RU2617153C2 - Method of gas field processing - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: proposed method according to which the gas is dried, pre-reduced and separated in the first separation stage to produce the aqueous and hydrocarbon condensates, and also gas, that is subjected to partial condensation due to cooling by the condensate and gas of the third separation stage with production of the condensate and gas of the second separation stage. The latter is reduced at the third separation stage upto the consumption pressure and separated to obtain the third stage condensate and gas, which after heating is extracted as the saleable. The condensate of the third stage, after heating in the mixture with the condensates of the first and the second stages is stabilized to form the stable condensate and degassing gas at least a part of which is fed to the first separation step to regenerate the adsorbent, and the rest is extracted from the plant and utilized.

EFFECT: invention allows to reduce operating costs and increase the yield of saleable products.

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Description

The invention relates to methods for field gas preparation by the method of low temperature separation and can be used in the gas industry.

A known method of gas preparation (AM Churakaev. Low-temperature rectification of petroleum gas. - M .: "Nedra", 1989, S. 6), including gas compression, adsorption drying and purification using adsorbent regeneration gas part of the dried gas and low-temperature gas processing during which the gas is cooled in recuperative heat exchangers and a propane cooler, separated with the formation of a separation gas, which is expanded on a turboexpander and fed to the demethanization column, and the condensate that is throttled is degassed they are heated in a gas separator and also fed to a demethanization column, where the degassing gas is mixed with the upper product of the demethanization column, the resulting mixture is heated in recuperative heat exchangers and removed from the unit, and the lower product of the demethanization column is partially heated in recuperative heat exchangers and fed to the deethanization column, the upper product of which they are also heated in recuperative heat exchangers and removed from the unit, and the bottom product of the deethanization column is removed from the unit in the form of BFLH.

The disadvantages of this method are:

- high fire and explosion hazard of the installation due to the high temperature of the adsorbent regeneration gas;

- significant capital and operating costs due to the large number of equipment, including dynamic.

These disadvantages determine the impossibility of using the known method for the preparation of gas in the field.

Closest to the claimed is a method of low-temperature gas separation (RU 2543867, publ. 03/10/2015, IPC B01D 3/14, B01D 3/28), comprising a three-stage gas separation with obtaining condensate and gas in the first stage, which in the second stage cooled under reflux conditions due to countercurrent gas and condensate of the third stage, the gas obtained is then reduced and separated in the third stage to produce gas that is heated and removed, and condensate that is heated and stabilized together with condensates of the first and second stage and to produce a weathering (degassing) gas that is recycled.

The disadvantages of this method are:

- consumption of hydrate inhibitor and related operating costs,

- low condensate yield due to the high pressure in the first stage separator (usually determined by reservoir pressure and hydraulic losses in the infield piping system), corresponding to low relative volatility of gas components and low definition of phase separation,

- low yield of commercial gas due to the condensation of a significant part of the light components at low temperature in the third stage separator and their loss during condensate stabilization.

The objective of the invention is to reduce operating costs and increase the yield of marketable products.

The technical result that can be obtained by the method: reducing the operating costs of the installation by eliminating the consumption of a hydrate inhibitor and increasing the yield of commercial products (mass yield of condensate and volumetric gas output) due to the preliminary implementation of adsorption drying and partial reduction of gas.

The specified technical result is achieved by the fact that in the known method comprising a three-stage gas separation, according to which the second stage gas is separated by refluxing it by countercurrent cooling with gas and condensate of the third stage, the gas obtained is then reduced and separated in the third stage with by producing a gas that is heated and removed, and a condensate that is heated, are mixed with condensates of the first and second stages and stabilized to produce a degassing gas, especially The fact is that in the first stage, the gas is additionally subjected to adsorption drying using at least part of the degassing gas to regenerate the adsorbent and is reduced to a minimum pressure that ensures the standard temperature of the dew point of the third stage gas hydrocarbons.

Preliminary adsorption drying of the gas provides a non-hydrate mode of gas preparation, which eliminates the use of a hydrate inhibitor and reduces operating costs. The use of at least a portion of the degassing gas as a stripping gas during regeneration of the adsorbent makes it possible to utilize the resulting regeneration gas containing desorbed water vapor, for example, as fuel for its own needs, without the use of additional equipment. The rest of the degassing gas can also be disposed of, for example, by recirculation into the gas stream of the second separation stage.

Preliminary partial reduction of gas allows gas separation at the first and second stages at relatively low pressure (preferably below critical pressure), which increases the mass yield of stable condensate and the volumetric yield of commercial gas by increasing the clarity of separation due to an increase in the relative volatility of gas components. The minimum pressure to which preliminary partial reduction is carried out, which ensures the achievement of a given dew point temperature for hydrocarbons of the third stage gas (prepared gas), at a given outlet pressure depends on the composition, temperature and pressure of the gas and in each case is determined by calculation.

The invention is illustrated in the drawing.

According to the proposed method, the raw gas 1 is fed to the first separation stage 2, where it is dried, pre-reduced (the pressure of the pre-reduced gas is set based on the condition that the set dew point temperature for the hydrocarbons of commercial gas 3 is maintained) and separated to obtain aqueous 4 and hydrocarbon 5 condensates as well as gas 6, which is sent to a reflux condenser 7, where it is refluxed by cooling with condensate 8 and gas 9 of the third stage to obtain condensate 10 and gas 11 of the second stage. The latter at the third stage of separation 12 is reduced to the consumption pressure and separated to obtain condensate 8 and gas 9 of the third stage, which is withdrawn as commercial gas 3 after heating in the reflux condenser 7. Condensate 8 of the third stage after heating in the reflux condenser 7 mixed with condensates of the first 5 and the second 9 steps are stabilized on block 13 to produce stable condensate 14 and a degassing gas, at least a portion of which 15 is fed to the first separation stage 2 for regenerating the adsorbent to produce a regeneration gas 16, and the rest Part 17 is removed from the installation and disposed of.

The performance of the proposed method is illustrated by the following example. Crude gas composition,% vol .: carbon dioxide 0.08; methane 85.42; ethane 6.96; propane 3.33; iso-butane 0.7; n-butane 0.73; components C ₅₊ 2.76 in the amount of 176.1 thousand nm ³ / h at a temperature of 25 ° C and a pressure of 5.5 MPa are dried using adsorbents to a dew point of minus 40 ° C, pre-throttled to 4.5 MPa and separated with the production of 24.1 t / h of hydrocarbon condensate and 168.8 thousand nm ³ / h of gas of the first separation stage, the latter is fed to the reflux condenser supply zone with two integrated heat and gas exchange sections, into which gas and condensate of the third separation stage are supplied as countercurrent refrigerant as refrigerants. 168.2 thousand nm ³ / h of gas of the second separation stage with a temperature of minus 5.7 ° C are removed from the top of the reflux condenser, throttled to 2.45 MPa and the resulting mixture is separated to obtain 0.6 t / h of condensate and 167.9 thousand nm ³ / h of gas of the third stage of separation with a temperature of -17.5 ° C, which, after heating in a reflux condenser, is removed from the installation as commercial gas with a hydrocarbon dew point temperature of minus 10.5 ° C. A mixture of hydrocarbon condensates of the first, second and third stages of separation in an amount of 26.4 t / h is stabilized to obtain 3.7 thousand nm ³ / h of degassing gas and 20.4 t / h of unstable condensate. A hydrate inhibitor was not used in gas preparation.

Under the conditions of the prototype, the volumetric yield of commercial gas was 149.4 nm ³ / h, the yield of stable condensate was 18.5 t / h, the consumption of methanol as a hydrate inhibitor was 240 kg / h.

Thus, the invention allows to reduce operating costs, increase the yield of commercial products and can be used in the gas industry.

Claims (1)

A field gas preparation method comprising a three-stage gas separation, according to which the second stage gas is separated at the second stage by refluxing it by countercurrent cooling with gas and condensate of the third stage, the gas obtained is then reduced and separated in the third stage to produce gas that is heated and the condensate that is heated is mixed with condensates of the first and second stages and stabilized to obtain a degassing gas, characterized in that in the first stage the gas they are additionally subjected to adsorption drying using at least part of a degassing gas to regenerate the adsorbent and reduce to a minimum pressure that ensures the standard temperature of the dew point of the third-stage gas hydrocarbons.

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