Chemical classification of naphthenic condensates and oils

Abstract

The hydrocarbon compositions of naptheninic gas condensates and oils from different fields located in the northern part of West Siberia have been examined by GC and GC-MS. The composition of the C 6–C 13 boiling point fraction was studied in detail and the identities of more than 400 components assigned. The composition of naphthenic condensates is dependent on their depth of occurrence and on the temperature of the oil-bearing beds. The condensates were divided into seven chemical types (sub-types) distinguished by the qualitative composition and the relative abundances of mono-, bi- and tricyclic alkanes. It is suggested that biodegradation is the main factor which influences the composition of different types of naphthenic condensates. The study of the “condensate” fraction of some naphthenic oils occurring close to condensates showed that the composition of the oils is close to that of the condensates. The similarity between the composition of the condensates and the C 6–C 13 fraction of the oils enables a chemical classification of naphthenic oils. Naphthenic condensates and oils seem to be genetically close and the condensates can be regarded as oil derivatives formed as a result of dissolution of light fractions in compressed gas.