RU2765440C1 - Method for optimizing process of preparing commercial condensate and device for its implementation - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to an installation of complex gas preparation, including a line for the supply of reservoir gas from wells, a separator of the first stage, an outlet of which is connected in series by pipelines to a desorber column, an outlet of which is connected through an air cooling device and heat exchangers to a separator of the second stage and through an ejector to a separator of the third stage, liquid separators of the first and the second stages, a degasser and at least one buffer tank, a line for the discharge of commercial gas into the main line, while the liquid separator of the first stage is equipped with a line for the discharge of reservoir water, and at least one buffer tank is equipped with a line for the discharge of commercial condensate into a condensate pipeline. A line for the discharge of a liquid phase is additionally introduced into the lower part of the degasser and at least one buffer tank, the liquid separator of the first stage is equipped with a condensate collector, wherein a bump cap with flanged edges is additionally introduced above the condensate collector, while the specified cap edges are located below the upper edge of the condensate collector. The invention also concerns a method for optimizing the process of preparing commercial condensate carried out in the specified installation.

EFFECT: increase in the efficiency of the installation of complex gas preparation.

2 cl, 5 dwg

Description

The group of inventions relates to the oil and gas industry and can be used in oil, gas and gas condensate fields in the preparation of well products for determining and removing an aqueous solution when separating unstable hydrocarbon condensate from formation gas.

Preparing unstable condensate at integrated gas treatment units (GTP) [Experience in operating the main process equipment for preparing Achimov horizon gas for transportation at GTP-22 of Gazprom Dobycha Urengoy LLC. O.A. Nikolaev, A.V. Bukin. Priority areas for the development of the Urengoy complex: Collection of scientific papers / OOO Gazprom dobycha Urengoy. - M.: "Nedra Publishing House", 2013. - 411 p.] is carried out in accordance with the mandatory standards for the preparation of marketable products [STO Gazprom 5.11-2008 "Unstable gas condensate. General Specification https://drive.google.com/file/d/0BwBxMSdckOLHSklxR09ZYVprUWs/view]. These requirements exclude the presence of water in the sales condensate at the outlet of the GTP, but at the same time, the physicochemical analysis of regularly taken samples indicates the periodic appearance of water (low-concentration water-methanol solution) in small quantities in the sales condensate stream. Minerals, in particular, salts, contained in the aqueous phase of the transported stream of commercial condensate, have a negative corrosive effect on process equipment and pipelines during the transportation and further processing of hydrocarbons.

In order to prevent the negative impact of corrosion processes on the process equipment and pipelines of the GTP, a decision was made to use corrosion inhibitor solutions (RIC) several years after the plant was put into operation. Methods, places of entry, as well as optimal concentrations of RIC were determined experimentally. When RIC gets into the well production flow, the possibility of emulsion formation is not ruled out, the properties of which will be determined by the corrosion inhibitor concentration, thermobaric conditions and the flow rate of the gas-liquid mixture in the pipeline.

Due to the design features of the first stage liquid separator, part of the liquid droplets enters the condensate collector and is then directed to the ventilator and buffer tanks with the total condensate flow. And since the main technical solutions at the GTP provide for the separation of the aqueous and hydrocarbon phases only in the first-stage liquid separator, then if water enters the gas condensate stream after the separator, there is no possibility of its further removal.

During the weekly sampling of gas unstable condensate (IGH), at the gas condensate metering unit in the sampling device, traces of the aqueous phase were periodically observed in the stable part of the condensate after degassing the sample. The presence of water in the sales condensate was confirmed in approximately 20% of sampling cases at the GTP.

The presence of RIC in the formation water, which is a surfactant, can lead to the formation of a stable emulsion at the phase boundary: formation water - gas condensate in separators and separators of the GTP. The presence of such a negative effect in the presence of corrosion inhibitors leads to incomplete separation of the mixture of gas condensate and associated extracted water and, as a result, to a violation of the technological mode of gas treatment. Also, due to the non-uniformity of pulsations in the turbulent fluid flow from the first-stage separator, zones arise in which the existence of water droplets of various critical diameters is possible. Getting into the zone of increased velocities, where there are drops of a certain critical size, large drops tend to break up. Entering the zones of lower velocities and smaller scales of pulsations, they will objectively experience a tendency to merge, which causes the appearance of a whole spectrum of water droplet diameters in the flow and explains the reasons for the entry of a clearly inhomogeneous emulsion into the separator.

Various methods and systems are known in the art for reducing the amount of water ingress into the gas condensate.

A known method for processing a liquid hydrocarbon stream containing water [RU 2553664, published 06.2015], which includes processing a liquid hydrocarbon stream containing water, while the liquid hydrocarbon stream is introduced into the first separator separating at least free water from the specified liquid hydrocarbon stream, the remainder of said liquid hydrocarbon stream is introduced into a system that converts free/condensed water in the liquid hydrocarbon stream in said system into gas hydrates and provides at least a first liquid stream and a second liquid stream in which said first liquid stream is a liquid phase containing gas hydrates, wherein said first liquid stream is recycled to the first separator, and in which the second liquid stream has a dry gas and condensate content.

The disadvantages of the known method is the complexity of the process, as well as the impossibility of the most accurate determination of water and water-methanol solution in commercial gas condensate.

A known method of modeling the operation of liquid separators of a gas and gas condensate treatment plant in low-temperature separation technology [Pisarev M.O., Dolganov I.M., Ivashkina E.N., Tomsk Polytechnic University. "Basic Research", Publishing House "Academy of Natural History" : Penza, No. 6 - 1, 2015, pp. 63-66].

The known modeling method cannot take into account all the real processes occurring in the separator, in particular, when the separator switches to a 4-phase mode: weathering gas, gas-water foam, unstable gas condensate, water-methanol solution.

A well-known separator for separating a gas-liquid mixture, which contains at least a receiving section separated by a partition, a separating section, inlet and outlets of the corresponding media, characterized in that it is equipped with one or more distributing devices with holes located above the liquid level and made with the provision the possibility of distributing the liquid phase from the receiving section flowing through the partition over the surface of the device and draining the liquid phase into the separating section through the holes, moreover, the separating section is equipped with a coalescing device designed to provide the possibility of separation from the liquid phase flowing down from one or more distributors, emulsified water, and the distribution devices are equipped with a baffle, made to prevent the flow of the liquid phase past the coalescing device, the baffle is provided with holes and is made with the possibility of passage gas phase escaping from the flowing liquid phase [RU 172733, published on 07/21/2017].

The disadvantage of the known device is the complexity of the design of the separator.

The technical problem to be solved by the group of inventions is the creation of a method for optimizing the process of preparing commercial condensate and a device for implementing this method in order to prevent the ingress of water (water-methanol solution) into the stream of commercial condensate in the process of preparing natural gas and gas condensate for subsequent transportation.

The technical result, to which the proposed group of inventions is directed, is to increase the efficiency of the complex gas treatment plant.

The technical result is achieved by the proposed group of inventions, including a complex gas treatment unit and a method for optimizing the process of preparing commercial condensate, carried out in the specified unit.

The complex gas treatment unit contains a line for supplying reservoir gas from wells, the first stage separator, the outlet of which is connected in series by pipelines to the desorber column, the outlet of which is connected through the air cooler and heat exchangers to the second stage separator and through the ejector to the third stage separator, liquid separators of the first and of the second stage, a ventilator and at least one buffer tank, a line for draining commercial gas into the main, while the first stage liquid separator is equipped with a line for draining formation water, and at least one buffer tank is equipped with a line for draining commercial condensate into the condensate pipeline, what is new is that that a liquid phase discharge line is additionally introduced into the lower part of the ventilator and at least one buffer tank, the liquid phase separator of the first stage is equipped with a condensate collector, and above the condensate collector a baffle cover with beaded edges is additionally introduced, while the indicated the edges of the cover are located below the upper edge of the condensate collector.

The method for optimizing the process of preparing commercial condensate carried out in the specified installation includes switching the weathering liquid and at least one buffer tank to the three-phase separation mode, in the first stage liquid separator, the operating interval of regulation is adjusted according to the level of unstable gas condensate and water-methanol solution by lowering the level of phase contact: weathering gas - gas condensate and gas condensate - water-methanol solution to the minimum possible value, periodic monitoring of the equipment operation efficiency is carried out by sampling the liquid phase from the lower part of the first stage liquid separator, the weatherer and the indicated buffer tank.

Correction of the operating interval of regulation in terms of the level of unstable gas condensate and water-methanol solution, in order to minimize the effect of the emulsion on the technological mode of operation of the first-stage liquid separator by lowering the level of phase contact: weathering gas - gas condensate and gas condensate - water-methanol solution to the minimum possible value allows to reduce the total the emulsion level at the boundary of the unstable gas condensate and water-methanol solution and, as a result, minimize the ingress of water into the condensate collector of the liquid separator. And to prevent the ingress of settled foam in the first stage liquid separator, a baffle cover is installed above the condensate collector, which prevents the ingress of water that appears after the foam settles above the indicated collector. Also, as an additional measure, ventilators and buffer tanks are switched to the mode of 3-phase liquid separators. If there is an aqueous phase in the apparatus, such a phase is removed from the bottom of the weatherers and buffer tanks, which makes it possible to completely exclude accumulated water (water-methanol solution) from the flow of commercial condensate in case of unsatisfactory operation of the equipment.

The essence of the claimed group of inventions is illustrated by the following figures and description.

In FIG. 1 shows the technological scheme of the GTP.

The technological scheme of the GTP is shown as a single unit, which includes all the devices necessary for the implementation of the proposed method:

1 - separator of the first stage;

2 - desorber column;

3 - separator of the second stage;

4 - separator of the third stage;

5 - liquid separator of the first stage;

6 - liquid separator of the second stage;

7 - weatherer;

8 - buffer tanks;

9 - level controller;

10 - ejector;

11- air cooler;

12 - heat exchangers;

13 - liquid phase withdrawal line;

14 - line for supplying reservoir gas from wells;

15 - formation water discharge line (water-methanol solution);

16 - line for the removal of commercial condensate into the condensate pipeline;

17 - line for the removal of commercial gas into the main.

In FIG. 2 shows the device of the first stage liquid separator, and shows the phases into which the gas-liquid mixture coming from the separator is divided:

18 - phase: weathering gas;

19 - phase: water-methanol solution;

20 - phase: gas-water foam;

21 - phase: gas condensate;

22 - shelf louvre attachment;

23 - condensate collector;

25 - exit line to the separator.

In FIG. 3 schematically shows the formation of foam in the first stage liquid separator, where:

18 - phase: weathering gas;

19 - phase: water-methanol solution;

20 - phase: gas-water foam;

21 - phase: gas condensate;

23 - condensate collector;

24 - water condensate emulsion zone.

In FIG. 4 shows the use of a baffle cover over the light phase collector in the first stage liquid separator, with a view of the baffle cover in section A-A and B-B, where 23 is a condensate collector, 26 is a baffle cover.

In FIG. Figure 5 shows the dynamics of the content of the volume fraction of water in condensate samples taken along the condensate outlet line from the first stage liquid separators using the example of GTP-22 of the Urengoy oil and gas condensate field.

The technology for preparing the production of gas condensate wells by the method of three-stage low-temperature separation consists in gradually lowering the temperature of the gas flow and separating the liquid phase from it, which is discharged in the separators of the first 1, second 3 and third 4 stages (Fig. 1). The decrease in the flow temperature is achieved through the use of recuperative heat exchangers 12 and gas flow throttling by the ejector 10 installed before the third separation stage 4. The liquid phase discharged from the separators 1, 3, 4 is sent to the liquid separators 5 and 6, where due to the density difference it is separated on hydrocarbon condensate and water (water-methanol solution). Streams of hydrocarbon condensate from the liquid separators 5, 6 are mixed and sent to the ventilator 7, where the condensate is partially degassed due to pressure reduction. The entire volume of gas released in the weatherer 7 is fed into the ejector 10 as a passive gas. The process is fully automated, the liquid levels in the devices (separators, separators, weatherers) are kept by means of regulators installed on the discharge pipelines (not shown).

The method is carried out as follows.

The downhole fluid enters through line 14 in the form of a three-phase mixture of gas, hydrocarbon condensate and water (water-methanol solution) with RIC. The phase volume ratio is approximately: gas - 85%, condensate - 14% and water-methanol solution - 1%. Due to the slug regime of the fluid flow in this area, bursts of a large volume of water (with RIC dissolved in it) are often observed at the complex gas treatment unit. The three-phase mixture enters the inlet separator 1, where the liquid phase is separated, namely, the so-called "heavy" fractions of the unstable gas condensate and water (methanol solution) with dissolved RIC.

From the separator 1, the separated liquid is discharged to the separator 5. To maintain the liquid level within the specified limits, a level controller 9 is installed on the liquid discharge pipeline from the separator 1, which controls the liquid flow by changing the flow area. Due to the sharp throttling of the liquid flow moving in the turbulent flow regime in the separator 5, the gas phase 18 (Fig. 2) and the water-methanol solution are mixed with the RIC 19, resulting in the formation of foam 20. The foam forms the fourth phase in this flow. Thus, the liquid separator 5 is operated in a four-phase mode:

- weathering gas 18;

- gas-water foam 20;

- unstable gas condensate 21;

- water-methanol solution 19.

The density of foam 20 is less than the density of condensate 21, respectively, after passing through the shelf louvre nozzle 22, foam 20 rises to the top and forms a thin film at the interface: weathering gas (18) - gas condensate (21). Having passed into an equilibrium state, sedimentation occurs in the lower part of the foam and, under the action of gravitational forces, drops of an aqueous solution fall into the lower part of the apparatus through a layer of hydrocarbon condensate 21.

The phase contact surface: gas condensate (21) - water-methanol solution (19) has blurred boundaries, which creates the possibility of water ingress from the water-condensate emulsion at increased costs of the installation.

Depending on the operating level in the separator 5, it is possible for emulsion to enter the outlet pipeline 25 along with the condensate stream 21.

To minimize the effect of emulsion 24 on the technological mode of operation of the separator 5, the operating interval of regulation is adjusted according to the level of gas condensate 21 and water-methanol solution 19 by lowering the level of phase contact: weathering gas (18) - gas condensate (21) and gas condensate (21) - water-methanol solution (19) to the lowest possible value. Reducing the level of phase contact is carried out by temporarily changing the degree of opening of the level regulators on the lines for discharging condensate (temporary closure) and water-methanol solution (temporary opening) from the apparatus. Since the production process is fully automated, this level is adjusted by changing the value of this level programmatically.

Ceteris paribus, this makes it possible to reduce the overall level of the emulsion at the boundary of the gas condensate (21) and water-methanol solution (19) and, as a result, to minimize the ingress of water into the condensate collector 23.

To prevent the ingress of settled foam into the condensate collector 23, a baffle cover 26 is installed in the separator 5, the use of which limits the flow of water that appears after the foam 20 has settled over the condensate collector 23, by reducing the area and direction of fluid intake in the apparatus. The baffle cover 26 is a square or rectangular plate with flanged edges, the edges of which are located below the upper edge of the condensate collector 23, when it is installed.

The switch of the ventilator 7 and buffer tanks 8 to the mode of three-phase liquid separators is carried out by installing an additional line 13, which discharges the water (water-methanol) phase from the lower part of the apparatuses (7 and 8). In this case, the removal of the hydrocarbon phase is carried out from the average level of the weatherer 7 and buffer tanks 8. The separation of the phases in these devices occurs due to the difference in the densities of these phases and gravitational forces. To exclude the possibility of currents and stagnant zones, the devices can be additionally equipped with stabilizing filtering baffles and nozzles.

To assess the efficiency of the equipment, liquid samples are periodically taken from the liquid separators 5, the evaporator 7 and the buffer tanks 8. The value of the volume fraction of water in the separator 5 depends on the flow rate of the liquid entering the apparatus. Drainage of water, depending on the content of methanol in it, is carried out in drainage tanks, followed by pumping into the liquid separator 5, or into the storage tank of the water-methanol solution.

The proposed method was tested at the UKPG-22 Urengoy oil and gas condensate field. From 2019 to 2020, there were 3 identical technological threads in operation, each of which contained a R-1 liquid separator in its composition (on the chart R-1.1, R-1.2 and R-1.3, respectively). In August 2019, work was carried out on line No. 2, including the installation of a baffle cover in the R-1.2 liquid separator. From the graph (Fig. 5) it can be seen that the content of the volume fraction of water in the condensate samples after installing the baffle cover in the R-1.2 separator decreased many times.

EFFECT: group of inventions ensures high efficiency of operation of the complex gas treatment plant in order to prevent the ingress of the aqueous phase into the flow of commercial gas condensate.

Claims (2)

1. A complex gas treatment plant, including a line for supplying formation gas from wells, a first-stage separator, the outlet of which is connected in series by pipelines to a desorber column, the outlet of which is connected through an air cooler and heat exchangers to a second-stage separator and through an ejector to a third-stage separator, liquid separators of the first and second stages, a vent and at least one buffer tank, a line for draining commercial gas into the main, while the first stage liquid separator is equipped with a line for draining formation water, and at least one buffer tank is equipped with a line for draining commercial condensate into the condensate pipeline, characterized in that a liquid phase discharge line is additionally introduced into the lower part of the weather breaker and at least one buffer tank, the first stage liquid separator is equipped with a condensate collector, and above the condensate collector there is additionally introduced a baffle cover with beaded edges, while indicating The marked edges of the cover are located below the upper edge of the condensate collector. 2. A method for optimizing the process of preparing commercial condensate, carried out in the installation according to claim 1, characterized in that the ventilator and at least one buffer tank of the specified installation are transferred to the three-phase liquid separation mode, in the first stage liquid separator, the operating interval of regulation is adjusted by level unstable gas condensate and water-methanol solution by lowering the level of phase contact: weathering gas - gas condensate and gas condensate - water-methanol solution to the minimum possible value, periodically monitor the efficiency of the equipment by taking samples of the liquid phase from the bottom of the first stage liquid separator, weatherer and specified buffer capacity.

Images