Hydrocarbon Composition of Oil from the Samotlor Field
Abstract Generated abstract
This paper characterizes the hydrocarbon composition of gasoline, kerosene, gas-oil, and higher boiling fractions from the Samotlor oil field. Using aniline-point analysis, adsorption separation, molecular sieve determination of normal paraffins, gas-liquid chromatography checks, and structural-group calculations by the n-d-M method, it reports changes in paraffinic, naphthenic, and aromatic components across distillation ranges. The results indicate that gasoline fractions are dominated by paraffinic hydrocarbons, mainly iso compounds, while aromatic content increases and methane-naphthenic content decreases with rising boiling temperature. The authors classify Samotlor oil as a naphthene-methane type oil and suggest that its gasoline may serve as platforming feedstock, with the crude suited to fuel-oriented refining.
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Hydrocarbon Composition of Oil from the Samotlor Field
N. M. SMOLYANINOVA, P. E. SHIPITSINA, G. B. NEMIROVSKAYA
The group hydrocarbon composition of the gasoline fractions is presented in Table 1. The analysis was carried out by the aniline-point method; the content of n-paraffins was determined by adsorption on CaA molecular sieves and checked by the GLC method.
The data in Table 1 show that paraffinic hydrocarbons predominate in all fractions, represented mainly by iso compounds. The content of aromatics increases—
Table 1
Group hydrocarbon composition of gasoline fractions of Samotlor oil
| Temperature limits for fraction selection, °C | Yield on oil, wt. % | Specific gravity, $\rho_4^{20}$ | $n_D^{20}$ | Aromatic hydrocarbons, wt. % | Naphthenic hydrocarbons, wt. % | Paraffinic hydrocarbons, total, wt. % | Paraffinic hydrocarbons, incl. n-structure, wt. % |
|---|---|---|---|---|---|---|---|
| 28—60 | 3.0 | 0.6450 | 1.3640 | 0 | 0 | 100 | 47 |
| 60—95 | 5.5 | 0.7116 | 1.3949 | 2 | 41 | 57 | 30 |
| 95—122 | 3.6 | 0.7364 | 1.4112 | 7 | 28 | 65 | 23 |
| 122—150 | 5.6 | 0.7470 | 1.4238 | 13 | 28 | 59 | 24 |
| 150—200 | 8.6 | 0.7907 | 1.4417 | 21 | 21 | 58 | 19 |
| 28—200 | 26.3 | 0.7500 | 1.4192 | 11 | 25 | 64 | 25 |
—with increasing boiling temperature of the fractions, while the naphthenic content decreases. In the broad gasoline cut (28—200°C), the amount of aromatic hydrocarbons is 11%, that of naphthenic and methane hydrocarbons is 64%, of which 25% consists of n-alkanes.
Thus, the gasoline has a methane–naphthenic character and, apparently, may be used as feedstock for platforming.
The group composition of the kerosene–gas-oil and oil fractions was determined by adsorption and aniline methods; the structural-group composition was calculated by the $n—d—M$ method. The results are presented in Tables 2, 3, 4.
As can be seen from the data given, the content of the sum of aromatic hydrocarbons increases with increasing boiling temperature of the fractions from 26 to 59%, while the methane–naphthenic content correspondingly decreases. This regularity is also confirmed by the indices of the structural-group composition (Table 4).
Table 2
Group hydrocarbon composition of 50-degree fractions boiling from 200 to 440°, determined by the adsorption method
| Temperature limits of selection, °C | Yield on oil, % | Density, $\rho_4^{20}$ | $n_D^{20}$ | Mol. wt., average | Sulfur content, % | Methane–naphthenic: $n_D^{20}$ | Methane–naphthenic: % | 1st aromatic group: $n_D^{20}$ | 1st aromatic group: % | 2nd aromatic group: $n_D^{20}$ | 2nd aromatic group: % | 3rd aromatic group: $n_D^{20}$ | 3rd aromatic group: % | 4th aromatic group: $n_D^{20}$ | 4th aromatic group: % | Sum of aromatics, % | Intermediate fractions and resins, % | Sulfur in paraffins, %* |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 28–200 | 26,3 | 0,7500 | 1,4192 | 120 | — | — | 89 | — | — | — | — | — | — | — | — | 11 | — | — |
| 200–250 | 9,2 | 0,8270 | 1,4610 | 178 | 0,17 | 1,4377—1,4496 | 74 | 1,4900—1,5180 | 15 | 1,5339 | 3 | 1,5622—1,5888 | 8 | — | — | 26 | — | — |
| 250–300 | 9,2 | 0,8563 | 1,4750 | 210 | 0,58 | 1,4460—1,4830 | 71 | 1,5084—1,5203 | 11 | 1,5343 | 5 | 1,5530—1,5887 | 9 | 1,5930—1,6004 | 4 | 29 | — | — |
| 300–350 | 10,0 | 0,8750 | 1,4896 | 256 | 1,10 | 1,4510—1,4800 | 62 | 1,5010—1,5230 | 13 | 1,5310—1,5440 | 7 | 1,5540—1,5770 | 10 | 1,5970—1,6015 | 7 | 37 | 1 | — |
| 350–400 | 9,6 | 0,9020 | 1,5027 | 310 | 1,39 | 1,4610—1,4835 | 49 | 1,4950—1,5285 | 20 | 1,5340—1,5480 | 9 | 1,5525—1,5875 | 15 | 1,5990—1,6230 | 5 | 49 | 2 | 9,8 |
| 400–440 | 7,0 | 0,9250 | 1,5160 | 353 | 1,61 | 1,4750—1,4890 | 38 | 1,4995—1,5295 | 33 | 1,5328—1,5472 | 10 | 1,5520—1,5832 | 10 | 1,5925—1,6205 | 6 | 59 | 3 | 13,8 |
* Paraffin melting point, respectively 49 and 54°C.
Table 3
Group composition of kerosene–gas oil fractions
| Distillation temperature, °C | Naphthenic hydrocarbons, wt % | Paraffinic hydrocarbons, wt % | Aromatic hydrocarbons, wt % |
|---|---|---|---|
| 28–200 | 25 | 64 | 11 |
| 200–250 | 24 | 50 | 26 |
| 250–300 | 21 | 50 | 29 |
| 300–350 | 20 | 42 | 37 |
| 28–350 | 23 | 56 | 21 |
Table 4
Structural-group composition of 50-degree fractions (by the n–d–M method)
| Distillation temperature, °C | \(C_A\), carbon distribution, % | \(C_H\), carbon distribution, % | \(C_{\mathrm{ring}}\), carbon distribution, % | \(C_P\), carbon distribution, % | \(K_A\), average number of rings per molecule | \(K_H\), average number of rings per molecule | \(K_O\), average number of rings per molecule |
|---|---|---|---|---|---|---|---|
| 200–250 | 13 | 33 | 46 | 54 | 0.28 | 0.77 | 1.05 |
| 250–300 | 17 | 31 | 48 | 52 | 0.43 | 0.76 | 1.19 |
| 300–350 | 19 | 25 | 44 | 56 | 0.59 | 0.83 | 1.42 |
| 350–400 | 20 | 24 | 44 | 56 | 0.76 | 1.16 | 1.92 |
| 400–450 | 23 | 22 | 45 | 55 | 1.00 | 1.36 | 2.36 |
Among the aromatics, representatives of the first group (benzene homologs) predominate.
The appearance of the fourth group of aromatic hydrocarbons in the 250–300° fraction is noteworthy, since this is usually uncharacteristic, as is the discrepancy between the high aromatic content in the fractions and the low values of \(C_A\). The former can apparently be explained by insufficiently sharp rectification, and the latter by the compositional features of Samotlor oil. It is interesting to note the comparatively low refractive-index values of the high-boiling distillates despite their considerable specific gravity. This fact can probably be explained by the high content, in these fractions, of hybrid hydroaromatic compounds with relatively short side radicals. The values of the average number of rings per molecule, especially the data for \(K_H\) and \(K_O\) (Table 4), support this assumption.
On the basis of the data presented, it may be concluded that Samotlor oil belongs to the naphthene–methane type (according to Dobryanskii’s classification) and can be used for fuel-oriented refining.