RU2831005C1 - Method of preparing natural gas for transportation - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to gas industry and is an improved method of field development during field preparation of gas condensate deposits. Method of natural gas preparation includes transportation of produced fluid via loops from gas well clusters to complex gas treatment units (CGTU), gas separation in inlet separators and plug catchers, compression at booster compressor station (BCS) in several stages and cooling at gas cooling units after each compression stages. Linear collector in the form of a cylindrical tank is installed on the trestle at the level of the inlet to the separator of the CGTU at the section between the pipeline leading from the gas cluster loops and the inlet to the first separation stage of the CGTU. Linear collector is connected for gas removal to the inlet of the CGTU separator by means of a pipeline, the section of which extends from the linear collector vertically upwards, and the separated liquid is removed from the linear collector via the pipeline to plug catchers and further utilization, the section of which leaves the linear collector vertically downwards.

EFFECT: reduction of metal consumption of the structure with increase in the useful volume of the separation tank, as well as simplification of the structure erection.

1 cl, 1 tbl, 2 dwg

Description

The invention relates to the field of gas industry and is an improved method for developing a field during industrial preparation of gas condensate deposits.

Gas preparation technology consists of cleaning natural gas extracted from wells from foreign components, the presence of which exceeds permitted values and does not allow its transportation to the consumer.

The conventional gas preparation technology is shown in Fig. 1 and includes transportation of the produced fluid along pipelines from gas well clusters 1 to integrated gas preparation units (IGPU), gas separation in inlet separators 2 and slug catcher tanks 3, compression at a booster compressor station (BCS) in several stages and cooling at gas cooling units after each compression stage.

Due to the differences in the field landscape elevation, during gas transportation from wells, liquid (a mixture of hydrocarbon condensate and water) accumulates in the low-lying areas of the gas collection network, accompanying the reservoir gas. The volume of liquid can reach several hundred cubic meters. When the operating mode of the gas treatment plant changes, the flow of the gas-liquid mixture switches to a plug mode, which leads to a salvo flow of accumulated liquid into the gas treatment unit. If the first stage of gas separation cannot cope with the volume of incoming liquid, there may be a risk of its breakthrough into subsequent nodes of the process line, which will harm both the quality of gas treatment and the equipment. To prevent this situation, additional lines are installed between the well cluster and the entrance to the gas treatment plant.

Known is patent No. 2687721 “Method and device for eliminating liquid plugs in gas collection manifolds” (dated 17.04.2018, authors Golyakov D.P. et al., patented by Gazprom Dobycha Yamburg LLC (RU), IPC class E21B 43/00). The essence of the invention is the removal of liquid plugs from a gas plume by connecting it using a switching valve to an additional line with an in-pipe separator and an ejector, the output of which is connected to the inlet separator of the CGTP. The additional line with an in-pipe separator and an ejector can be connected to any of the plumes connecting the production wells of the gas field with the CGTP. According to this method, it is possible to reduce the pressure at the input of each of the loops in the UCPG, which is necessary to maintain the minimum required pressure at the input of the BCS, and it also ensures the stability of the ejector operation by separating the liquid phase in the low-pressure gas flow before entering the BCS.

The disadvantage of this method is the complicated process of regulating the operating mode of such a CGPP: an additional line with a separator is connected at a certain moment only to one of the loops, so it is impossible to change the operating parameters of several loops at the same time. If the mode in the loops changes spontaneously, and more condensate accumulates in several loops at the same time than the system is capable of utilizing, this technical solution will not be able to prevent an emergency situation.

Patent No. 2794267 is known for the invention of a method for preparing natural gas for transportation, due to which an additional stage of separating gas from liquid is created (dated 12/27/2021, authors Basharov A.R., Kagarmanov A.I., patent region Gazprom Dobycha Irkutsk LLC (RU), IPC class E21B 43/34). This technical solution has been implemented at the Kovyktinskoye gas condensate field (GCF). The invention involves installing a trestle ring 4 in front of the first stage of separation of the UKPG, to which gas is supplied through gas gathering manifolds from gas well clusters 1 (see Fig. 1). This reduces the load on the equipment for cleaning natural gas at integrated gas treatment plants (UGTP). When the gas-liquid formation mixture enters the trestle ring 4, the gas and liquid are separated due to the shape of the ring. The gas rises to the upper part of the ring, and the liquid, under the action of gravity, falls to the lower part of the ring. The rising gas immediately enters the input separator 2 for further complex preparation and feeding into the main gas pipeline, the separated liquid goes to the plug catchers 3 for processing. This technical solution was chosen as a prototype.

The disadvantage of this technical solution is as follows. A two-tier load-bearing overpass is required to install this structure. Increasing the diameter of the overpass ring to increase the useful volume of incoming liquid will require a significant increase in the dimensions of the load-bearing overpass. This increases the volume of metal required and the labor intensity of construction and installation work.

The proposed invention is aimed at solving the problem of removing liquid plugs from fluid when a gas-liquid mixture enters a gas-liquid treatment plant. The technical result consists in reducing the metal consumption of the structure while increasing the useful volume of the separation tank, as well as in simplifying the installation of the structure.

The claimed technical result is achieved as follows. A method for preparing natural gas, including transporting the produced fluid along pipelines from gas well clusters to integrated gas treatment units (IGTU), separating the gas in inlet separators and slug catchers, compressing at a booster compressor station (BCS) in several stages and cooling at gas cooling units after each compression stage, characterized in that a linear manifold made in the form of a cylindrical container located on a rack at the level of the inlet to the IGTU separator is installed in the section between the pipeline leading from the gas well cluster pipelines and the inlet to the first stage of the IGTU separation, the linear manifold is connected to the inlet of the IGTU separator by means of a pipeline, a section of which extends vertically upward from the linear manifold, for removing gas, and the separated liquid is removed from the linear manifold via a pipeline to slug catchers and further disposal, a section of which extends vertically downward from the linear manifold.

When fluid (gas-liquid formation mixture) enters the linear collector 5, made in the form of a cylindrical container (hereinafter referred to as the collector), (see Fig. 2), the gas-liquid mixture is separated in the volume of the collector 5. Gas is removed from the collector through a pipeline, a section of which departs from the collector vertically upwards and is then directed through the pipeline to the separators 2 of the gas treatment plant. The separated liquid is removed through a liquid removal pipeline, a section of which departs from the linear collector vertically downwards, and is directed to the plug catchers 3 and further disposal.

The proposed technical solution has a lower metal consumption per unit of useful volume.

For two pipelines of radius R and horizontal section length 1 (upper and lower parts of the overpass ring), the useful volume will be equal to:

For these two pipelines, the total cross-section diameter is 4R=2*2R. For a collector with the same cross-section diameter as the total of the two pipelines - 4R, i.e. with a radius of 2R, the useful volume will be equal to:

That is, with the same total diameter of the cross-section of the pipes of the overpass ring and the collector, the useful volume of the collector will be twice as large.

The metal content can be estimated by the surface area of the pipes. For an overpass ring consisting of pipes of radius R, the total surface area of the pipes will be equal to

where 1 is the length of the horizontal sections of the ring, h is the height of the vertical sections of the ring.

For a collector with the same cross-sectional diameter as the total of two pipelines - 4R, the surface area will be equal to

That is, with the same total diameter of the pipes of the trestle ring and the collector, the surface area of the trestle ring is greater than the surface area of the collector by 4πRh. Accordingly, with the same thickness of the pipes for the trestle ring, more metal will be required compared to the collector by the volume of metal required for the vertical sections of the pipes.

Let's compare K _eff, the ratio of the required metal to the useful volume:

Therefore, for an overpass ring, the specific metal consumption to the useful volume will be higher, that is, more metal will be required per unit of useful volume, all other values being equal.

Considering that the overpass ring requires a two-tier overpass, the metal consumption for this structure and the labor costs for installation will be even greater than for the collector, which requires a single-tier overpass (see Fig. 1, 2, pp. 4, 5). This ensures the achievement of the technical result of reducing the metal consumption of the claimed structure while increasing the useful volume of the separation tank, as well as simplifying the installation of the structure.

This technical solution is illustrated by an example. The overpass ring installed at the gas treatment plant is constructed from a pipeline with a diameter of 700 mm. The useful volume of the ring for accumulating a salvo flow of liquid from the gas collection system is 60 m ³ . The length of the structure on the general plan of UKPG-2 is 90 m. The diameter of the ring pipelines is 700 mm, the total diameter of the two pipes is 1400 mm. To increase the useful volume of the incoming liquid of the gas collection ring, it will be necessary to increase the diameter of the ring pipelines, and this in turn will require a significant increase in the dimensions of the supporting overpass, since the structure will occupy two tiers (see Fig. 1). The use of a linear collector with a diameter even less than 2 diameters of the gas collection ring pipes (Du = 1200 mm) will increase the free volume for liquid with smaller dimensions of the supporting overpass (see Fig. 2). The useful volume of a collector with a diameter of 1200 mm and a length of 90 m will be 92 ^m3 , which is 53% more than the prototype.

The specific metal consumption of the prototype (overpass ring) is 1.2 tons/ ^m3 , the proposed technical solution is 0.85 tons/ ^m3 (see Table 1). That is, for this example, the specific metal consumption of the collector is less than that of the overpass ring even with a greater wall thickness and without taking into account the supporting structures. And taking into account the supporting structures, this metal consumption will be even less.

Method of preparing natural gas for transportation

Claims (1)

A method for preparing natural gas, including transporting the produced fluid along pipelines from gas well clusters to integrated gas treatment units (IGTU), separating the gas in inlet separators and slug catchers, compressing at a booster compressor station (BCS) in several stages and cooling at gas cooling units after each compression stage, characterized in that a linear manifold in the form of a cylindrical tank is installed in the section between the pipeline leading from the gas well cluster pipelines and the inlet to the first separation stage of the IGTU, located on a rack at the level of the inlet to the IGTU separator, the linear manifold is connected to the inlet of the IGTU separator by means of a pipeline for removing gas, a section of which extends vertically upward from the linear manifold, and the separated liquid is removed from the linear manifold via a pipeline to slug catchers and further disposal, a section of which extends vertically downward from the linear manifold.