Coal mine gas extraction treatment method

Abstract

The application provides a coal mine gas extraction treatment method, and relates to the technical field of coalbed methane treatment. The method comprises the following steps: during the exploration period, finding out the coalbed methane geological conditions of the exploration area and performing ground pre-extraction of gas; during the production construction period, performing ground pre-extraction of gas in the planning area according to the coalbed methane geological conditions, performing joint extraction of gas above and below the well in the preparation area, and performing underground extraction of gas in the production area; and during the closing period, performing ground and underground extraction of gas in the goaf. The extraction treatment mode realizes efficient treatment of gas in the whole life cycle of the coal mine.

Description

Technical Field

[0001] This application relates to the field of coalbed methane treatment technology, and in particular to a method for coal mine gas extraction and treatment. Background Technology

[0002] In the field of coalbed methane control technology, coal mine gas control is a key task. 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 the efficiency of coal mining. 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] This application provides a method for coal mine gas extraction and control, and at least to a certain extent provides a highly efficient gas control solution for the entire life cycle of a coal mine.

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

[0006] According to one aspect of this application, a method for coal mine gas extraction and control is provided. The coal mine operation period includes an exploration period, a production and construction period, and a closure period. The coal mine operation is spatially divided into an exploration area, a planning area, a preparation area, a production area, and a goaf area. The method includes: during the exploration period, ascertaining the coalbed methane geological conditions in the exploration area and conducting surface pre-extraction of gas; during the production and construction period, based on the coalbed methane geological conditions, implementing surface pre-extraction of gas in the planning area, implementing combined surface and underground gas extraction in the preparation area, and implementing underground gas extraction in the production area; and during the closure period, implementing surface and underground gas extraction in the goaf area.

[0007] In some embodiments, gas is extracted from the preparation area and the production area using waterproof wells and efficient extraction technology.

[0008] In some embodiments, gas extraction is carried out in the preparation area using a combined surface and ground gas extraction technology system based on directional fracturing and gas-driven production in downhole boreholes. In the preparation area, a combined surface and ground gas extraction system is used, which involves pre-extraction on the surface followed by pre-extraction in the long borehole area of ​​the well.

[0009] In some embodiments, the combined surface and underground gas extraction technology system based on downhole directional fracturing for enhanced gas production employs a combined surface and underground gas extraction approach in the preparation area, involving pre-extraction at the surface followed by pre-extraction in long downhole boreholes. This includes: selecting a drilling location on the surface above the preparation area based on the coalbed methane geological conditions, and drilling a surface pre-extraction well at that location; drilling a series of long boreholes in the preparation area using directional drilling technology, and fracturing the series of long boreholes; extracting gas through the surface pre-extraction wells and the fracturing series of long boreholes, and adjusting the strategies for downhole and surface gas extraction based on the gas pressure value in the preparation area to reduce the gas pressure value in the preparation area to a set value.

[0010] In some embodiments, the fracturing process of the series of long boreholes includes: performing segmented fracturing on the series of long boreholes; before extracting gas through the pre-drainage well and the series of long boreholes after fracturing, the process further includes: increasing the pressure in the preparation zone by correspondingly increasing the gas flow into the downhole according to the segmented fracturing plan of the series of long boreholes, wherein the segmented plan is adjusted according to the mining situation of the coal mine.

[0011] In some embodiments, the strategy of adjusting downhole gas extraction and surface gas extraction based on the gas pressure value of the preparation zone to reduce the gas pressure value of the preparation zone to a set value includes: continuously monitoring the gas pressure value of each area of ​​the preparation zone using a high-precision gas sensor and a real-time monitoring system; extracting gas through a surface pre-extraction well corresponding to any area when the gas pressure in any area exceeds a first pressure value; and extracting gas through a long borehole after fracturing treatment in the downhole corresponding to any area when the gas pressure value in any area decreases to a second pressure value, 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, a drilling location is selected and a surface pre-drainage well is drilled according to the coalbed methane geological conditions. This includes: on the ground above the preparation area, selecting a drilling area where the vertical distance between the ground and the gas space is less than a preset distance threshold, based on the coalbed methane geological conditions; selecting a drilling location from the drilling area based on the gas content and gas pressure in each region of the preparation area according to the coalbed methane geological conditions, wherein the gas content in the region corresponding to the drilling location in the preparation area is greater than a content threshold and / or the gas pressure is greater than a threshold pressure value; and drilling a surface pre-drainage well at the drilling location.

[0013] In some embodiments, the drilling location is the same as the orifice location of the waterproof grouting well in the coal mine; drilling a surface pre-drainage well at the drilling location includes: the surface pre-drainage well is an L-shaped structure, and the vertical well portion of the L-shaped well is a three-section structure; in the first section at the drilling location, a Φ346.1mm diameter roller cone drill bit is used to drill to 10m below the bedrock surface, and a Φ273.1mm surface casing is run in for cementing; in the second section, a Φ241.3mm drill bit is used to continue drilling to the K7 sandstone layer, and after reaching a predetermined depth, drilling is stopped and a Φ193.74mm casing is run in for cementing; in the third section, a Φ171.4mm drill bit is used to drill until the gas space corresponding to the drilling location is reached.

[0014] In some embodiments, nitrogen drilling technology is used during the three-stage drilling process, and drilling is stopped without re-air after open hole completion; wherein, when using nitrogen drilling, sealing measures are taken when changing single drill pipes or lifting drill pipes.

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

[0016] The technical solutions provided in the embodiments of this application, by ascertaining the coalbed methane geological conditions of the exploration area during the exploration period, enable the exploration area to be gradually converted to other areas during the production and construction period. Based on the coalbed methane geological conditions, the following methods can be implemented: surface pre-extraction of gas in the planning area, combined surface and underground gas extraction in the preparation area, underground gas extraction in the production area, and surface and underground gas extraction in the goaf during the closure period. This achieves efficient gas management throughout the entire life cycle of the coal mine. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0018] Figure 1 This document shows a flowchart of a coal mine gas extraction and control method according to one embodiment of the present application;

[0019] Figure 2 This diagram illustrates a coal mine generation cycle in one embodiment of the present application. Detailed Implementation

[0020] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary 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] Furthermore, the accompanying drawings are merely illustrative of this application and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0022] Figure 1 This application illustrates a flowchart of a coal mine gas extraction and control method according to an embodiment of the present application. Figure 1 As shown, the coal mine gas extraction and control method provided in this application embodiment includes the following steps S101 to S103. Wherein, as... Figure 2 As shown, the time cycle of coal mining includes the exploration period, the production and construction period, and the closure period. The spatial division of coal mining includes the exploration area, the planning area, the preparation area, the production area, and the goaf area.

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

[0024] The life 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 beginning stage of the coal mine's life cycle. During this period, the main task is to conduct geological exploration to determine the coal mine's reserves and the feasibility of mining.

[0025] In terms of space, coal mines can be divided into exploration areas, planning areas, preparation areas, production areas, and goaf areas. Before exploration, all areas within a coal mine are considered exploration areas.

[0026] The embodiments in this application do not limit the methods for determining the geological conditions of coalbed methane in the exploration area. For example, basic geological data and gas geological data of the exploration area can be systematically collected through technical methods such as literature review, analytical induction, experience summarization, field investigation, and analogy, and the geological conditions of coalbed methane in the exploration area can be obtained by summarizing them.

[0027] The embodiments in this application do not limit the specific methods for pre-extraction of gas on the ground. For example, boreholes can 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, implements surface pre-extraction of gas in the planning area, implements combined surface and underground gas extraction in the preparation area, and implements underground gas extraction in the production area.

[0029] In one embodiment, when performing surface pre-drainage of gas in a planning area, the gas extraction holes used when the planning area is an exploration area can be used for surface pre-drainage of gas.

[0030] In another embodiment, a gas extraction hole on the ground in the planning area can be selected again based on the current coalbed methane geological conditions, and then the ground pre-extraction of gas can be carried out based on the extraction hole.

[0031] In one embodiment, implementing combined surface and underground gas extraction in the preparation area may include: extracting gas in the preparation area through waterproof wells and efficient extraction technology.

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

[0033] In one embodiment, implementing combined surface and underground gas extraction in the preparation area may include: a combined surface and underground gas extraction technology system based on directional fracturing and gas-driven enhanced gas production in downhole boreholes, and adopting a combined surface and underground gas extraction system in the preparation area by first pre-extracting from the surface and then pre-extracting from the long borehole area in the well.

[0034] The embodiments of this application do not limit the specific implementation of the combined surface and underground gas extraction technology system based on directional fracturing and gas-driven enhanced gas production in the preparation area. This combined system may include: selecting drilling locations on the surface above the preparation area according to the coalbed methane geological conditions, and drilling surface pre-extraction wells at those locations; drilling a series of long boreholes underground using directional drilling technology, and fracturing these long boreholes; extracting gas through the surface pre-extraction wells and the series of fracturing-treated long boreholes, and adjusting the strategies for underground and surface gas extraction based on the gas pressure value in the preparation area to reduce the gas pressure value in the preparation area to a set value.

[0035] In one embodiment, on the ground above the preparation area, a drilling location is selected and a surface pre-drainage well is drilled based on the coalbed methane geological conditions. This includes: selecting a drilling area on the ground above the preparation area where the vertical distance between the ground and the gas space is less than a preset distance threshold, based on the coalbed methane geological conditions; selecting a drilling location from the drilling area based on the gas content and gas pressure in each region of the preparation area, wherein the gas content in the region corresponding to the drilling location in the preparation area is greater than a content threshold and / or the gas pressure is greater than a threshold pressure value; and drilling a surface pre-drainage well at the drilling location.

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

[0037] The embodiments of this application do not limit the methods for fracturing a series of long boreholes. In one embodiment, fracturing a series of long boreholes may include: performing segmented fracturing on the series of long boreholes; before extracting gas from the series of long boreholes after surface pre-drainage and fracturing, the method further includes: increasing the pressure in the preparation zone for downhole gas driving according to the segmented fracturing plan of the series of long boreholes, wherein the segmented plan is adjusted according to the mining situation of the coal mine.

[0038] Depending on the size of the preparation area, a series of long boreholes can be fracturing in stages, which allows for gas extraction in batches, facilitating more complete gas extraction and reducing the gas content in the preparation area.

[0039] In one embodiment, adjusting the strategy for downhole and surface gas extraction based on the gas pressure value in the preparation area to reduce the gas pressure value in the preparation area to a set value includes: continuously monitoring the gas pressure value in each area of ​​the preparation area using a high-precision gas sensor and a real-time monitoring system; extracting gas through a surface pre-extraction well corresponding to any area when the gas pressure in any area exceeds a first pressure value; and extracting gas through a long borehole after fracturing treatment in the downhole corresponding to any area when the gas pressure value in any area decreases to a second pressure value, 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.

[0040] The embodiments of this application do not limit the specific values ​​of the first, second, and third pressure values, and these values ​​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 location is the same as the orifice location of the waterproof grouting well in the coal mine; drilling a surface pre-drainage well at the drilling location may include: the surface pre-drainage well is an L-shaped structure, and the vertical well section of the L-shaped well is a three-section structure. In the first section at the drilling location, a Φ346.1mm diameter roller cone drill bit is used to drill to 10m below the bedrock surface, and a Φ273.1mm surface casing is run in for cementing; in the second section, a Φ241.3mm drill bit is used to continue drilling to the K7 sandstone layer. After reaching the predetermined depth, drilling is stopped and a Φ193.74mm casing is run in for cementing; in the third section, a Φ171.4mm drill bit is used to drill until the gas space corresponding to the drilling location is reached.

[0042] It should be noted that the diameter of the drill bit and the diameter of the casing inserted in each three-section structure are illustrative examples.

[0043] In one embodiment, nitrogen drilling technology is used, and drilling is stopped without re-air after open-hole completion; wherein, when using nitrogen drilling, sealing measures are taken when changing single drill pipes or lifting drill pipes.

[0044] By ascertaining the coalbed methane geological conditions of the exploration area during the exploration phase, and in order to facilitate the gradual conversion of the exploration area to other areas during the production and construction phase, the following gas extraction methods can be implemented based on the coalbed methane geological conditions: surface pre-extraction in the planning area, combined surface and underground gas extraction in the preparation area, underground gas extraction in the production area, and surface and underground gas extraction in the goaf during the closure period. This will enable efficient gas management throughout the entire life cycle of the coal mine.

[0045] Through the above-mentioned gas control methods, coal mining and gas extraction can be integrated, combining mining-driven pressure relief with gas extraction, and combining pre-extraction, extraction during mining, and extraction after mining, thus forming a unified and coordinated coal mining and gas extraction system.

[0046] In the exploration area, coalbed methane geological conditions were assessed, and different gas extraction and control methods were implemented in different zones. This approach, through analysis of surface drilling and underground extraction technologies, allowed for a rational spatial layout, leveraging the complementary advantages of both methods to minimize the limitations imposed by time and space on gas extraction. Combined surface and underground extraction further reduced spatial constraints, trading time for space. Upon entering the preparation and production areas, efficient well-to-well extraction technology shortened the pre-extraction time, again trading space for time. The gas content at the longwall face was also reduced to a low level. This progressive approach addressed the gas problem at the longwall face in advance, both in terms of time and space, ensuring a smooth transition between extraction, tunneling, and mining.

[0047] In the exploration area, surface pre-drainage of coal mine gas is carried out. Long-term surface drainage and depressurization can significantly reduce the gas content per ton of coal, providing safety assurance for coal mine construction. In the planning area, surface drainage is the primary method, with long-term drainage reducing the gas content and pressure of the coal reservoir. In the preparation area, a combined surface and underground drainage system is adopted, based on directional fracturing and gas-driven extraction technology using underground boreholes. This system combines underground kilometer-deep borehole fracturing and gas-driven extraction with secondary extraction from surface wells, underground protective layer mining, and large-area pre-drainage using a progressive long borehole group within the coal seam. In the production area, directional drilling rigs and equipment are used. Based on directional long boreholes, segmented fracturing and underground gas-driven extraction are implemented to achieve regional outburst mitigation and improve gas extraction efficiency. In closed areas (ghost areas) or abandoned mines, residual gas is extracted using methods such as pipe drainage, surface borehole drainage, roadway drainage, and closed-loop drainage.

[0048] The coal mine gas drainage and control method in this application adopts technical methods such as literature review, analysis and induction, experience summary, field investigation, and analogy to systematically collect basic geological data and gas geological data. This is to solve the problems of gas outburst and high gas emission before the implementation of underground mining projects, as well as to solve the problem of tight mining and excavation succession, ensure the balance of "drainage, excavation and mining" in the mine, realize the spatiotemporal connection between the five zones of the coal mine, namely exploration zone, planning zone, preparation zone, production zone and goaf zone, and surface and underground gas drainage technologies, as well as the spatiotemporal coordination technology of underground and surface drilling fracturing gas drainage. A set of integrated gas drainage technology based on true surface and underground joint drainage of the "five zones" is selected and integrated to form a gas disaster joint surface and underground drainage and control scheme.

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

[0050] 1. Indirect economic benefits

[0051] Before implementing underground mining operations, addressing issues such as gas outbursts and high gas emission rates, resolving tight mining succession, ensuring a balance between extraction, drilling, and extraction in the mine, and significantly increasing the output and progress per unit of mining operations. This saves on costs associated with bottom extraction roadway construction, floor drilling, and extraction, enabling the dual exploitation and comprehensive utilization of both coal and coalbed methane resources.

[0052] 2. Social benefits

[0053] To achieve gas disaster management, promote technological progress in the industry, 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] Furthermore, although the steps of the method in this application are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0057] From the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware.

[0058] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope of this application is indicated by the appended claims.

Claims

1. A method for controlling gas extraction in coal mines, characterized in that, The time cycle of coal mine mining includes the exploration period, the production and construction period, and the closure period. The spatial division of coal mine mining includes the exploration area, planning area, preparation area, production area, and goaf area. During the exploration period, the geological conditions of coalbed methane in the exploration area were ascertained, and surface pre-extraction of gas was carried out; During the production and construction period, based on the geological conditions of the coalbed methane, surface pre-extraction of gas is carried out in the planning area, combined surface and underground gas extraction is carried out in the preparation area, and underground gas extraction is carried out in the production area. During the shutdown period, gas extraction is carried out both on the surface and underground in the goaf area; The preparation area implements joint surface and surface gas extraction, including: a joint surface and surface gas extraction technology system based on directional fracturing gas-driven gas extraction in downhole boreholes, and a combined surface and surface gas extraction system in the preparation area that first pre-extracts gas from the surface and then pre-extracts gas from the long borehole area downhole. The aforementioned combined surface and underground gas extraction technology system based on directional fracturing and gas-driven enhanced gas production via downhole drilling employs a combined surface and underground gas extraction approach in the preparation area, involving pre-extraction on the surface followed by pre-extraction in long downhole boreholes. This includes: selecting drilling locations on the surface above the preparation area based on the coalbed methane geological conditions and drilling surface pre-extraction wells at these locations; drilling a series of long boreholes in the preparation area using directional drilling technology and fracturing these long boreholes; extracting gas through the surface pre-extraction wells and the fracturing series of long boreholes; and adjusting the strategies for downhole and surface gas extraction based on the gas pressure value in the preparation area to reduce the gas pressure value in the preparation area to a set value.

2. The method according to claim 1, characterized in that, Gas is extracted from the preparation area and the production area using waterproof wells and efficient extraction technology.

3. The method according to claim 1, characterized in that, The fracturing process performed on the series of long boreholes includes: The series of long boreholes were subjected to segmented fracturing treatment; Before extracting gas through the series of long boreholes after the aforementioned surface pre-extraction well and fracturing treatment, the process also includes: According to the segmented plan for fracturing a series of long boreholes, the pressure in the preparation zone is increased by corresponding downhole gas injection, and the segmented plan is adjusted according to the mining situation of the coal mine.

4. The method according to claim 1, characterized in that, The strategy of adjusting downhole and surface gas extraction based on the gas pressure value in the preparation zone to reduce the gas pressure value in the preparation zone to a set value includes: High-precision gas sensors and a real-time monitoring system are used to continuously monitor the gas pressure values ​​in each area of ​​the preparation zone. If the gas pressure in any area exceeds the first pressure value, gas is extracted through the pre-extraction well corresponding to the area. If the gas pressure in any area is reduced to the second pressure value, gas is extracted through the long borehole after fracturing treatment in the well corresponding to the area, so that the gas pressure in any area is reduced to below the 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.

5. The method according to claim 1, characterized in that, Above the preparation area, based on the coalbed methane geological conditions, a drilling location is selected and a surface pre-drainage well is drilled, including: Above the preparation area, based on 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. Based on the gas content and gas pressure in each region of the preparation area in the coalbed methane geological conditions, a drilling location is selected from the drilling area, wherein the gas content in the region corresponding to the drilling location in the preparation area is greater than a content threshold and / or the gas pressure is greater than a threshold pressure value. Drill a pre-drainage well at the drilling location.

6. The method according to claim 1 or 5, characterized in that, The drilling location is the same as the orifice location of the waterproof grouting well in the coal mine; Drilling a surface pre-extraction well at the drilling location includes: The surface pre-drainage well has an L-shaped structure. The vertical well section of the L-shaped well has a three-section structure. At the drilling location, a Φ346.1mm diameter roller cone drill bit is used to drill to 10m below the bedrock surface, and a Φ273.1mm surface casing is run in for cementing. The second drilling operation used a Φ241.3mm drill bit to continue drilling to the K7 sandstone layer. After reaching the predetermined depth, drilling was stopped and a Φ193.74mm casing was run in for cementing. The third drilling operation uses a Φ171.4mm drill bit to drill until it reaches the gas space corresponding to the drilling position.

7. The method according to claim 6, characterized in that, During the three-stage drilling process, nitrogen drilling technology was used, and drilling was stopped without re-air after open-hole completion; Among these measures, when using nitrogen drilling, sealing measures should be taken when changing single drill rods or lifting drill rods.

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