On the Composition of Gases of the Myldzhinskoye Field
Abstract Generated abstract
This study characterizes the gaseous resources associated with the Myldzhinskoye gas condensate field in Tomsk Oblast as potential fuel and chemical feedstock. Samples of separated gas, raw condensate, and stabilized condensate from several wells were analyzed, including stepwise degassing of raw condensate and gas liquid chromatographic determination of nonhydrocarbon gases, methane, and C2 to C5 hydrocarbons. Degassing of 1 cubic meter of raw condensate released about 40 cubic meters of gas, with the largest release during pressure reduction from 20 to 5 atm, and the degassing gas was enriched in ethane, propane, butanes, and pentanes relative to separated gas. The work also shows that stabilized condensate retains appreciable dissolved C3 to C4 hydrocarbons, dominated by butanes, while methane, ethane, and nitrogen were not detected.
Full Text
ON THE COMPOSITION OF GASES OF THE MYLDZHINSKOYE FIELD
N. M. Smolyaninova, A. A. Ponomareva, V. A. Kuznetsova, A. V. Kravtsov
(Presented by the scientific seminar of the Departments of Organic Synthesis of the Faculty of Chemical Technology)
The development of processes for the chemical processing of hydrocarbon gases creates a need to increase the resources of gaseous raw materials.
In Tomsk Oblast, the largest source of natural gas is the Myldzhinskoye gas-condensate field, whose reserves make it possible to use the gas on a large scale not only as fuel but also as feedstock for chemical processing.
Since the field is a gas-condensate field, condensate will drop out during gas separation in the separator.
The gas-separation process is usually carried out at a pressure of 40–50 atm and at a temperature from −5°C to +20°C; therefore, during degassing of the raw condensate (when the pressure is reduced to atmospheric and the temperature is raised to 20°C), a large quantity of gas is released, and the condensate is considered stable.
In order to determine the resources and composition of the gases, we carried out a study of the separation and degassing gases and of the gas dissolved in the stable condensate of the Myldzhinskoye field.
Samples of separated gas were taken from wells Nos. 12, 23, 29, 31, 44; samples of stable condensate from wells Nos. 23, 29, 31. At well No. 31, in addition, a sample of raw gas condensate was collected in a container at a pressure of 40 atm.
For this sample, stepwise degassing of the condensate down to atmospheric pressure was carried out, with determination of the volume and composition of the gases released at each stage.
During degassing of 1 m³ of raw condensate, about 40 m³ of gas is released; the most intensive gas evolution (43% of its total volume) occurs when the pressure is reduced from 20 to 5 atm.
The chemical composition of the degassing gas and of the separated dry gas was determined by gas–liquid chromatography on a KhL-4 chromatograph. Nonhydrocarbon gases and methane were separated on CaX molecular sieves; hydrocarbons C₂–C₅ were separated on vaseline oil deposited on the solid support INZ-600.
The results of the analysis are given in Table 1.
The data show that the gas released during degassing contains 59.3% methane, 12.6% ethane, and 17.1% propane. Butanes and pentanes account for about 9% and 2%, respectively.
The amount of methane in the separated gas is 86–91%, and ethane about 4%.
It should be noted that the separated gas contains significant amounts of butanes (0.8–1.7%) and pentanes (0.2–0.5%), which may be explained by the high separation temperatures, since the most complete removal of these hydrocarbons from the gas in the separator occurs only at low temperatures (1).
The composition of the gases and low-boiling hydrocarbons dissolved in the stabilized condensate was determined by the VNIIINP method (2), with certain modifications (ethyl bromide was used as the tracer substance).
It can be seen (Table 2) that the degassed condensate still contains a significant amount of gases up to \(C_4\) (from 4.2 to 6.5%). Butanes predominate in their composition. Methane, ethane, and nitrogen are absent.
REFERENCES
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A. S. Velikovskii, Ya. D. Savvina. Effect of pressure and temperature on condensate separation from gas of the Karadag field. Gas Industry, 10, 1958.
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N. A. Kudryavtseva, A. I. Tarasov. Chromatographic study of gaseous hydrocarbons dissolved in petroleum. Chemistry and Technology of Fuels and Oils, 5, 1964.
Composition of gases from separation and degassing of Myldzhinskoye field condensate
Table 1
| Well no. | Separator regime: pressure, atm | Separator regime: temperature, °C | $N_2$ | $CH_4$ | $C_2H_6$ | $C_3H_8$ | $i$-$C_4H_{10}$ | $n$-$C_4H_{10}$ | $i$-$C_5H_{12}$ | $n$-$C_5H_{12}$ |
|---|---|---|---|---|---|---|---|---|---|---|
| 23 | 69,45 | +11,0 | 4,60 | 86,00 | 4,20 | 3,00 | 0,80 | 0,90 | 0,30 | 0,20 |
| 29 | 37,77 | +19,2 | 4,20 | 89,00 | 3,50 | 2,00 | 0,40 | 0,50 | 0,20 | 0,20 |
| 31 | 40,00 | +5 | 5,20 | 86,70 | 3,60 | 2,80 | 0,60 | 0,70 | 0,20 | 0,20 |
| 44 | 17,83 | +10 | 0,90 | 90,80 | 4,00 | 2,90 | 0,70 | 0,60 | 0,30 | 0,20 |
| 12 | 53,0 | +20 | 2,60 | 90,70 | 3,40 | 2,10 | 0,40 | 0,40 | 0,10 | 0,10 |
| 31 | 40,00 | +5 | — | 59,30 | 12,60 | 17,10 | 3,50 | 5,30 | 1,20 | 1,00 |
Composition of gases and low-boiling hydrocarbons dissolved in condensate
Table 2
| Well no. | Hydrocarbons | Condensate yield, wt. % | $C_3H_8$ | $i$-$C_4H_{10}$ | $n$-$C_4H_{10}$ | $i$-$C_5H_{12}$ | $n$-$C_5H_{12}$ |
|---|---|---|---|---|---|---|---|
| 23 | a) up to $C_4$ | 5,9 | 3,0 | 24,6 | 72,4 | — | — |
| 23 | b) up to $C_5$ | 20,4 | 0,9 | 7,2 | 21,2 | 34,8 | 35,9 |
| 29 | a) up to $C_4$ | 4,2 | 7,6 | 26,6 | 65,8 | — | — |
| 29 | b) up to $C_5$ | 14,1 | 2,2 | 7,9 | 19,5 | 34,1 | 36,3 |
| 31 | a) up to $C_4$ | 6,5 | 14,8 | 24,0 | 61,2 | — | — |
| 31 | b) up to $C_5$ | 14,8 | 6,5 | 10,6 | 27,1 | 26,6 | 29,2 |