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 С19-30
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.