Component Balance of Associated Gas During Staged Degassing of Oil from the Sovetskoye Field

A. V. Kravtsova, N. M. Smolyaninova

(Presented by the scientific-methodological seminar of the CTF)

Schemes for the gathering and transportation, and variants of processing, of associated petroleum gas are determined to a considerable extent by the amount of light hydrocarbons it contains, mainly \(C_3—C_5\), a valuable feedstock for petrochemical production.

The total resources of associated gas and of its individual components consist of the gas dissolved in the oil and released from it under the given conditions of staged degassing, i.e., at the pressure and temperature under study. Data on the yields and component composition of petroleum gas during staged degassing of reservoir samples of Sovetskoye oil have been given previously.¹

In the present work, a complete balance of the components of associated gas is presented for various conditions of separation of reservoir oil from the Sovetskoye field (wells 17, 501, and 27). The yield and composition of the gases dissolved in the oil after its degassing to atmospheric pressure were determined by the method of the All-Union Scientific Research Institute for Oil Refining, using ethyl bromide as a tracer.

A qualitative test for hydrogen sulfide showed its absence in all samples. The results of the analysis are given in Table 1.

Table 1

Content of soluble gases in degassed oil, by components and in total
(% by weight of oil)

The calculation of the amount of free gas and gas dissolved in oil at various pressures in the stages was carried out on the basis of the data in Table 1 and the results of the preceding work.

The results presented in Table 2 show that the total amount—

Table 2

Balance of associated gas, in kg per 1 t of reservoir oil from the Sovetskoye field during staged degassing

amount of associated gas is approximately the same for all the oils investigated and lies within the range of 10—12 wt. % per reservoir sample.

Table 3 presents the balance of gas components during staged degassing of reservoir oil from the investigated wells, calculated—

Table 3

Balance of gas components during staged degassing of reservoir oil from the Sovetskoye field, kg/t of reservoir oil

Continuation of Table 3

… according to the data of Tables 1–2. It is evident that, during separation down to 6 atm, the main quantities of methane, ethane, and nonhydrocarbon gases are released from the reservoir oil.

The overwhelming portion of the hydrocarbons \(C_3—C_5\) can be recovered and used during separation of the oil from 6 to 0 atm and during its subsequent stabilization. The recoverable quantities of hydrocarbons \(C_3—C_5\) from 1 ton of reservoir oil from well 17 (bed A-1) and wells Nos. 27 and 501 (bed B-VIII) are, respectively, \(74{,}61\ \text{kg/t}\), \(81{,}10\ \text{kg/t}\), and \(75{,}93\ \text{kg/t}\).

Taking into account that at the Sovetskoye field by 1975 approximately 10 million tons of oil and more than \(0{,}5\) billion \(\text{m}^3\) of associated gas will be produced, the total resources of hydrocarbons will amount to approximately 1 million tons.

Conclusions

1. The yield and composition of gases dissolved in the oil of the Sovetskoye field after its degassing to atmospheric pressure have been determined.

2. A complete balance of the components of associated gas during staged degassing of oil from the Sovetskoye field has been compiled, calculated per reservoir oil.

3. It has been shown that the recoverable quantities of hydrocarbons \(C_3—C_5\) from 1 ton of reservoir oil for beds A-1 and B-VIII reach, respectively, \(75\ \text{kg/t}\) and \(80\ \text{kg/t}\).

1. N. M. Smolyaninova, A. V. Kravtsov, V. A. Kuznetsova. Study of the component composition of associated gas from the Sovetskoye field. Present collection. ↩