ADAMANTOIDS IN OILS AS INDICATORS OF PRESENCE OF THE DEEP SOURCE ROCKS, ABSHERON ARCHIPELAGO, SOUTH CASPIAN BASIN, AZERBAIJAN

Abstract

Petroleum is the only natural source for adamantane and its isomers. It is rigid and at same time stress-free molecule with three connected cyclohexane rings arranged in the “armchair” configuration and has high degree of symmetry. The spatial  rrangement of carbon atoms in the adamantane molecule is the same as in the diamond crystal, that is why adamantane type hydrocarbons are also called “diamond type hydrocarbons”. Detailed geochemical analysis, including Gas-chromatography and hromatography-mass-spectrometry were run on the oil samples from the fields located in Absheron archipelago. Biomarkers, including   damantanes and its homologs have been identified in the oils analyzed; distribution of adamantine C₁₀-C₁₄ and the role of adamantine on the genesis of the hydrocarbons have been studied as well. Analyses of the chromato-mass spectrometry data suggest that adamantine and its methyl substitution compounds are present in the sequence of increasing of the thermodynamic resistance in the following order: 2-MAd ˃ 1-MAd ˃ 3-MAd ˃ Ad. This indicates formation of the adamantine as a result of thermal transformations of normal alkanes. Oil samples with higher continental input source characterized by lower concentration of tricyclic terpanes С_19-30 in comparison with the same age oils but with marine source of sediment. Interpretation and analyses of the geochemical data, including concentration of diamondoids indicates presence of deep source rocks in the South Caspian basin.