Coal mine gas extraction treatment method

Abstract

The invention provides a coal mine gas extraction treatment method, and relates to the technical field of coal bed gas treatment. The method comprises the steps that in the exploration period, coal bed gas geological conditions of an exploration area are found out, and ground gas pre-extraction is conducted; in the production construction period, according to the geological conditions of coal bed gas, ground gas pre-extraction is carried out in a planning area, up-down combined gas extraction is carried out in a preparation area, and underground gas extraction is carried out in a production area; and in the closing period, ground and underground gas extraction is carried out in the goaf. By means of the extraction treatment mode, efficient treatment of gas in the whole life cycle of the coal mine is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of coalbed methane management, and in particular to a method for coal mine gas extraction and management. Background Art

[0002] In the field of coalbed methane control technology, coal mine gas control is the key task in coalbed methane control. Among the coal mines discovered in my country, high-gas outburst mines account for a relatively high proportion of the total number of coal mines. Efficient control of gas in coal mines can not only reduce the probability of accidents caused by gas in coal mines, but also improve coal mining efficiency. It is also a requirement for the realization of co-mining of coal and coalbed methane in the development of coal mining.

[0003] How to achieve efficient gas management throughout the entire life cycle of coal mines is an urgent problem to be solved. Summary of the invention

[0004] The present application provides a coal mine gas extraction and control method, which at least to a certain extent provides an efficient gas control solution for the entire life cycle of a coal mine.

[0005] Other features and advantages of the present application will become apparent from the following detailed description, or may be learned in part by the practice of the present application.

[0006] According to one aspect of the present application, a method for coal mine gas extraction and control is provided, wherein the time period of coal mine mining includes an exploration period, a production and construction period, and a closure period, and the spatial divisions of coal mine mining include an exploration area, a planning area, a preparation area, a production area, and a goaf area, including: during the exploration period, the coalbed methane geological conditions of the exploration area are ascertained, and ground pre-extraction of gas is carried out; during the production and construction period, according to the coalbed methane geological conditions, ground pre-extraction of gas is implemented in the planning area, combined above-and-below-the-ground gas extraction is implemented in the preparation area, and underground gas extraction is implemented in the production area; during the closure period, ground and underground gas extraction is implemented in the goaf.

[0007] In some embodiments, gas is extracted in the preparation area and the production area through waterproof wellbores and high-efficiency extraction technology.

[0008] In some embodiments, the preparation area implements joint up-and-down well gas extraction, including: a joint up-and-down well gas extraction technology system based on downhole drilling directional fracturing to increase gas production, and a combined joint up-and-down well gas extraction method of first ground pre-extraction and then downhole long borehole area pre-extraction is adopted in the preparation area.

[0009] In some embodiments, the above-and-below joint extraction technology system based on downhole drilling directional fracturing to drive gas production adopts a combined above-and-below joint extraction of gas in the preparation area, which includes: selecting a drilling location on the ground above the preparation area according to the coalbed methane geological conditions, and drilling a ground pre-extraction well at the drilling location; using directional drilling technology underground to drill a series of long boreholes in the preparation area, and fracturing the series of long boreholes; extracting gas through the ground pre-extraction well and the series of long boreholes after fracturing, and adjusting the strategies for underground gas extraction and ground gas extraction according to the gas pressure value of the preparation area to reduce the gas pressure value of the preparation area to a set value.

[0010] In some embodiments, the fracturing treatment of the series of long boreholes includes: performing segmented fracturing treatment on the series of long boreholes; before extracting gas from the series of long boreholes after the ground pre-pumping wells and fracturing treatment, it also includes: according to the segmented plan of the fracturing treatment of the series of long boreholes, increasing the pressure in the preparation area corresponding to the gas drive into the underground, and the segmented plan is adjusted according to the mining situation of the coal mine.

[0011] In some embodiments, the strategy of adjusting underground gas extraction and surface gas extraction according to the gas pressure value of the preparation area so as to reduce the gas pressure value of the preparation area to a set value includes: using a high-precision gas sensor and a real-time monitoring system to continuously monitor the gas pressure values ​​of various areas of the preparation area; when the gas pressure in any area exceeds a first pressure value, extracting gas through a ground pre-extraction well corresponding to any area, and reducing the gas pressure value in any area to a second pressure value, and extracting gas through a long borehole after downhole fracturing treatment corresponding to any area so as to reduce the gas pressure value in any area to below a third pressure value; wherein, the first pressure value is greater than the second pressure value, and the second pressure value is greater than the third pressure value.

[0012] In some embodiments, on the ground above the preparation area, according to the coalbed methane geological conditions, a drilling position is selected and a ground pre-pumping well is drilled, including: on the ground above the preparation area, according to the coalbed methane geological conditions, a drilling area is selected in which the vertical distance between the ground and the gas space is less than a preset distance threshold; according to the coalbed methane geological conditions, a drilling position is selected from the drilling area according to the gas content and gas pressure in each area of ​​the preparation area, wherein the gas content of the area corresponding to the drilling position in the preparation area is greater than the content threshold and / or the gas pressure is greater than the threshold pressure value; and a ground pre-pumping well is drilled at the drilling position.

[0013] In some embodiments, the drilling position is the same as the hole position of the waterproof grouting well in the coal mine; a ground pre-pumping well is drilled at the drilling position, including: the ground pre-pumping well is an L-shaped structure, and the vertical well part in the L-shaped well is a three-opening structure. At the drilling position, a Φ346.1mm diameter roller drill bit is used for the first opening, drilling to 10m below the bedrock surface, and a Φ273.1mm surface casing is inserted for cementing; a Φ241.3mm drill bit is used for the second opening, and drilling continues to the K7 sandstone layer. After reaching the predetermined depth, drilling is stopped and a Φ193.74mm casing is inserted for cementing; a Φ171.4mm drill bit is used for the third opening until the gas space corresponding to the drilling position is reached.

[0014] In some embodiments, nitrogen drilling technology is used during the three-opening drilling process, and after the open hole is completed, drilling is stopped without returning air; wherein, when using nitrogen drilling, sealing measures are taken when changing a single drill pipe and lifting the drill pipe.

[0015] The technical solutions provided in the embodiments of the present application include at least the following intended effects:

[0016] The technical solution provided in the embodiments of the present application can, by ascertaining the coalbed methane geological conditions of the exploration area during the exploration period, so that when the exploration area is gradually converted into other areas during the production and construction period, ground pre-extraction of gas can be implemented in the planning area, combined above-and-below-ground gas extraction can be implemented in the preparation area, underground gas extraction can be implemented in the production area, and during the closure period, ground and underground gas extraction can be implemented in the goaf area, thereby achieving efficient gas control throughout the life cycle of the coal mine. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A flow chart showing a method for coal mine gas extraction and control in one embodiment of the present application is shown;

[0019] Figure 2 A schematic diagram showing a coal mine generation cycle in one embodiment of the present application. DETAILED DESCRIPTION

[0020] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this application will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0021] In addition, the drawings are only schematic illustrations of the present application and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0022] Figure 1 A flow chart of a coal mine gas extraction and control method in an embodiment of the present application is shown as follows: Figure 1 As shown, the coal mine gas extraction and control method provided in the embodiment of the present application includes the following S101 to S103. Figure 2 As shown, the time period of coal mining includes the exploration period, the production and construction period and the closing period, and the spatial divisions of coal mining include the exploration area, planning area, preparation area, production area and goaf area.

[0023] S101, during the exploration period, identify the coalbed methane geological conditions in the exploration area and conduct ground pre-extraction of gas.

[0024] The time cycle of a coal mine can be divided into the exploration period, the production and construction period, and the closure period. The exploration period is the initial stage of the life cycle of a coal mine. During this period, the main task is to conduct geological surveys to determine the reserves of the coal mine and the feasibility of mining.

[0025] Spatially, a coal mine can be divided into exploration area, planning area, preparation area, production area and goaf area. Before a coal mine is surveyed, all areas in the coal mine are exploration areas.

[0026] The embodiments of this application do not limit how to find out the coalbed methane geological conditions in the exploration area. For example, the basic geological data and gas geological data of the exploration area can be systematically collected through literature research, analysis and induction, experience summary, field investigation, analogy and other technical methods to summarize the coalbed methane geological conditions in the exploration area.

[0027] The embodiments of the present application do not limit how to pre-extract gas from the ground. For example, holes may be drilled on the ground to pre-extract gas from the exploration area.

[0028] S102: During the production and construction period, based on the geological conditions of coalbed methane, ground pre-extraction of gas shall be implemented in the planning area, combined above-and-below-ground gas extraction shall be implemented in the preparation area, and underground gas extraction shall be implemented in the production area.

[0029] In one embodiment, when implementing ground pre-extraction of gas in a planned area, the gas extraction holes when the planned area is an exploration area can be used to perform ground pre-extraction of gas.

[0030] In another embodiment, it is also possible to select gas extraction holes on the ground in the planning area based on the current coalbed methane geological conditions, and then perform ground pre-extraction of gas based on the extraction holes.

[0031] In one embodiment, implementing combined up-and-down well gas extraction in the preparation area may include: extracting gas in the preparation area through waterproof wellbores and high-efficiency extraction technology.

[0032] In one embodiment, when underground gas extraction is implemented in a production area, the gas can be extracted through waterproof wellbores and efficient extraction technology.

[0033] In one embodiment, the implementation of joint up-and-down well gas extraction in the preparation area may include: a joint up-and-down well gas extraction technology system based on downhole drilling directional fracturing to drive gas production, and a combined joint up-and-down well gas extraction method in the preparation area that uses ground pre-extraction followed by pre-extraction in a long borehole area downhole.

[0034] The embodiments of the present application do not limit how to implement the combined upper and lower well gas extraction in the preparation area by first pre-extraction on the ground and then pre-extraction in the long borehole area underground. In one embodiment, based on the technical system of combined upper and lower well extraction for gas production increase by directional fracturing of underground drilling, the combined upper and lower well gas extraction in the preparation area by first pre-extraction on the ground and then pre-extraction in the long borehole area underground can include: selecting a drilling location on the ground above the preparation area according to the geological conditions of coalbed methane, and drilling a ground pre-extraction well at the drilling location; using directional drilling technology underground to drill a series of long boreholes in the preparation area, and fracturing the series of long boreholes; extracting gas through the ground pre-extraction well and the series of long boreholes after fracturing, and adjusting the strategies of underground gas extraction and ground gas extraction according to the gas pressure value of the preparation area, so as to reduce the gas pressure value of the preparation area to the set value.

[0035] In one embodiment, on the ground above the preparation area, according to the coalbed methane geological conditions, a drilling position is selected and a ground pre-pumping well is drilled, including: on the ground above the preparation area, according to the coalbed methane geological conditions, a drilling area is selected in which the vertical distance between the ground and the gas space is less than a preset distance threshold; according to the coalbed methane geological conditions, the gas content and gas pressure in each area of ​​the preparation area are selected from the drilling position from the drilling area, wherein the gas content of the area corresponding to the drilling position in the preparation area is greater than the content threshold and / or the gas pressure is greater than the threshold pressure value; and a ground pre-pumping well is drilled at the drilling position.

[0036] The embodiments of the present application do not limit the preset distance threshold, content threshold, and threshold pressure value, and they can be determined based on experience.

[0037] The embodiments of the present application do not limit how to perform fracturing treatment on a series of long boreholes. In one embodiment, performing fracturing treatment on a series of long boreholes may include: performing segmented fracturing treatment on a series of long boreholes; before extracting gas from a series of long boreholes after fracturing treatment through a ground pre-pumping well, further comprising: increasing the pressure in the preparation area corresponding to the underground gas drive according to the segmented plan of the fracturing treatment of the series of long boreholes, and adjusting the segmented plan according to the mining conditions of the coal mine.

[0038] Depending on the size of the preparation area, a series of long boreholes can be fractured in sections, and gas can be extracted in batches, which is conducive to more complete gas extraction and reducing the gas content in the preparation area.

[0039] In one embodiment, the strategies for underground gas extraction and surface gas extraction are adjusted according to the gas pressure value of the preparation area so that the gas pressure value of the preparation area is reduced to a set value, including: using a high-precision gas sensor and a real-time monitoring system to continuously monitor the gas pressure value of each area of ​​the preparation area; when the gas pressure in any area exceeds a first pressure value, gas is extracted through a surface pre-extraction well corresponding to any area, and when the gas pressure value in any area is reduced to a second pressure value, gas extraction is performed through a long borehole after underground fracturing treatment corresponding to any area so that the gas pressure value in any area is reduced to below a third pressure value; wherein the first pressure value is greater than the second pressure value, and the second pressure value is greater than the third pressure value.

[0040] The embodiments of the present application do not limit the specific values ​​of the first pressure value, the second pressure value, and the third pressure value, which can be determined based on experience. For example, the first pressure value is 1.0 MPa, the second pressure value is 0.7 MPa, and the third pressure value is 0.5 MPa.

[0041] In one embodiment, the drilling position is the same as the hole position of the waterproof grouting well in the coal mine; drilling a ground pre-pumping well at the drilling position may include: the ground pre-pumping well is an L-shaped structure, and the vertical well part in the L-shaped well is a three-opening structure. At the drilling position, a Φ346.1mm diameter roller drill bit is used for the first opening, drilling to 10m below the bedrock surface, and a Φ273.1mm surface casing is inserted for cementing; a Φ241.3mm drill bit is used for the second opening, and drilling continues to the K7 sandstone layer. After reaching the predetermined depth, drilling is stopped and a Φ193.74mm casing is inserted for cementing; a Φ171.4mm drill bit is used for the third opening until the gas space corresponding to the drilling position is reached.

[0042] It should be noted that the diameter of the drill bit and the diameter of the casing inserted each time in the three-opening structure are only exemplary.

[0043] In one embodiment, nitrogen drilling technology is used, and after the open hole is completed, drilling is stopped without returning air; wherein, when nitrogen drilling is used, plugging measures are taken when replacing a single drill pipe or lifting the drill pipe.

[0044] By finding out the coalbed methane geological conditions in the exploration area during the exploration period, so that when the exploration area is gradually converted into other areas during the production and construction period, ground pre-extraction of gas can be implemented in the planning area, combined above-and-below-ground gas extraction can be implemented in the preparation area, underground gas extraction can be implemented in the production area, and ground and underground gas extraction can be implemented in the goaf area during the closure period, thereby achieving efficient gas control throughout the life cycle of the coal mine.

[0045] Through the above-mentioned gas control methods, the integration of coal mining and gas production can be achieved, mining pressure relief can be combined with gas extraction, and pre-extraction before mining, extraction as mining progresses, and extraction after mining can be combined to form an integrated, coordinated and unified coal mining and gas production.

[0046] The geological conditions of coalbed methane were studied in the exploration area, and different gas extraction and management methods were carried out in different areas. The reasonable spatial arrangement of ground drilling and underground extraction technology was achieved, and the advantages of ground drilling and underground extraction were complemented to minimize the restrictions of time and space conditions on gas extraction projects. The upper and lower joint extraction can reduce the restrictions of space on gas extraction, and time is exchanged for space. After entering the preparation area and production area, the gas pre-extraction time can be shortened by implementing the wellbore docking efficient extraction technology, and space is exchanged for time. The gas content of the mining face has also dropped to a lower level. In this progressive way, the gas problem of the mining face is solved in advance in time and space, ensuring the normal succession of extraction, excavation and mining.

[0047] The exploration area carries out ground pre-extraction of coal mine gas. Long-term ground drainage and pressure-reducing gas extraction can significantly reduce the gas content per ton of coal, providing safety protection for coal mine construction. The planning area is mainly based on ground extraction, and long-term drainage reduces the gas content and gas pressure of coal reservoirs. The preparation area adopts a combined up-and-down well extraction method of first ground pre-extraction and then underground long borehole area pre-extraction. The up-and-down well extraction technology system based on underground borehole directional fracturing and gas drive and increased production, that is, the underground thousand-meter borehole fracturing and gas drive + ground well secondary production increase extraction + underground protective layer mining, and the progressive long borehole group of this coal seam large-area area pre-extraction of the up-and-down well extraction technology system. The production area uses directional drilling rigs and equipment. On the basis of directional long drilling, staged fracturing and underground gas drive and increased extraction are carried out to achieve the purpose of regional sudden elimination and improve the gas extraction effect. The closed pit area (goaf area) or abandoned mine adopts pipe extraction, ground drilling extraction and roadway extraction, and closed extraction to extract residual gas.

[0048] The coal mine gas extraction and control method in the embodiment of the present application adopts technical methods such as literature research, analysis and induction, experience summary, field investigation, analogy, etc. to systematically collect basic geological data and gas geological data, so as to solve the problems of gas outburst and high gas outburst before the implementation of underground mining projects, and solve the problem of tense mining succession, ensure the balance of "extraction and mining" in the mine, and realize the time and space connection of the "five zones" of the coal mine, namely the exploration zone, planning zone, preparation zone, production zone, and goaf zone with the above- and below-ground gas extraction technology, as well as the time and space coordination technology of underground and ground drilling and fracturing gas extraction, and optimize and integrate a set of "five zones" linkage gas extraction comprehensive technology based on true above- and below-ground joint extraction, to form a joint extraction and control plan for gas disaster wells.

[0049] The effect of implementing this plan can also be reflected in the following aspects:

[0050] 1. Indirect economic benefits

[0051] Before the implementation of underground mining projects, the problems of gas outburst and high gas outburst can be solved, the problem of mining and excavation succession tension can be solved, the balance of "extraction and mining" in the mine can be ensured, and the unit output and single input of mining projects can be greatly improved. The construction costs of bottom extraction tunnels and bottom plate through-layer drilling construction and extraction can be saved, and the dual resource mining and comprehensive utilization of coal and coalbed methane can be realized.

[0052] 2. Social Benefits

[0053] Realize gas disaster management, promote industry technological progress, ensure coal mine production safety, improve the level of national energy security, and promote economic and social development.

[0054] 3. Environmental benefits and other benefits

[0055] Reduce greenhouse gas emissions.

[0056] In addition, although the steps of the method in the present application are described in a specific order in the drawings, this does not require or imply that the steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps, etc.

[0057] Through the description of the above implementation modes, it is easy for those skilled in the art to understand that the example implementation modes described here can be implemented by software, or by combining software with necessary hardware.

[0058] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope of the present application is indicated by the appended claims.

Claims

1. A method for coal mine gas extraction and control, characterized in that: The time period of coal mining includes the exploration period, production and construction period and closure period, and the spatial division of coal mining includes the exploration area, planning area, preparation area, production area and goaf area, including: During the exploration period, the geological conditions of coal-bed methane in the exploration area shall be ascertained, and pre-extraction of gas shall be carried out on the ground; During the production and construction period, according to the coalbed methane geological conditions, ground pre-extraction of gas is implemented in the planning area, above-and-below combined gas extraction is implemented in the preparation area, and underground gas extraction is implemented in the production area; During the closure period, gas extraction is carried out on the surface and underground in the goaf.

2. The method according to claim 1, characterized in that Gas is extracted in the preparation area and the production area through waterproof wellbores and high-efficiency extraction technology.

3. The method according to claim 1, characterized in that Implementing combined up-and-down well gas extraction in the preparation area includes: Based on the underground drilling directional fracturing gas production enhancement technology system, a combined upper and lower well gas extraction method of first ground pre-extraction and then pre-extraction in the underground long borehole area is adopted in the preparation area.

4. The method according to claim 3, characterized in that The above-and-below well joint extraction technology system based on downhole directional fracturing and gas production enhancement adopts a combined above-and-below well joint extraction method of first pre-extraction on the ground and then pre-extraction in the long borehole area downhole in the preparation area, including: On the ground above the preparation area, a drilling location is selected according to the coalbed methane geological conditions, and a ground pre-extraction well is drilled at the drilling location; Drilling a series of long boreholes in the preparation area using directional drilling technology underground, and performing fracturing treatment on the series of long boreholes; Gas is extracted through the surface pre-extraction wells and the series of long boreholes after fracturing treatment, and the strategies of underground gas extraction and surface gas extraction are adjusted according to the gas pressure value of the preparation area to reduce the gas pressure value of the preparation area to a set value.

5. The method according to claim 4, characterized in that The fracturing treatment of the series of long boreholes comprises: Performing staged fracturing treatment on the series of long boreholes; Before extracting gas through the surface pre-draining well and the series of long boreholes after fracturing treatment, the method further includes: According to a staged plan of fracturing treatment for a series of long boreholes, the pressure in the preparation zone is increased corresponding to the downhole gas drive, and the staged plan is adjusted according to the mining conditions of the coal mine.

6. The method according to claim 4, characterized in that The strategy of adjusting the underground gas extraction and the surface gas extraction according to the gas pressure value of the preparation area so as to reduce the gas pressure value of the preparation area to a set value includes: Using high-precision gas sensors and real-time monitoring systems to continuously monitor the gas pressure values ​​in various areas of the preparation area; When the gas pressure in any area exceeds the first pressure value, gas is extracted through the ground pre-extraction well corresponding to the any area, and when the gas pressure value in the any area is reduced to the second pressure value, gas extraction is performed through the long borehole after downhole fracturing treatment corresponding to the any area, so that the gas pressure value in the any area is reduced to below the third pressure value; The first pressure value is greater than the second pressure value, and the second pressure value is greater than the third pressure value.

7. The method according to claim 4, characterized in that On the ground above the preparation area, according to the coalbed methane geological conditions, a drilling location is selected and a ground pre-drainage well is drilled, including: On the ground above the preparation area, according to the coalbed methane geological conditions, a drilling area is selected where the vertical distance between the ground and the gas space is less than a preset distance threshold; Selecting a drilling position from the drilling area according to the gas content and gas pressure of each area in the preparation area in the coalbed methane geological conditions, wherein the gas content of the area corresponding to the drilling position in the preparation area is greater than a content threshold value and / or the gas pressure is greater than a threshold pressure value; A surface pre-pumping well is drilled at the drilling location.

8. The method according to claim 4 or 7, characterized in that: The drilling position is the same as the opening position of the waterproof grouting well hole in the coal mine; Drilling a surface pre-pumping well at the drilling location includes: The ground pre-pumping well is an L-shaped structure, and the vertical well part in the L-shaped well is a three-opening structure. A roller drill bit with a diameter of Φ346.1 mm is used in the first opening at the drilling position to drill to 10 m below the bedrock surface, and a Φ273.1 mm surface casing is inserted for cementing; The second drilling used a Φ241.3mm drill bit and continued drilling to the K7 sandstone layer. After reaching the predetermined depth, drilling was stopped and a Φ193.74mm casing was lowered for cementing. The third opening uses a Φ171.4mm drill bit to drill until the gas space corresponding to the drilling position is reached.

9. The method according to claim 8, characterized in that During the three-hole drilling process, nitrogen drilling technology is used, and after the open hole is completed, drilling is stopped without return air; Among them, when using nitrogen drilling, sealing measures are taken when changing single drill pipes and lifting drill pipes.

Images