G.S. Martynova, O.P. Maksakova, R.G. Nanadzhanova, N.I. Velimetovа
Lokbatan oil field
Key words: Lokbatan oil; hydrocarbon composition; biomarkers; trace elements.
For citation: Martynova G.S., Maksakova O.P., Nanadzhanova R.G., Velimetova N.I. Lokbatan oil field. Geologiya nefti i gaza. 2022;(2):45–52. DOI: 10.31087/0016-7894-2022-2-45-52. In Russ.
The authors present the results of oil geochemical studies in one of the oldest Azerbaijan field Lokbatan. Following modern instrumental analytical methods were used in the studies: chromatography-mass spectrometry; simultaneous thermal analysis; elemental analysis; and inductively coupled plasma mass spectrometry. The better reservoir horizons in the field are VI–VIa occurring at the depth 500 to 700 m; although, all the horizons from I to VIII within the Lokbatan Fold are oil-bearing. Hydrocarbon column of VI–VIa horizons is 300 m. Studies of possible fractional composition of oil in the samples taken from the Lokbatan field were carried out using simultaneous thermal analyser. Hydrocarbon and biomarker composition of oil was carried out using chromatography-mass spectrometry method. It is shown that oil is paraffin-naphthene with aromatics content about 13–20 %. Pr/Ph indicator and absence of tricyclic terpanes Т19–Т26 characterise the sedimentation area and determine the Organic Matter source according to oleanane index that is indicative of substantial contribution of ground vegetation and sapropel-humic genesis of oil. Estimation of the ratios oleanane/H30 = 0.48 and regular steranes St27 / St28 / St29 = 26/25/49 is also indicative of predominance of higher land plants. The calculated oddity coefficient — СРI = 1.12–1.75 suggestive of high odd n-alkanes content is associated with oxidizing settings of sedimentation, which is indicative of the Organic Matter generation in a shallow-water basin. All the analysed oil samples taken from the Lokbatan field are iron-bearing; the authors propose a concentration range of trace elements found in the studied oil samples. In addition to iron, titanium and nickel dominate among the trace elements.