Mud volcanoes of western flank of South Caspian depression: geochemical features of oils and mud volcano oil shows

The authors discuss the results of naphtide genesis studies in Azerbaijan, which are aimed at discovery of oil and gas formation opportunities in deep sedimentary cover horizons in the region. The results of geochemical studies of the products of mud volcanoes activity and oil from the fields of the western sidewall of South Caspian depression are presented. Instrumental methods were for the first time used to analyse the trace element composition of material ejected from mud volcanoes (oil shows in Absheron, Shamakha-Gobustansky. and Nizhnekurinsky regions of Azerbaijan) and oil from the neighbouring fields of mentioned regions. Comparison of trace element content in oil samples and oil shows, as well as isotopic characteristics, composition, and biomarker features are indicative of common genesis of naphtides. Comparison of the products of volcanic activity and oil from Azerbaijan fields in certain regions, as well as involvement of the correlation analysis results for mud volcanism water content presented in the paper, will complement and enrich the results of previous studies. It was found that trace element concentrations in oil shows of mud volcanoes in three studied regions are considerably higher than in the oils. This phenomenon is related to supergene transformation of mud volcano oil shows, light fraction loss and escape, oxidation and biodegradation accompanied by increase in resinous-asphaltenic components and trace element content in them, and changes in biomarker characteristics. The revealed dependence of trace element composition of mud volcano waters in Azerbaijan on the composition of intermediate-level Earth’s crust, syngenesis of oils and oil shows of mud volcanism can be indicative of possible additional source of trace elements and involvement of deep-lying horizons in oil generation