Method for detecting overlying strata water flowing fractured zone and separation space of steeply inclined coal seam through ground trifurcate holes

Abstract

The invention discloses a method for detecting an overlying strata water flowing fissure zone and separation space of a steeply inclined coal seam through ground trident holes. The method comprises the steps that detection drill holes are arranged, specifically, the ground trident holes are adopted; geological casing pipes are placed in the main hole and the directional section of the S-shaped branch directional drill hole, the detection section of the S-shaped branch directional drill hole is an open hole, and the detection section is drilled into the fissure zone range of the steeply inclined coal seam or a coal seam roof; in the drilling process of the detection section, the leakage position and the leakage amount are comprehensively determined through a drilling flushing fluid consumption ground real-time monitoring system and a well leakage instrument, and the development height of the maximum water flowing fractured zone height of overlying strata of the horizontal section fully-mechanized caving stope of the steeply-inclined super-thick coal seam is obtained. And through in-hole acoustic logging and drilling peeping technologies, the spatial development characteristics of the overlying strata water flowing fractured zone and the separation layer are determined, and the development range and the communication condition of the mining-induced fractured zone are evaluated. Spatial development conditions and development degree data of the overlying strata water flowing fractured zone and the separation layer are accurately detected, drilling machine moving is reduced, engineering cost is saved, and efficient exploration of the overlying strata water flowing fractured zone of the steeply inclined coal seam is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of detection of water-conducting fracture zones in overburden rocks, and in particular to a method for detecting water-conducting fracture zones and separation spaces in overburden rocks of steeply inclined coal seams by using a ground three-pronged hole. Background Art

[0002] my country's western coal resources are rich in reserves, and there are large-scale steeply inclined and extra-thick coal seams in western mining areas such as Xinjiang and Gansu. Since most of the western mining areas are arid and semi-arid ecologically fragile areas, the problem of water shortage is serious. At present, the horizontal segmented fully mechanized caving method is often used for steeply inclined and extra-thick coal seams. Due to the special geological and mining conditions, the deformation and damage of the overburden are severe, and the development characteristics of the water-conducting fracture zone and the separation space are extremely complex. If the development range of the overburden water-conducting fracture zone caused by the mining of steeply inclined coal seams exceeds the limit, it will lead to water resource loss and mine water hazards. On the one hand, the mining-induced water-conducting fractures will drain the groundwater in the weakly cemented sandstone aquifer and the loose porous aquifer in the roof of the coal seam, resulting in a significant drop in the groundwater level, causing surface subsidence and aggravating surface desertification. On the other hand, the weakly cemented sandstone aquifer and the porous aquifer in the loose layer of the roof are prone to burst into the mine along the mining fractures, posing a threat of water and sand burst. At the same time, as the precipitation line in my country has moved westward in recent years, if extreme weather occurs suddenly during the rainy season, there is a danger that surface water will collapse into the mine along the collapse pit. Based on the above analysis, mine water hazards and water resource protection have become the bottleneck restricting the safe and efficient development of steeply inclined and extra-thick coal seams in western mining areas. It is extremely important to accurately determine the development of overburden water-conducting fracture zones and delamination spaces in the fully mechanized caving mining of steeply inclined and extra-thick coal seams.

[0003] The height of the overburden water-conducting fracture zone is closely related to factors such as coal seam mining thickness, mining method, coal seam inclination and overburden lithology. At present, the measurement technology of the height of the overburden water-conducting fracture zone includes ground drilling observation method, underground drilling observation method and geophysical detection method. The ground drilling observation method drills holes to the top of the coal seam through ground construction, and observes the development of overburden mining fractures by using the drilling leakage. This technology has the advantages of being intuitive and reliable, but the drilling workload is large and the cost is high. The underground drilling observation method constructs an inclined borehole underground and uses double capsule water injection to observe the development of roof rock fractures. Its advantage is that the drilling workload is relatively small, but there is a certain observation error. At the same time, the observation range is limited, which is difficult to adapt to the mining of extra-thick coal seams. Geophysical detection methods include electrical method, electromagnetic method, seismic wave method, etc. Its advantages are easy implementation and controllable cost, but its detection accuracy is greatly affected by inversion interpretation.

[0004] In recent years, there are some mature detection methods and processes for the height of the water-conducting fracture zone in the overburden of nearly horizontal coal seams. The characteristics of overburden migration and destruction in the mining face of steeply inclined coal seams are significantly different from those in the mining of nearly horizontal coal seams. The deformation and destruction of the overburden on the uphill side of the mining face of steeply inclined coal seams is severe; due to the filling effect of the falling gangue, the deformation and destruction of the overburden on the downhill measurement is suppressed. At the same time, the stability of the borehole in the steeply inclined strata is extremely poor, and the conventional drilling method is prone to hole collapse and drilling burial, which seriously affects the efficient implementation of water-conducting fracture zone observation. Therefore, the scope of overburden destruction in steeply inclined coal seams is asymmetric. Conventional methods have problems such as large drilling workload, frequent relocation of drilling sites, difficulty in coordination, and easy collapse of boreholes in steeply inclined strata. It is difficult to meet the needs of detecting water-conducting fractures and delamination spaces in the overburden of steeply inclined and extra-thick coal seams. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to provide a method for detecting the water-conducting fracture zone and the separation space of the overburden of steeply inclined coal seams through a ground three-pronged hole, so as to solve the problems of large drilling workload, frequent relocation of drilling sites, great coordination difficulty, and easy collapse of drilling holes in steeply inclined strata.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for detecting water-conducting fracture zones and separation spaces in overburden rocks of steeply inclined coal seams using a ground three-pronged hole comprises the following steps:

[0008] (A) Arrangement of exploratory drilling: Use ground three-pronged drilling, that is, determine the hole location on the ground, drill a main hole and three S-shaped branch directional holes;

[0009] (B) Geological casings are lowered in the directional sections of the main hole and the S-shaped branch directional drilling holes, and the detection section of the S-shaped branch directional drilling holes is an open hole. The detection section of the S-shaped branch directional drilling holes is drilled into the fracture zone range or the coal seam roof of the steeply inclined coal seam;

[0010] (C) During the drilling process of the detection section of the S-shaped branch directional drilling, the ground real-time monitoring system for the consumption of drilling fluid and the well leakage meter are used to comprehensively determine the specific leakage location and leakage amount, so as to obtain the maximum development height of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving mining area of ​​the steeply inclined and extra-thick coal seam. The development characteristics of the overburden water-conducting fracture zone and the stratum separation space are comprehensively determined by in-hole sonic logging and borehole peep technology, and the development range and connectivity of the mining fracture zone are evaluated.

[0011] The above-mentioned method of using a ground three-pronged hole to detect the overburden water-conducting fracture zone and delamination space of a steeply inclined coal seam, in step (A), the S-shaped branch directional drilling hole includes a middle branch hole, an uphill branch hole and a downhill branch hole in the mining area; wherein the middle branch hole in the mining area enters from the middle of the overburden water-conducting fracture zone of the steeply inclined coal seam to detect the maximum height of the water-conducting fracture zone and the height of the cross-fall zone in the middle of the mining area; the uphill branch hole enters from the uphill side of the overburden water-conducting fracture zone of the steeply inclined coal seam to detect the maximum height of the water-conducting fracture zone on the uphill side of the mining area; the downhill branch hole enters from the downhill side of the overburden water-conducting fracture zone of the steeply inclined coal seam to detect the maximum height of the water-conducting fracture zone and the delamination of the overburden on the uphill side of the mining area.

[0012] The above-mentioned method of using a ground three-pronged hole to detect the water-conducting fracture zone and the separation space in the overburden of the steeply inclined coal seam, in step (A), when there is no obvious collapse of the ground and there are no obstacles, the ground three-pronged drilling hole adopts a small S directional hole; the opening position of the ground three-pronged drilling hole is located on the ground directly above the working face of the water-conducting fracture zone in the overburden of the steeply inclined coal seam, the ground three-pronged hole lags behind the working face by 100 to 150 meters, and the ground three-pronged drilling hole adopts a three-level hole body structure.

[0013] In the above-mentioned method of using a ground three-pronged hole to detect the water-conducting fracture zone and the separation space in the overburden of a steeply inclined coal seam, in step (A), when the ground collapses significantly or there are obstacles, a large S directional hole is used for the ground three-pronged hole; the opening position of the ground three-pronged hole is arranged on the upper plate of the steeply inclined stratum and is located 5 to 10 meters outside the movement boundary of the stratum; the ground three-pronged hole lags behind the working face by 100 to 150 meters, and the ground three-pronged hole adopts a four-level hole body structure.

[0014] In the above-mentioned ground three-pronged borehole method for detecting the water-conducting fracture zone and the separation space of the overburden of the steeply inclined coal seam, in step (B), when the ground three-pronged borehole adopts a small S directional hole:

[0015] Step (S-1), first main hole construction: vertical main hole construction, enter the stable bedrock 10-20m, and lower the first-level geological casing;

[0016] Step (small S-2), construction of the directional section of the second S-shaped branch directional drilling hole: at the lower part of the first main hole, the directional section of the small S-shaped middle branch hole in the mining area, the directional section of the small S-shaped uphill branch hole and the directional section of the small S-shaped downhill branch hole are respectively constructed, entering the bedrock 60 to 120 meters above the mining fracture zone, and lowering the second geological casing;

[0017] Step (small S-3), construction of the detection section of the three-opening S-shaped branch directional drilling hole: the bottom of the directional section of the second-opening S-shaped branch directional drilling hole continues to be drilled into the detection section of the three-opening S-shaped branch directional drilling hole. The detection section is a bare hole, and the final hole depth of the detection section is to enter the fracture zone or the coal seam roof.

[0018] The above-mentioned ground three-pronged hole detection method for steeply inclined coal seam overburden water-conducting fracture zone and delamination space, in step (small S-1), the diameter of the first opening wellbore is 270-350 mm, the diameter of the first opening geological casing is 230-260 mm, and single-liquid cement slurry with a water-cement ratio of 0.6:1 is used for cementing; in step (small S-2), the diameter of the second opening wellbore is 215-225 mm, the second opening geological casing is 165-190 mm, and a special casing material is used to fill the annular space between the first opening to the second opening section of the borehole and the geological casing; in step (small S-3), the diameter of the third opening borehole is 110-150 mm;

[0019] The special casing material is prepared from clay powder, fly ash, cement, water and additives, wherein the additive is water glass, wherein the ratio of clay powder, fly ash, cement and water is 0.5:0.3:0.2:1, and the content of the additive is 0.3-1% of the cement mass.

[0020] In the above-mentioned ground three-pronged borehole method for detecting the water-conducting fracture zone and the separation space of the overburden of the steeply inclined coal seam, in step (B), when the ground three-pronged borehole adopts a large S directional hole:

[0021] Step (large S-1), construction of the vertical section of the first main hole: vertical main hole construction, enter the stable bedrock 10 to 20 meters, and lower the first-level geological casing;

[0022] Step (large S-2), construction of the S-shaped extension section of the second main hole: construct the S-shaped extension section of the second main hole at the lower part of the vertical section of the first main hole toward the steeply inclined coal seam, enter the position 150 to 200 meters above the coal seam, and the horizontal distance from the working face to be detected is 30 to 80 meters, and lower the geological casing of the second hole;

[0023] Step (large S-3), construction of the directional section of the three-opening large S-shaped branch directional drilling hole: at the lower part of the S-shaped extension section of the second main hole, the directional section of the large S-shaped stope middle branch hole, the directional section of the large S-shaped uphill branch hole and the directional section of the large S-shaped downhill branch hole are respectively constructed, and the target is inserted into the bedrock 30 to 60 meters above the water-conducting fracture zone, the S-shaped directional hole is converted into a vertical drilling hole, and the three-opening geological casing is lowered;

[0024] Step (Big S-4), construction of the detection section of the four-opening large S-shaped branch directional drilling hole: the bottom of the directional section of the three-opening large S-shaped branch directional drilling hole continues to be drilled into the detection section of the four-opening large S-shaped branch directional drilling hole. The detection section is a bare hole, and the final hole depth of the detection section is to enter the fracture zone or the coal seam roof.

[0025] The above-mentioned method for detecting the water-conducting fracture zone and delamination space of the overburden of the steeply inclined coal seam by using a ground three-pronged hole is as follows: in step (large S-1), the diameter of the first wellbore drilling hole is 270-390 mm, the diameter of the first geological casing is 250-280 mm, and single-liquid cement slurry with a water-cement ratio of 0.6:1 is used for cementing; in step (large S-2), the diameter of the second wellbore drilling hole is 215-225 mm, the diameter of the second geological casing is 165-195 mm, and a special casing material is used to fill the annular space between the first and second drilling holes and the geological casing; in step (large S-3), the diameter of the third wellbore is 155-175 mm, the third drilling casing is 125-150 mm, and a special casing material is used to fill the annular space between the third drilling hole and the geological casing; in step (large S-4), the diameter of the fourth drilling hole is 98-130 mm.

[0026] In the above-mentioned ground three-pronged hole method for detecting the water-conducting fracture zone and the separation space of the overburden of the steeply inclined coal seam, in step (C),

[0027] Step (C-1), during the drilling of the branch holes in the middle of the mining area, the uphill branch holes and the downhill branch holes: the ground real-time monitoring system is used to observe the leakage of the drilling flushing fluid, the ground real-time monitoring system dynamically and continuously monitors the leakage of the flushing fluid, and automatically calculates the leakage per unit borehole and the leakage per unit time per unit footage, and the leakage meter is used to test the specific leakage position and leakage size of the drilling flushing fluid within the entire depth range of the borehole, so as to comprehensively determine the height of the maximum water-conducting fracture zone in the middle of the mining area; the sonic logging is used to analyze the fracture rate of the fracture zone formation, and the development characteristics of the overburden water-conducting fracture zone and the separation layer space are comprehensively determined according to the in-hole sonic logging borehole peep technology, and the development range and connectivity of the mining fracture zone are evaluated;

[0028] Step (C-2), after the construction of the central branch hole, the uphill branch hole and the downhill branch hole in the mining area is completed, the casing of the directional section of the S-shaped branch directional drilling hole is cut off and pulled out, and the branch hole is sealed with 0.6:1 single-liquid cement slurry.

[0029] In the above-mentioned ground three-pronged hole method for detecting the water-conducting fracture zone and the separation space of the overburden of the steeply inclined coal seam, in step (C-1):

[0030] Obtain theoretical equation: The logarithmic spiral equation is used to fit the range of the water-conducting fracture zone in the overburden of the steeply inclined coal seam mining area. The six data points used are the three points determined by ground detection, P 上山 , P 中部 and P 下山 , and three points P0, P1 and P2 inherent in the coal seam;

[0031] Where: P 上山 is the location of water-conducting fractures detected by the branch boreholes on the upper mountain, P 中部is the location of water-conducting fractures detected by some branch holes in the stope, P 下山 is the location of water-conducting fractures detected by the downhill branch hole, P0 is the intersection of the upper level and the coal seam roof, P1 is the intersection of the upper level and the bottom plate, and P2 is the intersection of the lower level and the coal seam roof;

[0032] Assume the polar coordinate equation of the logarithmic spiral is:

[0033] r = a·exp(b·θ) (1);

[0034] Where r represents the radial distance, θ represents the rotation angle, and a and b are constants;

[0035] Transform formula (1) into:

[0036] lnr=bθ+lna (2);

[0037] Formula (2) satisfies the form of a straight line equation, and then the coefficients b and lna of formula (2) are fitted to obtain the best approximation;

[0038] Actual measurement: On the section perpendicular to the advancing direction of the mining field, a Cartesian rectangular coordinate system is established with the coal seam inclination direction as the X-axis and the normal direction as the Y-axis. The origin of the coordinate is located at the intersection of the upper level and the coal seam roof, and the coordinates of these 6 points are measured;

[0039] Take the intersection of the upper left roadway roof and the coal seam roof as the coordinate origin, rotate counterclockwise, establish a polar coordinate system, and transform the coordinates of the 6 data points into polar coordinates; use origin software to fit equation (2) and obtain the coefficients b and lna of equation (2);

[0040] Substituting the coefficients b and lna back into equation (1), the polar coordinate equation of the logarithmic spiral is obtained, and the boundary curve of the fracture zone on the section is given, which can predict the development range of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving working face of the steeply inclined and extra-thick coal seam.

[0041] The technical solution of the present invention achieves the following beneficial technical effects:

[0042] 1. The ground three-pronged hole detection technology of the present invention provides a new measurement method for the detection of water-conducting fracture zones and delamination spaces in overburden rocks of steeply inclined coal seams. According to whether there is obvious collapse of the ground or the existence of obstacles, the ground three-pronged boreholes are divided into small S ground three-pronged boreholes and large S ground three-pronged boreholes. Not only can the development of water-conducting fracture zones and delamination spaces in overburden rocks be accurately detected, but also the data on the degree of development of overburden mining fractures can be obtained. At the same time, the relocation of drilling rigs can be reduced, the amount of drilling projects can be greatly reduced, the engineering costs can be saved, the measurement engineering costs of water-conducting fracture zones and delamination spaces in overburden rocks can be reduced, and efficient detection of water-conducting fracture zones in overburden rocks of steeply inclined coal seams can be achieved.

[0043] 2. Use the flushing fluid ground real-time monitoring system and the well leakage meter to comprehensively determine the maximum water-conducting fracture zone height in the middle of the mining area, and use acoustic logging to analyze the fracture rate of the fracture zone formation. The technical solution of the present invention can not only accurately determine the leakage location, but also determine the degree of development of mining fractures. The middle hole of the mining area is used to detect the maximum fracture zone development height and the collapse zone height in the middle of the mining area; the uphill branch hole is used to detect the development height of the water-conducting fracture zone on the uphill side; the downhill branch hole is used to detect the development height of the water-conducting fracture zone on the downhill side and the overburden separation. The spiral equation is used to predict the development range of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving working face of the steeply inclined and extra-thick coal seam, and the equation parameters are obtained through linear regression analysis.

[0044] 3. In view of the asymmetric deformation and damage characteristics of the overburden of steeply inclined coal seams, the ground three-pronged drilling includes a main hole and an S-shaped branch drilling hole, which can realize the actual measurement of the deformation and damage of the overburden in the middle, uphill and downhill sides of the working face, which is intuitive and reliable. At the same time, a multi-level wellbore structure is adopted, and geological casing is lowered in the non-observation section to ensure the stability of the S-hole directional section drilling and avoid the collapse of the hole affecting the efficiency of on-site observation. The ground three-pronged drilling avoids the construction of new detection holes, which can greatly reduce the detection time and engineering costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Ground three-pronged drilling arrangement when there is no obvious ground collapse and no obstacles;

[0046] Figure 2 Ground three-pronged drilling arrangement when the ground has collapsed significantly or there are obstacles;

[0047] Figure 3 Schematic diagram of fitting the range of overburden water-conducting fracture zone in fully-mechanized stratified top-coal caving in steeply inclined and extra-thick coal seams.

[0048] The reference numerals in the figure are as follows: 1-ground three-pronged borehole; 2-main hole; 2-1-vertical section of the main hole; 2-2-S-shaped extension section of the main hole; 3-S-shaped branch directional borehole; 3-1-branch hole in the middle of the mining area; 3-2-uphill branch hole; 3-3-downhill branch hole; 4-steeply inclined coal seam; 5-overburden water-conducting fracture zone; 6-cross-fall zone; 7-loose layer; 8-bedrock; 9-directional drilling rig. DETAILED DESCRIPTION

[0049] Example 1: A mine in the west of China uses a ground three-pronged hole to detect the water-conducting fracture zone and the separation space of the overburden of the steeply inclined coal seam and a method and construction process.

[0050] Step (A), since the inclined length of the working face is only 70m, which is relatively small, there is no obvious collapse of the ground and there are no obstacles, the ground three-pronged drilling adopts a small S directional hole, and a ground three-pronged hole is set only in the middle of the ground just above the working face of the steeply inclined coal seam overburden water-conducting fracture zone, and the drilling adopts a three-level hole body structure.

[0051] Step (B),

[0052] Step (S-1), construction of the first main hole 2: vertical main hole construction, enter the stable bedrock 15m, lower the first-level geological casing; the first drilling hole diameter is Φ311.1mm, and the Φ244.5mm casing is lowered.

[0053] Step (small S-2), construction of the directional section of the second S-shaped branch directional drilling hole: at the lower part of the first main hole, the directional section of the small S-shaped middle branch hole 3-1 in the mining area, the directional section of the small S-shaped uphill branch hole 3-2 and the directional section of the small S-shaped downhill branch hole 3-3 are constructed respectively, entering the bedrock 60m above the mining fracture zone, and lowering the second geological casing; the diameter of the second drilling hole is Φ215.9mm, and a Φ177.8mm casing is inserted, and a special casing material is used to fill the annular space between the drilling hole and the geological casing from the first to the second section of the drilling hole.

[0054] The special casing material is made of clay powder, fly ash, cement, water and additives, the additive is water glass, and the ratio of clay powder, fly ash, cement and water is 0.5:0.3:0.2:1, and the content of the additive is 0.5% of the cement mass.

[0055] Step (small S-3), construction of the detection section of the three-opening S-shaped branch directional drilling hole: continue drilling the detection section of the three-opening S-shaped branch directional drilling hole at the bottom of the directional section of the second-opening S-shaped branch directional drilling hole. The detection section is a bare hole. The diameter of the three-opening borehole is Φ133mm. The final hole depth of the detection section is to enter the fracture zone or the coal seam roof.

[0056] Step (C), using the ground real-time monitoring system for drilling flushing fluid consumption and the well leakage meter to comprehensively determine the specific leakage location and leakage amount, so as to obtain the maximum development height of the water-conducting fracture zone in the middle of the mining area, and comprehensively determine the development characteristics of the overburden water-conducting fracture zone and the stratum space through in-hole sonic logging and borehole peek technology, and evaluate the development range and connectivity of the mining fracture zone.

[0057] During the construction of the detection section of the branch hole 3-1 in the middle of the stope, the ground real-time monitoring system reported that the consumption of drilling flushing fluid was 7.6m 3 / h, the well leakage instrument tested the well bottom vertical depth of 288.42m and lost 6.2m 3 / h, the estimated maximum water-conducting fracture zone height in the middle of the stope is 96.32m;

[0058] During the construction of the detection section of the uphill branch hole 3-2, the ground real-time monitoring system reported that the consumption of drilling fluid was 6.5m 3 / h, the well leakage instrument tested the well bottom vertical depth of 301.63m and lost 4.6m 3 / h, it is estimated that the maximum water-conducting fracture zone height in the mining area is 57.49m;

[0059] During the construction of the detection section of the downhill branch hole 3-3, the ground real-time monitoring system reported that the consumption of drilling fluid was 7.2m 3 / h, the well leakage instrument tested the well bottom vertical depth of 303.68m and lost 5.1m 3 / h, it is estimated that the maximum water-conducting fracture zone height in the mining area is 115.72m. During the drilling process, there was no drill drop phenomenon, and the borehole peeping showed that the overburden stratum was not developed.

[0060] In polar coordinates, P0, P1, P2, P 上山 , P 中部 , P 下山 The coordinates of these six points are shown in Table 1 below.

[0061] Table 1 Coordinates of points in polar coordinates of Example 1

[0062] serial number Radial distance (m) Angle θ(°) <![CDATA[p0]]> 2.8 0 <![CDATA[p1]]> 19.23 104 <![CDATA[p 上山 ]]> 50.86 186 <![CDATA[P 中部 ]]> 62.52 215 <![CDATA[P 下山 ]]> 68.42 245 <![CDATA[P2]]> 118.75 360

[0063] The coefficient b of formula (2) obtained by regression using oringin software is 0.594, lna=1.59. Therefore, formula (2) is

[0064] ln(r)=1.59+0.594θ;

[0065] Bringing it back to formula (1), we get

[0066] r = 1.59·exp(0.594θ) (1);

[0067] That is, the polar coordinate equation (1) of the logarithmic spiral gives the boundary curve of the fracture zone on the profile, which can predict the development range of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving working face of the steeply inclined and extra-thick coal seam.

[0068] Example 2: A mine in the west of China uses a ground three-pronged hole to detect the water-conducting fracture zone and the separation space of the overburden of the steeply inclined coal seam and a method and construction technology.

[0069] Step (A), due to ground collapse and water accumulation, the ground three-pronged drilling adopts a large S directional hole, arranged 20m outside the surface movement range, and the drilling adopts a four-level hole body structure.

[0070] Step (B),

[0071] In step (large S-1), the vertical section 2-1 of the first main hole is constructed: the vertical main hole is constructed, entering the stable bedrock 15m, and the first-level geological casing is lowered; the diameter of the first wellbore drilling hole is 381mm, the diameter of the first geological casing is 273.05mm, and the single-liquid cement slurry with a water-cement ratio of 0.6:1 is used for cementing;

[0072] In step (large S-2), the S-shaped extension section 2-2 of the second main hole is constructed: the S-shaped extension section of the second main hole is constructed at the lower part of the vertical section of the first main hole toward the steeply inclined coal seam, entering the position 200m above the coal seam, 50m horizontally away from the working face to be detected, and the second geological casing is lowered; the diameter of the second wellbore is 215mm, the diameter of the second geological casing is 193mm, and a special casing material is used to fill the annular space between the first and second section boreholes and the geological casing;

[0073] The special casing material is made of clay powder, fly ash, cement, water and additives, the additive is water glass, and the ratio of clay powder, fly ash, cement and water is 0.5:0.3:0.2:1, and the content of the additive is 0.5% of the cement mass.

[0074] In step (large S-3), the directional section of the three-opening large S-shaped branch directional drilling hole is constructed: the directional section of the large S-shaped stope middle branch hole 3-1, the directional section of the large S-shaped uphill branch hole 3-2 and the directional section of the large S-shaped downhill branch hole 3-3 are respectively constructed at the lower part of the S-shaped extension section of the second main hole, and the target is entered at 50m above the bedrock of the water-conducting fracture zone, and the S-shaped directional hole is converted into a vertical drilling hole, and the three-opening geological casing is lowered; the directional section of the three-opening large S-shaped branch directional drilling hole has a wellbore diameter of 171.45mm, and the three-opening casing is 139.7mm, and a special casing material is used to fill the annular space between the three-opening borehole and the geological casing;

[0075] In step (large S-4), the detection section of the four-opening large S-shaped branch directional drilling hole is constructed: the bottom of the directional section of the three-opening large S-shaped branch directional drilling hole continues to be drilled into the detection section of the four-opening large S-shaped branch directional drilling hole. The detection section is a bare hole, and the final hole depth of the detection section is to enter the fracture zone range or the coal seam roof; the aperture of the four-opening drilling hole is Φ114.3mm, and the final hole depth of the detection section is to enter the fracture zone range or the coal seam roof.

[0076] Using the same test method, we get:

[0077] During the construction of the detection section of the branch hole 3-1 in the middle of the large S-shaped stope, the ground real-time monitoring system reported that the consumption of drilling flushing fluid was 7.6m 3 / h, the well leakage instrument tested the well bottom vertical depth of 473.65m and lost 6.9m 3 / h, the estimated maximum water-conducting fracture zone height in the middle of the stope is 113.38m;

[0078] During the construction of the detection section of the large S-shaped uphill branch hole 3-2, the ground real-time monitoring system reported that the consumption of drilling fluid was 6.2m 3 / h, the well leakage instrument tested the well bottom vertical depth of 485.88m and lost 5.5m 3 / h, it is estimated that the maximum water-conducting fracture zone height in the mining area is 77.32m;

[0079] During the construction of the detection section of the large S-shaped downhill branch hole 3-3, the ground real-time monitoring system reported that the consumption of drilling fluid was 7.5m 3 / h, the well leakage instrument tested the well bottom vertical depth of 490.17m and lost 5.8m 3 / h, it is estimated that the maximum water-conducting fracture zone height in the mining area is 165.37m;

[0080] During the drilling process, the drill bit dropped 1.6m at a vertical depth of 502.3m, and borehole observation showed that there was a certain degree of detachment in the overburden.

[0081] In polar coordinates, P0, P1, P2, P 上山 , P 中部 , P 下山 The coordinates of these six points are shown in Table 2 below.

[0082] Table 2 Coordinates of points in polar coordinates of Example 2

[0083] serial number Radial distance (m) Angle θ(°) <![CDATA[p0]]> 3 0 <![CDATA[p1]]> 25.74 104 <![CDATA[p 上山 ]]> 72.73 186 <![CDATA[P 中部 ]]> 83.15 215 <![CDATA[P 下山 ]]> 88.17 245 <![CDATA[P2]]> 137.73 360

[0084] The coefficient b of formula (2) obtained by regression using oringin software is 0.605, lna=1.79. Therefore, formula (2) is

[0085] ln(r)=1.79+0.605θ;

[0086] Bringing it back to formula (1), we get

[0087] r = 1.79·exp(0.605θ) (1);

[0088] That is, the polar coordinate equation (1) of the logarithmic spiral gives the boundary curve of the fracture zone on the profile, which can predict the development range of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving working face of the steeply inclined and extra-thick coal seam.

[0089] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method for detecting water-conducting fracture zones and separation spaces in overburden rocks of steeply inclined coal seams using a ground three-pronged hole, characterized in that: The steps include: (A) Arrangement of exploratory drilling holes: Use ground three-pronged drilling (1); that is, determine the drilling position on the ground, drill a main hole (2) and three S-shaped branch directional drilling holes (3); (B) geological casings are lowered in the directional sections of the main hole (2) and the S-shaped branch directional drilling holes, the detection section of the S-shaped branch directional drilling holes is an open hole, and the detection section of the S-shaped branch directional drilling holes is drilled into the fracture zone range of the steeply inclined coal seam or the coal seam roof; (C) During the drilling process of the detection section of the S-shaped branch directional drilling, the ground real-time monitoring system for the consumption of drilling fluid and the well leakage meter are used to comprehensively determine the specific leakage location and leakage amount, so as to obtain the maximum development height of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving mining area of ​​the steeply inclined and extra-thick coal seam. The development characteristics of the overburden water-conducting fracture zone and the stratum separation space are comprehensively determined by in-hole sonic logging and borehole peep technology, and the development range and connectivity of the mining fracture zone are evaluated.

2. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 1, characterized in that: In step (A), the S-shaped branch directional drilling hole includes a middle branch hole (3-1), an uphill branch hole (3-2) and a downhill branch hole (3-3) in the mining field; wherein the middle branch hole in the mining field enters from the middle of the overburden water-conducting fracture zone (5) of the steeply inclined coal seam (4) to detect the maximum height of the water-conducting fracture zone in the middle of the mining field and the height of the cross-fall zone (6); the uphill branch hole (3-2) enters from the uphill side of the overburden water-conducting fracture zone of the steeply inclined coal seam to detect the maximum height of the water-conducting fracture zone on the uphill side of the mining field; the downhill branch hole (3-3) enters from the downhill side of the overburden water-conducting fracture zone of the steeply inclined coal seam to detect the maximum height of the water-conducting fracture zone on the uphill side of the mining field and the overburden separation condition.

3. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 1, characterized in that: In step (A), when there is no obvious collapse of the ground and no obstacles, a small S directional hole is used for the ground three-pronged drilling; the opening position of the ground three-pronged drilling hole is located on the ground just above the working face of the steeply inclined coal seam overburden water-conducting fracture zone, the ground three-pronged drilling hole lags behind the working face by 100 to 150 m, and the ground three-pronged drilling hole adopts a three-level hole body structure.

4. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 3, characterized in that: In step (A), when the ground collapses significantly or there are obstacles, the ground three-pronged drilling adopts a large S directional hole; the opening position of the ground three-pronged drilling is arranged on the upper plate of the steeply inclined stratum and is located 5 to 10 meters outside the stratum movement boundary. The ground three-pronged drilling lags behind the working face by 100 to 150 meters, and the ground three-pronged drilling adopts a four-level hole body structure.

5. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 3, characterized in that: In step (B), when the ground three-pronged drilling adopts a small S directional hole: Step (S-1), first main hole (2) construction: vertical main hole construction, enter the stable bedrock 10-20m, and lower the first-level geological casing; Step (small S-2), construction of the directional section of the second S-shaped branch directional drilling hole: at the lower part of the first main hole, the directional section of the small S-shaped middle branch hole (3-1), the directional section of the small S-shaped uphill branch hole (3-2) and the directional section of the small S-shaped downhill branch hole (3-3) are respectively constructed, entering the bedrock 60 to 120 meters above the mining fracture zone, and lowering the second geological casing; Step (small S-3), construction of the detection section of the three-opening S-shaped branch directional drilling hole: the bottom of the directional section of the second-opening S-shaped branch directional drilling hole continues to be drilled into the detection section of the three-opening S-shaped branch directional drilling hole. The detection section is a bare hole, and the final hole depth of the detection section is to enter the fracture zone or the coal seam roof.

6. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 5, characterized in that: In step (S-1), the diameter of the first wellbore drilling hole is 270-350 mm, the diameter of the first geological casing is 230-260 mm, and single-liquid cement slurry with a water-cement ratio of 0.6:1 is used for cementing; in step (S-2), the diameter of the second wellbore drilling hole is 215-225 mm, the second geological casing is 165-190 mm, and a special casing material is used to fill the annular space between the first and second drilling holes and the geological casing; in step (S-3), the diameter of the third drilling hole is 110-150 mm; The special casing material is prepared from clay powder, fly ash, cement, water and additives, wherein the additive is water glass, wherein the ratio of clay powder, fly ash, cement and water is 0.5:0.3:0.2:1, and the content of the additive is 0.3-1% of the cement mass.

7. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 4, characterized in that: In step (B), when the ground three-pronged drilling adopts a large S directional hole: Step (large S-1), construction of the vertical section (2-1) of the first main hole: construction of the vertical main hole, entering the stable bedrock 10 to 20 meters, and lowering the first-level geological casing; Step (large S-2), construction of the S-shaped extension section of the second main hole (2-2): construct the S-shaped extension section of the second main hole at the lower part of the vertical section of the first main hole toward the steeply inclined coal seam, enter the position 150 to 200 meters above the coal seam, and the horizontal distance from the working face to be detected is 30 to 80 meters, and lower the geological casing of the second hole; Step (large S-3), construction of the directional section of the three-opening large S-shaped branch directional drilling hole: at the lower part of the S-shaped extension section of the second main hole, the directional section of the large S-shaped stope middle branch hole (3-1), the directional section of the large S-shaped uphill branch hole (3-2) and the directional section of the large S-shaped downhill branch hole (3-3) are respectively constructed, and the target is inserted into the bedrock 30 to 60 meters above the water-conducting fracture zone, and the S-shaped directional hole is converted into a vertical drilling hole, and the three-opening geological casing is lowered; Step (Big S-4), construction of the detection section of the four-opening large S-shaped branch directional drilling hole: the bottom of the directional section of the three-opening large S-shaped branch directional drilling hole continues to be drilled into the detection section of the four-opening large S-shaped branch directional drilling hole. The detection section is a bare hole, and the final hole depth of the detection section is to enter the fracture zone or the coal seam roof.

8. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 7, characterized in that: In step (large S-1), the diameter of the first wellbore is 270-390 mm, the diameter of the first geological casing is 250-280 mm, and single-liquid cement slurry with a water-cement ratio of 0.6:1 is used for cementing; in step (large S-2), the diameter of the second wellbore is 215-225 mm, the diameter of the second geological casing is 165-195 mm, and a special casing material is used to fill the annular space between the first and second wellbore sections and the geological casing; in step (large S-3), the diameter of the third wellbore is 155-175 mm, the third casing is 125-150 mm, and a special casing material is used to fill the annular space between the third wellbore and the geological casing; in step (large S-4), the diameter of the fourth wellbore is 98-130 mm.

9. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 2, characterized in that: In step (C), Step (C-1), during the drilling of the branch holes in the middle of the mining area, the uphill branch holes and the downhill branch holes: the ground real-time monitoring system is used to observe the leakage of the drilling flushing fluid, the ground real-time monitoring system dynamically and continuously monitors the leakage of the flushing fluid, and automatically calculates the leakage per unit borehole and the leakage per unit time per unit footage, and the leakage meter is used to test the specific leakage position and leakage size of the drilling flushing fluid within the entire depth range of the borehole, so as to comprehensively determine the height of the maximum water-conducting fracture zone in the middle of the mining area; the sonic logging is used to analyze the fracture rate of the fracture zone formation, and the development characteristics of the overburden water-conducting fracture zone and the separation layer space are comprehensively determined according to the in-hole sonic logging borehole peep technology, and the development range and connectivity of the mining fracture zone are evaluated; Step (C-2), after the construction of the central branch hole, the uphill branch hole and the downhill branch hole in the mining area is completed, the casing of the directional section of the S-shaped branch directional drilling hole is cut off and pulled out, and the branch hole is sealed with 0.6:1 single-liquid cement slurry.

10. A method for detecting water-conducting fracture zones and separation spaces in overburden of steeply inclined coal seams by using a ground three-pronged hole according to claim 9, characterized in that: In step (C-1): Obtain theoretical equation: The logarithmic spiral equation is used to fit the range of the water-conducting fracture zone in the overburden of the steeply inclined coal seam mining area. The six data points used are the three points determined by ground detection, P 上山 , P 中部 and P 下山 , and three points P0, P1 and P2 inherent in the coal seam; Where: P 上山 is the location of water-conducting fractures detected by the uphill branch hole (3-2), P 中部 is the location of water-conducting fractures detected by the branch holes (3-1) in the stope, P 下山 is the location of water-conducting fracture development detected by the downhill branch hole (3-3), P0 is the intersection of the upper level and the coal seam roof, P1 is the intersection of the upper level and the bottom plate, and P2 is the intersection of the lower level and the coal seam roof; Assume the polar coordinate equation of the logarithmic spiral is: r = a·exp(b·θ) (1); Where r represents the radial distance, θ represents the rotation angle, and a and b are constants; Transform formula (1) into: lnr=bθ+lna (2); Formula (2) satisfies the form of a straight line equation, and then the coefficients b and lna of formula (2) are fitted to obtain the best approximation; Actual measurement: On the section perpendicular to the advancing direction of the mining field, a Cartesian rectangular coordinate system is established with the coal seam inclination direction as the X-axis and the normal direction as the Y-axis. The origin of the coordinate is located at the intersection of the upper level and the coal seam roof, and the coordinates of these 6 points are measured; Take the intersection of the upper left roadway roof and the coal seam roof as the coordinate origin, rotate counterclockwise, establish a polar coordinate system, and transform the coordinates of the 6 data points into polar coordinates; use origin software to fit equation (2) and obtain the coefficients b and lna of equation (2); Substituting the coefficients b and lna back into equation (1), the polar coordinate equation of the logarithmic spiral is obtained, and the boundary curve of the fracture zone on the section is given, which can predict the development range of the overburden water-conducting fracture zone in the horizontal segmented fully mechanized caving working face of the steeply inclined and extra-thick coal seam.

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