High-temperature and high-pressure rock mass in-situ drilling sealing and hydraulic fracturing experiment method

Abstract

The invention provides a high-temperature and high-pressure rock mass in-situ drilling sealing and hydraulic fracturing experiment method which comprises the following steps: S1, placing a drill bit device at a rock mass sample drilling position, and coaxially placing a drill bit sleeve at the tail part of the drill bit device; s2, a drill bit device is started for drilling; when the drill bit device drills, the drill bit sleeve synchronously extends into a drill hole; s3, when the drill bit device drills to a designated position, a drill bit sleeve extends into the bottom of the hole; s4, assembling a hollow water injection fracturing steel pipe; s5, the drill bit device is pulled out, and the drill bit sleeve is reserved; s6, the fracturing steel pipe sleeve is coaxially arranged in the drill bit sleeve; the fracturing steel pipe sleeve is pushed to the bottom of the hole; s7, the drill bit sleeve is taken out; and S8, a nut is used for sealing, and a high-pressure pump is connected for hydraulic fracturing operation. The method is simple and convenient to operate, and rapid and mechanical sealing between the hydraulic fracturing pipe and the hole wall can be achieved after in-situ drilling of the high-temperature and high-pressure large-size rock mass is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of large-size rock mass hydraulic fracturing experiments, and particularly relates to a high-temperature and high-pressure rock mass in-situ borehole sealing and hydraulic fracturing experiment method. BACKGROUND

[0002] In the fields of deep geothermal energy development and oil and gas exploration, it is crucial to carry out in-situ hydraulic fracturing experiments of large-size rock mass under high-temperature and high-pressure environment for studying rock mass fracture mechanism, evaluating reservoir fracturing property and engineering barrier integrity. Such experiments usually need to insert a fracturing pipe into a pre-set borehole and inject high-pressure fluid under simulated deep environment (high temperature and high pressure) to induce crack propagation.

[0003] The existing hydraulic fracturing experiments of large-size samples usually adopt an experimental process of “sealing at normal temperature first after the borehole is completed, and then installing the fracturing pipe and fracturing again”. The process of installing the fracturing pipe is complicated, and the traditional sealing materials (such as ordinary rubber sealing ring and unhardened cement) are prone to sealing failure under high temperature and high pressure, which leads to high-pressure fluid channeling or leakage along the pipe wall. At the same time, the experimental data obtained by fracturing after sealing are quite different from the in-situ characteristics of large-size rock mass under high-temperature and high-pressure environment. Meanwhile, the existing fracturing pipe has the following defects: (1) The sealing effect depends on the close contact of the rubber ring with the connecting pipe and the air bag with the hole wall. If the borehole has local diameter expansion, diameter reduction or uneven hole wall, the rubber ring cannot completely fill the gap, and the air bag is prone to uneven stress after expansion, so the fluid is easy to leak from the gap during fracturing. The rigid spring may be compressed excessively and fail under high temperature and high pressure, and cannot block the channeling of high-pressure fluid. The number of components is large and closely related, and the operation time is long.

[0004] (2) Whether it is a triple-sealed hole sealer or a double-sealed hole sealing device, the structure is relatively complex and contains multiple components. During installation in the well, it is necessary to accurately install and connect each component, which is tedious and difficult to install, and is prone to installation errors or component damage, affecting the sealing effect and construction progress. At the same time, the sealing capsule has certain limitations. After actual use, the capsule may be damaged, stick to debris, etc., and is easy to be further damaged during the recovery process, affecting its repeated use efficiency. The structure of the PVC pipe and the variable diameter area in the hole sealer needs to be well adapted to the borehole. If the borehole diameter is not uniform or there is local diameter expansion or reduction, it will affect the installation and sealing effect of the hole sealer.

[0005] (3) The air bag elastic material is prone to thermal aging at high temperature, resulting in a decrease in the expansion performance, and even local rupture; the protective shell has a rigid structure, and the thermal expansion coefficient thereof is greatly different from that of the air bag at high temperature, so that the air bag is easily extruded to generate cracks, and the long-term sealing requirement under high-temperature working conditions cannot be met; the protective shell is heavy and slides in dependence on the guide rod sliding groove, and if there is slight bending or diameter fluctuation in the drilling hole, the protective shell is easily stuck in the hole wall and cannot be moved, increasing the installation difficulty.

[0006] Therefore, it is necessary to provide an improved technical solution for the above-mentioned deficiencies of the prior art. SUMMARY

[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a test device and method capable of realizing rapid and mechanized sealing between a hydraulic fracturing pipe and a hole wall after a high-temperature and high-pressure large-size rock mass in-situ drilling is completed, so as to solve or alleviate the problems existing in the prior art.

[0008] In order to achieve the above-mentioned purpose, the present application provides the following technical solution: The present application provides a high-temperature and high-pressure rock mass in-situ drilling sealing method, and the improvement lies in that the drilling sealing method comprises the following steps: step S1, placing a drilling head device 1 at a rock mass sample drilling position, and coaxially placing a drilling head sleeve 2 at the tail of the drilling head device 1; The drilling head device 1 comprises a hydraulic drilling head 1-2; the tail end of the hydraulic drilling head 1-2 is connected with a hydraulic drilling rod 1-3; a sharp protrusion 1-1 is arranged on the top of the front end of the hydraulic drilling head 1-2; and a retractable hydraulic side blade 1-4 is arranged on the circumferential side of the front end of the hydraulic drilling head 1-2; Step S2, starting the drilling head device 1 to drill a hole; while the drilling head device 1 is drilling, the drilling head sleeve 2 is synchronously inserted into the drilling hole; Step S3, when the drilling head device 1 drills to a specified position, the drilling head sleeve 2 is inserted into the hole bottom; Step S4, assembling a hollow water fracturing steel pipe, comprising: placing the hollow water fracturing steel pipe in a fracturing steel pipe sleeve 3, and placing the plugging material and graphite gasket at equal intervals; Step S5, extracting the drilling head device 1, and leaving the drilling head sleeve 2; Step S6, coaxially arranging the fracturing steel pipe sleeve 3 of the assembled hollow water fracturing steel pipe in the drilling head sleeve 2; and pushing the fracturing steel pipe sleeve 3 of the assembled hollow water fracturing steel pipe to the hole bottom by using an alloy push rod; Step S7, taking out the drilling head sleeve 2; Step S8, sealing the plugging material and graphite gasket by using an annular metal gasket and an external thread nut, and after the plugging material and graphite gasket are stable, connecting a high-pressure pump to perform hydraulic fracturing operation.

[0009] Preferably, the retractable hydraulic side blade 1-4 is arranged on the outer wall of the hydraulic drill bit 1-2; the retractable hydraulic side blade 1-4 comprises a blade arranged axially parallel to the hydraulic drill bit 1-2 and circumferentially added to the outer wall of the hydraulic drill bit 1-2.

[0010] Preferably, the hydraulic drill bit 1-2 comprises: The sliding block 13 is arranged at the inner center of the hydraulic drill bit 1-2 and close to the front end of the hydraulic drill bit; The connecting rod 14 comprises a retractable rod; one end of the connecting rod 14 is connected to the sliding block 13, and the other end of the connecting rod 14 is connected to the blade of the retractable hydraulic side blade 1-4; The hydraulic drill bit 1-2 further comprises a spring 12, one end of the spring 12 is connected to the sliding block 13, and the other end of the spring 12 is connected to the inner front end of the hydraulic drill bit 1-2; The hydraulic drill bit 1-2 further comprises a sliding block blocking ring 11 arranged on the upper end of the central pipe, which is an annular protrusion integrated with the hydraulic drill bit.

[0011] Preferably, step S3 further comprises: when the drill bit device 1 reaches the specified position, blowing away the debris in the hole; the drill bit sleeve 2 further comprises pressure-in wind pipes arranged axially symmetrically on both sides of the drill bit sleeve 2; the diameter of the pressure-in wind pipe matches the width of the retractable hydraulic side blade 1-4 when it is fully extended.

[0012] Preferably, the hollow water injection fracturing steel pipe is a hollow steel pipe, and a thread axially added as an anti-skid pattern is arranged on the outer wall of the hollow water injection fracturing steel pipe; a protrusion is arranged at the bottom of the hollow water injection fracturing steel pipe, and two radially symmetrical through holes are arranged inside the protrusion.

[0013] Preferably, step S4 further comprises: cross-sleeving the plugging material 5 and the graphite gasket 6 on the hollow water injection fracturing steel pipe; the plugging material 5 comprises a sleeve; and the graphite gasket 6 comprises a grommet.

[0014] Preferably, step S7 comprises: step S7-1, determining that the fracturing steel pipe sleeve 3 has been pushed to the bottom of the hole and is stable; and step S7-2, placing a receiving tray at the drilling hole to collect the falling debris during the extraction process.

[0015] Preferably, step S8 further comprises step S8-1, annular metal gasket installation, comprising: S8-1-1, before installation, ensuring that the annular metal gasket is smooth, undamaged, and free of debris, and that the plugging material and the graphite gasket are cross-sleeved at the designed interval, with the lowermost being the graphite gasket; S8-1-2, aligning the high-temperature-resistant metal push rod axially with the outer wall of the annular metal gasket, and making the fracturing steel pipe sleeve 3 fit the annular metal gasket; S8-1-3, by the high-temperature-resistant metal push rod, the annular metal washer is pushed to the plugging material direction; S8-1-4, the high-temperature-resistant metal push rod is taken out, the distance between the annular metal washer and the drill hole wall is measured by a ruler, and it is confirmed that the hollow water fracturing steel pipe is in the drill hole center; at the same time, the plugging material is pushed by a metal thin rod, and it is checked whether the plugging material is fastened, loose or displaced.

[0016] Preferably, step S8 further comprises step S8-2, wherein the external thread nut is installed by using a special installation tool: one end of the external thread nut is an elongated hexagonal outer contour, and the external thread nut is installed by using a hexagonal external thread nut installation sleeve matched with the outer contour; Step S8-2-1, before installation, it is ensured that the external thread nut thread is not damaged and has no debris, and the plugging material 5 and the graphite washer 6 and the annular metal washer 7 have been installed in place according to the design; Step S8-2-2, the groove end of the external thread nut installation sleeve is aligned with the elongated hexagonal outer wall of the external thread nut, and is sleeved in the axial direction, so that the external thread nut installation sleeve is completely matched with the elongated hexagonal outer contour of the external thread nut; the coaxiality of the external thread nut and the hollow water fracturing steel pipe is ensured by visual inspection or ruler calibration; Step S8-2-3, the external thread nut installation sleeve is rotated by a torque wrench to drive the external thread nut, and the position of the external thread nut is observed in real time during the driving process, so that the external thread nut is in close contact with the annular metal washer below to form the last support; Step S8-2-4, the external thread nut installation sleeve is removed, and the fastening degree of the external thread nut is checked by pushing the external thread nut with a metal thin rod.

[0017] The application also relates to a hydraulic fracturing experiment method, which is improved in that the hydraulic fracturing experiment method comprises the following steps: Step S1, placing a rock mass sample in a high-temperature and high-pressure fracturing cabin and checking the experiment equipment; Step S2, applying confining pressure, axial pressure and high temperature to the rock mass sample, so that the core reaches an in-situ high-temperature and high-pressure state; Step S3, drilling and sealing the rock mass sample by using the above method; Step S4, performing a hydraulic fracturing experiment.

[0018] Compared with the closest prior art, the technical scheme of the application has the following beneficial effects: (1) The plugging material can dynamically adjust the plugging shape and expansion pressure according to different drill hole wall conditions and sealing requirements, thereby improving the reliability and durability of sealing. In addition, the plugging material can be recycled and reused, thereby reducing material waste during construction and having environmental benefits.

[0019] (2) The graphite gasket used has a very low creep relaxation rate, can keep sufficient sealing specific pressure for a long time, and ensures the durability of the seal. Meanwhile, the graphite gasket has excellent high-temperature and high-pressure resistance and corrosion resistance, ensures the continuous operation of the fracturing operation, improves the efficiency, and saves the cost.

[0020] (3) The hydraulic drill bit side blade used has scalability, can be directly pulled out through the sleeve after the drilling is completed, and avoids the influence of the sample breakage on the experiment.

[0021] (4) The sleeve used not only blows out the debris, but also ensures the safe pulling out of the drill bit. Meanwhile, the sleeve keeps the high-temperature and high-pressure in-situ state of the sample, and if the large-size rock mass sample is soft rock, the sleeve can better maintain the in-situ state, and enhances the accuracy of the test.

[0022] (5) The use of the annular metal gasket and the external thread nut not only provides the bottom support of the sealing material, but also ensures that the hollow water fracturing steel pipe is always in the center position of the drilling hole. Meanwhile, the problem that the sealing material blocks the water outlet due to excessive expansion is avoided, and the smooth operation of the hydraulic fracturing is ensured.

[0023] (6) The hollow water fracturing steel pipe adopts a three-hole structure design on the opposite side and the bottom, which can increase the effect of hydraulic fracturing on a specific position. The sealing material can be more evenly stressed during the expansion process, so as to better fill the gap between the drilling hole and the steel pipe, effectively preventing water leakage. Meanwhile, the smooth hollow water fracturing steel pipe can increase the adhesion and sealing effect between the hollow water fracturing steel pipe and the sealing material, effectively preventing the hollow water fracturing steel pipe from collapsing and leaking during the water injection process.

[0024] (7) The present application has fewer main components, and the functions of each component are clear, the installation process is simple, and the safety hidden trouble caused by the installation is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings accompanying the specification of the present application serve to provide a further understanding of the present application, the illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application. Among them: Figure 1 is a schematic diagram of the hydraulic drill bit involved in the present application; Figure 2 is a schematic diagram of the internal structure of the hydraulic drill bit involved in the present application Figure 3 is a schematic diagram of the hydraulic drill rod involved in the present application; Figure 4 is a schematic diagram of the sleeve involved in the present application; Figure 5 is a schematic diagram of the drill bit side blade extension and the drill bit sleeve on the drill bit; Figure 6Drill to the designated position schematic diagram involved in the present application; Figure 7 Drill bit side blade retraction schematic diagram involved in the present application; Figure 8 Fracturing steel pipe sleeve into the plugging device after connecting drill bit sleeve schematic diagram involved in the present application; Figure 9 Hollow water injection fracturing steel pipe schematic diagram involved in the present application; Figure 10 Push the plugging device to the hole bottom schematic diagram involved in the present application; Figure 11 Plugging completion schematic diagram involved in the present application; Figure 12 External thread nut structure schematic diagram involved in the present application; Figure 13 Water injection fracturing experiment schematic diagram involved in the present application;

[0026] BRIEF DESCRIPTION OF DRAWINGS 1, drill device; 1-2, hydraulic drill bit; 1-3, hydraulic drill rod; 1-4, retractable hydraulic side blade; 2, drill bit sleeve; 3, fracturing steel pipe sleeve; 4, hollow water injection fracturing steel pipe; 5, plugging material; 6, graphite gasket; 7, annular metal gasket, 8, external thread nut, 9, hollow water injection fracturing steel pipe, 10, press-in air pipe; 11, sliding block blocking ring; 12, spring; 13, sliding block; 14, connecting rod. DETAILED DESCRIPTION

[0027] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application, rather than limiting the present application. In fact, those skilled in the art will appreciate that modifications and variations can be made in the present application without departing from the scope or spirit of the present application. For example, features shown or described as part of one embodiment can be used in another embodiment to create yet another embodiment. It is therefore desired that the present application encompass such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0028] In the following description, the terms "first / second / third" are merely to distinguish similar objects, and do not represent a specific order of the objects. Understandably, the "first / second / third" can be interchanged with a specific order or sequence as allowed, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description herein is for the purpose of describing embodiments of the present disclosure only and is not intended to be limiting of the present disclosure.

[0030] In the description of the present application, the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and are not required to be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The terms "connected", "connected", "provided" used in the present application should be understood broadly, for example, it can be fixed connection or detachable connection; it can be directly connected or indirectly connected through intermediate components; it can be wired electrical connection, wireless electrical connection or wireless communication signal connection, and the specific meaning of the above terms can be understood by those skilled in the art according to the specific circumstances.

[0031] The present application relates to a hydraulic fracturing pipe sealing method, which is improved in that the sealing method comprises the following steps: Step S1, placing the drill bit device 1 at the drilling position of the large-size rock mass sample, and coaxially placing the drill bit sleeve 2 at the tail of the drill bit device 1.

[0032] Step S2, starting the drill bit device 1, and rotating the drill bit device 1 to drill; while the drill bit device 1 is drilling, the drill bit sleeve 2 is synchronously extended into the drill hole.

[0033] Preferably, as shown in Figure 1 The drill bit device 1 comprises a hydraulic drill bit 1-2; the hydraulic drill bit 1-2 is connected with a hydraulic drill rod 1-3 at the tail end; a sharp protrusion 1-1 is arranged at the top of the front end of the hydraulic drill bit 1-2; a retractable hydraulic side blade 1-4 is arranged on the circumferential side of the front end of the hydraulic drill bit 1-2, which is controlled to extend and retract by hydraulic pressure.

[0034] The retractable hydraulic side blade 1-4 is arranged on the outer wall of the hydraulic drill bit 1-2; the retractable hydraulic side blade 1-4 comprises a blade arranged axially parallel to the hydraulic drill bit 1-2 and added along the circumference of the outer wall of the hydraulic drill bit 1-2; the number of blades is set according to actual conditions.

[0035] As shown in Figure 2 The front part of the hydraulic drill bit 1-2 is a receiving cavity for arranging the retractable hydraulic side blade 1-4; the rear part of the hydraulic drill bit 1-2 is a solid structure with a central pipeline. The hydraulic drill bit 1-2 comprises: A sliding block 13 is arranged at the inner central position of the hydraulic drill bit 1-2 and close to the front end of the hydraulic drill bit.

[0036] Link 14 includes a telescopic rod-like component. One end of link 14 is connected to slider 13, and the other end is connected to the cutting edge of telescopic hydraulic side blade 1-4. The number of link 14 is determined based on the number of cutting edges, ensuring that each link 14 connects to one cutting edge. The telescopic rod-like component comprises two connected, relatively sliding rods, thereby enabling the extension and retraction of link 14. Preferably, the telescopic rod-like component consists of two coaxially connected sleeves, with the first sleeve capable of sliding within the second sleeve.

[0037] The hydraulic drill bit 1-2 also includes a spring 12, one end of which is connected to the slider 13, and the other end of which is connected to the front end of the hydraulic drill bit 1-2.

[0038] The hydraulic drill bit 1-2 also includes a slider blocking ring 11, which is located at the upper end of the central pipe. It is a ring-shaped protrusion directly cut out during the machining of the hydraulic drill bit and is integrated with the hydraulic drill bit. When the work is finished, the slider blocking ring 11 can block the slider 13 to prevent the slider from falling out.

[0039] Among them, such as Figure 3 As shown, one end of the hydraulic drill rod 1-3 has an external thread that connects to the hydraulic drill bit 1-2, for use during drilling. The other end of the hydraulic drill rod 1-3 has an internal thread. When the drilling depth is relatively deep, the length of the first drill rod is insufficient to continue drilling, requiring the connection of subsequent drill rods. The external thread ends of the latter two drill rods are connected to the internal thread end of the former drill rod. The hollow hydraulic drill rod 1-3 is used to deliver hydraulic pressure, enabling the extension and retraction of the retractable hydraulic side cutting edge 1-4. Specifically, the hydraulic system injects hydraulic fluid into the hydraulic drill bit through the hydraulic drill rod 1-3, pushing the slider 13, which in turn drives the connecting rod 14 to push the cutting edge until it is fully extended. When the work is finished, the hydraulic system releases the hydraulic pressure and returns the hydraulic fluid. The spring 12 pushes the slider 13 back, and simultaneously pulls the side cutting edge to retract via the connecting rod 14.

[0040] Among them, such as Figure 4 As shown, the drill bit sleeve 2 is a hollow tube, and its diameter matches the diameter of the hydraulic drill bit 1-2. Preferably, the drill bit sleeve 2 is made of a high-temperature resistant alloy. An internal thread is provided inside the drill bit sleeve 2, and an external thread is provided on the outer wall of the hydraulic drill bit 1-2, connecting the drill bit sleeve 2 to the hydraulic drill bit 1-2 via a threaded connection. This ensures that the drill bit sleeve 2 does not detach from the hydraulic drill bit 1-2 during drilling.

[0041] Step S3, as follows Figures 5 to 7 As shown, when the drill bit device 1 drills to the designated position, the drill bit sleeve 2 is inserted into the bottom of the hole.

[0042] Specifically, step S3 includes: when the drill bit device 1 drills to the designated position, blowing away the debris in the hole. The hydraulic device stops and pumps back the hydraulic fluid, and the retractable hydraulic side blade 1-4 is retracted after the drill sleeve 2 is extended into the hole bottom. When the hydraulic system releases the hydraulic pressure and the hydraulic fluid is withdrawn, the spring 12 can push the slider 13 back, and at the same time, the side blade is retracted by pulling the side blade through the connecting rod 14, so as to realize the retracting of the retractable hydraulic side blade 1-4. The slider blocking ring 11 can also block the slider 13 to prevent the slider from falling out.

[0043] Preferably, in order to handle the debris in the hole, a press-in air pipe is also arranged on both sides of the drill sleeve 2 which is axisymmetric, and the hydraulic drill 1-2 is air-cooled through the press-in air pipe, and at the same time, the drill cuttings of the hydraulic drill 1-2 can be cleaned, and the metal mesh arranged at the air outlet port of the air pipe can block the large debris. The press-in air pipe can be connected with the air compressor at the free end of the drill sleeve 2 to provide high-pressure airflow. The high-pressure airflow cools the hydraulic drill 1-2 through the press-in air pipe. The press-in air pipe is made of the same material as the sleeve and is welded inside the sleeve and arranged on both sides symmetrically. The diameter of the press-in air pipe matches the width of the hydraulic side blade when the hydraulic side blade is fully extended. The length of the press-in air pipe matches the length of the drill sleeve 2.

[0044] Step S4, as shown in Figures 8 to 10 , assembling the hollow water injection fracturing steel pipe includes: placing the hollow water injection fracturing steel pipe in the fracturing steel pipe sleeve 3, and placing the sealing material and graphite gasket at equal intervals.

[0045] Specifically, the hollow water injection fracturing steel pipe is a smooth hollow steel pipe, which can increase the adhesion between the sealing material and prevent the subsequent water injection process from leaking and the steel pipe from collapsing. Preferably, the axial direction of the hollow water injection fracturing steel pipe is a through hole, and a protrusion is arranged at the bottom of the hollow water injection fracturing steel pipe, and two radial through holes are arranged symmetrically inside the protrusion, forming a three-hole structure design of the hollow water injection fracturing steel pipe and the bottom, which can increase the effect of hydraulic fracturing at a specific position. It can also make the sealing material more evenly stressed during expansion, so as to better fill the gap between the drill hole and the steel pipe and effectively prevent water leakage.

[0046] The sealing material 5 and the graphite gasket 6 are cross-mounted on the hollow water injection fracturing steel pipe. The sealing material 5 is in the shape of a sleeve and is made of high-temperature and high-pressure resistant material; the graphite gasket 6 is a gasket. The size of the sealing material 5 and the graphite gasket 6 is set according to the actual situation, and the inner diameter matches the diameter of the hollow water injection fracturing steel pipe; the outer diameter is smaller than the inner diameter of the fracturing steel pipe sleeve 3.

[0047] The sealing material can be regarded as the first sealing material, which can expand under certain temperature and pressure to increase the sealing effect. The graphite gasket is regarded as the second sealing material, which is tightly combined with the hollow water injection fracturing steel pipe, strengthens the sealing material, prevents it from collapsing, and plays a fixed sealing role.

[0048] Step S5: Remove drill bit assembly 1, retaining drill bit sleeve 2. Specifically, when removing drill bit assembly 1, the hydraulic pressure must be completely released via the hydraulic device to ensure the retractable hydraulic side cutting edge is fully retracted, preventing the side cutting edge from scraping the borehole wall or the inner wall of the drill bit sleeve, which could cause damage to the borehole wall or deformation of the side cutting edge or sleeve. High-pressure airflow must be continuously supplied through a pressurized air duct to clean debris from the borehole until all debris is blown out. The removal process must be smooth to prevent loosening of the threaded connection between the hydraulic drill rod and the hydraulic drill bit.

[0049] Step S6: The fracturing steel pipe sleeve 3 of the assembled hollow water injection fracturing steel pipe is coaxially installed inside the drill bit sleeve 2; the fracturing steel pipe sleeve 3 of the assembled hollow water injection fracturing steel pipe is pushed to the bottom of the hole using an alloy push rod.

[0050] Specifically, when advancing the fracturing steel pipe casing 3 using an alloy push rod, it is necessary to push at a uniform speed to avoid excessive impact force that could cause the graphite gasket inside the fracturing steel pipe casing 3 to detach from the fracturing steel pipe, or cause abnormal engagement between the external thread of the casing and the internal thread of the drill bit sleeve 2. Before advancing the fracturing steel pipe casing 3, it is necessary to confirm that the sealing material 5 and the graphite gasket 6 are properly and cross-fitted onto the hollow water injection fracturing steel pipe at the designed spacing, without any looseness or misalignment; at the same time, check whether the inner wall of the fracturing steel pipe casing 3 is smooth and without protrusions to prevent scratching the sealing material during advancement, which would affect the sealing performance.

[0051] Step S7: Remove the drill bit sleeve 2. Specifically, in step S7-1, before removing the drill bit sleeve 2, check whether the fracturing steel pipe sleeve 3 has been pushed to the bottom of the hole and is stable. This is to prevent the fracturing steel pipe sleeve from shifting during the removal of the drill bit sleeve due to its lack of fixation, which could lead to misalignment of the sealing material. At the same time, wear high-temperature resistant gloves when removing the drill bit sleeve 2 to avoid direct contact with the high temperature of the sleeve. In step S7-2, place a receiving tray at the borehole opening to collect any debris that may fall during the removal process.

[0052] Step S8, as follows Figure 11 As shown, the sealing material is sealed with an annular metal washer 7 and an external thread nut 8. After the sealing material stabilizes, a high-pressure pump is connected to carry out hydraulic fracturing operations.

[0053] The annular metal washer, considered the third sealing material, is made of high-temperature resistant material and is directly pushed in using a high-temperature resistant metal push rod. It is used to tighten the first and second sealing materials and achieve a sealing effect. The external threaded nut, considered the fourth sealing material, is installed using a special installation tool and tightened onto the external testing device to complete the final seal.

[0054] In step S8-1, the annular metal gasket is installed, including: in step S8-1-1, before the annular metal gasket is installed, it is ensured that the annular metal gasket is smooth, undamaged, and free of debris, and the plugging material and the graphite gasket are cross-wrapped at a designed interval, with the graphite gasket at the bottom. In step S8-1-2, the high-temperature-resistant metal push rod is aligned with the outer wall of the annular metal gasket in the axial direction, and it is ensured that the fracturing steel pipe sleeve 3 is completely attached to the annular metal gasket; at this time, the annular metal gasket needs to be aligned with the hollow water injection fracturing steel pipe, and the alignment is checked by visual observation or a ruler, to ensure that the annular metal gasket is coaxial with the steel pipe. In step S8-1-3, the annular metal gasket is pushed towards the plugging material by the high-temperature-resistant metal push rod, and the position of the annular metal gasket is observed in real time during the pushing process, to ensure that it is in close contact with the plugging material below. In step S8-1-4, the high-temperature-resistant metal push rod is removed, the distance between the annular metal gasket and the wall of the drill hole is measured by a ruler, and it is confirmed that the hollow water injection fracturing steel pipe is at the center of the drill hole; at the same time, the plugging material is gently pushed by a metal rod, to check whether the plugging material is loose or displaced.

[0055] In step S8-2, the external thread nut is installed by using a special installation tool, including: one end of the external thread nut is an elongated hexagonal outer contour, which is installed by a special hexagonal installation sleeve matched with the outer contour. Specifically, as shown in Figure 12 , the center of the external thread nut is a through hole, including an integrally formed hexagonal outer contour and a cylindrical protrusion. The outer diameter of the cylindrical protrusion matches the diameter of the drill hole, and a thread is arranged on the outer wall of the cylindrical protrusion, to facilitate installation with the drill hole. The length of the cylindrical protrusion is designed according to actual experimental needs. The diameter of the hexagonal outer contour is larger than the diameter of the drill hole, to expand the contact range with the outside of the drill hole, so that the hollow water injection fracturing steel pipe is sealed more tightly. In step S8-2-1, before installation, it is ensured that the thread is undamaged and free of debris, and the first, second, and third plugging materials have been installed in place according to the design. In step S8-2-2, the recessed end of the installation sleeve is aligned with the elongated hexagonal outer wall of the external thread nut, and is axially sleeved, to ensure that the installation sleeve is completely attached to the elongated hexagonal outer contour of the external thread nut; the alignment is checked by visual observation or a ruler, to ensure that the external thread nut is coaxial with the hollow water injection fracturing steel pipe. In step S8-2-3, the installation sleeve is rotated by a torque wrench, to drive the external thread nut, and the position of the external thread nut is observed in real time during the driving process, to ensure that it is in close contact with the annular metal gasket below, to form the last support. In step S8-2-4, the installation sleeve is removed, and the external thread nut is gently pushed by a metal rod, to check whether the external thread nut is tightened, and whether it is loose or displaced.

[0056] The application also includes a hydraulic fracturing experiment method, as shown in Figure 13 , first, a cubic rock sample (100-200 mm in length) is subjected to high-pressure oil cylinder loading and high-temperature loading, then it is kept in a high-temperature and high-pressure state, and then drilling, sealing, and fracturing experiments are performed. Specifically, the hydraulic fracturing experiment method includes the following steps: Step SI, the rock sample is placed in the high temperature and high pressure fracturing cabin, and the experimental equipment is checked. Specifically, the experimental equipment checking and preparation includes: SI-1, the rock sample is placed in the high temperature and high pressure fracturing cabin. In the case of no temperature and pressure, the air tightness is checked. SI-2, according to the experimental requirements, clear water or special fracturing fluid is selected as the fracturing fluid medium, and the fluid pipeline is ensured to be free of bubbles. SI-3, the pressure sensor, temperature sensor, displacement sensor and the like are calibrated and zeroed. SI-4, the appropriate sampling frequency is set to capture the instantaneous signals of crack initiation and expansion.

[0057] Step SII, the confining pressure, axial pressure and high temperature are applied to the rock sample, so that the core reaches the in-situ high temperature and high pressure state. Specifically, the experimental loading and simulation includes: SII-1, the confining pressure is applied by the hydraulic servo to make the core bear uniform lateral pressure until the preset in-situ ground stress condition is reached. SII-2, the axial pressure is applied to the core by the piston to create a preset true triaxial stress state. SII-3, the heating system is started to heat the fracturing cabin and the core to the target temperature at a slow heating rate. The temperature and stress are kept stable for a period of time, so that the core inside reaches thermal equilibrium and stress equilibrium, and reaches the in-situ high temperature and high pressure state.

[0058] Step SIII, the rock sample is drilled and sealed by the method mentioned above.

[0059] Step SIV, the hydraulic fracturing experiment is performed. Specifically, the hydraulic fracturing experiment includes: SIV-1, after all the devices are installed and sealed, the hollow water injection fracturing steel pipe is connected to the liquid injection pump, the liquid injection pump is started, and the fracturing fluid (water) with the preset pressure and flow rate is injected into the sample. At the same time, the pressure and flow data at the beginning of the experiment are recorded. SIV-2, the temperature sensor is used to monitor the temperature change of the sample in real time, the pressure sensor is used to monitor the pressure change in the core in real time, and the data are recorded. SIV-3, when the experiment reaches the preset target or cannot continue fracturing, the liquid injection is stopped and the liquid injection pump is turned off, and the experiment is ended.

[0060] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for sealing a borehole drilled in-situ in a high-temperature high-pressure rock mass, characterized in that, The drilling sealing method comprises the following steps: step S1, placing a drill bit device (1) at a drilling position of a rock mass sample, and coaxially placing a drill bit sleeve (2) at the tail of the drill bit device (1); The drill bit device (1) comprises a hydraulic drill bit (1-2); the tail end of the hydraulic drill bit (1-2) is connected with a hydraulic drill rod (1-3); the top of the front end of the hydraulic drill bit (1-2) is provided with a sharp protrusion (1-1); the circumferential side of the front end of the hydraulic drill bit (1-2) is provided with a telescopic hydraulic side blade (1-4). Step S2, starting the drill bit device (1) to drill a hole; while the drill bit device (1) is drilling, the drill bit sleeve (2) is synchronously inserted into the hole. Step S3, when the drill bit device (1) drills to a specified position, the drill bit sleeve (2) is inserted into the bottom of the hole. Step S4, assembling a hollow water injection and fracturing steel pipe, comprising: placing the hollow water injection and fracturing steel pipe in a fracturing steel pipe sleeve (3), and placing the sealing material and graphite gasket at equal intervals. Step S5, pulling out the drill bit device (1) and leaving the drill bit sleeve (2). Step S6, coaxially arranging the fracturing steel pipe sleeve (3) of the assembled hollow water injection and fracturing steel pipe in the drill bit sleeve (2); and pushing the fracturing steel pipe sleeve (3) of the assembled hollow water injection and fracturing steel pipe to the bottom of the hole by using an alloy push rod. Step S7, taking out the drill bit sleeve (2). Step S8, sealing the sealing material and graphite gasket with an annular metal gasket and an external thread nut; after the sealing material and graphite gasket are stable, connecting a high-pressure pump to perform hydraulic fracturing operation.

2. The high temperature and high pressure in-situ borehole sealing method for rock mass according to claim 1, characterized in that, The telescopic hydraulic side blade (1-4) is arranged on the outer wall of the hydraulic drill bit (1-2); the telescopic hydraulic side blade (1-4) comprises a blade arranged axially parallel to the hydraulic drill bit (1-2) and added along the circumference of the outer wall of the hydraulic drill bit (1-2).

3. The method of claim 1, wherein the method is performed in-situ. The hydraulic drill bit (1-2) comprises: A sliding block (13) is arranged at the inner central position of the hydraulic drill bit (1-2) and close to the front end of the hydraulic drill bit; A connecting rod (14) comprises a telescopic rod; one end of the connecting rod (14) is connected with the sliding block (13), and the other end of the connecting rod (14) is connected with the blade of the telescopic hydraulic side blade (1-4); The hydraulic drill bit (1-2) further comprises a spring (12), one end of the spring (12) is connected with the sliding block (13), and the other end of the spring (12) is connected to the front end of the hydraulic drill bit (1-2). The hydraulic drill bit (1-2) further comprises a sliding block blocking ring (11) arranged on the upper end of the central pipeline, which is an annular protrusion integrated with the hydraulic drill bit.

4. The method of claim 1, wherein the method is performed in-situ in a high-temperature, high-pressure rock mass. Step S3 further comprises: when the drill bit device (1) reaches the specified position, blowing away the debris in the hole; the drill bit sleeve (2) further comprises a press-in air pipe arranged axially symmetrically on both sides of the drill bit sleeve (2); the diameter of the press-in air pipe matches the width of the telescopic hydraulic side blade (1-4) when the telescopic hydraulic side blade (1-4) is fully extended.

5. The method of claim 1, wherein the method further comprises, The hollow water injection and fracturing steel pipe is a hollow steel pipe, a thread is added axially on the outer wall of the hollow water injection and fracturing steel pipe as an anti-skid pattern; a protrusion is arranged at the bottom of the hollow water injection and fracturing steel pipe, and two radial through holes are symmetrically arranged in the protrusion.

6. The high temperature and high pressure in situ borehole sealing method for a rock mass according to claim 1, wherein Step S4 further comprises: cross-fitting the plugging material (5) and the graphite gasket (6) on the hollow water fracturing steel pipe; the plugging material (5) comprises a sleeve; and the graphite gasket (6) comprises a gasket.

7. The method of claim 1, wherein the method further comprises, Step S7 comprises: Step S7-1, determining that the fracturing steel pipe sleeve 3 has been pushed to the bottom of the hole and is stable; and Step S7-2, placing a receiving tray at the drilling hole opening to collect the falling debris during the extraction process.

8. The high temperature and high pressure in situ borehole sealing method for a rock mass according to claim 1, wherein Step S8 further comprises Step S8-1, annular metal gasket installation, comprising: S8-1-1, before installation, ensure that the annular metal gasket is smooth, undamaged, and free of debris, and that the plugging material and the graphite gasket have been cross-fitted at the designed spacing, with the lowermost being the graphite gasket; S8-1-2, align the high-temperature-resistant metal push rod along the axis with the outer wall of the annular metal gasket, and press the fracturing steel pipe sleeve 3 against the annular metal gasket; S8-1-3, advance the annular metal gasket in the direction of the plugging material by the high-temperature-resistant metal push rod; S8-1-4, remove the high-temperature-resistant metal push rod, measure the distance between the annular metal gasket and the wall of the drilling hole with a ruler, and confirm that the hollow water fracturing steel pipe is in the center of the drilling hole; at the same time, use a metal rod to gently push the plugging material to check whether the plugging material is tight, loose, or displaced.

9. The method of claim 1, wherein the method is performed in situ in a high-temperature, high-pressure rock mass. Step S8 further comprises Step S8-2, installation of the external thread nut using a special installation tool: one end of the external thread nut is an elongated hexagonal outer contour, which is installed through a hexagonal external thread nut installation sleeve that is adapted to the outer contour; Step S8-2-1, before installation, ensure that the external thread nut is undamaged and free of debris, and that the plugging material (5) and the graphite gasket (6) and the annular metal gasket (7) have been installed at the designed position; Step S8-2-2, align the recessed end of the external thread nut installation sleeve with the elongated hexagonal outer wall of the external thread nut, and axially fit it to ensure that the external thread nut installation sleeve completely fits the elongated hexagonal outer contour of the external thread nut; visually or with a ruler, ensure that the external thread nut is coaxial with the hollow water fracturing steel pipe; Step S8-2-3, turn the external thread nut installation sleeve by a torque wrench to drive the external thread nut, and observe the position of the external thread nut in real time during the driving process to ensure that it is in close contact with the annular metal gasket below, forming the final support; Step S8-2-4, remove the external thread nut installation sleeve, and use a metal rod to gently push the external thread nut to check the tightness of the external thread nut.

10. A method of hydraulic fracturing experiments, characterized by, The hydraulic fracturing experiment method comprises the following steps: Step S1, placing the rock sample into a high-temperature and high-pressure fracturing cabin, and checking the experimental equipment; Step S2, applying confining pressure, axial pressure, and high temperature to the rock sample to make the core reach the in-situ high-temperature and high-pressure state; Step S3, drilling and sealing the rock sample by the method of any one of claims 1-9; Step S4, performing a hydraulic fracturing experiment.

Images