CN117722179A - Water-retaining and anti-flushing coal mining method based on pressure relief fracture grouting to reconstruct anti-flushing water-resisting layer - Google Patents
Water-retaining and anti-flushing coal mining method based on pressure relief fracture grouting to reconstruct anti-flushing water-resisting layer Download PDFInfo
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Abstract
The invention discloses a water-retaining and anti-flushing coal mining method based on pressure relief crack grouting to reconstruct an anti-flushing water-resisting layer, which comprises the following steps: 1. exploration of mining area stratum information; 2. preparing a rock core sample and testing physical and mechanical parameters of each layer of stratum of a mining area; 3. layering the thick and hard sandstone layer; 4. carrying out multi-group directional drilling on a mining area; 5. hydraulic fracturing pressure relief; 6. constructing an anti-flushing waterproof layer; 7. constructing a fracture water-resisting layer; 8. water-retaining and water-flushing-preventing high-efficiency coal mining. The invention is characterized in that the pre-mining coal seam is layered and presplitting by covering the thick hard sandstone layer, the original hard sandstone layer is covered on the coal seam to be changed into the anti-impact waterproof layer, the impact problem caused by the thick hard sandstone layer in the coal mining process is solved, a great amount of slurry loss and waste in the grouting plugging process are avoided, the in-situ protection of the overlying strata is realized, the pressure relief fracturing and the grouting plugging are both realized by adopting the same drilling, the dynamic disaster and the permeable disaster in the coal mining process are prevented and treated, and the good effects of dual purposes of one hole and two disasters are realized.
Description
Technical Field
The invention belongs to the technical field of water retention and washout prevention coal mining, and particularly relates to a water retention and washout prevention coal mining method based on a pressure relief fracture grouting reconstructed washout prevention water-resisting layer.
Background
The western mining areas of China belong to arid and semiarid climates, water resources are short, the ecological environment is extremely fragile, the burial depth of coal beds of the western mining areas is relatively shallow, the coal resource reserves are large, the occurrence condition is good, and the method is suitable for large-scale and high-strength coal resource development. The large-scale and high-strength development and utilization of coal resources inevitably lead to the generation of ecological environment damage problems such as rock stratum fracture, earth surface subsidence, underground water loss and the like, the objectively existing problems can further cause engineering geological disasters such as roof falling, surrounding rock alteration, surrounding rock large deformation, mine water permeability accidents and the like, western mining areas in China are affected by sedimentation and sedimentation environments, thick-layer hard sandstones with strong integrity and good integrity are commonly formed above the dwarf coal seam in the mining area, the thick hard sandstones are important factors for mine rock burst, the safety exploitation of mine coal resources is severely restricted, the existence of the hard and thick sandstones leads to the increase of the interval of rock covering fracture, a large amount of elastic energy is accumulated in the overlying strata of a mine working face, when the hard and thick sandstone slides or breaks, the accumulated elastic energy is suddenly released, power disasters such as impact mine pressure or mine vibration are formed, the power disasters lead to the development and extension of water-guiding fissures, the original water-resisting layers and water-bearing layers in the stratum structures are destroyed, and the mine water burst accidents are further induced. Therefore, a water retention and anti-washout coal mining method is needed.
At present, domestic water-retention coal mining method researches are roughly divided into three types: the method comprises the steps of adjusting a coal mining process (such as layered mining, height-limited mining, strip mining and the like) before mining, grouting and plugging a water guide fracture zone in the mining process, and transferring and storing underground water resources after mining.
The pre-mining adjustment coal mining process is a water-retaining coal mining method which is used for reducing the production efficiency of mines and is at the expense of a large amount of coal resources, and the method does not meet the requirement of efficient development of coal resources in China. For example, patent application number CN201510030068.9 discloses a method for realizing water retention coal mining in a coal mining area, which combines layered spaced mining with height-limiting mining, adopts layered spaced mining under the premise of limiting the mining height of layered mining, ensures the stability of a overlying strata by adjusting the coal mining method and process parameters, and better protects water resources in the mining area, but the method achieves the aim of protecting the integrity of the aquifer by reducing the coal mining intensity and sacrificing the existing mine productivity, and does not fundamentally solve the problem of water permeability caused by the breakage of the overlying strata.
The grouting plugging of the water-guiding fracture zone in the mining process is the most applied water-retaining coal mining technology at present, but coal mining activities can lead the water-guiding fracture zone to longitudinally develop to the overburden aquifer, so that disturbance damage of the overburden aquifer is caused, and then a water-guiding fracture channel is formed, at the moment, grouting plugging can lead a large amount of slurry mixed underground water to flow into a goaf along the water-guiding fracture channel, the plugging effect is poor, large-area pollution of underground water can be caused, and the method belongs to a passive solution after the overburden aquifer is damaged, and in-situ protection of the overburden aquifer cannot be completed. For example, patent application number CN202210791263.3 discloses a dynamic grouting interception water shutoff method for a fully broken aquifer of a mining overburden, by conducting layered grouting on the aquifer of the overburden and the top of a water-guiding fracture zone, grouting the aquifer of the overburden into the aquifer of the overburden or the weakly permeable layer, and preventing water supply in the aquifer from the source aspect, the water inflow of a goaf is well controlled.
The post-mining groundwater resource transfer storage belongs to a passive solution method after a overburden aquifer and groundwater resources are damaged, for example, patent application number CN201410561497.4 discloses a water retention method for guiding water sources to store goafs by drilling holes in the ground of a coal mine area, the water sources are introduced into the underground goafs for storage in a mode of constructing water source drainage holes in the ground, the goafs are utilized to better protect the water resources, but the method needs to construct the drainage holes to finish the transfer storage of the water sources, a large number of drainage holes can cause secondary damage to the original overburden, further development and extension of mining cracks are very easy to cause, further engineering disasters such as overburden falling and roof water penetration are caused in mines, and great potential safety hazards are brought to mine work.
In summary, the water-retention coal mining method proposed at present mainly has the following problems: (1) The grouting plugging effect is poor, so that a great amount of slurry is easily lost and wasted, and the economic investment cost of a mine is increased; (2) The proposed passive solution method after the destruction of the overburden aquifer and the pollution of water resources is difficult to truly realize the in-situ protection of the overburden aquifer; (3) The problems associated with impact disasters and permeable disasters are ignored in the research, and no reasonable and effective water-retention and water-proof coal mining method can be used for simultaneously preventing and controlling dynamic disasters and permeable disasters.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the water-retaining anti-flushing coal mining method based on the pressure relief fracture grouting and the anti-flushing water-resisting layer, which can realize layered pre-splitting of the thick hard sandstone layer covered on the pre-mining coal seam, change the original thick hard sandstone layer covered on the coal seam into the anti-flushing water-resisting layer in a grouting modification mode, solve the problem of impact caused by the thick hard sandstone layer in the coal mining process, avoid great loss and waste of slurry in the grouting plugging process, realize in-situ protection of the overlying strata, and in addition, the pressure relief fracturing and the grouting plugging both adopt the same drilling, greatly reduce construction difficulty and economic cost, better control dynamic disasters and permeable disasters in the coal mining process, play a good role of 'one-hole dual-purpose' and 'two-one-treatment', and are convenient to popularize and use.
In order to solve the technical problems, the invention adopts the following technical scheme: the water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to remanufacture an anti-flushing water-resisting layer is characterized by comprising the following steps of:
step one, exploring stratum information of mining areas: carrying out mining area stratum overlying strata structural feature analysis based on hydrogeological exploration reports and drilling histograms of the mining area, and determining mining area stratum information, wherein the mining area stratum information comprises a surface soil layer, a loose permeable layer, a diving aquifer, a clay aquifer, a confined aquifer, a mudstone aquifer, a thick hard sandstone layer, a silty sandstone layer, a sandstone basic roof, a mudstone direct roof and space occurrence positions and thicknesses of coal seams;
step two, core sample preparation and physical and mechanical parameters of each layer of stratum in mining area are tested: drilling holes on site to obtain a core sample, and testing the core sample to obtain physical mechanical parameters of each layer of stratum in a mining area, wherein the physical mechanical parameters comprise volume weight, compressive strength, tensile strength, elastic modulus, water content and permeability;
step three, layering the thick and hard sandstone layer: layering the thick and hard sandstone layer according to the space occurrence position and the thickness of the thick and hard sandstone layer, wherein the thick and hard sandstone layer comprises an upper sandstone layer and a lower sandstone layer;
fourthly, carrying out multi-group directional drilling on the mining area: constructing a plurality of groups of directional drilling holes from the ground, wherein the directional drilling holes comprise a directional drilling hole vertical section and a plurality of directional drilling hole horizontal sections which are communicated with the directional drilling hole vertical section, the directional drilling hole vertical section is constructed from the ground to a overburden hard and thick sandstone layer, the directional drilling hole horizontal sections are constructed in an upper sandstone layering layer and a lower sandstone layering layer, and the directional drilling hole horizontal sections are parallel to the advancing direction of a coal face;
step five, hydraulic fracturing pressure relief: injecting hydraulic fracturing agents into the upper sandstone layer and the lower sandstone layer through a temporary water injection pump station, a movable water pump truck, a ground water delivery pipe, a high-pressure water injection pipe and a water flow injection pipe, and performing fracturing pressure relief on the upper sandstone layer and the lower sandstone layer to form pressure relief cracks in the upper sandstone layer and the lower sandstone layer;
step six, constructing an anti-impact waterproof layer: injecting anti-impact shock-absorbing slurry into the lower sandstone layer by layer through a ground grouting station and a grouting pipe 30 days before coal seam mining, modifying the lower sandstone layer into an anti-impact water-resisting layer through grouting, and closing a ground grouting valve when the grouting pressure in a grouting pipeline is greater than a preset pressure, and stopping grouting;
step seven, constructing a fracture water-resisting layer: in order to ensure the effect of the anti-flushing water-resisting layer, after the anti-flushing water-resisting layer is maintained for 7 days, crack water-resisting slurry is injected into the upper sandstone layer by layer through a ground grouting station and a grouting pipe, the upper sandstone layer is modified into the crack water-resisting layer through grouting, and when the grouting pressure in a grouting pipeline is greater than a preset pressure, a ground grouting valve is closed, and grouting is stopped;
step eight, water-retaining anti-flushing high-efficiency coal mining: and (3) extracting the coal seam to be extracted from front to back by using a coal mining machine along the length direction of the coal seam in the coal mining area.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the fourth step, the directional drilling is a hole with multiple bottoms, namely, a group of directional drilling comprises a drilling vertical section and drilling horizontal sections positioned at different layers, and the drilling horizontal sections positioned at different layers respectively carry out pressure relief fracturing and grouting water blocking on the upper sandstone layering and the lower sandstone layering.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the fourth step, the directional drilling arrangement mode is arranged in rows, and the horizontal intervals of the drilling holes of different drilling vertical sections are 10m.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the fifth step, the hydraulic fracturing pressure relief process comprises the following steps:
s1, constructing a cement water-retaining pipeline: after the construction of each group of directional drilling holes is finished, immediately extending a flexible rubber pipe into the directional drilling holes to the tail ends of the drilling holes, injecting cement paste into the flexible rubber pipe from the ground until the cement paste returns to the ground from the tail ends of the flexible rubber pipe to an annulus between the flexible rubber pipe and the walls of the directional drilling holes, forming an annular cement sleeve after the cement paste is solidified, and withdrawing the flexible rubber pipe after the annular cement sleeve reaches the design strength;
s2, assembling a ground fracturing device: connecting a high-pressure water injection pipe and a water flow injection pipe on the ground through a sleeve, installing the other end of the high-pressure water injection pipe to a temporary water injection pump station, fixing the temporary water injection pump station on the ground to ensure construction safety and fracturing efficiency in the hydraulic fracturing process, installing a ground water pipe to a first water injection connection port, fixing a ground water delivery pipe group, scheduling a movable water pump truck team to a ground fracturing area after the fracturing equipment is assembled, installing the other end of the ground water pipe to a second water injection connection port on the movable water pump truck, and after all fracturing equipment is checked to have normal performance and connection between the equipment is correct, conveying the water flow injection pipe and the high-pressure water injection pipe into the underground fracturing area along an annular cement sleeve;
s3, staged hydraulic fracturing operation: after the first water injection valve and the second water injection valve are sequentially opened, the water injection engine is started to pump the hydraulic fracturing agent to the water flow injection pipe for fracturing, and solid propping agents in the hydraulic fracturing agent can be embedded into the pressure relief cracks through the water flow injection pipe under the impact of high-pressure water flow in the fracturing process, so that the pressure relief cracks can be supported when the water flow pressure is released, and the cracks are kept in an open state continuously;
s4, section blocking isolation: after the fracturing of the first section of drilling area is completed, under the condition that the occurrence state of primary water resources in the pressure relief fracture is not affected, the hydraulic fracturing agent in the drilling is returned, and the hydraulic fracturing agent is sent into the annular cement casing through a cable-controlled blocking bridge plug to isolate the first section of fracturing area;
s5, repeating the steps S1 to S4 for a plurality of times, sequentially performing hydraulic fracturing pressure relief work of the thick and hard sandstone layer, and recovering a blocking bridge plug in the annular cement casing after the fracturing pressure relief work of the whole horizontal section of the drilling hole is completed.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the step S1, the thickness of the annular cement sleeve is 10-20 mm, so that the hydraulic fracturing efficiency of the annular cement sleeve can be improved, and the problem of water resource loss of an aquifer can be well solved.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate anti-flushing water-resisting layer comprises the following steps ofIs characterized in that: in step S3, the hydraulic fracturing agent includes active water and a solid propping agent, wherein the injection displacement of the active water in the water flow injection tube is 3m 3 /min～5m 3 And/min, wherein the solid propping agent is fine quartz sand, and the average sand-water ratio is 1:10.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the step S3, in the staged hydraulic fracturing process, water injection pressurization is carried out through the temporary water injection pump station, after the water injection pressure reaches the peak pressure, pressure maintaining water injection enables the pressure relief fracture to continue to expand, and after the water injection pressure is reduced and tends to be stable, the second water injection valve, the water injection engine and the first water injection valve are sequentially closed, so that hydraulic fracturing operation is stopped.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the sixth step, the anti-impact shock-absorbing slurry is prepared from fly ash, sodium silicate, silicate cement, synthetic fibers and water, wherein the fly ash is used as aggregate, the mass percentage is 40-50%, the sodium silicate is used as accelerator, the mass percentage is 3-5%, the modulus of the sodium silicate is 2.5-3, the mass percentage of the silicate cement is 15-25%, and the mixing ratio of the synthetic fibers is 2-3 kg of the anti-impact shock-absorbing slurry per cubic meter.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the seventh step, the crack water-resistant slurry is prepared from clay, sodium silicate, silicate cement, calcium hydroxide and water, wherein the clay is used as aggregate, the mass percentage is 40% -60%, the sodium silicate is used as accelerator, the mass percentage is 5% -10%, the modulus of the sodium silicate is 2.5-3, the mass percentage of the silicate cement is 10% -20%, and the mass percentage of the calcium hydroxide is 10% -15%.
The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to regenerate the anti-flushing water-resisting layer is characterized by comprising the following steps of: in the sixth step and the seventh step, the preset pressure is 6MPa to 8MPa.
Compared with the prior art, the invention has the following advantages:
1. the invention can simultaneously meet the requirements of hydraulic fracturing of hard and thick sandstone layers and directional drilling of grouting water blocking of mining cracks, and is convenient to popularize and use.
2. The invention can well prevent and treat dynamic disasters and permeable disasters in the coal mining process at the same time, realizes water retention coal mining, and has the advantages of reliability, stability and good use effect.
3. The method has simple steps, realizes the in-situ protection of the overburden aquifer in the coal mining process, and is convenient to popularize and use.
In summary, the method can realize layered pre-splitting of the thick hard sandstone layer on the pre-mining coal seam, changes the original thick hard sandstone layer on the coal seam into the anti-impact waterproof layer in a grouting modification mode, solves the impact problem caused by the thick hard sandstone layer in the coal mining process, avoids a great amount of slurry loss and waste in the grouting plugging process, realizes in-situ protection of the overlying strata, and in addition, the pressure relief fracturing and grouting plugging are both realized by adopting the same drilling, thereby greatly reducing construction difficulty and economic cost, well preventing and controlling dynamic disasters and permeable disasters in the coal mining process, achieving the good effects of 'one-hole dual-purpose' and 'two disasters one-treatment', and being convenient to popularize and use.
Drawings
FIG. 1 is a schematic diagram of a pre-production grouting construction anti-impact water-resistant layer of the invention.
FIG. 2 is a schematic diagram showing the distribution of the post-production anti-impact waterproof layer.
FIG. 3 is an overall schematic of the fracturing and pressure relief of the hard and thick sandstone layer of the present invention.
FIG. 4 is a partial schematic view of the hydraulic fracturing of the first stage of the hard and thick sandstone layer of the present invention.
FIG. 5 is a partial schematic view of staged hydraulic fracturing of a hard and thick sandstone layer of the present invention.
Fig. 6 is a flow chart of the method of the present invention.
Reference numerals illustrate:
1-surface vegetation; 2-surface soil layer; 3-a loose water permeable layer;
4-diving aquifers; 5-a clay water barrier; 6-confined aquifer;
7-mudstone water-resisting layer; 8-thick hard sandstone layer; 81-layering sandstone;
82-lower sandstone layering; 9-silty sandstone layer; 10-sandstone base roof;
11-mudstone direct roof; 12-coal seam; 13-sandstone bottom plate;
14-directional drilling; 141—directional drilling vertical section; 142—directional drilling horizontal section;
15-a temporary water injection pump station; 151-a first water injection valve; 152-water injection engine;
153-a first water injection connection port; 16-a mobile water pump truck; 161-a second water injection connection port;
162-a second water injection valve; 163-a water storage tank; 17-a ground water pipe;
18-annular cement sheath; 19-a high-pressure water injection pipe; 20-water flow injection tube;
201-connecting sleeve; 202—a first sealing plug; 203-a second sealing plug;
204, injection nozzle; 21-pressure relief fissures; 22-active water;
23-a solid proppant; 24-blocking bridge plugs; 25-a ground grouting station;
26-grouting pipe; 27-anti-impact shock-absorbing slurry; 28-crack water-blocking slurry;
29-a water-resistant layer; 30-fracture water barrier.
Detailed Description
In order to enable those skilled in the art to better understand the technical solutions of the embodiments of the present invention, the following description will make clear and complete descriptions of the technical solutions of the embodiments of the present invention with reference to the accompanying drawings, and it is apparent that the embodiments described in the present invention are only some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by a person skilled in the art without the benefit of the teachings of this invention, shall fall within the scope of the invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the invention and in the drawings are used for distinguishing between similar objects and not necessarily for describing a relative importance or a sequential or chronological order of the description of the objects. Thus, objects defining "first", "second" features are to be understood as data so used may be interchanged where appropriate in order to describe aspects of embodiments of the invention herein. In the description of the present invention, the term "plurality" means two or more, and is not otherwise specifically defined
The technical scheme of the present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments, it should be noted that the embodiments of the present invention and features in the embodiments may be combined with each other without conflict.
As shown in fig. 1 to 6, the water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting and the anti-flushing water-resisting layer comprises the following steps:
step one, exploring stratum information of mining areas: analyzing and researching hydrogeological exploration reports and drilling histograms of a mining area to obtain stratum overlying rock structural characteristics of the mining area and stratum information of the mining area, and determining the stratum information of the mining area, wherein the stratum information comprises spatial occurrence positions and thicknesses of a topsoil layer 2, a loose permeable layer 3, a diving aquifer 4, a clay water-resisting layer 5, a confined aquifer 6, a mudstone water-resisting layer 7, a thick and hard sandstone layer 8, a silty sandstone layer 9, a sandstone basic roof 10, a mudstone direct roof 11 and a coal seam 12 below a surface vegetation 1;
step two, core sample preparation and physical and mechanical parameters of each layer of stratum in mining area are tested: performing on-site drilling coring, preparing the obtained drilling core into a standard cylindrical sample, and performing rock mechanical property test in a cylindrical sample unfolding chamber, wherein the concrete test comprises the following steps: and (3) a uniaxial compression test, a Brazilian split test, a water content test and a penetration test, obtaining physical mechanical parameters such as volume weight, compressive strength, tensile strength, elastic modulus, poisson's ratio, water content, penetration characteristics and the like of the overburden rock layer of the mining area, evaluating the risk of the impact accident of the mining area based on the physical mechanical characteristics of each rock layer, and calculating the development degree of the mining fracture zone above the coal layer.
Step three, layering the thick and hard sandstone layer: according to the space occurrence position and thickness of the thick hard sandstone layer 8, a layering scheme of the thick hard sandstone layer 8 is preliminarily established, the hard sandstone layer 8 is divided into an upper sandstone layer 81 and a lower sandstone layer 82, and layering fracturing pressure relief and layering grouting modification work are carried out on the hard sandstone layer 8;
fourthly, carrying out multi-group directional drilling on the mining area: constructing a plurality of groups of directional drilling holes 14 from the ground, wherein the directional drilling holes 14 comprise a directional drilling hole vertical section 141 and a plurality of directional drilling hole horizontal sections 142 which are communicated with the directional drilling hole vertical section 141, the directional drilling hole vertical section 141 is constructed from the ground to the overburden hard and thick sandstone layer 8, the directional drilling hole horizontal sections 142 are respectively constructed in the upper sandstone layer 81 and the lower sandstone layer 82, and the directional drilling hole horizontal sections 142 are parallel to the advancing direction of the coal mining working face;
step five, hydraulic fracturing pressure relief: the hydraulic fracturing agent is injected into the upper sandstone layer 81 and the lower sandstone layer 82 at high pressure through the temporary water injection pump station 15, the movable water pump truck 16, the ground water pipe 17, the high-pressure water injection pipe 19 and the water flow injection pipe 20, and the upper sandstone layer 81 and the lower sandstone layer 82 are subjected to layered fracturing and pressure relief, so that pressure relief cracks 21 are formed in the upper sandstone layer 81 and the lower sandstone layer 82.
Step six, constructing an anti-impact waterproof layer: injecting the anti-impact shock-absorbing slurry 27 into the lower sandstone layering 82 through the ground grouting station 25 and the grouting pipe 26 30 days before coal seam mining, modifying the lower sandstone layering 82 into an anti-impact water-resisting layer 29 through grouting, and closing a ground grouting valve when the grouting pressure in a grouting pipeline is greater than a preset pressure, and stopping grouting;
step seven, constructing a fracture water-resisting layer: in order to ensure the effect of the anti-flushing waterproof layer 29, after the anti-flushing waterproof layer 29 is maintained for 7 days, crack water-blocking slurry 28 is injected into the upper sandstone layering 81 through the ground grouting station 25 and the grouting pipe 26, the upper sandstone layering 81 is modified into a crack waterproof layer 30 through grouting, and when the grouting pressure in a grouting pipeline is greater than a preset pressure, a ground grouting valve is closed, and grouting is stopped;
step eight, water-retaining anti-flushing high-efficiency coal mining: after the anti-flushing water-resisting layer 29 and the fracture water-resisting layer 30 which are covered on the coal mining area reach the maintenance time, the underground coal mining operation is carried out, and the coal seam 12 to be mined is mined back and forth by adopting mine mining equipment along the length direction of the coal seam 12 of the coal mining area.
In another alternative embodiment, the directional drilling holes 14 are multiple holes, that is, the group of directional drilling holes 14 includes one vertical drilling hole section 141 and horizontal drilling hole sections 142 at different levels, and the horizontal drilling hole sections 142 at different levels perform pressure relief fracturing and grouting water blocking on the upper sandstone layer 81 and the lower sandstone layer 82 respectively.
In another alternative embodiment, the directional drilling holes 14 are arranged in a row-to-row manner, and the horizontal intervals between the drilling holes of the different vertical drilling holes 141 are 10m, wherein the length of the vertical directional drilling holes 141 is the distance from the hard and thick sandstone layer 8 to the surface, and the length of the horizontal directional drilling holes 142 is slightly larger than the coal face.
In another alternative embodiment, in step five, the hydraulic fracturing pressure relief process includes the steps of:
s1, constructing a cement water-retaining pipeline: after the construction of each group of directional drilling holes 14 is completed, immediately extending a flexible rubber pipe into the directional drilling holes 14 to the tail end of the drilling holes, injecting cement slurry into the flexible rubber pipe from the ground until the cement slurry returns to the ground from the tail end of the flexible rubber pipe to an annulus between the flexible rubber pipe and the wall of the directional drilling holes 14, forming an annular cement sleeve 18 after the cement slurry is solidified, and withdrawing the flexible rubber pipe after the annular cement sleeve 18 reaches the design strength;
s2, assembling a ground fracturing device: connecting a high-pressure water injection pipe 19 and a water flow injection pipe 20 on the ground through a sleeve, mounting the other end of the high-pressure water injection pipe 19 to a temporary water injection pump station 15, fixing the temporary water injection pump station 15 on the ground to ensure construction safety and fracturing efficiency in the hydraulic fracturing process, mounting a ground water pipe 17 to a first water injection connection port 153, fixing a ground water delivery pipe group, after the fracturing equipment is assembled, dispatching a movable water pump truck team to a ground fracturing area, mounting the other end of the ground water pipe 17 to a second water injection connection port 161 on a movable water pump truck 16, and after all fracturing equipment is checked to have normal performance and connection between the equipment is correct, conveying the water flow injection pipe 20 and the high-pressure water injection pipe 19 into the underground fracturing area along an annular cement sleeve 18;
s3, staged hydraulic fracturing operation: after the first water injection valve 151 and the second water injection valve 162 are sequentially opened, the water injection engine 152 is started to pump the hydraulic fracturing agent to the water flow injection pipe 20 for fracturing, and the solid propping agent 23 in the hydraulic fracturing agent is embedded into the pressure relief fracture 21 through the water flow injection pipe 20 under the impact action of high-pressure water flow in the fracturing process, so that the pressure relief fracture 21 can be supported when the water flow pressure is released, and the fracture is kept in an open state continuously;
s4, section blocking isolation: after the fracturing of the first-stage drilling area is completed, under the condition that the occurrence state of the primary water resources in the pressure relief cracks 21 is not affected, the hydraulic fracturing agent in the drilling is returned, and is sent into the annular cement sleeve 18 through the cable-controlled blocking bridge plug 24, so that the first-stage fracturing area is isolated;
s5, repeating the steps S1 to S4 for a plurality of times, sequentially performing hydraulic fracturing pressure relief work of the thick and hard sandstone layer 8, and recovering the blocking bridge plug 24 in the annular cement sleeve 18 after the fracturing pressure relief work of the whole horizontal section of the drilling hole is completed.
In another alternative embodiment, the diameter of the annular cement pipeline in the hydraulic fracturing pressure relief process is 10 mm-20 mm, and the annular cement sleeve 18 can not only improve the hydraulic fracturing efficiency, but also well solve the problem of water resource loss of the aquifer.
In another alternative embodiment, the hydraulic fracturing agent in the hydraulic fracturing pressure relief process consists of active water and a certain proportion of solid propping agent, wherein the injection displacement of the active water in the water flow injection pipe 19 is 3m 3/min-5 m3/min, the solid propping agent is fine quartz sand, and the average sand-water ratio in the hydraulic fracturing agent is 10%.
In another alternative embodiment, the water flow injection tube 20 is composed of a connecting sleeve 201, a first sealing plug 202, a second sealing plug 203 and an injection nozzle 204, and in the hydraulic fracturing process, the first sealing plug 202 and the second sealing plug 203 form a closed space from the bottom of the annular cement sleeve 18 to the area of the second sealing plug 203, and meanwhile, the hydraulic fracturing agent is injected into the cracks around the drill hole at high pressure through the injection nozzle 204 to complete the hydraulic fracturing work.
In another alternative embodiment, in the stage hydraulic fracturing process, the temporary water injection pump station 15 is used for slowly injecting water to pressurize, when the water injection pressure reaches the peak pressure, the pressure maintaining water injection is performed for a period of time to enable the pressure relief fracture 21 to continue to expand, and when the water injection pressure is obviously reduced and tends to be stable, the second water injection valve 162, the water injection engine 152 and the first water injection valve 151 are sequentially closed to stop the hydraulic fracturing operation.
In another alternative embodiment, the anti-impact shock-absorbing slurry 27 is prepared from fly ash, sodium silicate, silicate cement, synthetic fibers and water, wherein the fly ash is used as aggregate, the mass percent is 40% -50%, the sodium silicate is used as accelerator, the mass percent is 3% -5%, the modulus of the sodium silicate is 2.5-3, the mass percent of the silicate cement is 15% -25%, and the mixing ratio of the synthetic fibers is 2 kg-3 kg of the anti-impact shock-absorbing slurry per cubic meter.
In another alternative embodiment, the crack water-resistant slurry 28 is prepared from clay, sodium silicate, portland cement, calcium hydroxide and water, wherein the clay is used as aggregate, the sodium silicate is used as accelerator, the mass percentage is 5% -10%, the modulus of the sodium silicate is 2.5-3, the mass percentage of the Portland cement is 10% -20%, and the mass percentage of the calcium hydroxide is 10% -15%.
In another alternative embodiment, in the water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to reconstruct an anti-flushing water-resisting layer, the preset pressure in the step six and the step seven is 8-10 MPa.
When the method is used, the hard and thick sandstone layers are subjected to layered fracturing and pressure relief, the cement ratio of grouting materials and grouting materials is selected, and the layered grouting is used for reconstructing the anti-flushing waterproof layer, hydraulic fracturing before mining is carried out by utilizing ground directional drilling, the anti-flushing waterproof layer is constructed by grouting, and the original hard and thick sandstone layers are transformed into the anti-flushing waterproof layer by changing the existing characteristics of the original hard and thick sandstone layers such as thickness, strength, toughness and the like, so that the impact problem in the coal mining process can be solved, the water permeability problem caused by vertical development of mining cracks can be solved, and the aim of water retention and coal mining is fulfilled; the method has the advantages that the impact-resistant water-proof layer can be reproduced by utilizing the ground directional drilling grouting before coal seam stoping under the condition of not changing the coal mining process, the occurrence characteristics of the thickness and strength of the original hard and thick sandstone layer are changed, and the optimization of the hard and thick sandstone layer in the thickness and toughness is realized, so that the mining impact problem is solved, the vertical development of mining cracks is inhibited, the purpose of in-situ protection of a overlying strata is achieved, and the win-win purpose of high-efficiency stoping of coal resources and water resource protection is achieved.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent structural changes made to the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.
Claims (10)
1. The water-retaining and anti-flushing coal mining method based on the pressure relief fracture grouting to remanufacture an anti-flushing water-resisting layer is characterized by comprising the following steps of:
step one, exploring stratum information of mining areas: carrying out mining area stratum overlying strata structural feature analysis based on hydrogeological exploration reports and drilling histograms of the mining area, and determining mining area stratum information, wherein the mining area stratum information comprises a surface soil layer (2), a loose permeable layer (3), a diving aquifer (4), a clay water-resisting layer (5), a confined aquifer (6), a mudstone water-resisting layer (7), a thick hard sandstone layer (8), a silty sandstone layer (9), a sandstone basic roof (10), a mudstone direct roof (11) and space occurrence positions and thicknesses of coal seams (12) below surface vegetation (1);
step two, core sample preparation and physical and mechanical parameters of each layer of stratum in mining area are tested: drilling holes on site to obtain a core sample, and testing the core sample to obtain physical mechanical parameters of each layer of stratum in a mining area, wherein the physical mechanical parameters comprise volume weight, compressive strength, tensile strength, elastic modulus, water content and permeability;
step three, layering the thick and hard sandstone layer: layering the thick and hard sandstone layer (8) according to the space occurrence position and thickness of the thick and hard sandstone layer (8), wherein the thick and hard sandstone layer (8) comprises an upper sandstone layer (81) and a lower sandstone layer (82);
fourthly, carrying out multi-group directional drilling on the mining area: constructing a plurality of groups of directional drilling holes (14) from the ground, wherein the directional drilling holes (14) comprise a directional drilling hole vertical section (141) and a plurality of directional drilling hole horizontal sections (142) which are communicated with the directional drilling hole vertical section (141), the directional drilling hole vertical section (141) is constructed from the ground to a overburden hard and thick sandstone layer (8), the directional drilling hole horizontal sections (142) are constructed in an upper sandstone layer (81) and a lower sandstone layer (82), and the directional drilling hole horizontal sections (142) are parallel to the advancing direction of a coal face;
step five, hydraulic fracturing pressure relief: injecting hydraulic fracturing agents into the upper sandstone layer (81) and the lower sandstone layer (82) through the temporary water injection pump station (15), the movable water pump truck (16), the ground water delivery pipe (17), the high-pressure water injection pipe (19) and the water flow injection pipe (20), and fracturing and pressure relief are carried out on the upper sandstone layer (81) and the lower sandstone layer (82), so that pressure relief cracks (21) are formed in the upper sandstone layer (81) and the lower sandstone layer (82);
step six, constructing an anti-impact waterproof layer: injecting anti-impact shock-absorbing slurry (27) into the lower sandstone layering (82) through a ground grouting station (25) and a grouting pipe (26) 30 days before coal seam mining, modifying the lower sandstone layering (82) into an anti-impact water-resisting layer (29) through grouting, and closing a ground grouting valve when the grouting pressure in a grouting pipeline is greater than a preset pressure, and stopping grouting;
step seven, constructing a fracture water-resisting layer: in order to ensure the effect of the anti-flushing waterproof layer (29), after the anti-flushing waterproof layer (29) is maintained for 7 days, injecting crack water-blocking slurry (28) into the upper sandstone layer (81) through a ground grouting station (25) and a grouting pipe (26), modifying the upper sandstone layer (81) into a crack waterproof layer (30) through grouting, and closing a ground grouting valve when the grouting pressure in a grouting pipeline is greater than a preset pressure, and stopping grouting;
step eight, water-retaining anti-flushing high-efficiency coal mining: and (3) stoping the coal seam (12) to be mined from front to back by using a coal mining machine along the length direction of the coal seam (12) in the coal mining area.
2. The water-retaining and washout-preventing coal mining method based on pressure relief fracture grouting for remanufacturing a washout-preventing water-resisting layer, according to claim 1, is characterized by comprising the following steps: in the fourth step, the directional drilling holes (14) are multiple bottoms, that is, a group of directional drilling holes (14) comprise a drilling vertical section (141) and drilling horizontal sections (142) positioned at different positions, and the drilling horizontal sections (142) positioned at different positions respectively perform pressure relief fracturing and grouting water blocking on the upper sandstone layering (81) and the lower sandstone layering (82).
3. The water-retaining and washout-preventing coal mining method based on pressure relief fracture grouting for remanufacturing a washout-preventing water-resisting layer, according to claim 1, is characterized by comprising the following steps: in the fourth step, a plurality of groups of directional drilling holes (14) are arranged in a row mode, and the horizontal spacing between the drilling holes of different drilling hole vertical sections (141) is 10m.
4. The water-retaining and washout-preventing coal mining method based on pressure relief fracture grouting for remanufacturing a washout-preventing water-resisting layer, according to claim 1, is characterized by comprising the following steps: in the fifth step, the hydraulic fracturing pressure relief process comprises the following steps:
s1, constructing a cement water-retaining pipeline: after the construction of each group of directional drilling holes (14) is completed, immediately extending a flexible rubber pipe into the directional drilling holes (14) to the tail end of the drilling hole, injecting cement slurry into the flexible rubber pipe from the ground until the cement slurry returns to the ground from the tail end of the flexible rubber pipe to an annulus between the flexible rubber pipe and the wall of the directional drilling holes (14), forming an annular cement sleeve (18) after the cement slurry is solidified, and withdrawing the flexible rubber pipe after the annular cement sleeve (18) reaches the design strength;
s2, assembling a ground fracturing device: connecting a high-pressure water injection pipe (19) and a water flow injection pipe (20) on the ground through a sleeve, mounting the other end of the high-pressure water injection pipe (19) to a temporary water injection pump station (15), fixing the temporary water injection pump station (15) on the ground to ensure construction safety and fracturing efficiency in the hydraulic fracturing process, mounting a ground water pipe (17) to a first water injection connector (153), fixing a ground water pipe group, after the fracturing equipment is assembled, dispatching a movable water pump truck to a ground fracturing area, mounting the other end of the ground water pipe (17) to a second water injection connector (161) on a movable water pump truck (16), and after checking that all the fracturing equipment is normal in performance and connection among the equipment is correct, conveying the water flow injection pipe (20) and the high-pressure water injection pipe (19) to a downhole fracturing area along an annular cement sleeve (18);
s3, staged hydraulic fracturing operation: after the first water injection valve (151) and the second water injection valve (162) are sequentially opened, the water injection engine (152) is started to pump the hydraulic fracturing agent to the water flow injection pipe (20) for fracturing, and solid propping agent (23) in the hydraulic fracturing agent can be embedded into the pressure relief fracture (21) through the water flow injection pipe (20) under the impact of high-pressure water flow in the fracturing process, so that the pressure relief fracture (21) can be supported when the water flow pressure is released, and the fracture is kept in an open state continuously;
s4, section blocking isolation: after the fracturing of the first-stage drilling area is finished, under the condition that the occurrence state of primary water resources in the pressure relief fracture (21) is not influenced, the hydraulic fracturing agent in the drilling is returned, and the hydraulic fracturing agent is sent into the annular cement sleeve (18) through a cable-controlled blocking bridge plug (24) to isolate the first-stage fracturing area;
s5, repeating the steps S1 to S4 for a plurality of times, sequentially carrying out hydraulic fracturing pressure relief work of the thick and hard sandstone layer (8), and recovering the blocking bridge plug (24) in the annular cement casing (18) after the fracturing pressure relief work of the whole horizontal section of the drilling hole is completed.
5. The water-retaining and washout-preventing coal mining method based on the pressure relief fracture grouting and the washout-preventing water-resisting layer is characterized by comprising the following steps of: in the step S1, the thickness of the annular cement sleeve (18) is 10-20 mm, and the annular cement sleeve (18) can not only improve the hydraulic fracturing efficiency, but also well solve the problem of water resource loss of an aquifer.
6. The water-retaining and washout-preventing coal mining method based on the pressure relief fracture grouting and the washout-preventing water-resisting layer is characterized by comprising the following steps of: in step S3, the hydraulic fracturing agent comprises active water (22) and a solid propping agent (23), wherein the injection displacement of the active water in the water flow injection tube (19) is 3m 3 /min～5m 3 And/min, wherein the solid propping agent is fine quartz sand, and the average sand-water ratio is 1:10.
7. The water-retaining and washout-preventing coal mining method based on the pressure relief fracture grouting and the washout-preventing water-resisting layer is characterized by comprising the following steps of: in the step S3, in the staged hydraulic fracturing process, water injection pressurization is carried out through the temporary water injection pump station (15), after the water injection pressure reaches the peak pressure, pressure maintaining water injection enables the pressure relief fracture (21) to continue to expand, and after the water injection pressure is reduced and tends to be stable, the second water injection valve (162), the water injection engine (152) and the first water injection valve (151) are sequentially closed, so that hydraulic fracturing operation is stopped.
8. The water-retaining and washout-preventing coal mining method based on pressure relief fracture grouting for remanufacturing a washout-preventing water-resisting layer, according to claim 1, is characterized by comprising the following steps: in the sixth step, the anti-impact shock-absorbing slurry (27) is prepared from fly ash, sodium silicate, silicate cement, synthetic fibers and water, wherein the fly ash is used as aggregate, the mass percentage is 40% -50%, the sodium silicate is used as accelerator, the mass percentage is 3% -5%, the modulus of the sodium silicate is 2.5-3, the mass percentage of the silicate cement is 15% -25%, and the mixing ratio of the synthetic fibers is 2 kg-3 kg of the anti-impact shock-absorbing slurry per cubic meter.
9. The water-retaining and washout-preventing coal mining method based on pressure relief fracture grouting for remanufacturing a washout-preventing water-resisting layer, according to claim 1, is characterized by comprising the following steps: in the seventh step, the crack water-resistant slurry (28) is prepared from clay, sodium silicate, silicate cement, calcium hydroxide and water, wherein the clay is used as aggregate, the mass percentage is 40% -60%, the sodium silicate is used as accelerator, the mass percentage is 5% -10%, the modulus of the sodium silicate is 2.5-3, the mass percentage of the silicate cement is 10% -20%, and the mass percentage of the calcium hydroxide is 10% -15%.
10. The water-retaining and washout-preventing coal mining method based on pressure relief fracture grouting for remanufacturing a washout-preventing water-resisting layer, according to claim 1, is characterized by comprising the following steps: in the sixth step and the seventh step, the preset pressure is 6MPa to 8MPa.
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| CN202311746796.0A CN117722179A (en) | 2023-12-18 | 2023-12-18 | Water-retaining and anti-flushing coal mining method based on pressure relief fracture grouting to reconstruct anti-flushing water-resisting layer |
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