RU2800096C1 - Method for stabilizing gas condensate - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: method for stabilizing hydrocarbon condensate is described, including primary separation of formation natural gas to obtain primary separation gas and unstable primary separation condensate, which is reduced and subjected to primary degassing to obtain primary degassing gas and primary degassing condensate, low-temperature separation of primary separation gas to obtain low-temperature separation condensate and low-temperature separation gas, stabilization of separated hydrocarbons by distillation to obtain a stable condensate and stabilization gas, while the primary degassing gas is sent either to the stage of low-temperature separation of the primary separation gas, or to the stage of stabilization of the separated hydrocarbons, the unstable primary degassing condensate after heating is reduced and subjected to secondary degassing with obtaining a stable secondary degassing condensate and secondary degassing gas, which after compression is sent for stabilization by rectification, the low-temperature separation condensate is subjected to degassing, while the resulting degassed low-temperature separation condensate is sent to the stage of stabilization of the separated hydrocarbons by rectification, the gas obtained at the stage of degassing of the low-temperature separation condensate, is sent either to the stage of low-temperature separation of primary separation gas, or to the stage of stabilization of separated hydrocarbons by rectification, the stabilization gas is either combined with low-temperature separation gas and sent to the consumer as a commercial gas, or sent to the stage of low-temperature separation of primary separation gas, and the stable condensate obtained at the stage of stabilization of the extracted hydrocarbons by rectification, they are combined with a stable condensate of secondary degassing and sent to the consumer as a commercial stable condensate.

EFFECT: increased reliability of operation of the GTU equipment, improved quality of commercial gas.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of the gas industry and can be used in gas condensate fields, where low-temperature treatment of produced natural gas and stabilization (debutanization) of the separated gas condensate are carried out.

A known method for the preparation of natural gas (Bekirov T.M., Lanchakov G.A. Technology for processing gas and condensate. M .: Nedra-Business Center LLC. 1999. S. 596), which consists in stabilizing gas condensate by degassing by heating and degassing. In this method, heating and stepwise degassing of condensate streams separated during the preparation of natural gas at a low-temperature separation unit (LTS) is carried out. The final degassing of the condensate is carried out at a pressure close to atmospheric and at a temperature below 100°C.

This method is applicable at integrated gas treatment plants (CGTP) with a low content of C ₅₊ hydrocarbons in the produced gas, for example, for gas from the pharmacy deposits of the Yamal Peninsula fields, as well as at plants processing condensate (in the event of an accident on condensate pipelines).

The disadvantages of this method are:

- insufficiently complete extraction of C ₅₊ hydrocarbons in the composition of a stable condensate;

- the need for the utilization of low-pressure substandard gases released during the degassing process by burning in flare installations.

These shortcomings cause the limited application of this method.

There is also a method for preparing hydrocarbon gas for transport (RF patent 2725320, B01D 19/00, publ. 07/02/2020), in which methanol is introduced into the hydrocarbon gas stream from well clusters to inhibit hydrate formation, the unstable hydrocarbon condensate stream after weathering is heated with a stable condensate stream, separated into degassing gas, degassed unstable condensate and water-methanol solution, the flow of degassed unstable condensate is heated by the flow of stable condensate, stabilized in the distillation column, the flow of stable condensate after the distillation column is cooled in two stages by flows of unstable condensate and removed from the installation of hydrocarbon gas and condensate, the flow of stabilization gases is cooled by the air flow, separated from the condensed wide fractions of light hydrocarbons, the pressure is increased by compression, cooled by the air flow, injected into the gas flow and the stream of light hydrocarbons is withdrawn from the hydrocarbon gas and condensate treatment unit, the stream of light hydrocarbons is withdrawn from the hydrocarbon gas and condensate treatment unit, the low-concentration mixture of methanol and formation water after the three-phase separation of the hydrocarbon liquid is introduced into the water-methanol solution stream after the three-phase separation of the unstable hydrocarbon condensate, the water-methanol solution stream is heated with the methanol water stream, rectified into methanol and methanol water, the methanol stream is cooled with air, condensed, recycled is introduced into the gas stream as a hydrate formation inhibitor, methanol water is removed after distillation, cooled by a low-concentration stream is removed from the gas and condensate treatment unit, the pressure of another part of the methanol water stream is increased, the methanol water stream is introduced into the unstable hydrocarbon condensate stream, methanol is extracted from the unstable condensate.

The known method provides a reduction in the consumption of a hydrate formation inhibitor in the process of preparing gas for transport, however, mixing the condensate obtained at the stage of primary separation of reservoir gas containing high-molecular hydrocarbons, including asphaltenes, and pure low-temperature condensate leads to the formation of asphalt, resin, and paraffin deposits (ARPD) and a decrease in equipment reliability.

The closest in technical essence and the achieved result to the proposed method within the framework of a single technological process at the GTP (prototype) is a method of stabilizing gas condensate, implemented at the Kirinskoye field (Kubanov A.N., Fedulov D.M., Atamanov G.B., Prokopov A.V., Tsatsoulina T.S. Research conditions for achieving the requirements for gas dew point temperatures at the GTP of the Kirinskoye and Yuzhno-Kirinskoye fields. // Science and technology in the gas industry, No. 2. 2020. S. 560-569), including the preparation of natural gas by cooling and three-stage separation of reservoir products and the stabilization of the separated gas condensate in a distillation column.

The known method is characterized by carrying out the process of stabilization of gas condensate by debutanization in a distillation column at a pressure of 1.5 MPa. A mixture of condensate separated at the stage of primary separation of formation gas and condensate separated at the stage of low-temperature gas separation of primary separation of formation gas is subjected to debutanization.

The implementation of the known method is carried out in accordance with the scheme of Fig. 1.

The known method is carried out at a low temperature stage "degassing-2" (up to minus 20°C) and high (more than 200°C) temperature of the media in the heat exchangers, the lower part of the debutanization column and in the bottom heater. The low temperatures of the "degassing-2" stage lead to the formation of ARPD in the capacitive equipment, and then the condensate is supplied for stabilization by distillation. At the same time, the circulating bottom liquid contacts the wall of the bottom heater tubing at a temperature of 300-350°C and higher, which leads to thermal destruction of high-molecular hydrocarbons and reagents present in the near-wall layer of the heat-transfer surfaces of heat exchangers and the tube grid of fired heaters, the formation of solid deposits in the devices and disruption of circulation pumps due to abrasive wear. These complications during the operation of the equipment to an even greater extent arise in the presence of oil impurities containing resins and asphaltenes in the produced formation gas.

The task to be solved by the present invention is the development of an alternative method for stabilizing gas condensate, implemented at field low-temperature natural gas treatment plants within a single technological scheme, which allows debutanization (stabilization) of gas condensate without the formation of ARPD on equipment surfaces.

The technical result, to which the present invention is directed, is to increase the reliability of operation of the GTP equipment due to the fact that the debutanization of the unstable condensate of the primary separation of formation gas containing high-molecular hydrocarbons is carried out by degassing, excluding the supply of the said stream to the debutanization stage by rectification, as well as increasing the yield of stable condensate due to the redistribution of flows directed to stabilization. The technical result is also to improve the quality of commercial gas by eliminating the negative effect of stabilization gas on the dew point temperature of commercial gas in the aqueous phase.

This technical result is achieved due to the fact that in the method of hydrocarbon condensate stabilization, including primary separation of reservoir natural gas to obtain primary separation gas and unstable primary separation condensate, which is reduced and subjected to primary degassing to obtain primary degassing gas and primary degassing condensate, low-temperature separation of primary separation gas to obtain low-temperature separation condensate and low-temperature separation gas, stabilization of separated hydrocarbons by rectification to obtain stable th condensate and stabilization gas, the primary degassing gas is sent either to the stage of low-temperature separation of the primary separation gas, or to the stage of stabilization of the separated hydrocarbons. The unstable primary degassing condensate after heating is reduced and subjected to secondary degassing to obtain a stable secondary degassing condensate and secondary degassing gas, which, after compression, is sent for stabilization by distillation. The low-temperature separation condensate is subjected to degassing, wherein the resulting degassed low-temperature separation condensate is sent to the stage of stabilization of the recovered hydrocarbons by rectification. The gas obtained at the stage of degassing of the low-temperature separation condensate is sent either to the stage of low-temperature separation of the primary separation gas, or to the stage of stabilization of the separated hydrocarbons by rectification. Stabilization gas is either combined with low-temperature separation gas and sent to the consumer as a commercial gas, or sent to the stage of low-temperature separation of the primary separation gas, and the stable condensate obtained at the stage of stabilization of the separated hydrocarbons by rectification is combined with the stable secondary degassing condensate and sent as a commercial stable condensate

The technological scheme for the implementation of the proposed method for stabilizing gas condensate is shown in the drawing of Fig. 2

The diagram shows the following elements:

- primary separation unit 1, including a cork catcher and a gas separator;

- throttle 2;

- primary degasser 3;

- condensate heating unit 4, including heat exchangers and heaters;

- throttle 5;

- degassing unit 6, including degassers;

- compressor 7;

- condensate stabilization unit (UKS) 8, which generally consists of heat exchangers, a distillation column (in some cases equipped with a reflux condenser) and a bottom heater;

- installation of low-temperature separation (LTS) 9, consisting of heat exchangers, devices for lowering the gas temperature and gas separators;

- degasser 10.

According to the scheme, the following stages are carried out:

- reservoir natural gas, which is a mixture of gas and hydrocarbon condensate, is subjected to separation in the primary separation unit 1 with the separation of primary separation gas and unstable primary separation condensate containing high molecular weight hydrocarbons;

- further, the unstable primary separation condensate is reduced to an excess pressure of 3 to 6 MPa by means of a throttle 2 and subjected to primary degassing in the degasser 3 to obtain primary degassing gas and degassed primary degassing condensate;

- degassed condensate separated at the primary degassing stage is heated in the condensate heating unit 4, reduced by means of a throttle 5 to a pressure of 1.02 to 1.05 MPa and subjected to secondary degassing at a temperature of 70°C to 120°C in the degassing unit 6 to obtain secondary degassing gas and stable (debutanized) condensate;

- degassing gas obtained at the stage of secondary degassing is compressed by means of a compressor 7 to a pressure of 1.3-1.8 MPa and sent for stabilization by distillation to USK 8;

- primary separation gas is sent to the NTS 9 unit, carried out in the end gas separator at a pressure of 5 to 7 MPa and a temperature of minus 20 to minus 40 ° C, resulting in low-temperature separation gas and low-temperature separation condensate;

- the low-temperature separation condensate is degassed in the degasser 10 at a pressure of 2.5 to 3.5 MPa and a temperature of 0 to minus 15°C to obtain degassing gas of the low-temperature separation condensate and degassed low-temperature separation condensate;

- degassed condensate of low-temperature separation is sent to USK 8 for stabilization (debutanization), carried out by distillation under pressure from 1.3 to 1.8 MPa;

- primary degassing gas is sent either to the NTS 9 unit (in case of a sufficient pressure level), involving the primary separation gas in the process of low-temperature separation, or to USK 8;

- the degassing gas of the low-temperature separation condensate is sent either to the NTS 9 unit (if the unit has a device for increasing the pressure of low-pressure gases, for example, a gas ejector), involving the primary separation gas in the low-temperature separation process, or to USK 8;

- as a result of stabilization of the extracted hydrocarbons by distillation at USK 8, stabilization gas and stable (debutanized) condensate are obtained;

- stabilization gas is either combined with low-temperature separation gas and sent to the consumer as commercial gas, or, if the content of C ₅₊ hydrocarbons in formation gas is below 50 g/m ³ , it is sent to the stage of low-temperature separation of primary separation gas at the NTS 9 unit.

The products obtained by implementing the proposed method are:

- commercial gas obtained at the LTS stage or as a result of mixing low-temperature separation gas and stabilization gas;

- commercial stable condensate obtained as a result of mixing stable condensate of secondary degassing and stable condensate obtained at the stage of stabilization by rectification.

Comparative performance achieved when implementing under similar conditions of the known and proposed methods in relation to the GTP of the Chayandinskoye field are shown in the table.

Column 3 of the table reflects the indicators if the stabilization gas is sent for mixing with the low-temperature separation gas.

Column 4 of the table reflects the indicators in case the stabilization gas is sent to the stage of low-temperature separation of the primary separation gas.

The main advantages of the proposed method are to eliminate or reduce the intensity of formation of paraffin deposits, reduce the overall characteristics of the column equipment and heat consumption in the distillation column by 27%.

In the case of directing the primary degassing gas and the gas obtained at the stage of degassing of the low-temperature separation condensate to the stage of stabilization of the obtained hydrocarbon streams, as well as in the case of directing the stabilization gas to the stage of low-temperature separation of the primary separation gas, the advantages of the proposed method lie in a significant decrease in the dew point temperature of the commercial gas in the water phase and an increase in the amount of commercial stable condensate.

Claims (1)

A method for stabilizing hydrocarbon condensate, including primary separation of reservoir natural gas to obtain primary separation gas and unstable primary separation condensate, which is reduced and subjected to primary degassing to obtain primary degassing gas and primary degassing condensate, low-temperature separation of primary separation gas to obtain low-temperature separation condensate and low-temperature separation gas, stabilization of separated hydrocarbons by rectification to obtain stable condensate and stabilization gas, characterized in that the primary degassing gas is sent to either the primary separation gas low temperature separation stage or the recovered hydrocarbons stabilization stage, the unstable primary degassing condensate after heating is reduced and subjected to secondary degassing to obtain a stable secondary degassing condensate and secondary degassing gas, which after compression is sent to stabilization by rectification, the low temperature separation condensate is degassed, and the resulting degassed low temperature separation condensate is sent gas obtained at the stage of degassing of the condensate of low-temperature separation is sent either to the stage of low-temperature separation of the primary separation gas, or to the stage of stabilization of the separated hydrocarbons by rectification, the stabilization gas is either combined with the gas of the low-temperature separation and sent as a commercial gas to the consumer, or sent to the stage of low-temperature separation of the primary separation gas, and the stable condensate obtained at the stage of stabilization of the separated hydrocarbons ov distillation, combined with a stable condensate of secondary degassing and sent to the consumer as a commercial stable condensate.