A system and method for drilling and injecting while drilling in complex formations in underground coal mines

Abstract

The present application relates to a system and method for drilling and grouting simultaneously while drilling in complex strata in a coal mine, belonging to the technical field of drilling in a coal mine, in which drilling fluid is used for drilling, and when serious hole collapse or fissure loss of drilling fluid is encountered, the drilling fluid is converted into grouting fluid on site, grouting is carried out, and a hole mouth pressure bearing device is matched to enable pressure operation, realizing drilling and grouting simultaneously, and the pressure operation can balance part of the stratum pressure / stratum collapse pressure, reducing the degree of hole collapse during drilling, thereby improving the hole completion rate and hole completion depth. Compared with the prior art, the present application uses pressure operation in the hole during drilling, realizes high-pressure grouting, improves the grouting reinforcement effect, can realize drilling and point grouting, can also realize multiple grouting, solves the hole collapse problem during directional drilling in complex strata in a coal mine, and no longer needs multiple reaming, multiple drilling and reaming, avoiding the defects and deficiencies of the existing grouting process.

Description

Technical Field

[0001] This invention belongs to the field of coal mine drilling technology, and relates to a drilling-while-injection system and method for directional drilling in complex formations in coal mines. Background Technology

[0002] Currently, directional drilling in coal mines has become the main means of precise gas control. During directional drilling, different strata (structural strata, fractured / fractured strata) need to be traversed, and accidents such as stuck drills and buried drills often occur, resulting in low hole formation rate, drilling depth not meeting design requirements, increased drilling costs, and affecting the gas control effect. Existing technologies have certain limitations and cannot effectively solve the problem of low hole formation rate. For example: (1) The commonly used branch hole process, although it can sometimes avoid collapsed strata, causes wasted footage; in many cases, it cannot be avoided; and subsequent pipe stringing operations cannot be realized. (2) The casing protection process cannot be implemented for multiple casing protection drilling, and the cost is high. (3) The grouting process / fixed-point grouting requires hole enlargement, multiple drilling and retraction, and the process is complex and difficult to implement. (4) The air / nitrogen drilling process is applicable to harsh geological conditions, has limited slag return capacity, and the cost of supporting equipment is high. (5) High-performance drilling fluid technology effectively solves the problem of hole collapse in water-sensitive mudstone and shale, but its effect is limited for tectonic strata and fractured / fractured strata.

[0003] The existing grouting process / point grouting mainly includes the following steps:

[0004] ① Removing the drill bit. When encountering a collapsed formation, normal drilling is impossible and grouting is required to resolve the issue. In this case, the drilling tools used for drilling must be removed from the hole first.

[0005] ② Deploy the drilling tool and enlarge the hole. Due to hole collapse, the grouting drill tool cannot be delivered to the grouting position. It is necessary to use an enlarging drill tool to enlarge the drilled hole to ensure the insertion of the grouting drill tool. The collapsed hole position is the grouting position.

[0006] ③Remove the drill bit. Remove the reaming drill bit.

[0007] ④ Send in the grouting drill bit. Send in the grouting drill bit until it reaches the grouting position. Due to hole enlargement, the larger the borehole (enlarged hole), the more severe the formation collapse will be, which may cause the grouting drill bit to encounter obstruction during the process of being sent into the hole and fail to reach the grouting position.

[0008] ⑤ Set the packer and grout. Because the packer is set in the open hole section, its sealing and pressure bearing are limited, the grouting pressure is not high, and the grouting fluid can only stay in the borehole and cannot enter the formation (the purpose of grouting is to reinforce the formation). Finally, a cement column (solidified body) will be formed in the borehole after it has been enlarged.

[0009] ⑥ Remove the grouting drill bit and wait for it to set.

[0010] ⑦ Insert the original drilling tools and drill plug. At this point, the original drilling tools and drill plug will form a cement ring inside the hole. During subsequent drilling, the agitation of the drilling tools may cause it to fall off, resulting in the risk of the drill getting stuck.

[0011] ⑧ If borehole collapse occurs again during subsequent drilling, grouting will be impossible. This is because the deeper the hole, the more difficult it is to reach the grouting position with the grouting tool. If the hole is enlarged again, it will destroy the cement ring formed by the previous grouting, leading to another borehole collapse. Summary of the Invention

[0012] In view of this, the purpose of the present invention is to provide a drilling-while-grouting system and method for directional drilling in complex formations in coal mines, so as to realize drilling-while-grouting.

[0013] To achieve the above objectives, the present invention provides the following technical solution:

[0014] A drilling and injection system for directional drilling in complex formations in coal mines includes a wellhead pressurization device that can be sealed to the drill string and wellhead to enable pressurized operation in the borehole. The wellhead pressurization device is connected to a wellhead pressure gauge to detect its internal pressure. The wellhead pressurization device is equipped with a slag discharge port to discharge slag and water. A slag and water outlet switch is provided at the slag discharge port to open or close the slag discharge port. A slag and water separation device is provided at the position corresponding to the slag discharge port to achieve slag and water separation. The outlet of the slag and water separation device is connected to a circulation tank. The circulation tank is connected to a mud pump and at least one replenishment tank. The replenishment tank is equipped with a control valve. The mud pump is connected to the drill string water injection port via a water injection pipe.

[0015] Optionally, the sludge-water separation device includes a vibrating screen, a storage tank, and a hydrocyclone arranged sequentially along the fluid flow direction.

[0016] The drilling-while-injection method for directional drilling in complex formations in underground coal mines includes the following steps:

[0017] S1: Drilling fluid is used for drilling;

[0018] S2: When encountering complex formations and grouting is required, the drill rod at the borehole opening should be replaced with a smooth drill rod that matches the borehole opening pressure device to facilitate the sealing and pressure bearing of the borehole opening pressure device.

[0019] S3: Grouting while drilling: Close the slag and water outlet switch of the pressure device at the borehole, add reinforcing material to the circulating tank with sufficient drilling fluid to form grouting fluid, start the pump to grout, observe the pressure change of the pressure device at the borehole, and start grouting when the pressure of the pressure device at the borehole is equal to the value of the mud pump pressure gauge, until the estimated volume is grouted.

[0020] S4: Replacement: After pumping the grouting fluid, first pump in a thick plug to replace the grouting fluid in the drill bit, then replace the thick plug in the drill bit with clean water. At the same time, observe the pressure change on the pressure device at the borehole opening, make it reach the peak value, and maintain it for a certain period of time. Then stop pumping, and the grouting is completed.

[0021] S5: Clean the drill string and wait for it to set;

[0022] S6: After waiting 24 hours for the ground to solidify, plug the drill and resume normal drilling.

[0023] Optionally, cleaning the drill bit includes the following steps: prepare enough clean water in the circulation tank, start the pump at a low flow rate, and slowly withdraw 3 drill rods to circulate clean water and clean the drill bit inside the hole.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention employs drilling fluid during construction. When encountering complex formations such as structural strata, fractured / fractured strata, or severe borehole collapse or leakage of drilling fluid due to fractures, the drilling fluid is converted into grouting fluid on-site for grouting. Simultaneously, a pressure-bearing device at the borehole opening is provided, enabling pressurized operation and achieving grouting while drilling. Furthermore, pressurized operation can balance some of the formation pressure / formation collapse pressure, reducing the degree of borehole collapse during drilling and thus improving the borehole formation rate and depth.

[0026] Compared with existing technologies, this invention adopts pressurized operation inside the hole during the drilling process, realizing high-pressure grouting, improving the grouting reinforcement effect, and enabling drilling-while-drilling / fixed-point grouting, as well as multiple grouting. It solves the problem of hole collapse during directional drilling in complex strata (structural strata, fractured strata) in coal mines, avoids the defects and shortcomings of existing grouting processes, and eliminates the need for multiple hole enlargement, drilling, and drilling withdrawal.

[0027] This invention compensates for the lack of mechanical balance of formation pressure / collapse pressure caused by the absence of hydraulic column pressure in the special scenario of underground coal mine drilling, thereby achieving the goal of injection while drilling throughout the entire underground coal mine drilling process.

[0028] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0030] Figure 1This is a schematic diagram of the orifice pressure device of the present invention;

[0031] Figure 2 This is a schematic diagram of the drilling and injection system of the present invention. Detailed Implementation

[0032] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0033] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0034] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0035] The lithology where borehole collapse occurs during underground coal mine drilling is mainly mudstone strata. Its clay mineral composition is primarily montmorillonite, illite, and illite-montmorillonite mixed layers. Its main structure is a crystal structure of silicon-oxygen tetrahedra and aluminum-oxygen octahedra and their combinations. It is highly susceptible to hydration and expansion upon contact with water. Adding potassium and calcium ions, which have inhibitory functions, to the drilling fluid forms a diffused double electric layer on the surface of the clay mineral crystal structure. This compresses the crystal lattice due to hydration expansion, allowing potassium ions to embed into the lattice and inhibit hydration. Anti-collapse agents with sealing properties penetrate the pores, fissures, and bedding planes of the mudstone and shale strata, sealing the bedding and fissures, improving the formation's cohesion, and simultaneously preventing water from entering the mudstone and shale strata. This invention uses drilling fluid for drilling during construction. When encountering complex formations such as structural strata, fractured / fractured strata, or severe borehole collapse or leakage of drilling fluid due to fractures, the drilling fluid is converted into grouting fluid on-site for grouting. At the same time, a pressure-bearing device at the borehole opening is provided to enable pressurized operation and achieve grouting while drilling.

[0036] Drilling fluid to grouting fluid conversion technology: During the drilling process, drilling fluid needs to be grouted while drilling / at fixed points. Based on the composition and performance characteristics of the drilling fluid, a certain concentration of activators and curing agents are added to the drilling fluid. During the reaction process, it safely passes through the drilling tool and is injected into the formation. When the curing time is reached, a solidified body is formed in the formation, thereby achieving the purpose of reinforcing the formation and preventing collapse.

[0037] This invention provides a drilling-while-injection system and method for directional drilling in complex formations (structural formations, fractured formations) in coal mines. It employs a pressure-bearing device at the wellhead, drilling tools, drilling fluid, and an activator. The grouting fluid is converted during drilling via a pressure-bearing system, eliminating the need to withdraw the drilling tools. This solves the problem of drilling-while-injection / fixed-point grouting during directional drilling in complex formations (structural formations, fractured / fractured formations) in coal mines. Specifically:

[0038] Please see Figures 1-2 A drilling and injection system for directional drilling in complex formations in coal mines includes a wellhead pressurization device that can be sealed to the drill string and wellhead casing to provide a pressurized, sealed environment that allows the near-horizontal borehole to be filled with drilling fluid, enabling pressurized drilling and balancing a portion of the formation pressure / formation collapse pressure. The wellhead pressurization device is equipped with a slag discharge port to discharge slag and water, and a slag and water outlet switch is provided at the slag discharge port to open or close the slag discharge port. The wellhead pressurization device is also connected to a wellhead pressure gauge to detect its internal pressure. A slag and water separation device is provided at the position corresponding to the slag discharge port to achieve slag and water separation. The outlet of the slag and water separation device is connected to a circulation tank, and the circulation tank is connected to a mud pump. The mud pump is connected to the water injection port of the drill string via a water injection pipe.

[0039] The present invention employs a borehole pressure device, which enables pressurized operation, balances a portion of the formation pressure / formation collapse pressure, reduces the degree of borehole collapse during the drilling process, and thus improves the borehole formation rate and borehole depth.

[0040] Optionally, the sludge-water separation device includes a vibrating screen, a storage tank, and a hydrocyclone arranged sequentially along the fluid flow direction; the circulation tank is connected to at least one replenishment tank, and the replenishment tank is equipped with a control valve.

[0041] A drilling-while-injection method for directional drilling in complex formations in coal mines includes the following steps:

[0042] The drilling-while-injection method for directional drilling in complex formations in underground coal mines includes the following steps:

[0043] S1: Drilling fluid injection;

[0044] S2: When encountering complex formations and grouting is required, the drill rod at the borehole opening should be replaced with a smooth drill rod that matches the borehole opening pressure device to facilitate the sealing and pressure bearing of the borehole opening pressure device.

[0045] S3: Grouting while drilling: Close the slag and water outlet switch of the borehole pressure device, add activator, curing agent and other reinforcing materials to the circulating tank with sufficient drilling fluid to form grouting fluid, start the pump to grout, observe the pressure change of the borehole pressure device, and start grouting when the pressure of the borehole pressure device is equal to the value of the mud pump pressure gauge, until the estimated volume is grouted.

[0046] S4: Replacement: After pumping the grouting fluid, first pump in a thick plug to replace the grouting fluid in the drill bit, then replace the thick plug in the drill bit with clean water. At the same time, observe the pressure change on the pressure device at the borehole opening, make it reach the peak value, and maintain it for a certain period of time. Then stop pumping, and the grouting is completed.

[0047] S5: Clean the drill bit and wait for it to solidify: Prepare enough clean water in the circulation tank, start the pump at a low flow rate, and slowly withdraw 3 drill rods to circulate clean water and clean the drill bit in the hole.

[0048] S6: Wait 24 hours for the ground to solidify, then plug the hole and resume normal drilling.

[0049] Example

[0050] A drilling-while-injection method for directional drilling in complex formations (structural formations, fractured formations) in coal mines includes the following steps:

[0051] S1: Drilling fluid injection;

[0052] S2: When encountering complex formations (structural formations, fractured / fractured formations) and grouting is required, determine the formula for converting the drilling fluid into grouting fluid, and replace the borehole drill rod with a smooth drill rod to facilitate use with the borehole pressure-bearing device for sealing and pressure bearing.

[0053] S3: Grouting while drilling: Close the slag and water outlet switch of the borehole pressure device, add activator, curing agent and other reinforcing materials to the circulating tank with sufficient drilling fluid to form grouting fluid, start the pump to grout, observe the pressure change of the borehole pressure device, and start grouting when the pressure of the borehole pressure device is equal to the value of the mud pump pressure gauge, until the estimated volume is grouted.

[0054] S4: Displacement: After pumping the grouting fluid, prepare 0.5 cubic meters of thick plug in the circulation tank and pump it into the drill bit for displacement. Calculate the time it takes for the thick plug to be displaced by the drill bit by the clean water according to the mud pump flow rate. At the same time, observe the pressure change on the pressure device at the borehole opening, make it reach the peak value and keep it constant for 5 minutes, then stop the pump and the grouting is completed.

[0055] S5: Clean the drill bit and wait for it to solidify: Prepare enough clean water in the circulation tank, start the pump at a low flow rate, and slowly withdraw 3 drill rods to circulate clean water and clean the drill bit in the hole.

[0056] S6: Wait 24 hours for the ground to solidify, then plug the hole and resume normal drilling.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A drilling-while-injection method for directional drilling in complex formations in underground coal mines, characterized in that: A drilling and injection system is provided for directional drilling in complex formations in coal mines. The system includes a wellhead pressurization device that can be sealed to the drill string and wellhead to enable pressurized operation in the well. The wellhead pressurization device is connected to a wellhead pressure gauge to detect its internal pressure. The wellhead pressurization device is equipped with a slag discharge port to discharge slag and water. A slag and water outlet switch is provided at the slag discharge port to open or close the slag discharge port. A slag and water separation device is provided at the position corresponding to the slag discharge port to achieve slag and water separation. The outlet of the slag and water separation device is connected to a circulation tank. The circulation tank is connected to a mud pump and at least one replenishment tank. The replenishment tank is equipped with a control valve. The mud pump is connected to the drill string water injection port via a water injection pipe. The drilling-as-you-go method includes the following steps: S1: Drilling fluid is used for drilling; S2: When encountering complex formations and grouting is required, the drill rod at the borehole opening should be replaced with a smooth drill rod that matches the borehole opening pressure device to facilitate the sealing and pressure bearing of the borehole opening pressure device. S3: Grouting while drilling: Close the slag and water outlet switch of the pressure device at the borehole, add reinforcing material to the circulating tank with sufficient drilling fluid to form grouting fluid, start the pump to grout, observe the pressure change of the pressure device at the borehole, and start grouting when the pressure of the pressure device at the borehole is equal to the value of the mud pump pressure gauge, until the estimated volume is grouted. S4: Replacement: After pumping the grouting fluid, first pump in a thick plug to replace the grouting fluid in the drill bit, then replace the thick plug in the drill bit with clean water. At the same time, observe the pressure change on the pressure device at the borehole opening, make it reach the peak value, and maintain it for a certain period of time. Then stop pumping, and the grouting is completed. S5: Clean the drill string and wait for it to set; S6: Drill plug, resume normal drilling.

2. The drilling and injection method for directional drilling in complex formations in coal mines according to claim 1, characterized in that: The sludge-water separation device includes a vibrating screen, a storage tank, and a hydrocyclone arranged sequentially along the fluid flow direction.

3. The drilling and injection method for directional drilling in complex formations in coal mines according to claim 1, characterized in that: Cleaning the drill bit involves the following steps: fill the circulation tank with clean water, start the pump at a low flow rate, and slowly withdraw the three drill rods to circulate the clean water and clean the drill bit inside the hole.

4. The drilling and injection method for directional drilling in complex formations in coal mines according to claim 1, characterized in that: After 24 hours of waiting for the solution to solidify, the plug was drilled.

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