On the method for technological calculation of the gas separation zone in oil and gas separators

UDK: 622.276.8:665.622
DOI: 10.24887/0028-2448-2021-4-106-109
Key words: technological calculations, gas separation, oil and gas separator, size of gas bubbles
Authors: M.Yu. Tarasov (Giprotyumenneftegas PJSC, HMS Group, RF, Tyumen)

In the field conditions, the gas-oil mixture entering the oil and gas separator from the supply pipeline consists of free gas separated at the separation pressure and a liquid phase with gas dissolved and dispersed in it. Free gas almost instantly passes into the gas space of the separator, the gas dissolved at the separation pressure remains in the liquid leaving the separator, and the dispersed gas is separated in the gas separation zone, and the time of its separation depends on the dispersion (size) of the bubbles. Technological calculations of the process of separating oil and gas in separation equipment are based on determining the ascent time of gas bubbles using the Stokes formula to determine the rate of their ascent. In this case, the main influence on the speed and, accordingly, on the ascent time is exerted by the size of the bubbles. As a rule, in calculations, the size of the bubbles is set based on data from field practice, or on the basis of experimental data. At the same time, there are theoretical methods for calculating the size of gas bubbles formed in the flow of a gas-liquid mixture entering an oil and gas separator. The paper gives an assessment of the applicability of these methods in technological calculations of the size of the gas separation zone of oil and gas separators, taking into account the time recommended by the field practice for the retention of liquid in this zone. The results of comparative calculations of the gas separation process for various types of oils in standard separation equipment are presented. It is shown that the most acceptable method is based on determining the average volume-surface diameter of bubbles formed in the gas-liquid mixture inlet nozzle. It was found that in the absence of experimental data, it is possible with accuracy acceptable for design calculations to use this technique to determine the size of gas bubbles in the gas-liquid mixture entering the separator degassing zone. Formulas were obtained for calculating the diameter of the apparatus and the length of the degassing zone with the filling factor of the separator equal to 0.5, depending on the ascent rate of the bubbles of the calculated size. This approach is used in the methods of technological calculation of oil and gas separators, oil and gas separators with water discharge, degassers, i.e. devices with a gas separation zone.

References

1. RD 39-0004-90. Rukovodstvo po proektirovaniyu i ekspluatatsii separatsionnykh uzlov neftyanykh mestorozhdeniy, vyboru i komponovke separatsionnogo oborudovaniya (Guidelines for the design and operation of oil field separation units, selection and layout of separation equipment), Ufa: Publ. of VNIISPTneft', 1990, 69 p.

2. Daletskiy V.M., Efimov V.B., Shlykova M.P., Eksperimental'noe izuchenie generirovaniya i otdeleniya melkodispersnoy gazovoy fazy v gazozhidkostnoy smesi (Experimental study of the generation and separation of a finely dispersed gas phase in a gas-liquid mixture), In: Problemy obustroystva i ekspluatatsii vysokoobvodnennykh neftyanykh mestorozhdeniy (Problems of arrangement and operation of highly watered oil fields), Kuybyshev: Publ. of Giprovostokneft', 1985, pp. 77–82.

3. Daletskiy V.M., Efimov V.B., Shlykova M.P., Razrabotka metoda rascheta razdeleniya gazozhidkostnykh smesey v separatsionnoy emkosti (Development of a method for calculating the separation of gas-liquid mixtures in a separation tank), In: Razrabotka i vnedrenie effektivnoy tekhniki i tekhnologii dobychi nefti (Development and implementation of effective equipment and technology for oil production), Kuybyshev: Publ. of Giprovostokneft', 1986, pp. 27–31.

4. RD 0352-131-98. Degazatory. Metodika tekhnologicheskogo rascheta (Degassers. Technological calculation method), Podol'sk: Publ. of DAO TsKBN, 1998, 55 p.

5. Medvedev V.F., Sbor i podgotovka neustoychivykh emul'siĭ na promyslakh (Gathering and preparation of unstable emulsions in the fields), Moscow: Nedra Publ., 1987, 144 p.

In the field conditions, the gas-oil mixture entering the oil and gas separator from the supply pipeline consists of free gas separated at the separation pressure and a liquid phase with gas dissolved and dispersed in it. Free gas almost instantly passes into the gas space of the separator, the gas dissolved at the separation pressure remains in the liquid leaving the separator, and the dispersed gas is separated in the gas separation zone, and the time of its separation depends on the dispersion (size) of the bubbles. Technological calculations of the process of separating oil and gas in separation equipment are based on determining the ascent time of gas bubbles using the Stokes formula to determine the rate of their ascent. In this case, the main influence on the speed and, accordingly, on the ascent time is exerted by the size of the bubbles. As a rule, in calculations, the size of the bubbles is set based on data from field practice, or on the basis of experimental data. At the same time, there are theoretical methods for calculating the size of gas bubbles formed in the flow of a gas-liquid mixture entering an oil and gas separator. The paper gives an assessment of the applicability of these methods in technological calculations of the size of the gas separation zone of oil and gas separators, taking into account the time recommended by the field practice for the retention of liquid in this zone. The results of comparative calculations of the gas separation process for various types of oils in standard separation equipment are presented. It is shown that the most acceptable method is based on determining the average volume-surface diameter of bubbles formed in the gas-liquid mixture inlet nozzle. It was found that in the absence of experimental data, it is possible with accuracy acceptable for design calculations to use this technique to determine the size of gas bubbles in the gas-liquid mixture entering the separator degassing zone. Formulas were obtained for calculating the diameter of the apparatus and the length of the degassing zone with the filling factor of the separator equal to 0.5, depending on the ascent rate of the bubbles of the calculated size. This approach is used in the methods of technological calculation of oil and gas separators, oil and gas separators with water discharge, degassers, i.e. devices with a gas separation zone.

References

1. RD 39-0004-90. Rukovodstvo po proektirovaniyu i ekspluatatsii separatsionnykh uzlov neftyanykh mestorozhdeniy, vyboru i komponovke separatsionnogo oborudovaniya (Guidelines for the design and operation of oil field separation units, selection and layout of separation equipment), Ufa: Publ. of VNIISPTneft', 1990, 69 p.

2. Daletskiy V.M., Efimov V.B., Shlykova M.P., Eksperimental'noe izuchenie generirovaniya i otdeleniya melkodispersnoy gazovoy fazy v gazozhidkostnoy smesi (Experimental study of the generation and separation of a finely dispersed gas phase in a gas-liquid mixture), In: Problemy obustroystva i ekspluatatsii vysokoobvodnennykh neftyanykh mestorozhdeniy (Problems of arrangement and operation of highly watered oil fields), Kuybyshev: Publ. of Giprovostokneft', 1985, pp. 77–82.

3. Daletskiy V.M., Efimov V.B., Shlykova M.P., Razrabotka metoda rascheta razdeleniya gazozhidkostnykh smesey v separatsionnoy emkosti (Development of a method for calculating the separation of gas-liquid mixtures in a separation tank), In: Razrabotka i vnedrenie effektivnoy tekhniki i tekhnologii dobychi nefti (Development and implementation of effective equipment and technology for oil production), Kuybyshev: Publ. of Giprovostokneft', 1986, pp. 27–31.

4. RD 0352-131-98. Degazatory. Metodika tekhnologicheskogo rascheta (Degassers. Technological calculation method), Podol'sk: Publ. of DAO TsKBN, 1998, 55 p.

5. Medvedev V.F., Sbor i podgotovka neustoychivykh emul'siĭ na promyslakh (Gathering and preparation of unstable emulsions in the fields), Moscow: Nedra Publ., 1987, 144 p.



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