Seven samples of crude oil from Kazakhstan fields are characterized with the ratios of isoprenoid alkanes (biomarkers), namely “pristane / phytane” ( R 1), “phytane / n -octadecane” ( R 2), and “pristane / n -heptadecane” ( R 3). Additionally, the following ratios rarely taken into account were also considered: “pristane / 2,6,10-trimethylpentadecane (norpristane)” ( R 4), “pristane / 2,6,10-trimethyltetradecane” ( R 5), and “pristane / 2,6,10-trimethyltridecane” ( R 6). It was concluded that the higher were the relative standard deviations of R -criteria (variation coefficients, dN, %) within series of any sample, the higher were their informativeness for distinguishing these samples. For instance, dN-values for criteria R 1 - R 3 were 36-62%, while for R 4 - R 6 they were 2-3 times less (13-34%). The reproducibility of R -criteria both at fixed conditions of analysis and at any variations of gas chromatographic separation parameters was characterized. In both cases the relative standard deviations (di, %) for criteria R1 - R 3 were approx. 3%, while for criteria R4 - R 6 - about 10%. Combining both parameters dN and dI allowed introducing the integral criterion for distinguishing the petroleum samples, K = dN / di. K -Values for criteria R 1 - R 3 varied within the range of 8-41, while those for criteria R 4 - R 6 varied within the range of 1.2-2.4, i.e., 10-20 times less. It means that expanding the lists of isoprenoid alkanes as biomarkers by considering such minor constituents as norpristane, 2,6,10-trimethyltetradecane, and 2,6,10-trimethyltridecane seems to be irrational due to the low information content.
|Translated title of the contribution||DETERMINATION OF C15-C20 ISOPRENOID ALKANES CHARACTERISTIC RATIOS IN THE OILS FROM KAZAKHSTAN FIELDS|
|Journal||АНАЛИТИКА И КОНТРОЛЬ|
|Publication status||Published - May 2019|