RU2588912C1 - Method of preparation for transportation of natural gas - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to production of natural gas, in particular its preparation for transportation, as well as operation of gas collector pipelines and heat exchange unit for reducing gas temperature after compression. Method of preparation for transportation of natural gas consists in delivery of gas from well to booster compressor station via gas line, cleaning, compression and cooling of gas in heat exchanger using water-methanol solution (WMS), which after heat exchanger in a heated condition is supplied for cooling gas cavity through pipeline of smaller diameter laid inside gas pipeline, and WMS cooled in gas pipeline is returned to heat exchanger along external pipeline; wherein depending on ambient temperature initially WMS can be directed towards well after heat exchanger in external pipeline, and from well to heat exchanger - along pipeline laid inside gas line.

EFFECT: technical task of invention is providing simultaneous efficient and trouble-free operation of two interconnected process systems: collection of natural gas and its cooling in heat exchange unit after compression.

1 cl, 1 dwg

Description

The invention relates to the field of natural gas production, in particular its preparation for further transportation, as well as the operation of gas collection pipelines and a heat exchange unit to lower the gas temperature after compression at a gas collection and treatment point.

When collecting and preparing for transportation of natural gas (hereinafter referred to as gas), there are two objective problems associated with the composition and properties of gas and the technological equipment used in gas fields, the solution of which will offer a unified technical solution.

One of the problems that arise at the stage of gas collection is the formation of deposits and plugs from ice and gas hydrates due to the presence of water in its composition in the pipeline system - gas pipelines. The reason for their formation is a gradual decrease in temperature and the constant presence of pressure in gas pipelines.

From the “prior art”, the most famous and common way to prevent the formation of ice and gas hydrates in gas pipelines is to supply inhibitors such as methanol and glycol to the gas pipelines (p. 395 source: Korotaev Yu.P., Shirkovsky AI Production, transportation and underground gas storage. A textbook for universities. - M .: Nedra, 1984. - 487 p.).

According to the invention, “A device for transporting gas and gas condensate in a well-gas pipeline system (plume) according to the invention patent No. 2372553 (publ. 10.11.2009) to prevent the formation of gas hydrates in a gas pipeline, a mixture of methanol with a polymer is dosed.

In the future, it is proposed to isolate inhibitors from gas pipeline products for subsequent use, which is a rather expensive technological procedure.

To maintain the temperature in the cavity of the gas pipeline above 273 K (0 ° C) to avoid ice formation and above the temperature at which gas hydrates are formed in the gas pipeline, it is possible to use heating cables laid outside or inside the gas pipeline. The method has only one drawback - this is the high cost of technology.

The second problem is the cooling of the fluid, which occurs at the stage of compression of the collected gas for its supply to the main gas pipeline, which takes heat from the gas heated to a temperature of 85-100 ° C in the heat exchange installation as a result of its compression.

In practice, air, gas condensate, or water are widely used as a cooling fluid. Accordingly, the cooling fluid after it is heated in the heat exchanger must be cooled with the help of expensive refrigeration units. The use of air with an ambient temperature in practical heat-exchange plants such as air-cooling units (hereinafter referred to as ABO) is beneficial from the technological point of view, but expensive because of the significant energy consumption of ABO electric drives. In addition, the air heated in ABO, as a rule, is removed into the surrounding atmosphere without the beneficial use of the received heat energy. When using water as a coolant in the winter, not only the external pipeline, but also the pipeline located in the gas pipeline will freeze, because when the water-methanol solution (hereinafter BMP) moves intensively after the gas pipeline through the external pipeline, its temperature may drop below 0 ° C winter time, which can lead to an emergency stop of BMP circulation in the pipeline system.

The proposed technical innovation solves both of the problems described above: a water-methanol solution in a heat exchange installation cools natural gas to the required temperature of about 30-40 ° C and at the same time heats up to 70-85 ° C.

The objective of the invention is to provide simultaneous efficient and trouble-free operation of two technological systems interconnected in gas fields: the collection of natural gas and its cooling in a heat exchange installation after compression.

The technical result is provided by a method of preparing for transportation of natural gas, which consists in delivering moist gas from a well to a booster compressor station through a gas pipeline, purifying gas from drip moisture, compressing gas at a compressor unit and cooling gas in a heat exchanger, in contrast to an analog, for gas cooling in the heat exchanger uses BMP, which after the heat exchanger in the heated state is sent for cooling to the cavity of the gas pipeline through a pipe of a smaller diameter, laid inside the gas pipeline yes, and the BMP cooled in the gas pipeline is returned to the heat exchanger via an external pipeline, and depending on the ambient temperature, initially BMP can be directed after the heat exchanger towards the well in the external pipeline, and from the well to the heat exchanger - through the pipeline laid in the gas cavity.

The proposed technical solution has a significant difference from the known methods of preparation for transportation of natural gas.

The use of BMP as a multifunctional fluid gives a priori two previously known positive effects and a new, previously unknown technical result:

- in the gas cooling heat exchanger BMP cools the gas and heats itself;

- for cooling, BMP is fed into the pipeline laid in the internal cavity of the gas pipeline, in which it also performs an additional function - prevents the formation of ice and gas hydrates by maintaining the temperature of the gas stream above the hydration temperature due to its elevated temperature;

- BMP will not freeze as a result of lowering its temperature below 0 ° C due to the presence of methanol in the solution.

A diagram of the proposed method for preparing for transportation of natural gas is shown in FIG. 1, where the following elements are indicated:

1 - gas production well,

2 - gas pipeline from the well to the compressor station,

3 - intracavitary pipeline for heating gas,

4 - external pipeline

5 - booster compressor station (DKS),

6 - gas cooling heat exchanger,

7 - main gas pipeline,

8 - capacity with BMP,

9 - BMP booster pump,

10 - a sampler for sampling BMP,

11 - pump

12 - valve

13 - valve

14 - valve

15 - valve

16 - gas separator.

A method of preparing for transportation of natural gas is implemented in the following sequence. From the well (1) to the heat exchanger (6) located in the area of the booster compressor station (5), two pipelines are laid: intracavitary (3) and external (4). The intracavitary pipeline is laid inside the gas pipeline using the pipe-in-pipe technology, and the external pipeline is laid outside the gas pipeline. Both pipelines are connected into a single circulation system through a heat exchanger (6) and filled with BMP. The movement of BMP in a single circulation system in one direction or another is organized using a pump (11) and four valves (12-15).

The implementation of the method is proposed in two modes of movement of the coolant along the pipeline system - intensive and passive.

1. Intensive mode. In the winter period of time, the heated BMP after the BCS (5) to a gas temperature of 15 to 20 ° C is supplied directly to the gas pipeline (2) through the pipeline (3) laid in the cavity of the gas pipeline (2). Gate valves (12) and (13) are open, and valves (14) and (15) are closed. The pump (11) directs the heat carrier - BMP, heated in the heat exchanger (6) to a temperature of 30 to 50 ° C, to the end of the gas pipeline (2). Through an external pipeline (4), the cooled coolant is returned to the heat exchanger (6). Further BMP cooling occurs when moving through an external pipe (4). This mode has two functions: it maintains the required temperature in the gas pipeline and cools the BMP coolant before it enters the heat exchanger, ensuring that the gas temperature in the gas pipeline is maintained above those temperatures at which ice and gas hydrates are formed.

2. Passive mode. Designed for the summer time, when the relevance of gas pipeline heating is reduced, but the need for cooling BMP remains the same as in winter. BMP with a gas temperature of 50 to 100 ° C after the BCS (5) is sent to the external pipeline (4) and is cooled to a temperature of 20 ° C along the way to the gas well. With the same temperature, BMP enters the internal pipeline (3) located in the cavity of the gas pipeline (2), and leaves the gas pipeline with a temperature of -10 ° C close to the gas temperature. Gate valves (12) and (13) are closed, and valves (14) and (15) are open. The pump (11) directs the coolant - BMP to the heat exchanger (6) and then to the external pipe (4) to cool the BMP. This mode performs the task of cooling the BMP and, as a result, ensures the operation of the heat exchanger.

BMP is stored in a container (8) and, if necessary, pump (9) is fed into a single circulation system. Such a need may arise when BMP leaks in the circulation system. The qualitative composition of the BMP in the system is controlled by periodic sampling from the sampler (10).

The method of preparation for transportation of natural gas proposed in the present invention, in our opinion, meets the criterion of novelty and has significant differences from previously known technical solutions in the following positions:

- For the first time in the practice of gas producers, one process fluid - BMP performs two functions: cooling natural gas in a heat exchanger and transferring heat to a gas in a gas pipeline in winter. Such a scheme, in contrast to existing installations and technologies, makes the most of its use of the energy spent in the field, primarily the energy of the drive of compressor stations in the compressor station;

- due to its component composition, BMP may also have a negative temperature in the circulation system, which is completely impossible in traditional circulation systems that use water as a coolant.

Claims (1)

A method of preparing for transportation of natural gas, which consists in delivering wet gas from the well to the booster compressor station through a gas pipeline, purifying gas from drip moisture, compressing gas at a compressor unit and cooling the gas in a heat exchanger, characterized in that a water-methanol solution is used to cool the gas in the heat exchanger (BMP), which, after the heat exchanger in the heated state, is sent for cooling to the cavity of the gas pipeline through a pipe of a smaller diameter, laid inside the gas pipeline, and cooled a first pipeline BMP returned to the heat exchanger on the outer pipe, wherein, depending on the ambient temperature initially BMP may be sent after the heat exchanger in the direction of the borehole into the outer pipe and from the wellhead to the heat exchanger - through a pipeline laid in the cavity of the pipeline.

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