RU2381428C1 - Method of condensate extraction from natural gas - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention can be used in oil-and-gas industry at gas-condensate fields. Condensate extraction form a natural gas method using gas cooling and gas separation in a process lines includes sequential three stage degassing of separated condensate, with utilisation of low pressure degassed gas with high pressure gas in ejectors. Low pressure second condensate degassing stage gas flows into ejector of a single process line, low pressure third condensate degassing stage gas flows into ejector of a another process line. Set up pressure in degassing equipment in a range of (3.0-3.8) MPa -second stage and (2.8-3.0) MPa - third stage.

EFFECT: degassing heavy hydrocarbons gas efficient utilisation method.

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Description

The invention relates to the oil and gas industry and can be used for field preparation of gas and gas condensate in gas condensate or oil and gas condensate fields as part of plants using a low-temperature condensation (separation) method for drying gas by moisture and heavy hydrocarbons and a method of stepwise degassing of condensate for its partial stabilization.

Known methods for low-temperature gas separation and stepwise degassing of gas condensate for field preparation of crude gas, including processes of two-phase and three-phase separation of flows with their cooling, in which the gas is degassed by single-stage gas-gas ejectors, and partially stabilized condensate is transported to the consumer through a condensate pipeline under the action of gas pressure in an end three-phase separator / Bekirov T.M., Lanchakov G.A. Gas and condensate processing technology - M., Nedra, 1999, pp. 290, 308, 309 /.

Also known are combined methods of field gas preparation with utilization of degassing gas in a condensate stabilization unit with a column apparatus / RF Patent No. 2096701, Cl. F25J. 3/02, Published November 20, 1997 /.

The simplest low-temperature gas separation units with a single-stage ejector recovery of condensate degassing gas have an insufficient degree of degassing gas utilization, and the implementation of combined installations with column units is economically justified only for their large unit capacities.

The closest prototype of the present invention is a method of utilizing condensate degassing gas at a comprehensive gas treatment unit (UKPG-2 V) of the Urengoy oil and gas condensate field. This installation contains several parallel production lines with sequentially connected separators, recuperative heat exchangers, ejectors and three-phase separators (separated condensate degassers as part of a three-stage degassing unit).

According to the method of connecting to the degassing gas sources (devices), UKPG-2V ejectors are combined into 2 groups:

- the first group of ejectors is connected to three-phase separators UKPG-2V;

- the second group of ejectors is connected to the condensate stabilization installation at the Urengoysky gas condensate processing plant due to its close location to UKPG-2V. / Bekirov T.M., Lanchakov G.A. Technology of gas and condensate processing-M., Nedra, 1999, pp. 309, 310, 482, 489 /.

With significant, for example, more than 100 km, distances between the gas treatment plant and the centralized condensate stabilization units, the pumped condensate supply to the condensate pipe is used. In this case, the gas pressure in the third (end) stage of condensate degassing at the gas treatment unit is set according to the suction conditions of the condensate pump, and a single-stage ejection of the degassing gas does not provide the necessary degree of compression of the degassing gas, which leads to its loss.

The technical task of the proposed method is to increase the efficiency of gas utilization of condensate degassing in field gas treatment plants at gas condensate fields.

The task is achieved in that the low-pressure gas of the second stage of degassing of the condensate enters the ejector of one production line, the low-pressure gas of the third stage of degassing is supplied to the ejector of the other production line, and the gas pressure in the degassers is set within (3.0-3.8) MPa for the second and (2.8-3.0) MPa - for the third stage of degassing.

The proposed method for the extraction of condensate from natural gas can be implemented on the installation, a schematic diagram of which is shown in figure 1. The installation contains connected to the pipeline of raw gas 1 (Figure 1), production lines 2 and 3, each of which includes separators 4, 5, recuperative heat exchangers 6 and 7, ejectors 8, 9 and bypass flow regulators of high-pressure gas 10.

The condensate degassing units are common for all production lines and contain three-phase separators 11, 12, 13, which form the first, second and third stages of condensate degassing, respectively. Drained gas is discharged through line 14, partially stabilized condensate - through line 15 using pump 16, and aqueous solutions - through lines 17.

Gas condensate degassing from a three-phase separator 11 is fed into the main gas stream at the inlet to the separators 5 under the influence of a pressure differential between the devices. Condensate degassing gases from three-phase separators 12 and 13 are fed into the main gas stream using ejectors 8 and 9, respectively. Gas pressure regulators 18, 19 are installed on the low-pressure gas supply pipelines from three-phase separators to ejectors.

For deposits with a condensate factor of more than 100 g / m ³ heat exchangers 6 can be made of two sections with an additional separator between the sections. The conditions of the northern deposits in front of the separators, heat exchangers and ejectors provide for the supply of methanol or another hydrate inhibitor to ensure reliable operation. The number of production lines is at least two and depends on the throughput of the installation.

The installation is as follows. Raw, high-pressure gas, for example, gas condensate field wells with a methane content of about 90 vol.%, Are preliminarily purified from liquid and solid components in the inlet separators 4 and cooled in regenerative heat exchangers 6. The liquid separated in the inlet separator is sent to a three-phase separator 11, where they are degassed and separated into hydrocarbon condensate and aqueous solutions. Wet gas from the heat exchangers 6 is sent to the separators 5 through the upstream units of ejection and gas flow control. The temperature of the gas in the separators 5 is regulated bypass bypass bypass gas flow in the heat exchangers 6 and the change in pressure drop of high-pressure gas flows at the sites of ejection and gas flow control.

The condensate separated in the separator 11 of the first degassing stage is sent to the separators 12 and 13 of the second and third degassing stages, respectively, by reducing the gas pressure in these apparatuses. The low-pressure degassing gases from the separator 12 are disposed of by the ejector 8, from the separator 13 by the ejector 9. The stable operation of the separators 12 and 13 according to the pressure of the low-pressure condensation degassing gases in these devices when, for example, the inlet pressure of the high-pressure gas is varied, is ensured by the pressure differential across the regulators 18 and 19 degassing gas pipelines from separators to ejectors. Drained gas and partially stabilized condensate of heavy hydrocarbons are sent to interfield pipelines.

The operability of the method of condensate extraction from natural gas is confirmed in the conditions of pilot industrial operation of the ejection units on the production lines of the complex gas and gas condensate treatment unit of the North Urengoy gas condensate field. Typical operating parameters of the installation are given in the table. As can be seen from the table, the connection of the ejector of one production line of the gas treatment plant to the separator of the second stage of degassing of condensate, and the ejector of another technological line to the separator of the third stage of degassing provides an increase in the rate of degassing gas by 4.7%. When reducing the pressure of the end degassing, the positive effect of the application of the method increases.

Table Operational parameters of the gas treatment facility at the North Urengoysky gas condensate field using the condensate extraction method from natural gas. No. Parameter Value one The flow rate of commercial gas, thousand nm ³ / hour 280 2 The number of working technological lines, pcs. 2 3 Inlet gas pressure, MPa 8.9 four Gas pressure in a low-temperature separator, (С-2), MPa 5,4 5 The temperature of the low-temperature gas separation, ° C minus 31 6 Gas pressure in the separator of the first stage, (P-1), MPa 5.45 7 Gas pressure in the separator of the second stage, (P-2), MPa 3.25 8 Gas pressure in the separator of the third stage, (P-3), MPa 3.00 9 Low-pressure gas pressure at the inlet to the ejectors, MPa 2.0-2.2 10 The gas consumption of degassing from R-1, thousand nm ³ / hour 3.56 eleven The gas consumption of degassing from R-2, thousand nm ³ / hour 6.93 12 The gas consumption of degassing from R-3, thousand nm ³ / hour 0.58 13 Commodity gas pressure, MPa 5.32 fourteen The specific yield of condensate, g / nm ³ 177.6

Claims (1)

A method for extracting condensate from natural gas by cooling and gas separation in production lines, including sequential three-stage degassing of the separated condensate with the utilization of low-pressure degassing gas by high-pressure gas in ejectors, characterized in that the low-pressure gas of the second condensate degassing stage enters the ejector of one production line, low-pressure gas the third stage of condensate degassing - into the ejector of another technological line, and the gas pressure in the degassers was set vayut in the range (3.0-3.8) and for the second MPa (2.8-3.0) MPa for the third degassing step.