A device and method for cementing a terminal hole of an upwardly inclined directional long borehole in a coal mine underground

Abstract

The application discloses a kind of coal mine underground upward inclined directional long borehole terminal hole well cementing device and method, including terminal hole casing string, pressure retaining one-way valve and terminal hole well cementing tee joint;The end of terminal hole casing string is connected with pressure retaining one-way valve, and pressure retaining one-way valve can be lowered into borehole with terminal hole casing string;The head end of terminal hole casing string extends out of borehole mouth and is connected with terminal hole well cementing tee joint, and terminal hole well cementing tee joint is installed at borehole mouth.The application establishes the reverse circulation flow of pure cement slurry injected after terminal hole casing is lowered into, and pressure retaining pressure retaining solidifies well, realizes the pressure retaining flow of pure cement slurry in casing outer annulus and fills the whole casing outer annulus space, to realize efficient and high-quality well cementing, effectively seal the annular space between terminal hole casing string and terminal hole, and effectively prevent the difficult problem that fracturing layer section penetrates layer and fracturing effect is poor due to poor terminal hole well cementing quality effect.

Description

Technical Field

[0001] This invention belongs to the field of underground drilling engineering in coal mines, and relates to a cementing device and method for final hole cementing of an upward-inclined directional long borehole in coal mines. Background Technology

[0002] Currently, directional long borehole technology in coal mines is widely used in areas such as gas disaster control, water hazard prevention, and rockburst mitigation. Among these, the directional long borehole segmented fracturing gas extraction technology for coal seam roof fracturing, a method for controlling high-gas coal seams in soft coal seams, has stringent requirements for borehole cementing quality, especially the final cementing quality of the directional long borehole. The final cementing quality of the directional long borehole is crucial to the effectiveness of subsequent segmented fracturing operations; if the cementing quality is poor, the segmented fracturing process is highly susceptible to cross-contamination. Currently, the common cementing method for each stage of directional long boreholes in coal mines is as follows: After drilling is completed, a casing is lowered, and several meters of cement slurry are wrapped around one end of the casing head to seal the annular space of several meters between the casing and the borehole wall (hereinafter referred to as the outer annulus). Then, a thin tube is inserted and passes through the sealing section of the cement slurry, and then a blower is used to inject the required volume of pure cement slurry into the outer annulus through the thin tube, ultimately achieving the cementing and sealing of the gap between the casing and the borehole wall for each stage. This common cementing method is easily affected by irregular or uneven wellbore trajectories, which can easily cause different flow velocities of pure cement slurry in different sections of the outer annulus, resulting in gaps where cement is not filled in certain areas, seriously affecting the cementing quality. At the same time, it is difficult to guarantee the bonding strength between the cement sheath and the borehole wall and casing wall using this method, especially in the final hole cementing process of up-dip directional long boreholes in coal mines, where the above problems are particularly prominent. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a cementing device and method for top-inclination directional long boreholes in coal mines, thereby achieving efficient and high-quality cementing, effectively sealing the annular space between the final borehole casing and the final borehole, and effectively preventing the difficulties caused by poor cementing quality in the final borehole, such as cross-layer fracturing and poor fracturing effect.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A coal mine up-inclination directional long borehole cementing device includes a borehole casing string, a pressure-blocking check valve, and a borehole cementing tee. The end of the borehole casing string is connected to the pressure-blocking check valve, which can be lowered into the borehole along with the borehole casing string. The head end of the borehole casing string extends out of the borehole opening and is connected to the borehole cementing tee, which is installed at the borehole opening.

[0006] The pressure-blocking one-way valve includes a valve body, and also includes a float valve, a float valve positioning rod, a spring, a float valve mounting component I, and a float valve mounting component II, all disposed in the central through hole of the valve body. The valve body has a male thread end and a cement slurry inlet end at its two ends, respectively. The male thread end of the valve body is coaxially connected to the end of the final hole sleeve string, and the cement slurry inlet end faces the bottom of the drill hole. The float valve is connected to one end of the float valve positioning rod, and the spring is sleeved on the float valve positioning rod. The float valve mounting component I has a central hole, and the float valve mounting component II has a guide hole and a central guide hole. The float valve, the float valve positioning rod, and the spring are disposed between the float valve mounting component I and the float valve mounting component II. The spring can apply force to the float valve to block it at the central hole of the float valve mounting component I, and the other end of the float valve positioning rod passes through the central guide hole of the float valve mounting component II.

[0007] The final cementing tee includes a tee body, a transition connecting short casing, a sealing reducer, a double male short casing, and a pressure gauge. The tee body has three ports: a grouting port, a connection port, and a return grout port. The grouting port is connected to the grouting channel. The connection port is installed at the borehole opening via a connecting sleeve. The sealing reducer is installed on the inner wall of the return grout port, and the transition connecting short casing is installed inside the sealing reducer, connecting to the double male short casing. The head end of the final cementing casing string passes through the connection port into the tee body and is fixedly connected to the tee body via the double male short casing. The pressure gauge is located at the connection port.

[0008] The present invention also includes the following technical features:

[0009] Specifically, the final hole casing string is composed of multiple casings connected coaxially; multiple centralizers are arranged at intervals on the outer wall of the final hole casing string to ensure that the final hole casing string is centered in the borehole; after the final hole casing string is lowered into the borehole, its end is 3-5m away from the bottom of the borehole, and its head extends 2-3m out of the borehole opening.

[0010] Specifically, the valve body has an annular limiting platform and an internal thread on its inner wall; the internal thread is close to the cement slurry inlet end, and the annular limiting platform is close to the male thread end of the valve body.

[0011] Specifically, the float valve mounting component I has a cylindrical structure. One end of the float valve mounting component I has a thread on its outer wall, which can be threaded to engage with the internal thread on the inner wall of the valve body. The other end of the float valve mounting component I has its outer wall tightly fitted to the inner wall of the valve body. Both ends of the center hole of the float valve mounting component I are tapered and flared. The end face of the float valve mounting component I near the cement slurry inlet end has a keyway.

[0012] Specifically, the float valve mounting component II is an integral structure, including a cylindrical wall and a circular end plate. The cylindrical wall is tightly fitted with the inner wall of the valve body, and the circular end plate is limited at the annular limiting platform. The center of the circular end plate is the central guide hole, and the circular end plate is also provided with multiple flow guide holes.

[0013] Specifically, a sealing gasket that fits tightly against the inner wall of the valve body is provided between the float valve mounting component I and the float valve mounting component II.

[0014] Specifically, the connection port and the return port of the three-way body are coaxial; the end of the return port is provided with an ear hole;

[0015] The outer diameter of the final hole casing string is smaller than the inner diameter of the connection port and the slurry return port.

[0016] Specifically, the inner wall of the slurry return port is a variable diameter flared shape; the sealing variable diameter tube includes a small diameter end and a large diameter end; the inner wall of the small diameter end is provided with internal threads, and the outer wall of the large diameter end is provided with external threads; the shape of the sealing variable diameter tube matches the inner wall of the slurry return port, and the large diameter end of the sealing variable diameter tube is threadedly connected to the inner wall of the slurry return port.

[0017] The outer wall of the conversion connection short sleeve is threaded, and the conversion connection short sleeve is threaded to the small diameter end of the sealing reducer outside it.

[0018] One end of the double male short sleeve is threadedly connected to the final hole sleeve, and the other end is threadedly connected to the conversion connection short sleeve.

[0019] A cementing method for a coal mine underground up-inclination directional long borehole cementing device includes the following steps:

[0020] Step 1: Circulate and flush the borehole until no rock cuttings are returned from the borehole. Disconnect the drill pipe from the drilling circulation mud pump and connect the drill pipe to the air compressor system or the underground ventilation duct system of the coal mine to return all the liquid accumulated in the borehole to the borehole.

[0021] Step 2: Lower the final hole casing string, and connect the end of the final hole casing string to the pressure-reducing check valve via thread;

[0022] Step 3: Install a final hole cementing tee at the end of the final hole casing string. Connect the connection port to the open casing with a thread. At the slurry return port, use a double male short casing to connect the end of the final hole casing string to the final hole cementing tee. At the same time, at the slurry return port, use a double male short casing, a conversion connecting short casing, and a sealing reducer to seal the annular gap between the final hole casing string and the final hole cementing tee. First, connect the grouting port to the grouting valve with a thread. The grouting valve is connected to the pure cement slurry grouting channel. A pressure gauge is set at the connection port to monitor the pressure of the pure cement slurry in the outer annulus of the final hole casing string in real time, and to observe the pressure fluctuations that reflect the opening of the float valve.

[0023] Step 4: The cementing mud pump pumps the pure cement slurry, prepared according to specific gravity, into the grouting channel, the grouting port of the final hole cementing tee, and the gap between the final hole casing string and the final hole cementing tee. At this time, the pure cement slurry is diverted. The diverted pure cement slurry flows to the bottom of the borehole under the condition of continuous pumping of pure cement slurry by the cementing mud pump. At this time, the value of the pressure gauge on the final hole cementing tee slowly increases. When the entire annulus of the final hole casing string and the gap between the final hole casing string and the final hole cementing tee are filled with mud, the value of the pressure gauge increases rapidly. When the pressure value increases to the pressure at which the pressure-holding check valve opens, the pressure value displayed on the pressure gauge will show a sudden change point. The spring is compressed, and the float valve drives the float valve positioning rod to slide in the central guide hole. At this time, it indicates that the pressure-holding check valve has been opened.

[0024] Pure cement slurry flows through the float valve, through the guide hole and into the annulus inside the final hole casing string. At the same time, a drill string without a drill bit is lowered into the end of the final hole cementing tee return port to a distance of 3-5m from the pressure-blocking check valve. The drill string is connected to a mud pump, which pumps in clean water to clean the backflow and the pure cement slurry adhering to the final hole casing string and return it to the annulus inside the final hole casing string.

[0025] After the designed volume of pure cement slurry is injected, the grouting valve is closed. At this time, there is no continuous slurry supply to the outer annulus of the final borehole casing string, and the pressure of the pressurized pure cement slurry decreases. When the pressure of the pressurized pure cement slurry is less than the opening pressure of the pressurized one-way valve, the pressurized one-way valve closes. This achieves the pressurization and solidification of the pure cement slurry injected into the outer annulus of the final borehole casing string, thereby achieving well cementing and sealing the annular space between the final borehole casing string and the final borehole.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (1) The present invention can achieve the pressure-bearing and solidification of pure cement slurry injected into the outer annulus of the casing, thereby achieving efficient and high-quality cementing, effectively sealing the annular space between the final hole casing and the final hole, and effectively preventing the problems of segmented fracturing layer penetration and poor fracturing effect caused by poor final hole cementing quality.

[0028] (2) The use of the present invention to implement the final cementing of the upward inclined directional long borehole can efficiently fill the entire outer annulus of the casing with cement slurry, and will not form gaps in the outer annulus of the casing where cement slurry is not filled.

[0029] (3) The present invention can realize the cement slurry of the outer annulus of the casing can be solidified under pressure and pressure-holding conditions, thereby effectively ensuring the bonding strength between the cement ring formed after the cementing is completed and the casing wall and the final hole wall.

[0030] (4) The present invention can effectively prevent the problem of poor fracturing effect caused by poor cementing quality at the end of the hole, resulting in the fracturing layer crossing the layer.

[0031] (5) The cementing method of the present invention can effectively improve the radial stress at the cement sheath interface and the sealing capacity of the cement sheath; at the same time, it can effectively prevent gas from returning into the hole along the gap formed between the cement sheath and the casing wall or the wall of the final hole during the gas extraction process after the implementation of segmented fracturing, thereby effectively ensuring the gas extraction volume and ensuring the normal production of the gas extraction hole. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the cementing device connection of the present invention.

[0033] Figure 2 This is a schematic diagram of the pressure-retaining one-way valve structure of the present invention.

[0034] Figure 3 This is a schematic diagram of the final hole cementing tee structure of the present invention.

[0035] Figure 4 This is a schematic diagram of the lower mounting bracket structure for the float valve of the present invention.

[0036] Figure 5 This is a schematic diagram of the mounting bracket structure on the float valve of the present invention.

[0037] Figure 6 This is a schematic diagram of the cementing device of the present invention before cementing in the formation without grouting.

[0038] Figure 7 This is a schematic diagram illustrating the process of using the cementing device of the present invention for grouting cementing within the formation.

[0039] The meanings of the labels in the diagram are as follows:

[0040] 1. End-hole casing string; 2. Pressure-holding check valve; 3. End-hole cementing tee; 4. Coal seam roof; 5. Coal seam; 201. Valve body; 202. Float valve; 203. Float valve positioning rod; 204. Spring; 205. Float valve mounting part I; 206. Float valve mounting part II; 301. Tee body; 302. Converter connecting short casing; 303. Sealing reducer; 304. Double male short casing; 305. Pressure gauge; 306. Grouting port; 307. Connection port; 308. Return grouting port; 309. Open casing. Detailed Implementation

[0041] This invention provides a cementing device and method for upward-inclined directional long boreholes in coal mines. The aim is to establish a reverse circulation flow of pure cement slurry injected after the casing is lowered into the final borehole, and to achieve pressurized cementing under pressure. This allows the pure cement slurry to flow under pressure in the outer annulus of the casing, filling the entire outer annulus space. Once the pressure of the pressurized pure cement slurry rises to the pressure that allows the pressure-holding check valve to open, the pressurized pure cement slurry returns from the inner annulus of the casing. After the designed volume of pure cement slurry is injected and completed, the wellhead grouting valve is closed, and there is no continuous slurry supply to the outer annulus of the casing. The pressure of the pressurized pure cement slurry gradually decreases. When the pressure of the pressurized pure cement slurry is less than the opening pressure of the pressure-holding check valve, the pressure-holding check valve closes, achieving pressurized cementing under pressure in the outer annulus of the casing. This enables efficient and high-quality cementing, effectively sealing the annular space between the final borehole casing and the final borehole. This method involves installing a final-hole cementing tee at the borehole opening. One end of the tee is a casing head connection, threaded to an open casing head. The final-hole casing passes through the tee, and at the other end, the slurry return end of the tee, along with a double male short casing, a conversion connecting short casing, and a sealing reducer, seals the annular space between the final-hole casing and the tee. The grouting end of the tee is connected to a pure cement slurry injection pipeline, effectively ensuring that all injected cement slurry enters the outer annulus of the final-hole casing. After final-hole drilling, a pressure-reducing check valve is connected to the end of the casing string inserted into the borehole. This pressure-reducing check valve effectively… To ensure that the outer annulus of the final-hole casing is filled with pure cement slurry, and to continuously pressurize the injected pure cement slurry, when the pure cement slurry reaches a certain pressure, the pressurization check valve opens, and the pure cement slurry flows through the pressurization check valve into the inner annulus of the final-hole casing. When the injected pure cement slurry reaches the designed volume, the grouting valve is closed at the grouting end of the final-hole cementing tee. At this time, there is no continuous supply of pure cement slurry to the outer annulus of the final-hole casing, and the pressurization check valve closes, allowing the pure cement slurry injected into the outer annulus of the casing to pressurize and solidify under pressure conditions, thus achieving efficient and high-quality cementing and effectively sealing the annular space between the final-hole casing and the final hole.

[0042] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0043] Example 1:

[0044] like Figures 1 to 6 As shown, this embodiment provides a coal mine underground up-tilt directional long borehole final cementing device, including a final casing string 1, a pressure-blocking one-way valve 2, and a final cementing tee 3; the end of the final casing string 1 is connected to the pressure-blocking one-way valve 2, which can be lowered into the borehole along with the final casing string 1; the head end of the final casing string 1 extends out of the borehole opening and is connected to the final cementing tee 3, which is installed at the borehole opening.

[0045] The pressure-holding check valve 2 includes a valve body 201, and also includes a float valve 202, a float valve positioning rod 203, a spring 204, a float valve mounting component I 205, and a float valve mounting component II 206 disposed in the central through hole of the valve body 201; the two ends of the valve body 201 are a male valve body end and a cement slurry inlet end, respectively, the male valve body end being coaxially connected to the end of the final hole sleeve string 1, and the cement slurry inlet end facing the bottom of the borehole; the float valve 202 is connected to one end of the float valve positioning rod 203, and the spring 204 is sleeved on... The float valve positioning rod 203 is located on the float valve; the float valve mounting part I 205 is provided with a central hole, and the float valve mounting part II 206 is provided with a guide hole and a central guide hole; the float valve 202, the float valve positioning rod 203 and the spring 204 are located between the float valve mounting part I 205 and the float valve mounting part II 206. The spring 204 can apply force to the float valve 202 to block it at the central hole of the float valve mounting part I 205, and the other end of the float valve positioning rod 203 passes through the central guide hole of the float valve mounting part II 206.

[0046] The final hole cementing tee 3 includes a tee body 301, a conversion connecting short casing 302, a sealing reducer 303, a double male short casing 304, and a pressure gauge 305. The three ports of the tee body 301 are a grouting port 306, a connection port 307, and a return grouting port 308. The grouting port 306 is connected to the grouting channel. The connection port 307 is installed at the borehole opening via a connecting open casing 309. A sealing reducer 303 is installed on the inner wall of the return grouting port 308. The conversion connecting short casing 302 is installed inside the sealing reducer 303 and is connected to the double male short casing 304. The head end of the final hole casing string 1 passes through the connection port 307 into the tee body 301 and is fixed to the tee body 301 via the double male short casing 304. The pressure gauge 305 is located at the connection port 307.

[0047] The final casing string 1 is composed of multiple casings coaxially connected; multiple centralizers are spaced apart on the outer wall of the final casing string 1 to ensure that the final casing string 1 is centered within the borehole; after the final casing string 1 is lowered into the borehole, its end is 3-5m from the bottom of the borehole, and its head extends 2-3m beyond the borehole opening. In this embodiment, a centralizer is installed on the outside of the casing every 4 casings.

[0048] The inner wall of valve body 201 is provided with an annular limiting platform and an internal thread; the internal thread is close to the cement slurry inlet end, and the annular limiting platform is close to the male thread end of the valve body.

[0049] The float valve mounting component I205 has a cylindrical structure. One end of the float valve mounting component I205, which is near the cement slurry inlet, has threads on its outer wall that can engage with the internal threads on the inner wall of the valve body 201 for threaded connection. The outer wall of the other end of the float valve mounting component I205 is in close contact with the inner wall of the valve body 201. Both ends of the center hole of the float valve mounting component I205 are tapered and flared. The end face of the float valve mounting component I205 near the cement slurry inlet is provided with a keyway.

[0050] The float valve mounting component II206 is an integral structure, including a cylindrical wall and a circular end plate. The cylindrical wall fits tightly against the inner wall of the valve body, and the circular end plate is limited at the annular limiting platform. The center of the circular end plate has a central guide hole, and the circular end plate is also provided with multiple flow guide holes. In this embodiment, the float valve mounting component II is designed with six circular flow guide holes and one central guide hole.

[0051] A sealing gasket is provided between the float valve mounting part I205 and the float valve mounting part II206, which is in close contact with the inner wall of the valve body 201.

[0052] The connection port 307 and the return port 308 of the three-way body 301 are coaxial; the end of the return port 308 is provided with an ear hole;

[0053] The outer diameter of the final hole sleeve string 1 is smaller than the inner diameter of the connection port 307 and the return slurry port 308.

[0054] The inner wall of the return port 308 is a variable diameter flared opening; the sealing reducer 303 includes a small diameter end and a large diameter end; the inner wall of the small diameter end is provided with internal threads, and the outer wall of the large diameter end is provided with external threads; the shape of the sealing reducer 303 matches the inner wall of the return port 308, and the large diameter end of the sealing reducer 303 is threadedly connected to the inner wall of the return port 308.

[0055] The outer wall of the conversion short sleeve 302 is threaded, and the conversion short sleeve 302 is threaded to the small diameter end of the sealing reducer 303 outside it.

[0056] One end of the double male short sleeve 304 is threaded to the final hole sleeve string 1, and the other end is threaded to the conversion connection short sleeve 302.

[0057] Example 2:

[0058] This embodiment provides a cementing method for a coal mine up-dip directional long borehole cementing device according to Embodiment 1. First, the formation fracturing pressure P of the drilled stratum is determined based on relevant characteristic parameters such as the formation mechanics of the roof of the drilled coal seam. f Existing empirical formulas can be used to calculate the frictional resistance loss P that needs to be overcome to inject pure cement grout to the bottom of the final hole in an upward-sloping directional long borehole. s Existing empirical formulas can be used to calculate this; therefore, the range of cementing grouting pressure is determined as follows: the grouting pressure must be greater than the frictional resistance loss P. s The pressure bearing range of the cement grout in the outer annulus of the final casing must be less than the formation fracturing pressure P. f Otherwise, it will cause rock strata to leak. Therefore, it is possible to design the settling pressure of the cement grout in the outer annulus of the final casing and the opening pressure of the one-way valve to both be P. c And its value range is: P s <P c <P fThe settling pressure value of pure cement slurry in the outer annulus of the final hole casing and the pressure P required for the pressure-holding check valve to open were determined. c After determining the value, a spring that can trigger the opening of the pressure-blocking check valve under this pressure condition is preferred. The preferred spring can be calculated using the formula: F = P c =Kx, with the preferred elastic coefficient being P. c A spring of a certain size. After drilling to the designed depth in an upward-sloping directional long borehole, the mud pump discharge rate is adjusted to a larger rate than normal drilling to fully circulate and flush the borehole and remove clean rock cuttings from the borehole.

[0059] Includes the following steps:

[0060] Step 1: Circulate and flush the borehole until no rock cuttings are returned from the borehole. Disconnect the drill pipe from the drilling circulation mud pump and connect the drill pipe to the air compressor system or the underground ventilation duct system of the coal mine to return all the liquid accumulated in the borehole to the borehole.

[0061] Step 2: Lower the final hole casing string. Install a centralizer on the outside of the casing every 4 casings to ensure that the final hole casing string is centered in the borehole. At the same time, connect the end of the final hole casing string to the pressure-blocking check valve threadedly. The final hole casing string is designed to be lowered 3-5m from the bottom of the borehole, and the head of the final hole casing string extends 2-3m out of the borehole opening.

[0062] The assembly sequence of the pressure-holding check valve is as follows: First, install float valve mounting part II into the valve body from the cement slurry inlet end. Float valve mounting part II matches the valve body size and can be directly lowered into the valve body, limiting its position to the annular limiting platform of the valve body. Next, install the float valve positioning rod, spring, and float valve. The float valve positioning rod passes through the inner hole of the spring, and one end of the float valve positioning rod is threaded to the float valve; the other end of the float valve positioning rod passes through the central guide hole. Finally, install float valve mounting part I into the valve body from the cement slurry inlet end. The lower, smaller end of float valve mounting part I matches the valve body size and can be directly lowered into the valve body. The upper part of float valve mounting part I... The large-size end is connected to the valve body via a threaded seal. A sealing gasket is installed between float valve mounting part I and float valve mounting part II to seal the gap between the lower small-size end of float valve mounting part I and the valve body, while also reducing the mutual force between float valve mounting part I and float valve mounting part II. A keyway is used for the threaded fastening tool of float valve mounting part I to be inserted. The male thread end of the valve body is threaded to the final hole sleeve string. No device is connected to the cement slurry inlet end to facilitate the entry of pure cement slurry into the pressure-blocking check valve. The precise length of the final hole sleeve string from the bottom of the borehole and the extension to the borehole opening should be adjusted according to the actual borehole length.

[0063] Step 3: Install a final hole cementing tee at the end of the final hole casing string. Connect the connector to the threaded end of the first open casing. At the slurry return port, connect the end of the final hole casing string to the final hole cementing tee using a double male short casing. Simultaneously, at the slurry return port, seal the annular gap between the final hole casing string and the final hole cementing tee using a double male short casing, a transition short casing, and a sealing reducer. Specifically, one end of the double male short casing is threaded to the end hole casing head, and the other end is threaded to the transition short casing. The transition short casing is designed with a male thread that mates with the inner thread of the small diameter end of the sealing reducer. The outer side of the small diameter end of the pipe is designed to be smooth, and its size matches the size of the final hole cementing tee body. It can be directly lowered into the final hole cementing tee body. The outer side of the large diameter end of the sealing reducer is designed with a male thread type to connect with the thread of the final hole cementing tee body. The return slurry port end is designed along the ear hole for hoisting the final hole cementing tee. The grouting port is first connected to the grouting valve thread. The grouting valve is connected to the pure cement slurry grouting channel. The pressure gauge is installed with an outlet pipe device for installing the pressure gauge. The pressure gauge is set at the connection port to monitor the pressure of the pure cement slurry in the outer annulus of the final hole casing string in real time, and to observe the pressure fluctuation that reflects the opening of the float valve.

[0064] Step 4: Prepare pure cement slurry according to the cementing design requirements, and simultaneously cement the casing string at the final hole using a cementing mud pump. The cementing mud pump will pump the pure cement slurry prepared according to the specific gravity into the grouting channel, the grouting port of the final hole cementing tee, and the gap between the final hole casing string and the final hole cementing tee. At this point, the pure cement slurry will be diverted. Figure 7 As shown in the figure, the arrow marks the circulation flow line of the cement slurry. The diverted cement slurry flows to the bottom of the borehole under the condition that the cementing mud pump continuously injects cement slurry. At this time, the pressure gauge on the final hole cementing tee increases slowly. When the entire annulus of the final hole casing string and the gap between the final hole casing string and the final hole cementing tee are filled with mud, the pressure gauge value increases rapidly. When the pressure value increases to the pressure Pc that opens the pressure-holding check valve, the pressure value displayed on the pressure gauge will show a sudden change point. The spring is compressed, and the float valve drives the float valve positioning rod to slide in the central guide hole. At this time, it indicates that the pressure-holding check valve has been opened.

[0065] Pure cement slurry flows through the float valve, through the guide hole and into the annulus inside the final hole casing string. At the same time, a drill string without a drill bit is lowered into the end of the return slurry port of the final hole cementing tee to a distance of 3-5m from the pressure-blocking check valve. The drill string is connected to a mud pump, and clean water is pumped in with a small pump displacement to clean the backflow and the pure cement slurry adhering to the final hole casing string and return it to the annulus inside the final hole casing string.

[0066] After the designed volume of pure cement slurry is injected, the grouting valve is closed. At this time, there is no continuous slurry supply to the outer annulus of the final-hole casing string, and the pressure of the pressure-bearing pure cement slurry decreases. When the pressure of the pressure-bearing pure cement slurry is less than the opening pressure of the pressure-bearing one-way valve, the pressure-bearing one-way valve closes. This achieves pressure-bearing and solidification of the pure cement slurry injected into the outer annulus of the final-hole casing string, thereby achieving efficient and high-quality cementing, effectively sealing the annular space between the final-hole casing string and the final hole, and effectively preventing the difficulties caused by poor cementing quality at the final hole, such as fracturing layer penetration and poor fracturing effect.

Claims

1. A cementing device for final drilling of an upward-inclined directional long borehole in a coal mine, characterized in that, It includes a final hole casing string (1), a pressure-blocking check valve (2), and a final hole cementing tee (3); the end of the final hole casing string (1) is connected to the pressure-blocking check valve (2), which can be lowered into the borehole along with the final hole casing string (1); the head end of the final hole casing string (1) extends out of the borehole opening and is connected to the final hole cementing tee (3), which is installed at the borehole opening; The pressure-holding one-way valve (2) includes a valve body (201), and also includes a float valve (202), a float valve positioning rod (203), a spring (204), a float valve mounting component I (205), and a float valve mounting component II (206) disposed in the central through hole of the valve body (201); the two ends of the valve body (201) are the valve body male thread end and the cement slurry inlet end, respectively. The valve body male thread end is coaxially connected to the end of the final hole sleeve string (1), and the cement slurry inlet end faces the bottom of the borehole; the float valve (202) is connected to one end of the float valve positioning rod (203), and the spring (204) The float valve is fitted onto the float valve positioning rod (203); the float valve mounting part I (205) has a central hole, and the float valve mounting part II (206) has a flow guide hole and a central guide hole; the float valve (202), the float valve positioning rod (203) and the spring (204) are located between the float valve mounting part I (205) and the float valve mounting part II (206), and the spring (204) can apply force to the float valve (202) to block it at the central hole of the float valve mounting part I (205), and the other end of the float valve positioning rod (203) passes through the central guide hole of the float valve mounting part II (206); The final cementing tee (3) includes a tee body (301), a conversion connecting short casing (302), a sealing reducer (303), a double male short casing (304), and a pressure gauge (305); the three ports of the tee body (301) are a grouting port (306), a connection port (307), and a return grouting port (308); the grouting port (306) is connected to the grouting channel, and the connection port (307) is installed at the borehole opening by connecting an open casing (309). A sealing reducer (303) is installed on the inner wall of the return slurry port (308), and a conversion connecting short sleeve (302) is installed inside the sealing reducer (303). The conversion connecting short sleeve (302) is connected to the double male short sleeve (304). The head end of the final hole sleeve string (1) passes through the connection port (307) into the tee body (301) and is fixedly connected to the tee body (301) through the double male short sleeve (304). The pressure gauge (305) is installed at the connection port (307). The inner wall of the return port (308) is a variable diameter flared shape; the sealing reducer (303) includes a small diameter end and a large diameter end; the inner wall of the small diameter end is provided with internal threads, and the outer wall of the large diameter end is provided with external threads; the shape of the sealing reducer (303) matches the inner wall of the return port (308), and the large diameter end of the sealing reducer (303) is threadedly connected to the inner wall of the return port (308); The outer wall of the conversion connection short sleeve (302) is threaded, and the conversion connection short sleeve (302) is threaded to the small diameter end of the sealing reducer (303) outside it; One end of the double male short sleeve (304) is threaded to the final hole sleeve string (1), and the other end is threaded to the conversion connection short sleeve (302).

2. The coal mine underground up-inclined directional long borehole cementing device as described in claim 1, characterized in that, The final hole casing string (1) is composed of multiple casings connected coaxially; multiple centering devices are arranged at intervals on the outer wall of the final hole casing string (1) so that the final hole casing string (1) is located in the center of the borehole; after the final hole casing string (1) is lowered into the borehole, its end is 3~5m away from the bottom of the borehole, and its head extends 2~3m out of the borehole opening.

3. The coal mine underground up-inclined directional long borehole cementing device as described in claim 1, characterized in that, The valve body (201) has an annular limiting platform and an internal thread on its inner wall; the internal thread is close to the cement slurry inlet end, and the annular limiting platform is close to the male thread end of the valve body.

4. The coal mine underground upward-inclined directional long borehole cementing device as described in claim 3, characterized in that, The float valve mounting component I (205) is a cylindrical structure. One end of the float valve mounting component I (205) has a thread on its outer wall, which can be threaded to the inner thread of the valve body (201). The other end of the float valve mounting component I (205) is tightly fitted to the inner wall of the valve body (201). The two ends of the center hole of the float valve mounting component I (205) are tapered and flared. The end face of the float valve mounting component I (205) near the cement slurry inlet end is provided with a keyway.

5. The coal mine underground up-inclined directional long borehole cementing device as described in claim 4, characterized in that, The float valve mounting component II (206) is an integral structure, including a cylindrical wall and a circular end plate. The cylindrical wall is tightly fitted to the inner wall of the valve body, and the circular end plate is limited at the annular limiting platform. The center of the circular end plate is the central guide hole, and the circular end plate is also provided with multiple flow guide holes.

6. The coal mine underground up-inclined directional long borehole cementing device as described in claim 5, characterized in that, A sealing gasket is provided between the float valve mounting part I (205) and the float valve mounting part II (206) to fit tightly against the inner wall of the valve body (201).

7. The coal mine underground up-inclined directional long borehole cementing device as described in claim 1, characterized in that, The connection port (307) and the return port (308) of the three-way body (301) are coaxial; the end of the return port (308) is provided with an ear hole; The outer diameter of the final hole sleeve string (1) is smaller than the inner diameter of the connection port (307) and the return slurry port (308).

8. A cementing method for a coal mine underground up-inclination directional long borehole cementing device as described in claim 1, characterized in that, Includes the following steps: Step 1: Circulate and flush the borehole until no rock cuttings are returned from the borehole. Disconnect the drill pipe from the drilling circulation mud pump and connect the drill pipe to the air compressor system or the underground ventilation duct system of the coal mine to return all the liquid accumulated in the borehole to the borehole. Step 2: Lower the final hole casing string, and connect the end of the final hole casing string to the pressure-reducing check valve via thread; Step 3: Install a final hole cementing tee at the end of the final hole casing string. Connect the connection port to the open casing with a thread. At the slurry return port, use a double male short casing to connect the end of the final hole casing string to the final hole cementing tee. At the same time, at the slurry return port, use a double male short casing, a conversion connecting short casing, and a sealing reducer to seal the annular gap between the final hole casing string and the final hole cementing tee. First, connect the grouting port to the grouting valve with a thread. The grouting valve is connected to the pure cement slurry grouting channel. A pressure gauge is set at the connection port to monitor the pressure of the pure cement slurry in the outer annulus of the final hole casing string in real time, and to observe the pressure fluctuations that reflect the opening of the float valve. Step 4: The cementing mud pump pumps the pure cement slurry, prepared according to specific gravity, into the grouting channel, the grouting port of the final hole cementing tee, and the gap between the final hole casing string and the final hole cementing tee. At this time, the pure cement slurry is diverted. The diverted pure cement slurry flows to the bottom of the borehole under the condition of continuous pumping of pure cement slurry by the cementing mud pump. At this time, the value of the pressure gauge on the final hole cementing tee slowly increases. When the entire annulus of the final hole casing string and the gap between the final hole casing string and the final hole cementing tee are filled with mud, the value of the pressure gauge increases rapidly. When the pressure value increases to the pressure at which the pressure-holding check valve opens, the pressure value displayed on the pressure gauge will show a sudden change point. The spring is compressed, and the float valve drives the float valve positioning rod to slide in the central guide hole. At this time, it indicates that the pressure-holding check valve has been opened. Pure cement slurry flows through the float valve, through the guide hole and into the annulus inside the final hole casing string. At the same time, a drill string without a drill bit is lowered into the end of the return slurry port of the final hole cementing tee to a distance of 3-5m from the pressure-blocking check valve. The drill string is connected to a mud pump, which pumps in clean water to clean the return flow and the pure cement slurry adhering to the final hole casing string and return it to the annulus inside the final hole casing string. After the designed volume of pure cement slurry is injected, the grouting valve is closed. At this time, there is no continuous slurry supply to the outer annulus of the final borehole casing string, and the pressure of the pressurized pure cement slurry decreases. When the pressure of the pressurized pure cement slurry is less than the opening pressure of the pressurized one-way valve, the pressurized one-way valve closes. This achieves the pressurization and solidification of the pure cement slurry injected into the outer annulus of the final borehole casing string, thereby achieving well cementing and sealing the annular space between the final borehole casing string and the final borehole.

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