Chemical Composition and Geochemical Applications of Waxes Isolated from Pakistani Crude Oil

摘要

Almost all crude oils even condensates contain some amount of high molecular weight hydrocarbons(HMWHCs)which include waxes and asphaltenes.These compounds are mainly associated with wax deposition problems during production which reduce the recovery rate and ultimately enhance the cost of drilling program.In this study,an attempt has been made to investigate hydrocarbon composition of wax isolated from Rajian field oil and to determine source rock depositional environment.Alumina adsorption sequential soxhlet extraction method was used to isolate wax and asphaltene from crude oil.Wax hydrocarbons were fractionated into rc-alkanes and branched and cyclic(QIC)alkanes by liquid chromatography using molecular sieves(Silicalite S115)and analyzed by high temperature gas chromatography(HTOC).HTGC of wax branched and cyclic alkanes has shown an odd predominance of n-alkylcyclohexanes in HMW region(Cjsto C45),which is characteristic of marine depositional environment,therefore source rock paleoenvironment of Rajian oil is marine.HTGC provide an inexpensive and very effective analytical tool to establish geochemistry of geological samples.