Directional hydraulic fracturing device and method
By guiding high-pressure water to fracture along the preset direction through directional fracturing pipes and sealing devices, combined with intelligent control, the problems of poor directionality and device reusability in hydraulic fracturing technology are solved, achieving efficient and precise rock crushing effects.
Patent Information
- Application Number
- CN202511148820.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-09-23
AI Technical Summary
Existing hydraulic fracturing technology lacks a directional guidance structure, resulting in chaotic fracture development directions, insufficient directional accuracy, poor device reusability, and a lack of real-time feedback and dynamic adjustment, which affects the achievement rate and efficiency of engineering goals.
Directional fracturing pipes, plugging devices, conversion joints and high-pressure water injection equipment are used, combined with multiple directional fractures and pressure monitoring devices to achieve high-pressure water fracturing along the preset direction. High and low pressure water flows are switched through two-speed control valves, and intelligent construction is achieved in combination with pressure monitoring.
It ensures that cracks expand along the preset project path, improves the achievement rate of project goals, reduces equipment costs, and improves construction efficiency and accuracy. It is suitable for engineering scenarios such as mines and tunnels.
Smart Images
Figure CN120684208A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of coal and rock mining, and in particular to a directional hydraulic fracturing device and method. Background Art
[0002] In mining, tunneling, underground engineering construction, and other fields, rock crushing is a critical step in ensuring project progress. Traditional rock crushing methods rely primarily on explosive blasting. While this technology can achieve rapid rock crushing, it has significant drawbacks. First, the shock waves, flying rocks, and toxic gases generated during blasting pose a serious threat to surrounding rock structures, engineering facilities, and the safety of construction workers, making safety and stability difficult to guarantee. Second, the random nature of energy released during blasting makes it difficult to precisely control the direction of rock fracture, which can easily lead to over- or under-fracture, increasing the difficulty of subsequent engineering treatment. This technology is particularly unsuitable for scenarios where pre-defined fracture boundaries are required.
[0003] With the development of engineering technology, hydraulic fracturing has gradually become a mainstream alternative to traditional explosive blasting due to its advantages such as high safety, controllable energy, and low environmental impact. Its principle is to inject high-pressure water into the borehole, using the water pressure to create and expand cracks within the rock, ultimately achieving rock fragmentation. However, in actual engineering applications, directional fracturing remains a core challenge facing hydraulic fracturing technology: most existing hydraulic fracturing devices lack specialized directional guidance structures, and the force of high-pressure water tends to be uniformly distributed along the natural weak points of the rock, random cracks, or along the radial direction of the borehole, resulting in chaotic crack development and failure to expand according to the predetermined engineering path.
[0004] Specifically, existing technologies have the following limitations: First, the directional accuracy is insufficient, making it difficult to ensure that cracks develop preferentially along the specified direction, resulting in a low rate of achievement of engineering goals; second, the device has poor reusability, and some directional structures fail after a single fracturing, increasing engineering costs; third, there is a lack of real-time feedback and dynamic adjustment mechanisms for the development of cracks, making it impossible to optimize subsequent construction parameters based on the previous fracturing effects, further affecting the accuracy and efficiency of directional fracturing. Summary of the Invention
[0005] In order to solve the technical problems existing in the prior art regarding rock crushing, the present invention provides a directional hydraulic fracturing device and method.
[0006] The technical solutions of the present invention are as follows: A directional hydraulic fracturing device, comprising: A directional fracturing tube, the outer diameter of which is smaller than the borehole diameter, can be integrally extended to the pre-splitting position of the borehole, and a water injection channel is provided inside the directional fracturing tube; A plugging device is installed at both ends of the directional fracturing tube. The plugging device is in communication with the directional fracturing tube. When low-pressure water is injected into the directional fracturing tube through the water injection channel, the plugging device can expand and tightly adhere to the inner wall of the borehole, forming a sealed cavity between the directional fracturing tube and the inner wall of the borehole; A conversion joint is provided at one end of the outer plugging device and is used to connect the high-pressure water injection equipment with the water injection channel, and the end of the conversion joint away from the plugging device is connected to the water inlet pipe; Directional fractures are provided around the directional fracturing pipe and are connected to the water injection channel. High-pressure water is sprayed onto the borehole wall through the directional fractures, extending along the length of the directional fracturing pipe. The extension direction forms a preset angle with the axial direction of the directional fracturing pipe, so that the high-pressure water can fracture the inner wall of the borehole along the preset direction to form cracks. High-pressure water injection equipment is connected to the water injection channel of the directional fracturing pipe through a conversion joint and is used to inject water into the directional fracturing pipe; A pressure monitoring device is installed outside the directional fracturing pipe to monitor the water pressure in the sealed cavity in real time; The control device is connected to the high-pressure water injection equipment and is used to control the opening and closing of the high-pressure water injection equipment, as well as to adjust the injection pressure and injection time of the water source, and to receive water pressure data from the pressure monitoring device, to judge the initial cracks and the development status of the cracks, and to judge whether to perform secondary injection of high-pressure water based on the initial cracks and the development status.
[0007] In order to improve the fracturing efficiency and effect and select the actual pre-splitting angle required for drilling, a plurality of directional fractures are opened along the circumference of the directional fracturing tube, and two adjacent directional fractures are distributed at a preset interval along the circumference of the directional fracturing tube.
[0008] In order to increase the pre-cracking area and ensure the pre-cracking effect, the length of the directional pre-cracking is not less than 1 / 2 of the axial extension length of the directional pre-cracking pipe.
[0009] The specific design of the plugging device is that the plugging device includes a plugging sleeve, and a plugging cavity connected to the water injection channel is provided in the plugging sleeve. When low-pressure water is injected into the directional fracturing pipe through the water injection channel, the plugging sleeve can expand and fit tightly to the inner wall of the borehole.
[0010] The specific design of the sealing sleeve is that the sealing sleeve is a cylindrical structure, and its outer end surface is provided with multiple layers of annular corrugations arranged in the axial direction, and the outer peripheral end surface of the annular corrugations is set to be pointed, and the tips of the annular corrugations of the upper and lower groups of sealing sleeves are inclined in opposite directions.
[0011] To facilitate plugging and ensure the length of the sealed cavity after plugging, improve the pre-splitting length and pre-splitting effect, the plugging sleeve is made of an elastic material, and in the initial state, the maximum outer diameter of the plugging sleeve is not less than the inner diameter of the drill hole, and the length of the directional fracturing tube is 3-4 times that of the plugging sleeve.
[0012] The fracturing device further includes a two-stage control valve for switching the water pressure introduced into the directional fracturing tube, which is installed on the water inlet pipe and includes: A high-pressure cartridge valve that can directly transfer the large flow rate and high pressure of the high-pressure water source to the directional fracturing tube; A low-pressure proportional valve that can convert the high-pressure input into a stable low-flow and low-pressure water flow and transfer it to the directional fracturing tube; An electromagnetic reversing valve: realizes rapid switching of the valve core through electromagnetic drive, and controls the on-off states of the high-pressure cartridge valve and the low-pressure proportional valve respectively and the directional fracturing tube.
[0013] A directional hydraulic fracturing method using the described directional hydraulic fracturing device, which is characterized by including the following steps: S10: Drill a hole based on the rock formation to be pre-fractured; S20: Assemble and connect the directional pre-fracturing tube, plugging device, and adapter to the water inlet pipe, and after assembly, extend them to the pre-fracturing position of the drill hole; S30: Pre-fracture the pre-fracturing position; S310: Formation of the sealed cavity, Control to open the high-pressure water injection device, and switch to low-pressure water through the two-stage control valve to communicate with the water inlet pipe. The low-pressure water enters the injection channel and the plugging sleeve, causing the plugging sleeve to collide, and a sealed cavity is formed between the upper and lower groups of plugging sleeves; S320: Formation of the initial cracks on the inner wall of the drill hole, Control the two-stage control valve to switch to high-pressure water to communicate with the water inlet pipe. The high-pressure water is discharged at the directional fracture position through the injection channel and fractures the rock formation. The inner wall of the drill hole forms initial cracks under the instant impact of the high-pressure water; S40: Detection of pressure decay in the transition stage, After the initial cracks are formed, switch to low-pressure water within the time t1, record the pressure P_end of the pressure monitoring device at the end of the impact and the pressure P_pass after t1, and calculate the pressure decay rate v1, v1 = (P_end - P_pass) / t1, If v1 ≥ v_std, it indicates that the initial cracks have been formed, and proceed to step S50; If v1 < v_std, it is determined that the initial cracks have not been effectively formed, then control the plugging sleeve to shrink after pressure relief to drain the water in the sealed cavity, and repeat step S30; Where v_std is the judgment threshold of the pressure decay rate for whether effective initial cracks are formed at this pre-fracturing position; S50: Detection of cracks in the pressure holding stage; Continue to flow low-pressure water for t2 time, record the initial pressure Pover and the stable pressure Pstable after t2 time, calculate the pressure rise slope k, where k = (Pstable-Pover) / t2, If k≤kmark, indicating that the crack development in the pressure holding stage meets the standard, step S60 is executed; If k>k mark, indicating that the crack expansion is insufficient during the pressure holding stage, the plugging sleeve is controlled to shrink after pressure relief to discharge the water in the sealing cavity, and step S30 is repeated; Where k is the threshold value for the pressure rise slope after the crack is formed at the pre-crack position; S60: Control and shut down the high-pressure water injection equipment and the two-speed control valve, remove the fracturing device, observe the pre-crack position through the borehole peep instrument, determine the development position of the crack, and then determine the next pre-crack position; S70: Repeat steps S30-S60 to open a crack at the next pre-crack position.
[0014] In step S50, when k>k mark, low-pressure water is first continuously introduced for time t3 before controlling the pressure relief, and the pressure rise slope k is recalculated. If k>k mark at this time, step S30 is performed, otherwise step S60 is performed.
[0015] In order to monitor pressure changes conveniently and quickly, the pressure sensor is a high-frequency dynamic pressure sensor, which is installed close to and completely avoids the directional crack.
[0016] The beneficial effects of the present invention are as follows: the present invention provides a directional hydraulic fracturing device and method. By using directional cracks with preset angles on the directional fracturing tube and a sealed cavity formed by a plugging device, high-pressure water can be guided to act concentratedly on the borehole wall along a preset direction. This solves the problems of random and poorly directional energy release from traditional explosive blasting, as well as the defect of disordered crack development in existing hydraulic fracturing devices. It ensures that cracks expand along the preset project path, significantly improving the achievement rate of project goals. The plugging device is made of elastic material and has a specific structural design. It can be re-used by shrinking after pressure relief, avoiding the problem of some directional structures failing after a single crack in existing technologies, significantly reducing engineering equipment costs. The two-speed control valve setting enables efficient switching between high-pressure impact and low-pressure holding, eliminating the need for frequent equipment replacement, further improving the practicality and cost-effectiveness of the device. Crack detection can be completed without removing the fracturing device, avoiding the time loss and crack status distortion caused by the removal-test-replacement process in existing technologies. In existing technologies, after the fracturing device is removed, the pressure release in the borehole may cause the formed cracks to close or change their shape, resulting in a deviation between the detection results and the actual crack status. However, this solution monitors the water pressure in the sealed chamber and completes the detection while the crack remains in its initial state, ensuring that the data truly reflects the initiation and expansion of the crack, improving the accuracy and timeliness of crack detection. By simplifying the process and reducing ineffective operations, it significantly improves the construction efficiency of directional fracturing. It is particularly suitable for engineering scenarios such as mines and tunnels with high continuity requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] By reading the detailed description of the preferred embodiment below, the solutions and advantages of the present application will become clear to those skilled in the art. The accompanying drawings are only for illustrating the preferred embodiment and are not to be considered as limiting the present invention.
[0018] In the attached figure: Figure 1 A schematic diagram of the use of the fracturing device; Figure 2 This is the side view of the directional fracturing tube; Figure 3 Schematic diagram of adjusting the position of the fracturing device; The components represented by the reference numerals in the figure are: 1. Directional fracturing pipe; 2. Drilling hole; 3. Plugging device; 4. Sealing chamber; 5. Adapter; 6. High-pressure water injection equipment; 7. Water inlet pipe; 8. Directional fracturing; 9. Fracturing; 10. Pressure monitoring device; 11. Two-speed control valve. DETAILED DESCRIPTION
[0019] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. It should be noted that these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. The present disclosure can be implemented in various forms and should not be limited by the embodiments described herein.
[0020] Example The directional hydraulic fracturing device described in this embodiment is an integrated device designed for directional rock crushing in mining, tunneling, and other projects. Its core goal is to achieve precise guidance and efficient expansion of fractures through structural optimization and intelligent control, while also balancing the device's reusability and ease of operation. The overall structure and working mechanism of the device are as follows: The directional hydraulic fracturing device in this embodiment specifically includes a directional fracturing pipe 1, combined with Figure 1 and Figure 2The directional fracturing tube 1 is made of high-strength alloy material and has an outer diameter smaller than the aperture of the borehole 2. In this solution, its outer diameter is strictly controlled to be 5%-10% smaller than the aperture of the borehole 2 to ensure that the entire tube can smoothly extend into any pre-cracking position in the borehole 2. A water injection channel is provided inside the directional fracturing tube 1, and the inner wall of the channel is precisely polished to reduce water flow resistance to ensure pressure transmission efficiency. The high-pressure water outlet hole in the existing technology is short in length (usually a local opening with a small aperture) and can only act on a very small area in the borehole, which cannot meet the needs of long-section pre-cracking. The device needs to be frequently moved and adjusted to cover the entire hole section, which is cumbersome to operate. In this solution, a plurality of directional cracks 8 are distributed circumferentially on the tube body of the directional fracturing tube 1, all of which are connected to the water injection channel. These cracks 9 extend along the length direction of the directional fracturing tube 1, and the extension direction of each crack 9 can be at a certain preset angle to the axial direction of the tube body, which can be adjusted according to engineering requirements. Single-stage fracturing provides a wider coverage area, enabling efficient directional pre-fracture of long boreholes and reducing the number of device movements. Furthermore, existing technologies have a small number of high-pressure water outlet holes with fixed orientations, making it impossible to flexibly adjust the fracturing direction according to project requirements (e.g., when multiple sets of intersecting fractures are required). In this solution, two adjacent directional fractures 8 are spaced at a preset interval along the circumference of the directional fracturing tube 1 (i.e., spaced at a preset arc), forming multi-directional pressure injection channels. This allows high-pressure water to fracture the inner wall of the borehole 2 in a preset direction, forming cracks 9. This not only meets the need for concentrated fracturing in a single direction, but also enables the simultaneous development of multiple fractures through angle combinations. In this embodiment, two directional fractures 8 are provided along the circumference of the directional fracturing tube 1, spaced 180 degrees apart, and parallel to the length of the directional fracturing tube 1.
[0021] Based on the above structure, the length of each directional crack 8 is not less than 1 / 2 of the total axial length of the directional fracturing tube 1 to ensure sufficient pre-cracking range and avoid the deviation of the fracture direction caused by local stress concentration.
[0022] In the prior art, two sealing capsules are usually installed on the outside of the water delivery pipe. By opening a water hole connected to the water delivery pipe, low-pressure water is delivered to the sealing capsule so that it collides with the inner wall of the drill hole. Although it can achieve a certain sealing effect, there are corners and resistances in the water flow during the delivery process, resulting in a delay in pressure transmission when the low-pressure water is injected and a slow expansion speed of the capsule. In this embodiment, combined with Figure 1 and Figure 2A sealing device 3 is installed at both ends of the directional fracturing tube 1. The sealing device 3 is made of an elastic material, such as rubber, and includes a cylindrical sealing sleeve. The sealing device 3 has a sealing cavity within it, which is connected to the directional fracturing tube 1. When low-pressure water is injected into the directional fracturing tube 1 through the water injection channel, the sealing device 3 expands and tightly adheres to the inner wall of the borehole 2, forming a sealed cavity 4 between the directional fracturing tube 1 and the inner wall of the borehole 2. The two sealing devices 3 are directly connected to the directional fracturing tube 1, and water pressure is quickly transmitted to the sealing cavity, causing the sealing sleeve to quickly expand and adhere to the inner wall of the borehole 2, thereby improving sealing efficiency.
[0023] It should be noted that, in its initial state, the maximum outer diameter of the plugging sleeve is slightly larger than the inner diameter of borehole 2, facilitating a quick initial fit after the device is placed in borehole 2. When low-pressure water is injected, the plugging sleeve expands due to the pressure within the cavity, and the multiple layers of annular corrugations on its outer end face tightly press against the inner wall of borehole 2, forming a reliable seal. Existing plugging capsules are independently mounted on the outside of a water pipeline, relying solely on friction or simple snap-fitting to secure the pipeline. Furthermore, the capsule's outer end face is relatively smooth, making it prone to relative misalignment when subjected to high-pressure water impact. In contrast, the outer end face of the plugging sleeve is specially designed with multiple layers of annular corrugations arranged axially. The tips of the annular corrugations of the upper and lower groups of plugging sleeves are tilted in opposite directions (the upper group's tip points downward, the lower group's tip points upward). This reverse friction further enhances the sealing effect and prevents high-pressure water leakage from both ends. The length of the directional fracturing tube 1 is set to 3-4 times the length of a single plugging sleeve to ensure a sufficiently long sealed cavity 4 is formed in the middle after both ends are sealed, meeting the requirements of pre-fractures of varying depths.
[0024] In this scheme, combined with Figure 1 In order to provide a water source with a certain pressure to the directional fracturing pipe 1 and the plugging device 3, a conversion joint 5 is installed at the outer end of the outer plugging device 3. The end away from the plugging device 3 is connected to the water inlet pipe 7. The internal flow channel design ensures that high-pressure water enters the water injection channel without eddy current loss. The other end of the water inlet pipe 7 is connected to the high-pressure water injection equipment 6.
[0025] In addition, different from the prior art, a two-speed control valve 11 is installed on the water inlet pipe 7, which is electrically connected to the control device, including: a high-pressure cartridge valve, which can directly transmit a large flow and high-pressure water flow from a high-pressure water source; a low-pressure proportional valve, which can convert a high-pressure input into a stable low-pressure and small-flow water flow; an electromagnetic reversing valve realizes rapid switching of the valve core through electromagnetic drive, accurately controls the on-off of the high and low pressure water paths and the directional fracturing pipe 1, and controls the electromagnetic reversing valve through the control device to meet the pressure requirements of different stages. By switching during the sealing stage, Low-pressure water is introduced to the low-pressure proportional valve side, using water pressure to expand the plugging sleeve until it is tightly attached to the inner wall of the borehole 2, forming a seal. During the fracturing stage, the valve is switched to the high-pressure cartridge valve side, adopting a "full-open" design. When switched to the impact gear, the valve is fully open, directly transmitting the high pressure and large flow of the water source to the directional fracturing pipe 1, ensuring sufficient instantaneous impact energy. The instantaneous high-pressure water is ejected at the directional fracture 8 to form a crack 9 on the inner wall of the borehole 2. After the crack 9 is formed, the valve is switched to the low-pressure proportional valve side, adopting a "throttling" design. When switched to the pressure-holding gear, the valve reduces the high-pressure input pressure and limits the flow through the precise throttling port, while continuously introducing low-pressure water. The effect of the crack 9 is reflected by observing the water pressure changes in the sealing chamber 4, and then it is determined whether to perform a second high-pressure water impact. Only one high-pressure water injection device 6 is required, distributed through the valve, to meet the needs of both stages, eliminating the need to configure two water sources (a "high-pressure pump" and a "low-pressure pump"), reducing equipment cost and pipeline complexity.
[0026] In this embodiment, to monitor water pressure changes within the sealed chamber 4 and reflect the effectiveness of the crack 9, a pressure monitoring device 10 is designed. This high-frequency dynamic pressure sensor is installed outside the directional fracturing tube 1, near the plugging device 3, and positioned away from the injection range of the directional crack 8 to prevent direct impact from the water flow and affect measurement accuracy. This allows real-time acquisition of water pressure data within the sealed chamber 4. The control device, linked to the high-pressure water injection equipment 6, the two-speed control valve 11, and the pressure sensor, performs three major functions: first, controlling the equipment's start and stop, and adjusting injection pressure and time; second, receiving pressure data and calculating parameters such as the pressure decay rate and rising slope; and third, determining the development status of the crack 9 based on these parameters and automatically deciding whether to perform secondary injection, thus achieving intelligent construction.
[0027] In addition, this solution designs a matching fracturing method based on the above-mentioned directional hydraulic fracturing device, which realizes precise pre-cracking through the closed-loop control of "pre-cracking-detection-adjustment". Specifically, it includes the following steps: The first is the preliminary preparation stage, including steps S10 and S20. S10: Drilling a borehole 2 based on the rock formation to be pre-splitting, and using a drilling rig to drill a borehole 2 with a matching diameter in the target rock formation according to the rock formation pre-splitting design plan.
[0028] S20: Assemble and connect the directional pre-splitting pipe, the plugging device 3, and the adapter 5 to the water inlet pipe 7, connect the high-pressure water injection device 6, and send the assembled body into the pre-splitting position in the borehole 2 through the pushing mechanism to ensure that the directional fracture 8 is aligned with the preset fracture direction.
[0029] Secondly is the pre-splitting stage, including step S30, pre-split the determined pre-splitting position. S310: Formation of the sealing cavity 4. Control to open the high-pressure water injection device 6, and switch to low-pressure water to communicate with the water inlet pipe 7 through the two-stage control valve 11. The low-pressure water enters the plugging cavity through the water injection channel, causing the plugging sleeve to slowly expand and fit the inner wall of the borehole 2, forming a closed sealing cavity 4 between the two end plugging sleeves. At this time, the low-pressure water flows out at the directional fracture 8 and fills the entire sealing cavity 4, providing pre-filled water for the subsequent high-pressure impact, which can reduce the cavity pressure fluctuation during high-pressure water injection and make the impact force more concentrated on the target area corresponding to the directional fracture 8. S320: Formation of the initial crack 9 on the inner wall of the borehole 2. Control the two-stage control valve 11 to switch to high-pressure water to communicate with the water inlet pipe 7. The high-pressure water is discharged at the directional fracture 8 through the water injection channel and fractures the rock formation. The inner wall of the borehole 2 forms an initial crack 9 after being instantaneously impacted by the high-pressure water. The direction of the crack 9 is guided by the preset angle of the fracture 9.
[0030] After the initial crack 9 is formed, in the prior art, the fracturing device is usually directly taken out to pre-split the next pre-splitting position. In this way, the pre-splitting effect of this pre-splitting position cannot be guaranteed. Only after detecting through the borehole 2 peephole, if it does not meet the standard, the direct device is put back again for pre-splitting or directly pre-split the next pre-splitting position twice to ensure the pre-splitting effect. The pre-splitting effect of the pre-splitting position being carried out cannot be detected in real time, resulting in a poor overall pre-splitting effect. Therefore, this solution designs to monitor the effect of the initial crack 9, mainly reflected by the pressure decay in the transition stage, including step S40. After the initial crack 9 is formed, switch to low-pressure water within the time t1, record the pressure P_end of the pressure monitoring device 10 at the end of the impact and the pressure P_pass after t1, and calculate the pressure decay rate v1, v1 = (P_end - P_pass) / t1. If v1 ≥ v_std, it indicates that the initial crack 9 has been formed, and proceed to step S50 to carry out the pressure holding stage to detect the development of the crack 9. If v1 < v_std, it is determined that the initial crack 9 has not been effectively formed. Then control the pressure relief and the plugging sleeve to contract to drain the water in the sealing cavity 4, that is, relieve the water pressure on the plugging device 3, causing the plugging sleeve to contract and drain the water in the sealing cavity 4. Repeat step S30 and conduct another high-pressure water impact. The v mark is the pressure decay rate judgment threshold for whether an effective initial crack 9 is formed at the pre-crack position. This threshold is determined based on indoor experiments, rock mechanical properties and engineering experience. The core logic is that effective cracks 9 must have the ability to quickly relieve pressure. The essence of effective initial cracks 9 is "the formation of a connected pore-crack network inside the rock." High-pressure water can quickly penetrate and relieve pressure through this network, resulting in a sudden drop in pressure; while invalid microcracks (not connected) cannot form a pressure relief channel, and the pressure decays slowly.
[0031] If the initial cracks 9 have met the requirements, the crack 9 development detection is performed, which includes step S50: crack 9 detection during the pressure maintenance phase, continuously passing low-pressure water for time t2, recording the initial pressure Pover and the stable pressure Pstable after time t2. The initial pressure at this time is consistent with the water pressure after time t1 in step S40, and the pressure rise slope k is calculated, where k = (Pstable - Pover) / t2. If k≤kmark, indicating that the crack 9 has developed to the standard during the pressure holding stage, step S60 is executed; If k>k mark, indicating that the crack 9 is insufficiently expanded during the pressure holding stage, the plugging sleeve is controlled to shrink after pressure relief to discharge the water in the sealing cavity 4, and step S30 is repeated; The mark k is the judgment threshold of the pressure rise slope after the crack 9 is formed at the pre-crack position. The water addition flow rate during the continuous pressure maintenance stage is stable. If the crack 9 is large enough (the internal volume continues to increase with expansion), the injected water will preferentially fill the space in the crack 9, resulting in a slow pressure rise in the sealed cavity 4 (small slope). If the crack 9 does not expand effectively (small volume or closed), the injected water cannot be accommodated by the crack 9 and can only accumulate in the sealed cavity 4, resulting in a rapid pressure rise (large slope).
[0032] It should be noted that when k>k mark, that is, when the crack 9 has not expanded sufficiently, low-pressure water should continue to be introduced for time t3 before controlling the pressure relief, so that the crack 9 can continue to develop for a period of time to avoid wasting energy due to another impact due to insufficient development time, and recalculate the pressure rise slope k. If k>k mark at this time, it indicates that the early impact effect of the crack 9 is poor, which affects the subsequent pressure maintenance development. Therefore, the crack 9 needs to be re-impacted, and step S30 is performed. If after maintaining the pressure for t3 time, the rising slope k≤k mark, step S60 is executed.
[0033] Next, the cycle and finishing work of the crack 9 is carried out, including steps S60 and S70, wherein the cycle work includes controlling and closing the high-pressure water injection device 6 and controlling the two-speed control valve 11, taking out the fracturing device, observing the pre-crack position through the borehole 2 peep instrument, determining the development position of the crack 9, and then determining the next pre-crack position. After observation, the next pre-crack area is pre-cracked below the previously formed crack 9 area to ensure the connection of the crack 9. After determining the position, repeat steps S30-S60, combined with Figure 3 , crack 9 is opened at the next pre-crack position until the directional fracturing construction of the entire hole section is completed.
Claims
1. A directional hydraulic fracturing device, characterized in that: include: A directional fracturing tube, the outer diameter of which is smaller than the borehole diameter, can be integrally extended to the pre-splitting position of the borehole, and a water injection channel is provided inside the directional fracturing tube; A plugging device is installed at both ends of the directional fracturing tube. The plugging device is in communication with the directional fracturing tube. When low-pressure water is injected into the directional fracturing tube through the water injection channel, the plugging device can expand and tightly adhere to the inner wall of the borehole, forming a sealed cavity between the directional fracturing tube and the inner wall of the borehole; A conversion joint is provided at one end of the outer plugging device and is used to connect the high-pressure water injection equipment with the water injection channel, and the end of the conversion joint away from the plugging device is connected to the water inlet pipe; Directional fractures are provided around the directional fracturing pipe and are connected to the water injection channel. High-pressure water is sprayed onto the borehole wall through the directional fractures, extending along the length of the directional fracturing pipe. The extension direction forms a preset angle with the axial direction of the directional fracturing pipe, so that the high-pressure water can fracture the inner wall of the borehole along the preset direction to form cracks. High-pressure water injection equipment is connected to the water injection channel of the directional fracturing pipe through a conversion joint and is used to inject water into the directional fracturing pipe; A pressure monitoring device is installed outside the directional fracturing pipe to monitor the water pressure in the sealed cavity in real time; The control device is connected to the high-pressure water injection equipment and is used to control the opening and closing of the high-pressure water injection equipment, as well as to adjust the injection pressure and injection time of the water source, and to receive water pressure data from the pressure monitoring device, to judge the initial cracks and the development status of the cracks, and to judge whether to perform secondary injection of high-pressure water based on the initial cracks and the development status.
2. A directional hydraulic fracturing device according to claim 1, characterized in that: There are multiple directional fractures along the circumference of the directional fracture tube, and two adjacent directional fractures are distributed at a preset interval along the circumference of the directional fracture tube.
3. A directional hydraulic fracturing device according to claim 2, characterized in that: The length of the directional pre-crack is not less than 1 / 2 of the axial extension length of the directional pre-crack pipe.
4. A directional hydraulic fracturing device according to claim 1, characterized in that: The plugging device includes a plugging sleeve, which is provided with a plugging cavity connected to the water injection channel. When low-pressure water is injected into the directional fracturing pipe through the water injection channel, the plugging sleeve can expand and fit tightly to the inner wall of the borehole.
5. A directional hydraulic fracturing device according to claim 4, characterized in that: The sealing sleeve is a cylindrical structure, and its outer end surface is provided with multiple layers of annular corrugations arranged in the axial direction. The outer peripheral end surface of the annular corrugations is set to be pointed, and the tips of the annular corrugations of the upper and lower groups of sealing sleeves are inclined in opposite directions.
6. A directional hydraulic fracturing device according to claim 4, characterized in that: The plugging sleeve is made of elastic material, and in the initial state, the maximum outer diameter of the plugging sleeve is not less than the inner diameter of the borehole, and the length of the directional fracturing tube is 3-4 times the length of a single plugging sleeve.
7. The directional hydraulic fracturing device according to claim 1, characterized in that: The fracturing device also includes a two-speed control valve for switching the water pressure in the directional fracturing pipe, which is installed with the water inlet pipe and electrically connected to the control device, including: High-pressure cartridge valve, capable of transferring high-pressure water flow and high pressure directly to the directional fracturing pipe; Low-pressure proportional valve, which can convert high-pressure input into a stable low-pressure and small-flow water flow and transmit it to the directional fracturing pipe; Solenoid reversing valve: The control device realizes rapid switching of the valve core through electromagnetic drive, controls the high-pressure cartridge valve and the low-pressure proportional valve respectively, and controls the on-off state of the directional fracturing pipe.
8. A directional hydraulic fracturing method, using the directional hydraulic fracturing device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S10: Drilling based on the rock formation to be pre-split; S20: Assemble the directional pre-splitting pipe, the plugging device, and the conversion joint and connect them to the water inlet pipe. After the assembly is completed, extend them to the pre-splitting position of the drilled hole; S30: Pre-split the pre-splitting position; S310: Formation of the sealing cavity, Control to open the high-pressure water injection device, and switch to low-pressure water through the two-stage control valve to connect with the water inlet pipe. The low-pressure water enters the injection channel and the plug sleeve, causing the plug sleeves to collide, and a sealing cavity is formed between the upper and lower groups of plug sleeves; S320: Formation of the initial cracks on the inner wall of the borehole, Control the two-stage control valve to switch to connect the high-pressure water with the water inlet pipe. The high-pressure water is discharged at the directional fracture position through the injection channel and fractures the rock formation. The initial cracks are formed on the inner wall of the borehole by the instantaneous impact of the high-pressure water; S40: Detection of pressure decay in the transition stage, After the initial cracks are formed, switch to low-pressure water within the time t1, record the pressure P_end of the pressure monitoring device at the end of the impact and the pressure P_pass after t1, and calculate the pressure decay rate v1, where v1 = (P_end - P_pass) / t1, If v1 ≥ v_std, it indicates that the initial cracks have been formed, and proceed to step S50; If v1 < v_std, it is determined that the initial cracks have not been effectively formed, then control the plug sleeve to shrink after pressure relief to drain the water in the sealing cavity, and repeat step S30; where v_std is the judgment threshold of the pressure decay rate for whether effective initial cracks are formed at the pre-splitting position; S50: Detection of cracks in the pressure-holding stage; Continuously inject low-pressure water for the time t2, record the starting pressure P_pass and the stable pressure P_stable after the time t2, and calculate the pressure rise slope k, where k = (P_stable - P_pass) / t2, If k ≤ k_std, it indicates that the crack development in the pressure-holding stage meets the standard, and execute step S60; If k > k_std, it indicates that the crack expansion in the pressure-holding stage is insufficient, then control the plug sleeve to shrink after pressure relief to drain the water in the sealing cavity, and repeat step S30; where k_std is the judgment threshold of the pressure rise slope after cracks are formed at the pre-splitting position; S60: Control to close the high-pressure water injection device and the two-stage control valve, remove the fracturing device, observe the pre-splitting position through a borehole peephole to determine the crack development position, and then determine the next pre-splitting position; S70: Repeat steps S30 - S60 to open cracks at the next pre-splitting position until the entire hole section of the borehole is pre-split.
9. A directional hydraulic fracturing method according to claim 8, characterized in that: In step S50, when k > k_std, continue to inject low-pressure water for the time t3 before controlling pressure relief, recalculate the pressure rise slope k. If k > k_std at this time, proceed to step S30, otherwise execute step S60.
10. The directional hydraulic fracturing method according to claim 8, characterized in that: The pressure sensor is a high-frequency dynamic pressure sensor, which is installed close to and entirely avoids the directional fracture.