Casing drilling tool for crossing complex broken formations

Abstract

The utility model relates to the technical field of coal mine drilling, disclose a casing drilling tool through complex broken stratum, including casing and center open -close type drill bit, center open -close type drill bit includes drill bit body, the center hole is opened in the drill bit body center, the front end part of drill bit body is equipped with fixed cutting tool and movable cutting tool, movable cutting tool can be opened under pressure, the front end part of drill bit body is equipped with the water eye for washing hole, the working end of casing is connected with the rear end part of drill bit body, the rubber plug is placed in casing, the rubber plug is driven to enter the center hole of drill bit body under pressure and will movable cutting tool open, the utility model discloses simple operation can pass through complex broken stratum and carry out primary casing consolidation, realize '' one trip '' operation, simplify the construction process, save construction cost, improve construction efficiency.

Description

Technical Field

[0001] This utility model relates to the field of underground drilling technology in coal mines, specifically a casing drill bit for traversing complex and fractured strata. Background Technology

[0002] Drilling is a primary technical means of controlling gas in coal mines. Drilling typically begins within an already excavated roadway drilling site, extending into the distant coal seam. Due to stress redistribution caused by roadway and drilling site excavation, the coal seam near the drilling site is fractured, resulting in extremely unstable borehole walls, frequent drill bit jamming accidents, and difficult drilling. However, after traversing the complex and fractured borehole opening section, the borehole enters the original stable strata, where the coal structure is relatively intact and the borehole walls are more stable. Currently, to successfully traverse the complex and fractured strata at the borehole opening and ensure the borehole extends into the original stable strata as designed, the commonly used technical method is to run multi-stage casing to extend and seal the fractured strata in stages, providing a safe and reliable slag removal channel for construction in the stable strata.

[0003] However, as Figure 1 As shown, existing casing sealing technology in complex and fractured formations typically involves running two or even three levels of casing, resulting in repeated drilling sections and overlapping casing sections. Each level of casing requires at least one tripping up and down of the drill pipe and one casing run, and grouting is required to solidify the hole after each level of casing is run. Furthermore, in some formations prone to diameter reduction or fracture, borehole wall collapse after drill string lifting makes casing running difficult, requiring multiple tripping up and down of the drill string to clean the hole. This not only severely impacts the construction period but also wastes materials and increases the labor intensity of workers.

[0004] Therefore, drilling through complex and fractured strata is difficult, and gas control is time-consuming and ineffective. This not only exacerbates the conflict between coal mining and extraction, resulting in wasted production costs, but also creates drainage blind zones due to insufficient drilling depth, posing significant safety hazards. Therefore, a new casing drilling tool for fractured strata is urgently needed to solve these problems. Utility Model Content

[0005] To address the problems of long construction cycles, poor treatment effects, and high labor intensity in existing multi-stage casing sealing technology for traversing complex and fractured strata, as well as the traditional casing drilling technology which requires pilot drilling with conventional drill rods, followed by multiple drilling operations using different reaming drill bits, and finally the "multiple drilling trips" problem of lowering the casing into the borehole, this utility model provides a casing drilling tool for fractured strata that can achieve single-stage casing sealing and "one-trip drilling" in complex and fractured strata. This simplifies the construction process, reduces the difficulty of drilling and hole formation, saves production costs, and improves the safety of drilling operations through complex and fractured strata.

[0006] To achieve the above objectives, this utility model provides the following technical solution: A casing drill bit for traversing complex and fractured strata includes a casing and a center-opening drill bit. The center-opening drill bit includes a drill bit body with a center hole at the center. The front end of the drill bit body is provided with a fixed cutting tool and a movable cutting tool, and the movable cutting tool can be opened under pressure. The front end of the drill bit body is provided with a water passage for cleaning the hole; The working end of the casing is connected to the rear end of the drill bit body; A rubber plug is placed inside the casing. Under pressure, the plug is driven into the center hole of the drill bit body, opening the movable cutting tool. The plug is made of rubber and can be broken by the drill bit without affecting the construction of the casing section. The plug's dimensions match the inner diameter dz of the drill bit body's center hole and the inner diameter of the casing. Under the flushing medium of the mud pump, it can be moved to the center-opening drill bit and push open the movable cutting tool.

[0007] As a further technical solution, the movable cutting tool is connected to the front end of the drill bit body by a hinge.

[0008] As a further technical solution, the sleeve is formed by sequentially connecting rod units.

[0009] As a further technical solution, the rod unit includes a rod, a male connector with an external thread is fixed on one side of the rod, and a female connector with an internal thread is fixed on the other side; the male connector of the previous rod unit is threadedly connected to the female connector of the next rod unit, and all rod units are connected in sequence to form a sleeve.

[0010] As a further technical solution, the outer wall of the casing is provided with a spiral conveyor belt for slag discharge; the spiral conveyor belt is formed by welding a spiral steel strip or milling a spiral groove.

[0011] As a further technical solution, the rubber stopper is driven by a pressurized flushing medium.

[0012] As a further technical solution, the flushing medium is high-pressure water.

[0013] As a further technical solution, the connecting end of the casing is connected to a water delivery device, the water delivery device is connected to a mud pump, and the mud pump inputs high-pressure water into the casing through the water delivery device.

[0014] As a further technical solution, the rear end of the drill bit body is threadedly connected to the male connector of the working end of the casing.

[0015] Compared with the prior art, the beneficial effects of this utility model are: 1) This utility model adopts the method of casing drilling and direct casing protection without lifting the drill, which avoids the problem of difficulty in lowering the casing after lifting the drill, simplifies the casing section construction process, ensures that the casing is lowered into place and reliably protects the hole in complex and broken strata, and improves construction efficiency.

[0016] 2) After the casing section is drilled to the designed hole depth, this utility model does not require manual lowering of a special drill rod to open the center channel of the drill bit. Instead, a rubber plug is used to quickly open the channel under high pressure, which improves the opening efficiency of the center channel and reduces the labor intensity of workers.

[0017] 3) This utility model allows for flexible setting of the sleeve length through the rod unit structure of the sleeve, eliminating the need for embedding multiple levels of sleeves; it reduces the number of sleeves required for sleeve section construction and the amount of grouting material required for sealing the sleeve, effectively saving material costs.

[0018] This utility model is reasonably designed and easy to operate. It can perform single-stage casing sealing without drilling through complex and fractured strata, realizing "one-trip drilling" operation. It simplifies the construction process, saves construction costs, and improves construction efficiency, and has great practical application value. Attached Figure Description

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 A cross-sectional view of a casing-sealed borehole for drilling through complex and fractured strata using existing technology.

[0021] Figure 2 This is a cross-sectional view of the casing sealing borehole of this utility model traversing complex and fractured strata.

[0022] Figure 3 This is a schematic diagram of the casing drill bit of this utility model.

[0023] Figure 4 This is a schematic diagram of the structure of the center-opening and closing drill bit of this utility model.

[0024] Figure 5 This is a schematic diagram of the structure of the sleeve of this utility model.

[0025] In the diagram, L1-casing section, L2-outlet casing section; 1-center-opening drill bit, 11-drill bit body, 12-fixed cutting tool, 13-moving cutting tool, 14-water passage, 2-casing, 21-male connector, 22-female connector, 23-rod body, 24-spiral conveyor belt, 3-rubber plug, 4-water feeder, 5-mud pump. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0027] like Figure 1 As shown, the existing technology uses a "multi-pass drilling" method for multi-stage casing sealing. Here, d0 is the diameter of the drill bit used to construct the casing section, d1 is the diameter of casing T1, D1 is the diameter of the drill bit for the first-stage casing section, d2 is the diameter of casing T2, D2 is the diameter of the drill bit for the second-stage casing section, d3 is the diameter of casing T3, and D3 is the diameter of the drill bit for the third-stage casing section.

[0028] The specific construction steps are as follows: S1: Design the borehole trajectory: Design the borehole trajectory according to the needs of coal seam gas control in the working face, and divide the borehole body structure into casing section L1 and casing exit section L2; S2: Construction of the first-level casing section: Using a conventional drill bit and conventional drill rod with a diameter of D1, the first-level casing is constructed to the designed hole depth. After completion, the drill is lifted. The casing T1 with a diameter of d1 is lowered, and after grouting solidifies, a pressure test is performed.

[0029] S3: Construction of the secondary casing section: Using a conventional drill bit and conventional drill rod with a diameter of D2, the secondary casing is constructed to the designed hole depth. After completion, the drill is lifted; the casing T2 with a diameter of d2 is lowered, and pressure testing is carried out after grouting solidifies.

[0030] S4: Construction of the third-level casing section: Using a conventional drill bit and conventional drill rod with a diameter of D2, the drill is constructed to the designed depth of the third-level casing. After completion, the drill is lifted; the casing T3 with a diameter of d3 is lowered, and pressure testing is carried out after grouting solidifies.

[0031] S5: After the casing section L1 is completed, a directional drilling tool assembly or a conventional drilling tool assembly with a diameter of d0 is lowered to construct the casing section L2, and the drilling tool is moved into the target layer according to the design trajectory.

[0032] To overcome the shortcomings of existing technologies, such as cumbersome construction and high construction costs, this utility model designs a casing drilling tool for traversing complex and fractured strata. (Referencing...) Figures 2-5As shown: This casing drill includes a casing 2 and a center-opening drill bit 1. The center-opening drill bit 1 includes a drill bit body 11 with a center hole. The front end of the drill bit body 11 is provided with a fixed cutting tool 12 and a movable cutting tool 13. The movable cutting tool 13 is connected to the front end of the drill bit body 11 by a hinge. Under no external pressure, the movable cutting tool 13 is fixedly closed at the front end of the drill bit body 11. The working end of the casing 2 is connected to the rear end of the drill bit body 11. A rubber plug 3 is placed inside the casing 2. Under pressure, the rubber plug 3 is driven into the center hole of the drill bit body 11, which opens the movable cutting tool 13. Furthermore, the front end of the drill bit body 11 has a water passage 14 for hole washing, and the rear end is threadedly connected to the male connector 21 of the working end (tail rod unit) of the casing 2.

[0033] The inner diameter of the cavity of the central hole of the drill bit body 11 is dz, which can be used by a directional drilling tool or a conventional rotary drilling tool with a diameter of d0 required for the construction of the casing section L2, i.e., dz > d0.

[0034] Furthermore, sleeve 2 is composed of rod units connected sequentially. For example... Figure 3 As shown, the rod unit includes a rod 23, with a male connector 21 with external threads fixed on one side and a female connector 22 with internal threads fixed on the other side. The male connector 21 of the preceding rod unit is threadedly connected to the female connector 22 of the following rod unit. All rod units are connected in sequence to form a sleeve 2. The outer wall of the sleeve 2 is provided with a spiral conveyor belt 24 for slag discharge. This spiral conveyor belt 24 is formed by welding a spiral steel strip or milling a spiral groove.

[0035] The outer diameter of casing 2 matches the dimensions of the drilling rig chuck and spindle slips required for construction, allowing for the connection and disconnection of casing 2 via the drilling rig. The minimum inner diameter of casing 2 is dt, which allows for the use of directional drilling tools with a diameter of d0 and conventional rotary drilling tools required for construction of casing section L1, i.e., dt > d0.

[0036] Furthermore, such as Figure 3 As shown, the connecting end of the casing 2 is connected to the water supply device 4, the water supply device 4 is connected to the mud pump 5, and the mud pump 5 inputs high-pressure water into the casing 2 through the water supply device 4.

[0037] The rubber plug 3 is sized to match the inner diameter dz of the central hole of the drill bit body 11 and the inner hole of the casing 2. Under the action of high-pressure water delivered by the mud pump 5, it can be moved to the central hole of the center-opening drill bit 1 and push open the movable cutting tool 13. The rubber plug 3 is made of rubber material and can be broken by the center-opening drill bit 1 without affecting the construction of the casing section L1.

[0038] like Figures 2-5As shown, L1 is the casing section, and L2 is the outlet casing section. This utility model only requires the construction of one casing stage to complete the construction of casing section L1. The specific construction steps are as follows: Step 1: Design the drilling trajectory The borehole trajectory is designed according to the needs of coal seam gas control, and the borehole structure is divided into casing section L1 and casing exit section L2.

[0039] Step 2: Construction of casing section L1 2.1 Drilling Adjust and reinforce the drilling rig according to the inclination and azimuth angles designed in the first step. Use a center-opening PDC drill bit 1 with a diameter of D and a casing 2 with a diameter of d for construction; the construction depth is 0.5~1m after the designed depth of the casing section L1.

[0040] Note: Before drilling, close the center-opening PDC drill bit 1, that is, close the movable cutting tool 13 above the center hole.

[0041] 2.2 Hole Cleaning Thoroughly flush the borehole with flushing medium. Mud pump 5 supplies high-pressure water into the casing 2 via water feeder 4. The high-pressure water flows out from the water passage 14 of the center-opening / closing drill bit 1 (with the movable cutting tool 13 closed), flowing outwards along the annular gap between the casing 2 (which acts as the drill rod) and the borehole. Simultaneously, it carries drill cuttings and other debris out of the borehole, completing the flushing process. After flushing, the center-opening / closing PDC drill bit 1 is lifted to a depth of 0.5-1m from the bottom of the hole. Once the pressure from mud pump 5 stabilizes, the pressure value is recorded as B1, and mud pump 5 is shut off.

[0042] 2.3 Insert the rubber stopper Remove the water supply unit 4 from the sleeve 2 and insert the rubber stopper 3 through the inner hole of the sleeve 2; reconnect the water supply unit 4.

[0043] 2.4 Opening the opening and closing body Turn on mud pump 5 and record pressure B2; Under water pressure, the rubber plug 3 enters the center-opening PDC drill bit 1 and pushes the movable cutting tool 13 (the pressure of the mud pump 5 rises from B2 to B3) until the movable cutting tool 13 is pushed open; then, when the pressure of the mud pump 5 drops from B3 to B1, the mud pump 5 is shut off.

[0044] During this process, as the high-pressure water flows towards the bottom of the hole, it pushes the rubber plug 3 to the center of the open-closed PDC drill bit 1 at the bottom of the hole. During this process, the pressure of the mud pump 5 is relatively low. When the rubber plug 3 enters the center hole, it is obstructed and cannot move forward; the pressure of the high-pressure water flow increases, and the pressure of the mud pump 5 rises, causing the thrust acting on the rubber plug 3 to increase synchronously until it pushes open the movable cutting tool 13. The high-pressure water pushes the rubber plug 3 out of the center open-closed PDC drill bit 1. At this point, the high-pressure water flow channel is fully restored, the pressure of the mud pump 5 drops, and the mud pump 5 is shut off.

[0045] 2.5 Inject cement grout Disconnect the water supply device 4 and inject grout into the inner hole of the casing 2 (the grout in the inner hole will be cleaned later) or the annulus between the outer wall of the casing 2 and the hole wall; after the grout solidifies, the construction of casing section L1 is completed.

[0046] Step 3: Constructing the casing section L2 The casing section is constructed using a directional drilling tool combination or a conventional drilling tool combination with a diameter of d0, so that the borehole enters the stable formation according to the design trajectory.

[0047] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A casing drill bit for traversing complex and fractured strata, comprising a casing (2) and a center-opening / closing drill bit (1), wherein the center-opening / closing drill bit (1) comprises a drill bit body (11), wherein a center hole is formed in the center of the drill bit body (11), and a fixed cutting tool (12) and a movable cutting tool (13) are provided at the front end of the drill bit body (11), wherein the movable cutting tool (13) can be opened under pressure; characterized in that: The front end of the drill bit body (11) is provided with a water passage (14) for cleaning the hole. The working end of the casing (2) is connected to the rear end of the drill bit body (11); A rubber plug (3) is placed inside the casing (2). The rubber plug (3) is driven into the center hole of the drill body (11) under pressure, which opens the movable cutting tool (13).

2. The casing drill string for traversing complex and fractured strata according to claim 1, characterized in that: The movable cutting tool (13) is connected to the front end of the drill body (11) by a hinge.

3. The casing drill string for traversing complex and fractured strata according to claim 2, characterized in that: The sleeve (2) is formed by connecting the rod units in sequence.

4. The casing drill string for traversing complex and fractured strata according to claim 3, characterized in that: The rod unit includes a rod (23), one side of which is fixed with an externally threaded male connector (21) and the other side is fixed with an internally threaded female connector (22); the male connector (21) of the previous rod unit is threadedly connected to the female connector (22) of the next rod unit, and all rod units are connected in sequence to form a sleeve (2).

5. The casing drill string for traversing complex and fractured strata according to claim 4, characterized in that: The outer wall of the casing (2) is provided with a spiral conveyor belt (24) for slag discharge.

6. The casing drill string for traversing complex and fractured formations according to claim 1 or 5, characterized in that: The rubber stopper (3) is driven by a pressurized flushing medium.

7. The casing drill string for traversing complex and fractured strata according to claim 6, characterized in that: The rinsing medium is high-pressure water.

8. The casing drill string for traversing complex and fractured formations according to claim 7, characterized in that: The connecting end of the casing (2) is connected to the water supply device (4), the water supply device (4) is connected to the mud pump (5), and the mud pump (5) inputs high-pressure water into the casing (2) through the water supply device (4).

9. The casing drill string for traversing complex and fractured formations according to claim 8, characterized in that: The rear end of the drill bit body (11) is threadedly connected to the male connector (21) at the working end of the casing (2).

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