various isomers are controlled by "electronic effect" and "steric effect".Geochemical parameters related to methylated naphthalenes can be used to indicate the differences of maturity,biodegradation,and source input between oil and sedimentary organic matters.Oil samples selected from Damintun Depression in Bohai Bay Basin have been analyzed for methylated naphthalene series.The results show that the high waxy oils are more thermally mature than normal oils,even though some saturated hydrocarbon composition such as steranes and terpanes isomeric ratios get to equilibrium end.This conclusion is consistent with the geological background and the basin modeling results in the study area.It is proved that these methylated naphthalene parameters are very useful geochemical indicators.