CN115405800A - Method for eliminating blockage of natural gas hydrate for gas transmission pipeline - Google Patents

Abstract

The invention discloses a method for eliminating natural gas hydrate blockage for gas transmission pipelines. A method for eliminating natural gas hydrate blockage of a gas transmission pipeline according to the present invention comprises the following steps: passing an inert gas into the natural gas hydrate blockage section of the gas transmission pipeline to replace the natural gas, and keeping the natural gas hydrate blockage section two If the gas space pressure at the end is balanced, the natural gas hydrate in the gas pipeline will be decomposed. The method of the invention uses the inert gas to replace the original natural gas in the gas transmission pipeline, thereby changing the chemical potential difference of the natural gas between the hydrate phase and the gas phase in the pipeline, thereby realizing the decomposition of the hydrate.

Description

A method for eliminating natural gas hydrate blockage for gas pipelines

technical field

The invention belongs to the technical field of oil and gas pipeline transportation flow safety assurance, and in particular relates to a method for eliminating natural gas hydrate blockage used in gas transmission pipelines.

Background technique

Natural gas hydrate is a cage crystal compound formed by water and methane, ethane, carbon dioxide and other gases. In the process of oil and gas extraction and transportation, due to high pressure and low temperature conditions, it is easy to form gas hydrates to block pipelines and hinder normal production. Since hydrate blockage was first discovered abroad in natural gas pipelines in 1934, safety accidents caused by hydrate blockage and improper blockage removal methods have occurred frequently with the development of oil and gas resources in deep water and ultra-deep water. Research on the method of eliminating hydrate blockage in oil and gas pipelines has become a hot spot in the field of flow safety assurance.

At present, the commonly used hydrate plugging removal methods mainly include heating method, depressurization method and inhibitor injection method, but these methods have certain shortcomings in the actual application process. The heating method consumes more energy and needs to heat the clogging block evenly to prevent pipeline rupture and secondary hydrate formation caused by local increase. The step-down method mainly includes single-end step-down and double-end step-down. During the application of single-ended decompression, due to the large pressure difference between the two ends of the block, it is easy to cause the block to move at a high speed and cause the pipeline to rupture. The application of the double-end depressurization method is greatly limited due to the special structure of the deepwater production and transportation system and the existence of the deepwater hydrostatic head. The method of injecting inhibitors has the disadvantages of large dosage of inhibitors, poor economy, and strong environmental pollution. Therefore, there is an urgent need for a safe, economical, and simple method for eliminating hydrate blockage in gas pipelines.

Contents of the invention

The object of the present invention is to provide a method for eliminating natural gas hydrate blockage used in gas transmission pipelines.

The method of the invention uses the inert gas to replace the original natural gas in the gas pipeline, thereby changing the chemical potential difference of the natural gas between the hydrate phase and the gas phase in the pipeline, thereby realizing the decomposition of the hydrate.

The invention provides a method for eliminating natural gas hydrate blockage of gas pipelines, comprising the following steps:

The natural gas hydrate in the gas pipeline is decomposed by injecting inert gas into the gas hydrate blockage section of the gas pipeline to replace the natural gas, and maintaining the pressure balance of the gas phase space at both ends of the gas hydrate blockage section.

In the above method, the inert gas is selected from at least one of nitrogen, argon and helium, and the above inert gas is not easy to form hydrate with natural gas to facilitate replacement.

In the above method, the gas phase space at both ends of the hydrate block of the gas transmission pipeline is connected through the intake pipeline, and the intake pipeline is connected with the intake tank through a pipeline; filled with said inert gas;

The gas phase space at both ends of the hydrate block of the gas pipeline is connected through the exhaust pipeline, and the exhaust pipeline is connected with the exhaust tank through a pipeline; the inside of the exhaust tank is at normal pressure before the replacement starts Air.

In the above method, pressure sensors and intake valves are respectively arranged at both ends of the intake pipeline connected to the gas phase space at both ends of the hydrate block of the gas transmission pipeline;

A gas flow meter, a pressure regulating valve and a gas compressor are arranged on the pipeline connecting the inlet pipeline and the inlet tank.

In the above method, exhaust valves are respectively arranged at both ends of the exhaust pipeline connected to the gas phase space at both ends of the hydrate block of the gas transmission pipeline;

A gas flow meter and a pressure relief valve are arranged on the pipeline connecting the exhaust pipeline to the exhaust tank.

In the above method, a safety valve and a back pressure valve are installed on the upper part of the exhaust tank.

In the above method, a gas chromatograph is also connected to the exhaust tank.

In the above method, before the replacement starts, the pressure of the inert gas output from the gas inlet tank is adjusted to be 0.5MPa-1.0MPa higher than the pressure of the gas phase space at both ends of the gas pipeline hydrate blockage.

In the above method, before the replacement starts, the pressure in the exhaust tank is set to the pressure of the gas phase space at both ends of the gas pipeline hydrate blockage block.

In the above method, when the gas chromatograph measures that the gas components in the exhaust tank do not contain natural gas components, stop feeding the inert gas for replacement.

The beneficial effects of the present invention are:

Common inert gas is used to replace the natural gas in the pipeline to decompose the blockage of hydrate. This method does not require complex supporting equipment and the inert gas used is easy to obtain, cheap and harmless, so it is simpler, more economical and safer than the heating method and the inhibitor injection method. Compared with the depressurization method, the operation of this method is not affected by the structure of the deepwater production and transportation system and the static pressure head, and the pressure at both ends of the hydrate block can be basically kept the same, so the operation is safer and the applicability is wider. To sum up, the present invention has great significance for ensuring the safety of oil and gas pipeline transportation flow.

Description of drawings

Fig. 1 is a schematic flow chart of eliminating hydrate blockage in a gas pipeline by the method of the present invention.

1 Hydrate blocking block; 2 Pressure sensor; 3 Intake valve; 4 Intake pipeline; 5-1 Gas flow meter 1; 5-2 Gas flow meter 2; 6-1 Pressure regulating valve 1; 6-2 Pressure regulating valve 2; 6-3 pressure regulating valve 3; 7 gas compressor; 8 intake tank; 9 exhaust valve; 10 exhaust pipeline; 11 exhaust tank; 12 safety valve; 13 back pressure valve; 14 gas chromatograph.

Detailed ways

The experimental methods used in the following examples are conventional methods unless otherwise specified.

The materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

In order to facilitate those skilled in the art to understand the technical solution, the present invention will be further described below in conjunction with the accompanying drawings in the embodiments, and the content of the described embodiments does not limit the present invention. All other embodiments obtained by those skilled in the art without creative efforts on the basis of the present invention fall within the protection scope of the present invention.

As shown in Figure 1, it is a schematic flow chart of a natural gas hydrate blockage removal method for gas pipelines according to the present invention. This method uses inert gas to replace the original natural gas in the gas pipeline, thereby changing the hydrate phase and the gas phase in the pipeline. The chemical potential difference of natural gas between them can realize the decomposition of hydrate.

In order to achieve the above object, the method for eliminating natural gas hydrate clogging of gas pipelines according to the present invention adopts the following technical solutions:

The natural gas at both ends of the hydrate blockage 1 of the gas pipeline is gradually replaced with an inert gas, and the pressure at both ends of the hydrate blockage 1 is kept basically the same during the replacement process, thereby realizing the elimination of the hydrate blockage 1 .

Further, pass the gas phase space at both ends of the gas pipeline hydrate blocking block 1 through the pressure sensor 2, the intake valve 3, the intake pipeline 4, the gas flow meter 1 5-1, the pressure regulating valve 1 6-1, the regulating valve Pressure valve 2 6-2 and gas compressor 7 are connected with intake tank 8.

Further, the air intake tank 8 needs to be filled with an inert gas before the replacement starts, and the inert gas is nitrogen, argon, helium and other gases that are not easy to form hydrates or a mixture thereof.

Further, the gas phase space at both ends of the gas pipeline hydrate blocking block 1 is connected to the exhaust tank 11 through the exhaust valve 9, the exhaust pipeline 10, the gas flow meter 2 5-2 and the pressure regulating valve 3 6-3 .

Further, a safety valve 12 and a back pressure valve 13 are installed on the upper part of the exhaust tank 11, and the inside thereof is air at normal pressure before the replacement starts, and the exhaust tank 11 is connected with a gas chromatograph 14 instrument.

The method for eliminating natural gas hydrate blockage of gas pipelines according to the present invention adopts the following specific steps:

(1) Before the replacement starts, adjust the outlet pressure of the gas compressor 7 through the pressure regulating valve 6-1 and the pressure regulating valve 6-2, so that it is 0.5 higher than the pressure of the gas phase space at both ends of the gas pipeline hydrate block 1 MPa～1.0MPa;

(2) Before the replacement starts, the pressure of the back pressure valve 13 on the upper part of the exhaust tank 11 is set to the pressure of the gas phase space at both ends of the gas pipeline hydrate blocking block 1;

(3) After the replacement starts, open the intake valve 3 and the exhaust valve 9, so that the inert gas in the intake tank 8 gradually replaces the natural gas in the gas phase space at both ends of the gas pipeline hydrate blocking block 1;

(4) During the replacement, the pressure in the gas phase space at both ends of the gas pipeline hydrate blocking block 1 is maintained basically the same by adjusting the openings of the intake valve 3 and the exhaust valve 9;

(5) When replacing, measure the gas composition in the exhaust tank 11 by the gas chromatograph 14 at regular intervals, and when no natural gas component is detected in the exhaust tank 11, stop the replacement until the hydrate blocks the block 1 eliminate.

Therefore, the present invention uses common inert gas to displace the natural gas in the pipeline to decompose the hydrate plugging block 1 . This method does not require complex supporting equipment and the inert gas used is easy to obtain, cheap and harmless, so it is simpler, more economical and safer than the heating method and the inhibitor injection method. Compared with the depressurization method, this method is not affected by the structure of the deepwater production and transportation system and the static pressure head, and the pressure at both ends of the hydrate plugging block 1 can be basically kept the same, so the operation is safer and the applicability is wider. To sum up, the present invention has great significance for ensuring the safety of oil and gas pipeline transportation flow.

Claims (10)

1. A natural gas hydrate blockage removal method for a gas transmission pipeline comprises the following steps:

and introducing inert gas into the natural gas hydrate blocking section in the gas transmission pipeline to replace natural gas, and keeping the pressure balance of gas phase spaces at two ends of the natural gas hydrate blocking section, so that the natural gas hydrate in the gas transmission pipeline is decomposed.

2. The method of claim 1, wherein the inert gas is selected from at least one of nitrogen, argon, and helium.

3. The method according to claim 1 or 2, characterized in that the gas phase spaces at the two ends of the hydrate blocking block of the gas transmission pipeline are communicated through a gas inlet pipeline, and the gas inlet pipeline is connected with a gas inlet tank through a pipeline; the gas inlet tank is filled with the inert gas before replacement begins;

communicating gas phase spaces at two ends of the hydrate blocking block of the gas transmission pipeline through a gas exhaust pipeline, wherein the gas exhaust pipeline is connected with an exhaust tank through a pipeline; the interior of the exhaust tank is atmospheric air before the start of the replacement.

4. The method according to claim 3, wherein a pressure sensor and an air inlet valve are respectively arranged at two ends of an air inlet pipeline connected with the gas phase spaces at two ends of the hydrate plugging block of the gas pipeline;

and a pipeline of the air inlet pipeline connected with the air inlet tank is provided with a gas flowmeter, a pressure regulating valve and a gas compressor.

5. The method according to claim 3 or 4, characterized in that exhaust valves are respectively arranged at two ends of an exhaust pipeline connected with the gas phase space at two ends of the gas pipeline hydrate plugging block;

and a gas flowmeter and a pressure relief valve are arranged on a pipeline of the exhaust pipeline connected with the exhaust tank.

6. The method according to any one of claims 3 to 5, wherein a safety valve and a back pressure valve are installed at an upper portion of the canister.

7. The method of any one of claims 3-6, wherein a gas chromatograph is further coupled to the vent tank.

8. The method according to any one of claims 3-7, wherein the pressure of the inert gas output by the gas inlet tank is adjusted to be 0.5MPa to 1.0MPa higher than the pressure in the gas phase space across the hydrate-plugged block of the gas delivery pipeline before the replacement begins.

9. A method according to any one of claims 3 to 8, wherein the pressure in the gas discharge tank is set to the pressure in the gas phase space across the hydrate-blocking block of the gas pipeline before the replacement is commenced.

10. The method of any one of claims 7-9, wherein the purging of the inert gas replacement is stopped when the gas chromatograph measures that the gas composition in the vent tank is free of natural gas composition.

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