Deep coal bed gas and tight gas combined mining ground gathering and transportation method

Abstract

This invention relates to a surface gathering and transportation method for the combined production of deep coalbed methane and tight gas, comprising the following steps: The deep coalbed methane well site is connected to a valve group via a low-pressure pipeline, allowing coalbed methane to flow into the valve group through the low-pressure pipeline; the tight gas well site is connected to the valve group via a gas production pipeline, allowing tight gas to flow into the valve group through the gas production pipeline; the coalbed methane and tight gas exiting the valve group jointly enter a gathering station via a gathering and transportation trunk line, where they are sequentially separated, pressurized, dehydrated, and metered before being sent to a booster station for further pressurization and then transported externally. This invention can reduce pipeline laying, lower pipeline pressure drop, reduce back pressure at the tight wellhead, facilitate the release of tight gas well potential, and increase production.

Description

Technical Field

[0001] This invention relates to the field of natural gas gathering and transportation technology, specifically to a surface gathering and transportation method for the combined extraction of deep coalbed methane and tight gas. Background Technology

[0002] Currently, unconventional gas in Shanxi mainly includes tight gas and coalbed methane. Tight gas and coalbed methane have different gathering and transportation methods and characteristics based on their unique properties.

[0003] Tight gas wellhead pressure is relatively high, and it is gathered and transported using a three-stage station layout: wellhead – gathering station – booster station. Currently, the operating pressure of tight gas production wells in the Shenfu area is between 2MPa and 4MPa. Individual wells can be directly connected to the gathering trunk line via the production pipeline, or they can be connected to the gathering network via a branch-to-branch connection. The gathering station does not have booster facilities; the gas undergoes gas-liquid separation, dehydration, and metering before entering the booster station for processing. Unlike tight gas, coalbed methane uses tubing pumping and casing gas production. Shallow coalbed methane is characterized by low single-well pressure and rapid production decline.

[0004] However, existing technologies generally employ methods such as Figure 1 The illustrated method involves separate gathering and transportation of tight gas and coalbed methane. Tight gas from tight gas wells is introduced into a gathering station via high-pressure pipelines, while coalbed methane from deep coalbed methane wells is introduced into the gathering station via low-pressure pipelines. A booster compressor is installed at the gathering station to pressurize the incoming low-pressure coalbed methane to the same pressure as the incoming tight gas. The pressurized coalbed methane and tight gas are then mixed, dehydrated using molecular sieves, metered, and transported externally. The disadvantages of this method are increased pipeline investment due to separate pipeline laying; and the centralized pressurization of coalbed methane at the gathering station results in a large volume of gas with a high pressure ratio, often requiring large-scale reciprocating compressors, leading to substantial equipment investment. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to provide a surface gathering and transportation method for the combined production of deep coalbed methane and tight gas, which can reduce pipeline laying, lower pipeline transportation pressure drop, reduce tight wellhead back pressure, facilitate the release of tight gas well potential, and increase production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The surface gathering and transportation method for combined deep coalbed methane and tight gas extraction according to the present invention includes the following steps:

[0008] Deep coalbed methane well sites are connected to valve groups via low-pressure pipelines so that coalbed methane can be introduced into the valve groups through low-pressure pipelines.

[0009] Tight gas well sites are connected to valve groups via gas production pipelines so that tight gas can be introduced into valve groups through gas production pipelines.

[0010] Coalbed methane and tight gas from the valve group enter the gas gathering station through the gathering and transmission trunk line. In the gas gathering station, they are separated, pressurized, dehydrated and metered in sequence before being sent to the booster station for further pressurization and then transported out.

[0011] The aforementioned method for surface gathering and transportation of deep coalbed methane and tight gas, preferably, includes a valve group comprising a three-phase separator, a booster pump, a compressor, and an air cooler;

[0012] The compressor's air inlet is connected to the deep coalbed methane well site via a low-pressure pipeline, and its air outlet is connected to an air cooler and then leads to the gas gathering station via a gathering and transmission trunk line.

[0013] The air inlet of the three-phase separator is connected to the tight gas well site through the gas production pipeline. Its gas phase outlet and liquid phase outlet are connected to the main collection and transmission line through the gas phase pipeline and condensate pipeline, respectively. Its water phase outlet is connected to the booster pump and then connected to the sewage treatment station through the water collection pipeline.

[0014] The aforementioned method for surface gathering and transportation of deep coalbed methane and tight gas, preferably, includes a specific diversion method for the valve group as follows:

[0015] Coalbed methane extracted from casing in deep coalbed methane well sites is pressurized by a compressor through a low-pressure pipeline, cooled by an air cooler, and then fed into the gathering and transmission trunk line.

[0016] Tight gas in the tight gas well site is fed into a three-phase separator through the gas production pipeline. After being separated by the three-phase separator, the tight gas and condensate are mixed with the cooled coalbed methane and then transported to the gas gathering station through the gathering and transmission trunk line.

[0017] When the pressure at the tight gas wellhead decreases in the later stages, the tight gas separated by the three-phase separator and the coalbed methane are pressurized together by the compressor and then sent to the gas gathering station through the gathering and transmission trunk line.

[0018] The aforementioned method for surface gathering and transportation of combined deep coalbed methane and tight gas preferably further includes the following steps:

[0019] Water extracted from the oil pipes in deep coalbed methane well sites is fed into the well site water pump via water pipes, and then into the sewage treatment plant via water collection pipelines.

[0020] The present invention has the following advantages due to the adoption of the above technical solutions:

[0021] (1) In this invention, coalbed methane is pressurized by a valve group and transported to the gas gathering station together with tight gas through the gathering and transportation trunk line, which reduces the laying of pipelines; most of the free water in the tight gas is separated by the valve group separator, which reduces the pipeline transportation pressure drop and the back pressure at the tight gas wellhead is reduced, which is conducive to the release of the potential of the tight gas well; in the later stage, the pressure of the tight gas well drops, and in order to maintain the inlet pressure unchanged, the tight gas can be connected to the valve group compressor for pressurization and external transmission to increase the output without affecting the tight gas production;

[0022] (2) In the later stages of tight gas development, due to the decrease in wellhead pressure, the inlet pressure of the gas gathering station needs to be reduced in order to ensure the production capacity of tight gas wells. Therefore, all tight gas gathering stations are equipped with pressurization facilities to ensure the external transmission of natural gas. After adopting an integrated gathering and transmission scheme, low-pressure tight gas can be connected to the valve group for pressurization in the later stages, further reducing the need for pressurization facilities in the gathering station and greatly reducing investment.

[0023] (3) Through the optimized design of the valve group, it is possible to share the gas gathering trunk line of coalbed methane and tight gas, and also to reduce the amount of water entering the gas gathering trunk line of tight gas by using the sewage return facility of the coalbed methane valve group, so as to realize the separation of oil and gas and water, effectively reduce the investment of the gas gathering trunk line, and also provide a guarantee for the stable operation of the gas gathering station; according to the integrated process design, the tight gas and coalbed methane logistics can realize the closed transportation of the whole process, reduce VOC emissions, and avoid environmental pollution. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0025] Figure 1 This is a flowchart of the separate gathering and transportation process for tight gas and deep coal seams in existing technologies;

[0026] Figure 2 This is a flowchart of the tight gas and deep coal seam co-gathering and transportation process in this invention;

[0027] Figure 3 yes Figure 2 The process flow diagram of the valve assembly. Detailed Implementation

[0028] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0029] This invention provides a surface gathering and transportation method for the combined production of deep coalbed methane and tight gas, taking into account the overall development of tight gas and deep coal seams. It adopts an integrated gathering and transportation method of "valve group pressurization, shared trunk line, and regular pipeline cleaning", which reduces the duplication of gas gathering trunk line construction and lowers investment. The design of the deep coalbed methane gathering valve group is optimized. By adding a separator to the valve group, the oil, gas and water three-phase separation of the tight gas well flow is carried out. The oil, gas and water are separated by utilizing the deep coalbed methane water gathering pipeline network, which effectively solves the problems of liquid accumulation in the gas gathering pipeline network and high liquid handling load of the gas gathering station.

[0030] like Figure 2 and Figure 3 As shown, the surface gathering and transportation method for combined deep coalbed methane and tight gas extraction provided by the present invention includes the following steps:

[0031] (1) Deep coalbed methane well sites are connected to valve groups through low-pressure pipelines so that coalbed methane can be introduced into valve groups through low-pressure pipelines;

[0032] (2) Tight gas well sites are connected to valve groups through gas production pipelines so that tight gas can be introduced into valve groups through gas production pipelines;

[0033] (3) The coalbed methane and tight gas coming out of the valve group enter the gas gathering station through the gathering and transmission trunk line. In the gas gathering station, they are separated, pressurized, dehydrated and metered in sequence before being sent to the pressurization station for pressurization and then transported out.

[0034] In the above embodiments, preferably, the valve group includes a three-phase separator, a booster water pump, a compressor, and an air cooler;

[0035] The compressor's air inlet is connected to the deep coalbed methane well site via a low-pressure pipeline, and its air outlet is connected to an air cooler and then leads to the gas gathering station via a gathering and transmission trunk line.

[0036] The air inlet of the three-phase separator is connected to the tight gas well site through the gas production pipeline. Its gas phase outlet and liquid phase outlet are connected to the main collection and transmission line through the gas phase pipeline and condensate pipeline, respectively. Its water phase outlet is connected to the booster pump and then connected to the sewage treatment station through the water collection pipeline.

[0037] In the above embodiments, preferably, the specific flow diversion method of the valve group is as follows:

[0038] Coalbed methane extracted from casing in deep coalbed methane well sites is pressurized by a compressor through a low-pressure pipeline, cooled by an air cooler, and then fed into the gathering and transmission trunk line.

[0039] Tight gas in the tight gas well site is fed into a three-phase separator through the gas production pipeline. After being separated by the three-phase separator, the tight gas and condensate are mixed with the cooled coalbed methane and then transported to the gas gathering station through the gathering and transmission trunk line.

[0040] When the pressure at the tight gas wellhead decreases in the later stages, the tight gas separated by the three-phase separator and the coalbed methane are pressurized together by the compressor and then sent to the gas gathering station through the gathering and transmission trunk line.

[0041] It should be noted that the compressor boosts the low pressure to 2-2.5 MPa, which is determined by the back pressure at the tight gas wellhead; the inlet pressure of the gas gathering station is 1-1.5 MPa.

[0042] In the above embodiments, preferably, the present invention further includes the following steps:

[0043] (4) The water extracted from the oil pipes in the deep coalbed methane well site is fed into the well site water pump through the water pipe, and then into the sewage treatment station through the water collection pipeline.

[0044] Furthermore, it should be noted that, compared to the separate transportation of tight gas and coalbed methane, this invention utilizes a combined gas gathering trunk line for transportation, reducing pipeline laying. Due to valve group pressurization, the pipeline gathering pressure increases, and the diameter of the gas gathering pipeline is reduced. From a well site perspective, compared to tight gas, coalbed methane has a lower liquid content. By optimizing the appropriate gas gathering pipeline diameter, combined transportation enhances the liquid-carrying capacity of tight gas and reduces back pressure at the wellhead. In the later stages of tight gas development, due to the drop in wellhead pressure, the inlet pressure of the gas gathering station needs to be reduced to ensure tight gas well productivity. Therefore, all tight gas gathering stations are equipped with pressurization facilities to ensure natural gas output. With the integrated gathering and transportation scheme, low-pressure tight gas can be connected to the valve group for pressurization in the later stages, further reducing the need for pressurization facilities at the gas gathering station and significantly reducing investment.

[0045] To accommodate the integrated gathering and transportation of tight gas and deep coalbed methane, the gas gathering valve group was optimized. For coalbed methane wells, a casing-based gas production and tubing-based water production method is used. Gas from each coalbed methane well site is collected in the valve group, then pressurized and cooled before being transported out. Deep coalbed methane extraction involves large volumes of fracturing flowback fluid and initial water production. Wastewater return pipelines are installed at the well sites and valve groups. To reduce investment, gas and water pipelines are laid in the same trench. Production water from each well site is collected in the valve group and then transported to the water treatment plant via the main water collection line.

[0046] Based on the experience of tight gas development in the Shenfu area, the current gas-liquid ratio is 0.5–2m. 3 In the later stages of gas field development, the liquid content of tight gas shows a continuous increasing trend. According to the component analysis of the gas gathering station, most of the separated liquid phase is water. To address the problems of large liquid accumulation, high pipeline pressure loss, large water treatment volume at the gas gathering station, and frequent truck transport in the gas gathering pipeline, the tight gas well site logistics are connected to the coalbed methane valve group nearby during integrated development. A three-phase separator separates the oil, gas, and water phases. The separated natural gas and condensate are collected with the coalbed methane and enter the gas gathering pipeline. The separated water is pumped through a booster pump to the deep coalbed valve group's water collection pipeline and then uniformly discharged into the wastewater treatment plant.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surface gathering and transportation method for the combined extraction of deep coalbed methane and tight gas, characterized in that, Includes the following steps: Deep coalbed methane well sites are connected to valve groups via low-pressure pipelines so that coalbed methane can be introduced into the valve groups through low-pressure pipelines. Tight gas well sites are connected to valve groups via gas production pipelines so that tight gas can be introduced into valve groups through gas production pipelines. Coalbed methane and tight gas from the valve group enter the gas gathering station through the gathering and transmission trunk line. In the gas gathering station, they are separated, pressurized, dehydrated and metered in sequence before being sent to the pressurization station for further pressurization and then exported. The valve assembly includes a three-phase separator, a booster pump, a compressor, and an air cooler. The compressor's inlet is connected to the deep coalbed methane well site via a low-pressure pipeline, and its outlet is connected to the air cooler and then leads to the gas gathering station via a gathering and transmission trunk line. The three-phase separator's inlet is connected to the tight gas well site via a gas production pipeline, and its gas phase outlet and liquid phase outlet are connected to the gathering and transmission trunk line via gas phase pipeline and condensate pipeline, respectively. Its water phase outlet is connected to the booster pump and then leads to the wastewater treatment station via a water collection pipeline.

2. The surface gathering and transportation method for combined deep coalbed methane and tight gas extraction according to claim 1, characterized in that, The specific flow diversion method of the valve group is as follows: Coalbed methane extracted from casing in deep coalbed methane well sites is pressurized by a compressor through a low-pressure pipeline, cooled by an air cooler, and then fed into the gathering and transmission trunk line. Tight gas in the tight gas well site is fed into a three-phase separator through the gas production pipeline. After being separated by the three-phase separator, the tight gas and condensate are mixed with the cooled coalbed methane and then transported to the gas gathering station through the gathering and transmission trunk line. When the pressure at the tight gas wellhead decreases in the later stages, the tight gas separated by the three-phase separator and the coalbed methane are pressurized together by the compressor and then sent to the gas gathering station through the gathering and transmission trunk line.

3. The surface gathering and transportation method for combined deep coalbed methane and tight gas extraction according to claim 2, characterized in that, It also includes the following steps: Water extracted from the oil pipes in deep coalbed methane well sites is fed into the well site water pump via water pipes, and then into the sewage treatment plant via water collection pipelines.

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