Method for changing abandoned high pumping roadway into mining dynamic horizontal well

Abstract

The present application belongs to the technical field of coalbed methane exploitation. The purpose is to provide a method for converting abandoned high pumping roadway into mining horizontal well, which integrates abandoned high pumping roadway and directional straight well, serves as a new type of mining horizontal well for gas control of coal mining face, and effectively prolongs the continuous gas production time of coalbed methane mining straight well. The following technical solutions are adopted: S1, determining the spatial distribution range of the structural fissure zone above the mining face; S2, determining the spatial positional relationship between each abandoned high pumping roadway around the mining face and the structural fissure zone; S3, optimizing the abandoned high pumping roadway; S4, organizing equipment access; S5, drilling the first well; S6, drilling the second well; S7, drilling the third well, and stopping drilling when the drilling fluid leaks; S8, sectional hole blowing operation; S9, lowering the air screw drill, penetrating the roof of the abandoned high pumping roadway, and drilling to the position close to the floor to stop drilling, and lowering the production screen pipe; S10, installing the wellhead device. The present application is used for coalbed methane exploitation above the mining face.

Description

Technical Field

[0001] This invention relates to a method for converting abandoned high-level extraction roadways into horizontal wells, belonging to the field of coalbed methane extraction technology. Background Technology

[0002] During underground mining operations, proximity to goafs or gas-bearing strata often leads to a significant increase in gas emissions, seriously threatening safe production. To effectively control gas emissions, a dedicated roadway is typically pre-excavated within the fractured zone of the upper strata of the coal seam for gas drainage; this roadway is called an elevated drainage roadway. As mining concludes, the abandoned elevated drainage roadway gradually closes under ground stress, but retains numerous fractures. These fractures continuously connect to surrounding gas-rich areas, becoming important channels for gas migration.

[0003] While mining-induced vertical wells are a technologically mature, structurally simple, and relatively low-cost well type, they suffer from limited contact area with coalbed methane reservoirs and relatively low gas recovery rates in practical applications. In contrast, L-shaped horizontal wells can significantly increase the reservoir contact range, effectively improve coalbed methane recovery efficiency, and reduce environmental disturbance from surface engineering. However, they are technically complex, difficult, and require significant investment, and their horizontal sections are prone to shearing and faulting under mining-induced conditions. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for converting abandoned high-level extraction roadways into mining-driven horizontal wells. This method integrates abandoned high-level extraction roadways as a pre-set horizontal section with directional vertical wells, making them a key component of L-shaped horizontal wells. This serves as a new type of mining-driven horizontal well for gas control in coal mining faces and effectively extends the continuous gas production time of coalbed methane mining-driven vertical wells.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for converting an abandoned high-pressure extraction roadway into a horizontal well, comprising the following steps: S1. Based on geological information, numerical simulation is used to determine the spatial distribution range of structural fracture zones above the mining face that are conducive to coalbed methane migration. S2. Comprehensive analysis to clarify the spatial relationship between abandoned high-level extraction roadways and structural fracture zones around the longwall face; S3. Preferably, the abandoned high-level extraction roadway located in the structural fracture zone above the mining face is prepared as the horizontal section of the mining shaft. The wellhead location of the directional vertical shaft is determined based on the spatial orientation of the abandoned high-level extraction roadway, taking into account the distribution of surface buildings and terrain limitations. S4. Organize the necessary power system, water storage system, power system and related auxiliary equipment to enter the site, and complete the installation and commissioning; S5. Once drilling begins and is completed, the surface casing is run in, with the top of the surface casing flush with the ground surface, and then cemented. S6. After drilling is completed, the technical casing is run in, with the top of the technical casing above the ground, and then cementing is performed. S7. Drilling in the third stage, stop drilling when drilling fluid leaks into the structural fracture zone; S8. Lower the drill rod and drill bit into sections to carry out blowhole operation; S9. After completing the blow-through operation of the entire well section, the air screw drill bit is lowered to carry out directional drilling. After penetrating the roof of the abandoned high-pressure pumping roadway, drilling continues until it is close to the floor of the abandoned high-pressure pumping roadway and then stops. After drilling is completed, the production screen pipe is lowered and suspended at the bottom of the second-stage technical casing. S10. Check the wellbore condition through the downhole inspection system. After confirming that everything is in order, install the wellhead device.

[0006] Preferably, S1 specifically involves: integrating mine geological data and using numerical simulation software to analyze the stress changes and collapse patterns of the strata in the horizontal and vertical directions during the coal mining process, thereby determining the spatial distribution range of structural fracture zones that are conducive to coalbed methane migration.

[0007] Preferably, in S5, during the initial drilling of the vertical well section, a drill string combination of a Φ444.5mm PDC drill bit and a Φ127mm screw and water-soluble bentonite drilling fluid is used to drill to 20m below the stable bedrock in a low-displacement manner. After drilling is completed, a surface casing of steel grade J55, Φ339.7mm, and wall thickness of 8.38mm is installed. When cementing, use Grade G oil well cement and allow it to set for 24 hours after cementing is completed.

[0008] Preferably, in step S6, the second drilling operation uses a Φ311.15mm PDC drill bit paired with a Φ203mm drill bit. The 1.5° screw drill string assembly completed the second vertical well and the directional drilling operation. After drilling was completed, a Φ244.5mm, 13.84mm thick technical casing was run in, with the technical casing extending 0.28m above the ground. During cementing, Grade G oil well cement is used, and 48 hours are allowed to set after cementing is completed.

[0009] Preferably, in step S7, the third section uses a Φ171.5mm PDC drill bit paired with a Φ135.00mm drill bit. A 1.5° screw drill string assembly is used for water-based drilling fluid drilling.

[0010] Preferably, in step S9, a Φ171.5mm PDC drill bit is used in conjunction with a Φ135.00mm drill bit. Drilling with a 1.5° air screw drill bit combination, producing a screen pipe of steel grade N80, Φ139.70mm, wall thickness 7.72mm, and the overlap length between the top of the production screen pipe and the bottom of the second-stage technical casing is not less than 3 meters.

[0011] Preferably, wireless tracking and monitoring are used during the drilling process of S5, S6, and S7.

[0012] Preferably, in step S6, after the second drilling is completed, open-hole logging should be performed first to ensure that the drilling trajectory meets the design requirements before the technical casing is run in.

[0013] Preferably, in step S6, after the second cementing is completed, logging and injection pressure tests are performed, and step S7 is performed only after the cementing quality is assessed as qualified.

[0014] Compared with the prior art, the present invention has the following beneficial effects.

[0015] This invention provides a new gas extraction path that is both economical and efficient. It utilizes abandoned high-level extraction roadways as the natural horizontal section of the mining shaft. Only a directional vertical shaft needs to be constructed to connect with the abandoned high-level extraction roadway to form a new type of mining horizontal shaft. The abandoned high-level extraction roadway increases the communication range between the directional vertical shaft and the structural fracture zone, achieving extraction efficiency comparable to or even better than that of conventional L-shaped horizontal shafts. This significantly reduces construction costs and risks. Furthermore, selecting abandoned high-level extraction roadways located in the structural fracture zone above the working face and the goaf can significantly reduce the gas concentration in the upper corner of the working face, ensuring safe production at the coal mining face. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below.

[0017] Figure 1 This is a diagram showing the location relationship between the abandoned high-efficiency extraction roadway and the favorable area of ​​the mining shaft in this invention.

[0018] Figure 2 This is a schematic diagram of the mining-driven horizontal well formed by the directional vertical shaft and the abandoned high-extraction roadway in this invention.

[0019] Figure 3 This is a schematic diagram of the directional vertical well structure in this invention.

[0020] Figure 4 This is a schematic diagram showing the gas production of a production-driven horizontal well constructed using the method of this invention.

[0021] Figure 5 To and Figure 4 A schematic diagram of the gas production of the horizontal well and the vertical well in the same production face.

[0022] In the diagram: 1 is the abandoned high-efficiency extraction roadway, 2 is the location of the wellhead, 3 is the bottom of the directional vertical shaft, 4 is the directional vertical shaft, 5 is the unmined coal seam, 6 is the fracture, 7 is the direction of gas migration, 8 is the longwall face, 9 is the goaf of the longwall face, 10 is the wellhead, 11 is the surface casing, 12 is the technical casing, 13 is the production screen pipe, and 14 is the screen pipe fixing flange. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The present invention provides the following embodiments.

[0025] like Figure 1 , Figure 2 , Figure 3 As shown, the present invention discloses a method for converting an abandoned high-pressure extraction roadway into a horizontal well, comprising the following steps: S1. Based on geological information, numerical simulation was used to determine the spatial distribution range of the structural fracture zone above the mining face 8 that is conducive to coalbed methane migration. Specifically, this involves integrating mine geological data and using numerical simulation software to analyze the stress changes and collapse patterns of the strata in the horizontal and vertical directions during the coal mining process, thereby determining the spatial distribution range of structural fracture zones that are conducive to coalbed methane migration.

[0026] S2. Comprehensive analysis clarifies the spatial relationship between the abandoned high-level extraction roadways and the structural fracture zone around the 8th longwall face.

[0027] S3. Preferably, the abandoned high-extraction roadway 1 located in the structural fracture zone above the longwall face 8 is prepared as the horizontal section of the mining shaft, and the wellhead position 2 of the directional vertical shaft 4 is determined according to the spatial orientation of the abandoned high-extraction roadway 1, taking into account the distribution of surface buildings and terrain limitations.

[0028] S4. Organize the necessary power system, water storage system, power system and related auxiliary equipment to enter the site, and complete the installation and commissioning.

[0029] S5. Once drilling begins and drilling is completed, the surface casing 11 is lowered in. The top of the surface casing 11 is flush with the ground surface, and then the well is cemented. Specifically, when drilling the vertical well section, a drill string combination of a Φ444.5mm PDC drill bit and a Φ127mm screw rod and water-soluble bentonite drilling fluid was used to drill to 20m below the stable bedrock in a low-displacement manner. After drilling was completed, a surface casing 11 with steel grade J55, Φ339.7mm and wall thickness of 8.38mm was installed. When cementing, use Grade G oil well cement and allow it to set for 24 hours after cementing is completed.

[0030] S6. After drilling is completed, the technical casing 12 is run in, with the top of the technical casing 12 above the ground, and then cemented. Specifically, the second section uses a Φ311.15mm PDC drill bit with a Φ203mm drill bit. The 1.5° screw drill string assembly completes the second-stage vertical well and the directional drilling section. After the second-stage drilling is completed, open-hole logging is performed to ensure that the drilling trajectory meets the design requirements. Then, the Φ244.5mm, 13.84mm thick technical casing 12 is run in, with the technical casing 12 extending 0.28m above the ground. During cementing, Grade G oil well cement is used, and 48 hours are allowed to set after cementing is completed. After cementing is completed, logging and injection pressure tests are performed. Once the cementing quality is deemed satisfactory, step S7 is performed.

[0031] S7. Drilling in the third stage, stop drilling when drilling fluid leaks into the structural fracture zone; Specifically, the third section uses a Φ171.5mm PDC drill bit with a Φ135.00mm drill bit. A 1.5° screw drill string assembly is used for water-based drilling fluid drilling.

[0032] S8. Lower the drill rod and drill bit into sections to carry out blowhole operation.

[0033] S9. After completing the blow-through operation for the entire well section, lower the air screw drill string to carry out directional drilling. After penetrating the roof of the abandoned high-pressure extraction roadway 1, continue drilling until you are close to the floor of the abandoned high-pressure extraction roadway 1 and then stop drilling. Figure 1 As shown, the bottom position 3 of the directional vertical shaft is near the bottom plate of the abandoned high-extraction roadway 1. After drilling is completed, the production screen pipe 13 is lowered and suspended at the bottom end of the second-stage technical casing 12 through the screen pipe fixing flange 14. Specifically, a Φ171.5mm PDC drill bit is used with a Φ135.00mm drill bit. The drilling tool combination of 1.5° air screw is used for drilling. The production screen is made of N80 steel grade, Φ139.70mm, and wall thickness 7.72mm. The overlap length between the top of the production screen 13 and the bottom of the second-opening technical casing 12 is not less than 3 meters.

[0034] S10. Check the wellbore condition through the downhole inspection system. After confirming that everything is in order, install the wellhead device at wellhead 10.

[0035] Wireless tracking and monitoring are used during the drilling processes of S5, S6, and S7.

[0036] like Figure 2 As shown, this invention utilizes the abandoned high-level extraction roadway 1 as the natural horizontal section of the mining-initiated shaft. Only the construction of a directional vertical shaft 4 is needed to connect the abandoned high-level extraction roadway 1, thus forming a new type of mining-initiated horizontal shaft. During extraction, coalbed methane moves through the fractures 6 in the structural fracture zone along the gas migration direction 7 into the abandoned high-level extraction roadway 1 and the directional vertical shaft 4, and is finally extracted to the surface. The abandoned high-level extraction roadway 1 increases the communication range between the directional vertical shaft 4 and the structural fracture zone, achieving extraction efficiency comparable to or even better than that of a conventional L-shaped horizontal shaft, significantly reducing construction costs and risks. Furthermore, selecting the abandoned high-level extraction roadway 1 located in the structural fracture zone above the working face 8 and the goaf 9 can significantly reduce the gas concentration in the upper corner of the working face 8, ensuring safe production at the coal mining face.

[0037] The method of this invention has been put into practical use and has been used to modify the 030 working face in our company.

[0038] In the modified mining horizontal well, the first wellbore has a diameter of 444.5 mm and a depth of 82.55 m, and is cemented; the second wellbore has a diameter of 311.15 mm and a depth of 800 m, with its bottom located in the unmined coal seam 5 (D). 5-6 The top of the coal seam is 10m, and directional drilling to build up the inclined section begins at a well depth of 355m, followed by cementing; the third well opening has a diameter of 171.5mm and a depth of 888m, connecting with the selected abandoned high-extraction roadway 1, without cementing.

[0039] Engineering verification results confirm that the mining-driven horizontal well based on the renovation of abandoned high-extraction roadway 1 possesses excellent long-term stable production capabilities. For example... Figure 4 As shown, the gas production data from 2024 indicates that the horizontal well maintained high production for the first four months, after which production smoothly transitioned to a stable plateau period with relatively small declines in both magnitude and rate. In contrast, as... Figure 5 As shown, the high-production period of the vertical well in the same production face as the horizontal well is relatively short, and the gas production during the descent phase decreases sharply. Its production level after stabilization is also significantly lower than that of the horizontal well.

[0040] Meanwhile, after the horizontal well was put into operation, the gas concentration in the upper corner of the working face successfully decreased from 0.6% to about 0.2%, effectively ensuring the safety of the mining operation. The effectiveness of the industrial application and the reliability of operation of this invention have been fully verified.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for converting abandoned high-extraction roadways into horizontal wells, characterized in that... Includes the following steps: S1. Based on geological information, numerical simulation was used to determine the spatial distribution range of the structural fracture zone above the mining face (8) that is conducive to the migration of coalbed methane. S2. Comprehensive analysis to clarify the spatial relationship between the abandoned high-level extraction roadways and the structural fracture zone around the mining face (8); S3. Preferably, the abandoned high-extraction roadway (1) located in the structural fracture zone above the mining face (8) is prepared as the horizontal section of the mining shaft. Based on the spatial orientation of the abandoned high-extraction roadway (1), the wellhead position (2) of the directional vertical shaft (4) is determined, taking into account the distribution of surface buildings and terrain limitations. S4. Organize the necessary power system, water storage system, power system and related auxiliary equipment to enter the site, and complete the installation and commissioning; S5. Once drilling begins, after drilling is completed, the surface casing (11) is lowered in. The top of the surface casing (11) is flush with the ground surface, and then the well is cemented. S6. After drilling is completed, the technical casing (12) is lowered into the well. The top of the technical casing (12) is higher than the ground surface, and then cementing is performed. S7. Drilling in the third stage, stop drilling when drilling fluid leaks into the structural fracture zone; S8. Lower the drill rod and drill bit into sections to carry out blowhole operation; S9. After completing the blow-hole operation of the entire well section, the air screw drill is lowered to carry out directional drilling. After penetrating the roof of the abandoned high-extraction roadway, the drilling continues until it is close to the bottom of the abandoned high-extraction roadway and then stops. After the drilling is completed, the production screen pipe (13) is lowered and suspended at the bottom of the second-stage technical casing (12). S10. Check the wellbore condition through the downhole inspection system. After confirming that everything is in order, install the wellhead device.

2. The method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 1, characterized in that: Specifically, S1 involves integrating mine geological data and using numerical simulation software to analyze the stress changes and collapse patterns of the strata in the horizontal and vertical directions during the coal mining process, thereby determining the spatial distribution range of structural fracture zones that are conducive to coalbed methane migration.

3. A method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 1 or 2, characterized in that: In S5, during the initial drilling of the vertical well section, a drill string combination of a Φ444.5mm PDC drill bit and a Φ127mm screw and water-soluble bentonite drilling fluid is used to drill to 20m below the stable bedrock in a low-displacement manner. After drilling is completed, a surface casing (11) of steel grade J55, Φ339.7mm and wall thickness 8.38mm is installed. When cementing, use Grade G oil well cement and allow it to set for 24 hours after cementing is completed.

4. A method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 1 or 2, characterized in that: In S6, the second opening uses a Φ311.15mm PDC drill bit with a Φ203mm drill bit. The drilling tool assembly with 1.5° screw completed the second vertical well and the directional drilling operation. After the drilling was completed, the Φ244.5mm and 13.84mm thick technical casing (12) was lowered into the well. The technical casing (12) was 0.28m above the ground. During cementing, Grade G oil well cement is used, and 48 hours are allowed to set after cementing is completed.

5. A method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 1 or 2, characterized in that: In S7, the third section uses a Φ171.5mm PDC drill bit with a Φ135.00mm drill bit. A 1.5° screw drill string assembly is used for water-based drilling fluid drilling.

6. A method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 1 or 2, characterized in that: In S9, a Φ171.5mm PDC drill bit is used in conjunction with a Φ135.00mm drill bit. 1.5° air screw drilling tool combination drilling, the production screen pipe (13) is steel grade N80, Φ139.70mm, wall thickness 7.72mm, and the overlap length between the top of the production screen pipe (13) and the bottom of the second-opening technical casing (12) is not less than 3 meters.

7. The method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 3, characterized in that: Wireless tracking and monitoring are used during the drilling processes of S5, S6, and S7.

8. The method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 4, characterized in that: In S6, after the second drilling is completed, open-hole logging must be performed first to ensure that the drilling trajectory meets the design requirements before the technical casing (12) is run in.

9. A method for converting an abandoned high-pressure extraction roadway into a horizontal well according to claim 1 or 2, characterized in that: In S6, after the second cementing is completed, logging and injection pressure tests must be performed, and S7 can only be carried out after the cementing quality is assessed as qualified.

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