A method for recovering a trajectory of branch grouting and hole cleaning in directional drilling of a rock formation

Abstract

The present application relates to the technical field of geological engineering in coal mine underground, and provides a broken rock stratum directional drilling branch grouting and holing trajectory recovery method, which comprises the following steps: S1, identifying the branch position and hole collapse in the broken rock stratum directional drilling, and determining the target section needing grouting reinforcement; S2, injecting slurry into the target section, filling the branch, hole collapse and rock stratum fissure, and realizing hole wall reinforcement; S3, after the slurry solidifies, using a directional drilling machine to perform secondary holing on the reinforced target section along the original drilling design trajectory, and dredging the target section drilling; S4, after the holing is completed, trying to find back the original drilling trajectory, if successful, withdrawing the directional drilling tool, and continuing subsequent drilling construction or installing a fracturing tool string; if unsuccessful, re-conducting new drilling near the original drilling; the present application realizes accurate positioning of the drilling bottom broken area, efficient filling of the drilling bottom hole collapse and branch, and stable hole wall structure, and guarantees smooth installation of the subsequent fracturing tool string or continuous drilling.

Description

Technical Field

[0001] This invention relates to the field of underground geological engineering technology in coal mines, and in particular to a method for restoring the trajectory of branch grouting in directional drilling in fractured rock strata. Background Technology

[0002] In engineering projects such as hydraulic fracturing of coal mine roofs, oil and gas resource development, and geological exploration, directional drilling technology is widely used in engineering construction under complex geological conditions because it can precisely control the drilling trajectory and achieve long-distance drilling.

[0003] However, when encountering fractured rock formations, the poor integrity and well-developed fissures of the rock strata can easily lead to problems such as borehole collapse and borehole branching during drilling. Borehole branching, in particular, can obstruct the descent of the drill string and cause deviations from the designed path. Improper handling can not only result in borehole abandonment and increased project costs, but may also trigger downhole safety accidents.

[0004] Currently, the main methods for dealing with borehole branches in fractured rock formations include re-drilling abandoned holes, casing isolation, and grouting reinforcement. Although re-drilling abandoned holes is simple to operate, it has the disadvantages of extended construction period and increased cost. Casing isolation technology is only suitable for shallow branch treatment and is difficult to effectively isolate long branches in deep holes. Summary of the Invention

[0005] This invention provides a method for restoring the trajectory of branch grouting in directional drilling of fractured rock strata. This method addresses the shortcomings of existing technologies in coal mines where directional drilling in fractured rock strata is prone to hole collapse and branching at the bottom, leading to jamming of fracturing tool strings and preventing their lowering. Furthermore, traditional methods are ill-suited to complex underground conditions. The method achieves precise positioning of the fractured area at the bottom of the borehole, efficient filling of collapsed and branched sections, and stabilization of the borehole wall structure. This ensures the smooth installation of subsequent fracturing tool strings or continued drilling, while simultaneously reducing engineering costs, shortening the construction period, and ensuring underground construction safety.

[0006] This invention provides a method for restoring the grouting trajectory of directional drilling branches in fractured rock strata, comprising the following steps: Step S1: Identify the branch locations and borehole collapse conditions within the directional borehole of the fractured rock strata, and determine the target section that needs grouting reinforcement; Step S2: Inject grout into the target section to fill branches, collapsed holes and rock fissures, thereby reinforcing the borehole wall; Step S3: After the grout has solidified, a directional drilling rig is used to perform secondary drilling along the original borehole design trajectory to clear the target section after reinforcement. Step S4: After the hole is removed, try to find the original borehole trajectory. If the retrieval is successful, exit the directional drilling tool and continue subsequent drilling or install the fracturing tool string. If the retrieval fails, drill a new hole near the original borehole.

[0007] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, in step S1, the target section ranges of branches and collapsed holes are determined through drilling construction records, downhole trajectory monitoring data and the sticking position of the on-site tool string.

[0008] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, injecting grout into the target section in step S2 includes: At the drill hole opening corresponding to the determined target section, install a grouting casing, a hole opening grouting device and a grouting pipeline. The hole opening grouting device integrates a high-pressure valve, a pressure sensor and a pressure relief valve. The grouting pipeline connects the grouting power unit and the grout preparation unit. The grouting power unit is a pneumatic grouting pump or a mud pump truck matched with a directional drill rig, and the grout preparation unit is a pneumatic mixing barrel.

[0009] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, the grouting casing has a length of 3-5m and a casing diameter of 146mm. Before grouting, the casing is sealed and fixed with a mixed grout of cement and water glass, and the downhole grouting is carried out after the casing fixing grout solidifies.

[0010] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, the grout is a nano-modified single-fluid grouting material KCZ-1, KCZ-3, or a cement grout prepared from 325# ordinary Portland cement, the water-cement ratio of the grout is (0.7-1.0):1, and the grouting pressure is controlled at 5-10MPa.

[0011] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, on-site samples of the grout are taken during the grouting process to test the initial setting time and strength.

[0012] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, during the secondary hole reaming process in step S3, the drill hole trajectory is monitored in real time, and the drilling parameters are adjusted through the directional drill rig to ensure that the reaming trajectory is consistent with the original designed drill hole trajectory.

[0013] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, after the secondary hole reaming is completed, the rock cuttings in the drill hole are cleaned before withdrawing the directional drilling tool, and then the fracturing tool string is installed. During the installation process, the running resistance of the tool string is monitored in real time. If the resistance exceeds a preset value, stop running and recheck the condition inside the drill hole.

[0014] According to the method for recovering the trajectory of directional drilling branch grouting and hole reaming in broken rock strata provided by the present invention, when retrieving the original drill hole trajectory in step S4, the real-time drilling trajectory is compared with the original designed trajectory through the trajectory measurement system of the directional drill rig. If the trajectory deviation is less than 500mm, it is determined that the retrieval is successful; if the deviation is greater than 500mm and cannot be corrected continuously, it is determined that the retrieval fails.

[0015] According to the method for restoring the grouting trajectory of directional drilling branches in fractured rock strata provided by the present invention, when re-drilling a new hole in step S4, the horizontal distance between the new hole and the original hole shall not be less than 5m.

[0016] This invention provides a method for restoring the trajectory of branch grouting in directional drilling of fractured rock strata. Through multi-dimensional identification methods combining drill string lowering resistance monitoring, drill trajectory re-measurement, and in-hole imaging detection, the method accurately locates the branch section's position and extension range. Grouting fills the branch holes and fissures, forming a reinforced layer, thus solving the problem of borehole wall instability caused by branch grouting in fractured rock strata and preventing borehole wall collapse during secondary drilling. Using directional drilling equipment and a trajectory monitoring unit, secondary drilling is performed along the original design trajectory, and trajectory deviations are compared in real time. Parameter adjustments are made to restore the original trajectory, eliminating the need to abandon already constructed long borehole sections as in traditional abandoned borehole re-drilling schemes. This significantly reduces drilling workload, ensures drilling continuity, and guarantees the smooth lowering of the fracturing tool string to the designed depth. Compared to traditional abandoned borehole re-drilling, this method shortens the construction period and avoids the additional costs of new borehole construction, balancing technical reliability and economic rationality. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for restoring the trajectory of branch grouting in directional drilling of fractured rock strata, provided in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the branch grouting state of directional drilling into fractured rock strata provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] The following is combined with Figures 1-2 This invention describes a method for restoring the grouting trajectory of directional drilling branches in fractured rock strata.

[0022] This invention provides a method for restoring the grouting trajectory of directional drilling branches in fractured rock strata, comprising the following steps: Step S1: Identify the branch locations and borehole collapse conditions within the directional borehole of the fractured rock strata, and determine the target section that needs grouting reinforcement.

[0023] Step S2: Inject grout into the target section to fill branches, collapsed holes and rock fissures, thereby reinforcing the borehole wall.

[0024] Step S3: After the grout has solidified, a directional drilling rig is used to perform secondary drilling along the original borehole design trajectory to clear the target section.

[0025] Step S4: After the hole is removed, try to find the original borehole trajectory. If the retrieval is successful, exit the directional drilling tool and continue subsequent drilling or install the fracturing tool string. If the retrieval fails, drill a new hole near the original borehole.

[0026] As can be seen from the above scheme, the present invention uses a multi-dimensional identification method combining drill string lowering resistance monitoring, borehole trajectory re-measurement, and in-hole imaging detection to accurately locate the branch hole section and its extension range. By grouting to fill the branch hole and fissures, a reinforcing layer is formed, solving the problem of borehole wall instability caused by fractured rock branch and avoiding borehole wall collapse during secondary drilling. By using directional drilling equipment and trajectory monitoring unit, secondary drilling is carried out along the original design trajectory and the trajectory deviation is compared in real time. The original trajectory is retrieved by adjusting parameters. Unlike the traditional abandoned borehole re-drilling scheme, it does not require abandoning the already constructed long hole section, greatly reducing the amount of drilling work, ensuring the continuity of drilling function, and ensuring that the fracturing tool string can be successfully lowered to the design depth. Compared to traditional methods of re-drilling abandoned holes, this method shortens the construction period while avoiding the additional costs of constructing new holes, thus balancing technical reliability and economic rationality.

[0027] In this embodiment, in step S1, the target section range of the branch and the collapsed hole is determined by drilling construction records, borehole trajectory monitoring data, and the location of tool string jamming on site. This invention is for directional boreholes already drilled in fractured rock strata. When the installation of the fracturing tool string is obstructed, the location of the branch section and the extension range of the branch are determined by monitoring the resistance of the drill string descent, re-measuring the borehole trajectory, and in-hole imaging detection. The directional borehole is a hydraulic fracturing directional long borehole in the roof of the coal mine working face. For example, the branch section is located at a drilling depth of 120-150m and the borehole diameter is 120mm.

[0028] In some embodiments, a three-in-one branch positioning technology integrating drilling resistance monitoring, trajectory re-measurement, and in-hole imaging can be used, and the specific operation is as follows: By installing a tension sensor with a measuring range of 0-50kN at the top of the fracturing tool string, the output signal of the sensor is transmitted to the surface operation console through a wired connection. When the running resistance of the tool string suddenly increases or irregular fluctuations occur, it is determined that there is a branch hole or hole collapse. By adopting an electromagnetic measurement while drilling instrument, the full-section trajectory of the borehole is re-measured starting from the orifice, and coordinate data is recorded every 5m of drilling. By comparing with the originally designed trajectory, the depth and coordinate deviation of the branch deviation point are determined. By selecting an underground high-definition camera with a diameter of 50mm, the aperture change of the branch hole section, the degree of hole collapse and the extension direction of the branch are visually observed. The camera has waterproof (IP68) and pressure-resistant (20MPa) properties, with a resolution of no less than 1080P. The camera is lowered to the suspected branch hole section through a cable to shoot the aperture, quantity and hole collapse situation of the branch hole section, and generate an in-hole imaging report. Through the above technologies, the positioning accuracy of the branch hole section and the identification accuracy of branch parameters (quantity, aperture, extension length) are improved.

[0029] In this embodiment, injecting slurry into the target section in step S2 includes: installing a grouting casing, an orifice grouting device and a grouting pipeline at the borehole orifice corresponding to the determined target section. The orifice grouting device integrates a high-pressure valve, a pressure sensor and a pressure relief valve. The grouting pipeline connects the grouting power unit and the slurry preparation unit. The grouting power unit is a pneumatic grouting pump or a mud pump truck supporting a directional drilling rig, and the slurry preparation unit is a pneumatic mixing barrel.

[0030] Optionally, the high-pressure valve is a gate valve conforming to API6A standard, with a nominal pressure of no less than 16MPa. The pressure sensor has an accuracy class of no less than 0.5, a measuring range of 0-20MPa, and an output signal of 4-20mA analog quantity, which can transmit pressure data to the on-site operation console in real time for the convenience of operators to monitor. The pressure relief valve adopts a pilot-operated structure, and the set pressure relief pressure is 10±0.5MPa. When the system pressure exceeds the set value, it will automatically open for pressure relief, and the pressure relief port faces the non-sidewalk side of the roadway. The length of the pressure relief pipe is no less than 1.5m, and a splash-proof baffle is arranged at the end to prevent the slurry from spraying and injuring people. In addition, the orifice grouting device is also equipped with a slurry backflow prevention valve, which adopts a one-way valve structure with an opening pressure of no more than 0.3MPa and a closing sealing pressure of no less than 10MPa, so as to prevent the slurry in the borehole from flowing back and polluting the pipeline after grouting is completed.

[0031] Optionally, the grouting casing is 3-5m long, made of seamless steel pipe with a diameter of 146mm, a wall thickness of not less than 8mm, and made of 20# high-quality carbon steel. Its inner wall roughness Ra≤6.3μm is used to avoid excessive resistance to grout flow. The outer wall of the casing is provided with annular anti-slip bosses with a boss spacing of 300mm and a boss height of 5mm to enhance the bonding strength between the casing and the grouting body on the borehole wall and prevent the casing from shifting under grouting pressure. The grouting power unit is a pneumatic grouting pump of model 2ZBQ12 / 10 or a mud pump truck matched with a directional drilling rig, and the grout preparation unit is a pneumatic mixing tank of model JQW-100S.

[0032] In some embodiments, the casing also includes a casing fixing assembly, comprising a rubber sealing ring and an expansion anchoring clip. The rubber sealing ring is made of nitrile rubber and is disposed at both ends of the casing to achieve initial sealing between the casing and the borehole wall. The expansion anchoring clips are arranged at 1m intervals along the axial direction of the casing. The clips are driven to open by the grouting pressure to form a mechanical anchor with the borehole wall, further improving the stability of the casing. Furthermore, before grouting, the casing is sealed and fixed with a mixture of cement (nano-modified single-liquid grout KCZ-1, KCZ-3 or 325# ordinary silicate cement) and water glass (sodium silicate). After the grout has solidified, grouting is performed inside the borehole. In this way, the solidification of the mixed grout forms a sealing barrier and anchoring structure, providing a stable borehole environment for subsequent branch grouting and filling.

[0033] like Figure 2 As shown, after the sealing grout has solidified, the grouting power unit is started to inject the prepared grout into the branch hole section at a grouting pressure of 5-10MPa, ensuring that the grout fills the branch hole, crack and collapsed area, forming a hole wall reinforcement layer.

[0034] In some embodiments, the grout is a cement grout prepared with nano-modified single-component grouting material KCZ-1, KCZ-3 or 325# ordinary Portland cement, with a water-cement ratio of (0.7-1.0):1, and the grouting pressure is controlled at 5-10MPa. During the preparation of the grout, a pneumatic mixing tank is used for mixing, for example, the mixing speed is 60-120r / min, and the mixing time is not less than 10min. During the mixing process, an external concentration meter is connected through the grout concentration monitoring interface to adjust the water-cement ratio in real time to ensure the uniformity of the grout.

[0035] It should be noted that KCZ is an abbreviation for mining grouting. KCZ-1 and KCZ-3 are used for coal seams and rock strata, respectively. The composition is the same as that disclosed in the existing patent CN116144040B, which will not be repeated here.

[0036] In some feasible embodiments, the grout is sampled on-site during the grouting process to test the initial setting time and strength. For example, after the grout is prepared, three grout samples of the same volume are taken and cured at the ambient temperature in the well. The compressive strength is tested at 12h, 24h and 48h using a pressure testing machine. When the compressive strength at 24h is not less than 3MPa, it is determined that the design initial setting strength has been reached and secondary hole removal can be carried out.

[0037] This setup allows for timely detection of slurry mix ratio deviations or the impact of environmental factors (temperature, humidity) on performance through on-site sampling and testing. For example, in engineering projects, adjusting the water-cement ratio can solve the problem of excessively long initial setting time, and increasing the water glass content can enhance the strength of the two-component slurry. This ensures that each batch of slurry meets the design standards and avoids problems such as incomplete branch filling and failure of hole wall reinforcement due to substandard slurry performance.

[0038] In this embodiment, the grouting process adopts the intermittent grouting method. For example, after grouting for 10-15 minutes, the pump is stopped for 5-8 minutes, and this is repeated 3-4 times. During this period, the pressure change in the hole is monitored by a pressure sensor. When the pressure continues to rise and stabilizes at the designed final pressure, it is determined that the branch is filled densely. If the pressure does not rise or drops, it is determined that there is grout leakage. Manual sealing or injection of two-component grout is used to plug the leak. The curing speed of the two-component grout is controlled by adjusting the water glass dosage to ensure that the grout flow time is not less than 5 minutes.

[0039] In step S3 of this implementation, the drilling trajectory is monitored in real time during the secondary hole-cutting process, and the drilling parameters are adjusted by the directional drilling rig to ensure that the hole-cutting trajectory is consistent with the original drilling design trajectory.

[0040] Specifically, after the grout reaches the designed initial setting strength, the grouting device at the borehole is removed, and directional drilling equipment is deployed. The directional drilling equipment can be a combination of a Φ120mm PDC drill bit and a Φ89mm directional drill string. The drill string is equipped with a trajectory measurement unit to monitor the drilling trajectory in real time. The trajectory measurement unit can be an electromagnetic measurement while drilling instrument with a measurement accuracy of ±0.5° azimuth and ±0.1° inclination. The actual trajectory coordinates are recorded every 5m of drilling and compared with the original design trajectory. The deviation is corrected by adjusting the inclination and azimuth of the drilling rig.

[0041] During the secondary drilling, a Φ100mm pilot drill bit is first used to enlarge the hole, and then a 120mm PDC drill bit is used for finishing. During the enlargement process, the drill bit is lowered at a uniform speed to avoid the collapse of the hole wall due to excessive drilling speed. After the grouting reinforcement section is cleared, low displacement and low drilling pressure are used to drill and gradually explore the original borehole channel. When the resistance of the drill bit is restored to normal and the trajectory measurement unit shows that it coincides with the original design trajectory, it is determined that the original trajectory has been successfully retrieved.

[0042] It should be noted that after the secondary drilling is completed, the rock cuttings inside the hole should be cleaned before the directional drilling tool is removed, and then the fracturing tool string should be installed. During the installation process, the resistance of the tool string during descent should be monitored in real time. If the resistance exceeds the preset value, the descent should be stopped and the condition inside the hole should be re-checked.

[0043] In step S4, when retrieving the original borehole trajectory, the real-time drilling trajectory is compared with the original design trajectory using the trajectory measurement system of the directional drilling rig. If the trajectory deviation is less than 500mm, it is determined that the retrieval was successful; if the deviation is greater than 500mm and cannot be corrected, it is determined that the retrieval failed.

[0044] In some embodiments, if the original borehole trajectory cannot be found after multiple attempts in step S4, a new directional borehole is drilled near the original borehole. The horizontal distance between the new borehole and the original borehole is not less than 5m. The borehole coordinates are adjusted according to the coordinates of the branch deviation point of the original borehole. The design trajectory of the new borehole is arranged parallel to the design trajectory of the original borehole. For example, the vertical height from the top of the coal seam is still 36m, the borehole azimuth is 246°, the inclination is 7°, the sloping section is 285m, the straight section is 453m, and the final borehole depth is 744m.

[0045] Optionally, during the construction of new directional boreholes, an advanced detection process is adopted. That is, when drilling reaches the depth corresponding to the branch section of the original borehole 10m before reaching the original borehole, the drilling speed is reduced, and the rock strata in the borehole are closely monitored through the measurement while drilling system. If new branch signs are found, low-pressure grouting (2-4MPa) is used for pretreatment in advance to prevent the new borehole from branching.

[0046] In this embodiment, a warning zone is set up 5m before and after the grouting construction site, and personnel are strictly prohibited from passing through. During grouting, the construction personnel stand on the upwind side, at least 3m away from the grouting point. The pump must be stopped and the pressure released before disconnecting or connecting the grouting pipeline. The air pipe and liquid pipe are connected with U-shaped clamps and then tied with iron wire. First aid equipment, including stretchers, first aid kits, burn dressings, etc., is provided at the construction site, and the on-site personnel are familiar with the location of the first aid equipment and how to use it.

[0047] In this embodiment, quality acceptance is carried out after construction is completed: the grouting quality is tested by drilling sonic testing to detect the rock mass integrity coefficient of the grouting reinforced section, which is required to be no less than 0.8; the secondary hole-cutting quality is tested by in-hole video inspection, which requires that the hole wall be flat, without obvious hole collapse, and the hole diameter deviation not exceed ±5mm; the original trajectory recovery accuracy is tested by trajectory retesting, which requires that the actual trajectory deviate from the original design trajectory in the vertical direction not exceed 0.2m and in the horizontal direction not exceed 0.3m.

[0048] This invention is based on the technical concept of first reinforcing and then repairing. First, the location and extension range of the branch hole section are accurately located. Second, grout is injected into the branch hole section to fill the branch hole and cracks, while reinforcing the hole wall to form a stable grouting-reinforced section. Third, a second borehole is excavated in the grouting-reinforced section using directional drilling equipment. During the excavation process, the drilling trajectory is monitored in real time, and the trajectory deviation is corrected by adjusting the drilling parameters. Finally, after the excavation passes through the grouting-reinforced section, the original borehole trajectory is gradually recovered, and subsequent drilling and fracturing operations are resumed.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering the trajectory of branch grouting in directional drilling of fractured rock strata, characterized in that, comprising the following steps: Step S1: Identify the branch positions and hole collapse conditions in the directional borehole of the broken rock stratum, and determine the target section requiring grouting reinforcement; determine the range of the target section of branches and hole collapses through borehole construction records, in-borehole trajectory monitoring data and the sticking position of the on-site tool string; Step S2: Inject grout into the target section to fill the branches, hole collapses and rock fractures, so as to realize borehole wall reinforcement; Step S3: After the grout is solidified, use a directional drilling rig to perform secondary reaming on the reinforced target section along the original borehole design trajectory to dredge the borehole of the target section; monitor the borehole trajectory in real time during the secondary reaming process, and adjust the drilling parameters through the directional drilling rig to ensure that the reaming trajectory is consistent with the original borehole design trajectory; Step S4: After the reaming is completed, attempt to retrieve the original borehole trajectory. If the retrieval is successful, withdraw the directional drilling tool, and proceed with subsequent borehole construction or install the fracturing tool string; if the retrieval fails, construct a new borehole near the original borehole. When retrieving the original borehole trajectory, compare the real-time drilling trajectory with the original design trajectory through the trajectory measurement system of the directional drilling rig. If the trajectory deviation is less than 500mm, the retrieval is determined to be successful; if the deviation is greater than 500mm and cannot be corrected continuously, the retrieval is determined to be failed.

2. The method for restoring the grouted hole trajectory of directional drilling in fractured rock strata according to claim 1, characterized in that, Injecting grout into the target section in step S2 comprises: Installing a grouting casing, a borehole grouting device and a grouting pipeline at the borehole orifice corresponding to the determined target section, wherein the borehole grouting device integrates a high-pressure valve, a pressure sensor and a pressure relief valve, the grouting pipeline connects the grouting power unit and the grout preparation unit, the grouting power unit is a pneumatic grouting pump or a mud pump truck matched with the directional drilling rig, and the grout preparation unit is a pneumatic mixing barrel.

3. The method for restoring the grouted hole trajectory of directional drilling in fractured rock strata according to claim 2, characterized in that, The grouting casing has a length of 3-5m and a casing diameter of 146mm. Before grouting, the casing is sealed and fixed with a mixed grout of cement and water glass, and the in-borehole grouting is performed after the casing fixing grout is solidified.

4. The method for restoring the grouted hole trajectory of directional drilling branches in fractured rock strata according to claim 1, characterized in that, The grout is a cement grout prepared from nano-modified single-fluid grouting materials KCZ-1, KCZ-3 or 325# ordinary Portland cement, the water-cement ratio of the grout is (0.7-1.0):1, and the grouting pressure is controlled at 5-10MPa.

5. The method for restoring the grouted hole trajectory of directional drilling in fractured rock strata according to claim 4, characterized in that, On-site samples of the grout are retained during the grouting process to test the initial setting time and strength.

6. The method for restoring the grouted hole trajectory of directional drilling branches in fractured rock strata according to claim 1, characterized in that, After the secondary reaming is completed, the rock cuttings in the borehole are cleaned before withdrawing the directional drilling tool, and then the fracturing tool string is installed. During the installation process, the lowering resistance of the tool string is monitored in real time. If the resistance exceeds a preset value, stop lowering and recheck the conditions inside the borehole.

7. The method for restoring the grouted hole trajectory of directional drilling in fractured rock strata according to claim 1, characterized in that, When constructing a new borehole again in step S4, the horizontal spacing between the new borehole and the original borehole is no less than 5m.

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