CN113586148A - Method for determining water storage coefficient of underground reservoir of open pit coal mine - Google Patents
Method for determining water storage coefficient of underground reservoir of open pit coal mine Download PDFInfo
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Abstract
The invention discloses a method for determining the water storage coefficient of an underground reservoir of an open pit coal mine, and relates to the technical field of water resource protection of open pit mines. The method comprises the following steps: firstly, uniformly distributing a plurality of water injection drill holes on the surface of an underground reservoir of an open pit coal mine, and determining the properties of a reconstructed soil layer of a dumping site by adopting an acoustic detection technology in combination with the drill holes; then, in the drilling process, a drilling television is arranged, and the porosity of the rock stratum is measured; then, carrying out a drilling water injection test on the basis of drilling, measuring the layered permeability of the water storage medium, and calculating the layered porosity of the water storage medium; and finally, layering along the elevation based on contour line information of the underground reservoir, calculating the water storage capacity of each layer, and calculating the total water storage capacity of the underground reservoir through accumulation. The method has the advantages that the basic properties of each reconstruction layer are clarified layer by layer through a water injection test and an advanced detection technology, and a foundation is provided for calculating the water storage coefficient; meanwhile, the pore properties of the reconstructed rock stratum of the surface mining waste are determined by various technical means, so that the reliability of the calculation result is improved.
Description
Technical Field
The invention relates to the technical field of surface mining mine water resource protection, in particular to a method for determining the water storage coefficient of an underground reservoir of an open pit coal mine.
Background
In the process of surface mining, a surface soil layer and an overlying rock-soil layer need to be peeled off and then coal resources are extracted, the coal mining mode brings ecological problems of land digging loss and occupation, water resource loss, vegetation degradation and the like, wherein water resource damage is a key factor for restricting the ecological restoration of a mining area. At present, under the requirement of zero emission, part of mining areas store mine water by establishing a reservoir on the earth surface. The method can not only cause a large amount of water resource evaporation waste, but also possibly cause mine water to diffuse to the periphery of the water pool to cause environmental pollution.
One of the important processes in the open-pit mining process is to pile the stripped surface soil layer to form a dump and build an open-pit coal mine underground reservoir by utilizing the dump, which is a key technology and approach for realizing open-pit mining water resource protection. The size of the storage capacity of the underground reservoir of the open coal mine is a key for guaranteeing regional water resources and protecting ecological environment, and the core of the storage capacity evaluation is the determination of the water storage coefficient. However, the problems of complex internal structure, difficult detection and the like exist after the reservoir is built, so that the water storage coefficient is determined to be one of the problems in the construction of the underground reservoir of the open pit coal mine.
Disclosure of Invention
Aiming at the defects of the prior art, the invention discloses a method for determining the water storage coefficient of an underground reservoir of an open pit coal mine, which realizes the determination of the water storage coefficient of the underground reservoir of the open pit coal mine, guides key technologies such as design and monitoring of the storage capacity of the underground reservoir of the open pit coal mine and the like, and provides a foundation for protecting water resources in open pit mining. Aiming at the problems of different compactibility and rock porosity of each layered water storage medium of the underground reservoir of the open pit coal mine, starting from surface drilling and water injection experiments, combining technologies such as a drilling television and a sound wave test, calculating the porosity and permeability coefficient of the rock layer in the reservoir, further determining the size of the water storage coefficient, and providing a foundation for the construction of the underground reservoir of the open pit coal mine.
The invention provides a method for determining the water storage coefficient of an underground reservoir of an open coal mine, which comprises the following steps:
the method comprises the following steps: according to the construction range of the open pit coal mine underground reservoir, the position of a water injection well and possible stratum conditions, a plurality of water injection drill holes are uniformly distributed on the surface of the open pit coal mine underground reservoir, and the final hole of each drill hole is positioned at the bottom of the underground reservoir or below the underground reservoir.
Step two: and (4) determining the properties of the reconstructed soil layer of the waste dump by combining drilling and adopting an acoustic detection technology.
Step three: during drilling, a drilling television is arranged to determine the formation porosity.
Step four: and (3) carrying out a drilling water injection test on the basis of drilling, measuring the layered permeability of the water storage medium, and calculating the layered porosity of the water storage medium.
Step five: and (4) layering along the elevation based on contour line information of the underground reservoir, calculating the water storage capacity of each layer, and calculating the total water storage capacity of the underground reservoir through accumulation.
Preferably, in the first step, when the drilling machine drills holes to a preset depth, the casing pipe is placed, and the thickness of sediment at the bottom of the hole is less than or equal to 10 cm; and arranging a filtering perforated pipe when drilling construction is carried out to a layer needing water injection.
Preferably, the method for determining the properties of the reconstructed soil layer of the refuse dump in the second step comprises the following steps:
s1, detecting the underground reservoir of the coal mine through a sound wave detection technology, and preliminarily obtaining the porosity of each layer of water storage medium of the refuse dump.
And S2, preliminarily evaluating the physical and mechanical properties and the water physical properties of each reconstructed rock stratum by combining the sound wave detection result and the drill core analysis, and obtaining the porosity of the water storage medium.
Preferably, the method for determining the porosity of the rock formation by arranging the borehole television in the third step comprises the following steps:
and S1, detecting the drill hole by using the drill hole television in the field drilling process, and reconstructing lithology and porosity of the rock stratum through inversion of the image data of the drill hole television.
And S2, further analyzing the basic properties of each reconstructed rock stratum by combining the coring condition of the drill hole and the detection result of the acoustic wave.
And S3, analyzing the result obtained in the second step, and finally determining the mechanical property, the hydraulic mechanical parameter and the porosity of the reconstructed rock stratum.
Preferably, the water injection test for the drill hole in the fourth step comprises the following steps:
s1, observing the underground water level as a basis for calculating the zero line of the pressure; the water level observation interval is 5min, and when the amplitude of the observation data for two times is less than 5cm/min, the water level observation can be finished.
S2, performing a water injection test by using a disposable full-section water injection method, wherein the measured data is the permeability of the water storage medium at the average depth of the filtering floral tube.
S3, injecting clear water into the sleeve by using a water injection pipe or a measuring cylinder with a flowmeter, keeping the water level in the sleeve higher than the underground water level by a certain height or to an orifice and keeping the water level constant, and observing the injection flow; adopt water table and ultrasonic flowmeter simultaneous measurement water injection volume in order to reduce experimental error, adopt the stopwatch to measure time interval in the testing process.
Preferably, in the step S3, according to the drilling water injection test rule, the flow observation interval is 5min for 5 times at the beginning, and the flow is observed once every 20min and at least twice; when the difference between the two continuous observed flows is less than or equal to 10%, the test can be ended, and the last injection flow is taken as a calculated value; when the water leakage amount of the test section is larger than the water supply capacity, recording the maximum water supply amount; the injection flow rate q (L/min) per unit time was calculated in accordance with the time interval measured by the stopwatch.
Preferably, the permeability of the test horizon water storage medium is calculated using the following formula:
when the test soil layer is positioned below the underground water level, calculating the permeability coefficient of the test soil layer by adopting a formula (1):
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); a is a shape factor (cm).
When the test soil layer is located above the underground water level, calculating the permeability coefficient of the test soil layer by adopting a formula (2):
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); and r is the borehole radius (cm).
Preferably, the method for calculating the total water storage capacity of the open pit coal mine underground reservoir comprises the following steps:
and S1, generalizing the discharged materials at the same elevation of the waste dump into the same material, wherein the discharged materials at the same elevation are in the same stress environment and compaction state.
And S2, calculating the permeability coefficient based on the 2 or more groups of drilling water injection tests, calculating the functional relation between the permeability and the elevation of the water storage medium by adopting a statistical induction method, and calculating the layered permeability of the water storage medium.
The S3, based on the kozen and kalman formula calculates the stratified porosity of the water storage media, the formula of which is as follows:
in the formula: k is the permeability coefficient; eta is the dynamic viscosity coefficient of water; ρ is the density of water; g is the acceleration of gravity;
porosity (expressed in decimal numbers); spIs the surface area per unit pore volume; c is a constant depending on the degree of cementation and other factors.
S4, on the basis that the water storage medium is well layered and the porosity of each layer is known, calculating the water storage capacity of each layer through a layer summation method, and then summing all the layers to calculate the water storage coefficient of the underground reservoir:
in the formula: q is the water storage capacity of the underground reservoir;
the porosity of the ith layer of the water storage medium of the underground reservoir; h isiThe layering thickness of the ith layering of the water storage medium of the underground reservoir; siThe water storage area of the ith layer of the underground reservoir; n is the number of layers.
Compared with the prior art, the method for determining the water storage coefficient of the underground reservoir of the open pit coal mine disclosed by the invention has the advantages that:
(1) the method determines the pore properties of the reconstructed rock stratum of the surface mining waste through various technical means, and improves the reliability of the calculation result.
(2) The invention proves the basic properties of each reconstruction layer by layer through a water injection test and an advanced detection technology, and provides a foundation for calculating the water storage coefficient.
(3) The large-aperture drilling technology provided and applied by the invention realizes the water pumping and injecting test of the unconsolidated reconstructed rock stratum of the open-pit coal mine underground reservoir, solves the problem that the water storage coefficient of the open-pit coal mine underground reservoir is difficult to determine, and provides a basis for protecting water resources in open-pit mining.
Drawings
For a clearer explanation of the embodiments or technical solutions of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for a person skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of water storage capacity calculation by a longitudinal section layering summation method of an open pit coal mine underground reservoir.
Fig. 2 shows site selection of west reservoir area of underground reservoir of opencast coal mine in baorischiler.
FIG. 3 is a schematic cross-sectional view of a borehole.
In the figure: 1, drilling a hole I; 2, drilling a second hole; 3, drilling a hole III; 4, drilling a hole IV; 5, drilling a hole five; 6-drilling six holes.
Detailed Description
The following provides a brief description of embodiments of the present invention with reference to the accompanying drawings. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any inventive work belong to the protection scope of the present invention.
The invention discloses a method for determining the water storage coefficient of an underground reservoir of an open coal mine, which comprises the following steps:
the method comprises the following steps: according to the construction range of the open pit coal mine underground reservoir, the position of a water injection well and possible stratum conditions, a plurality of water injection drill holes are uniformly distributed on the surface of the open pit coal mine underground reservoir, and the final hole of each drill hole is positioned at the bottom of the underground reservoir or below the underground reservoir. When the drilling machine drills holes to a preset depth, the casing is put, and slurry drilling is strictly forbidden. The thickness of the sediment at the bottom of the hole is less than or equal to 10cm, and the test soil layer is prevented from being disturbed. And arranging a filtering perforated pipe when drilling construction is carried out to a layer needing water injection.
Step two: detecting the underground reservoir of the coal mine by using a sound wave detection technology to preliminarily obtain the porosity of each layer of water storage medium of the refuse dump; and preliminarily evaluating the physical and mechanical properties and the water physical properties of each reconstructed rock stratum by combining the sound wave detection result and the drill core analysis to obtain the porosity of the water storage medium.
Step three: in the field drilling process, a drilling television is arranged, the drilling television is used for detecting the drilling, and lithology and porosity of the rock stratum are reconstructed through inversion of image data of the drilling television. And further analyzing the basic properties of each reconstructed rock stratum by combining the coring condition of the drill hole and the detection result of the acoustic wave. And analyzing the result obtained in the second step to finally determine the mechanical property, the hydraulic mechanical parameter and the porosity of the reconstructed rock stratum.
Step four: and (3) carrying out a drilling water injection test on the basis of drilling, measuring the layered permeability of the water storage medium, and calculating the layered porosity of the water storage medium. The method specifically comprises the following steps:
s1, observing the underground water level as a basis for calculating the zero line of the pressure; the water level observation interval is 5min, and when the amplitude of the observation data for two times is less than 5cm/min, the water level observation can be finished.
S2, performing a water injection test by using a disposable full-section water injection method, wherein the measured data is the permeability of the water storage medium at the average depth of the filtering floral tube.
S3, injecting clear water into the sleeve by using a water injection pipe or a measuring cylinder with a flowmeter, keeping the water level in the sleeve higher than the underground water level by a certain height or to an orifice and keeping the water level constant, and observing the injection flow; adopt water table and ultrasonic flowmeter simultaneous measurement water injection volume in order to reduce experimental error, adopt the stopwatch to measure time interval in the testing process. According to the drilling water injection test rule, the flow observation interval is 5min for 5 times, and the flow is observed once every 20min and at least twice; when the difference between the two continuous observed flows is less than or equal to 10%, the test can be ended, and the last injection flow is taken as a calculated value; when the water leakage amount of the test section is larger than the water supply capacity, recording the maximum water supply amount; the injection flow rate q (L/min) per unit time was calculated in accordance with the time interval measured by the stopwatch.
And calculating the permeability of the water storage medium at the test layer position by adopting the following formula:
when the test soil layer is positioned below the underground water level, calculating the permeability coefficient of the test soil layer by adopting a formula (1):
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); a is a shape factor (cm).
When the test soil layer is located above the underground water level, calculating the permeability coefficient of the test soil layer by adopting a formula (2):
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); a is the shape factor (cm); and r is the borehole radius (cm).
Step five: and (4) layering along the elevation based on contour line information of the underground reservoir, calculating the water storage capacity of each layer, and calculating the total water storage capacity of the underground reservoir through accumulation. The method specifically comprises the following steps:
and S1, generalizing the discharged materials at the same elevation of the waste dump into the same material, wherein the discharged materials at the same elevation are in the same stress environment and compaction state.
And S2, calculating the permeability coefficient based on the 2 or more groups of drilling water injection tests, calculating the functional relation between the permeability and the elevation of the water storage medium by adopting a statistical induction method, and calculating the layered permeability of the water storage medium.
The S3, based on the kozen and kalman formula calculates the stratified porosity of the water storage media, the formula of which is as follows:
in the formula: k is the permeability coefficient; eta is the dynamic viscosity coefficient of water; ρ is the density of water; g is the acceleration of gravity;
porosity (expressed in decimal numbers); spIs the surface area per unit pore volume; c is a constant depending on the degree of cementation and other factors.
S4, on the basis that the water storage medium is well layered and the porosity of each layer is known, calculating the water storage capacity of each layer through a layer summation method, and then summing all the layers to calculate the water storage coefficient of the underground reservoir:
in the formula: q is the water storage capacity of the underground reservoir;
the porosity of the ith layer of the water storage medium of the underground reservoir; h isiThe layering thickness of the ith layering of the water storage medium of the underground reservoir; siThe water storage area of the ith layer of the underground reservoir; n is the number of layers.
The underground reservoir water storage capacity is calculated by taking the Baori Sihler coal mine as an example.
The underground reservoir in the western precious coal district mainly carries out the following three aspects of work: designing a drilling scheme based on the construction condition of an underground reservoir to complete the drilling work of a waste dump; carrying out a drilling water injection test on the basis of drilling, measuring the layered permeability of the water storage medium, and calculating the layered porosity of the water storage medium; and thirdly, layering along the elevation based on contour line information of the underground reservoir, calculating the water storage capacity of each layer, and calculating the total water storage capacity of the underground reservoir through accumulation.
The underground reservoir site selection in the west precious coal district is considered by taking the low concave topography of the west side and the low concave topography of the east side of a shaft field as an underground water convergence area, reconstructing a sandstone aquifer as a water storage body by utilizing an inner soil discharge field, taking the position of a rubble groove as the water taking position of the underground reservoir of an open coal mine, taking the rubble groove as the boundary water taking position, and preliminarily determining the underground reservoir site selection according to the contour line of the No. 1 coal seam bottom plate. According to the distribution of the water gathering area, the underground reservoir of the west region of the baori schiler open-pit mine is located, as shown in fig. 2.
(1) Drilling conditions
The arrangement of the pumping and water injection well of the underground reservoir of the Baorischile opencast coal mine comprehensively considers the factors such as the application requirement of the underground reservoir, the engineering quantity, the stripping and mining history of the opencast mine and the like. In consideration of fully utilizing the stored water in the reservoir, the pumping well is arranged at the lowest position of the coal bed floor in the reservoir range. Meanwhile, the drilling in the area with the lower elevation of the earth surface is selected as much as possible on the premise of meeting the construction requirement of the underground reservoir, so that the engineering difficulty is reduced and the construction speed is accelerated. The underground reservoir of the dumping site mainly utilizes the holes of the dumping materials to store water, so that in order to avoid the stored mine water polluting underground water, a pumping and injecting water well needs to avoid the unexplored area of the strip mine, namely the position of a drilling final hole needs to be within the deep boundary of the strip mine stope and is in a normal dumping area of an inner dumping site. According to the influence factors of the arrangement of the drainage wells of the refuse dump, 6 drill holes are arranged in a reservoir building area in the southwest of the refuse dump of the Baozihler opencut coal mine, wherein the 6 drill holes are respectively a first drill hole 1, a second drill hole 2, a third drill hole 3, a fourth drill hole 4, a fifth drill hole 5 and a sixth drill hole 6. The drill hole layout is shown in fig. 2, and the drill hole coordinates and engineering quantities are shown in table 1.
Table 1 drilling parameters for pumping and injection system of underground reservoir in open pit coal mine dump
Note: 1. the final hole depth of each well is determined according to the height of the coal seam floor. The final hole of the pumping well is about 3m below the coal seam floor, so that a pumping pump can be conveniently arranged and the water collection effect can be improved; the final holes of the water injection well, the monitoring well and the like are arranged on the coal seam floor; the actual final hole coordinates and depth are determined from the drilling results.
2. The hole diameter of the borehole is constructed in advance to meet the basic principle of applying a 100-type pump in a pumping test, and the hole diameter of the borehole is temporarily determined to be about 330 mm; the hole diameter of the later construction drilling is determined by comprehensively considering water pumping and water injection and construction experience, and the size is preferably large and not small.
According to the preliminarily determined underground reservoir construction range, the position of the water pumping and injecting well and the possible stratum conditions, the adopted drilling construction scheme is as shown in figure 3: the hole is selected at the lower part of the waste dump, and the depth of the hole is reduced. An opening elevation 670 is drilled and a final hole coordinate 555 is designed to predict a hole depth of 115 m. The actual drilling depth of the underground reservoir test drilling hole SG1 of the dumping site which has been carried out by the Baorischiler opencast coal mine reaches 120m, so that the hole drilling device is considered from the viewpoint of the hole depthA worker is feasible. Secondly, the hole drilling structure is adjusted to be the hole opening aperture phi 325mm, the risk of construction is reduced by reducing the aperture, and the hole forming probability is increased. Thirdly, after the hole is drilled, a seamless steel pipe with the diameter of 127 multiplied by 6mm is put into the whole hole, the annular space outside the pipe is 99mm, the thickness of the filled aggregate is ensured, and the hole collapse is avoided during the water pumping test. Fourthly, the inner diameter of the steel pipe is 105mm, a water pump with the diameter of 98mm can be arranged, and the water pumping flow can reach 5m3And h, simultaneously has the space of the lower measuring tube and the measuring rope. The construction is carried out under the favorable weather conditions of warmth in 4-6 months and less rain, so that the drilling efficiency and the time utilization rate are improved.
(2) On-site water injection test
The water injection test regulations of the hydraulic and hydroelectric engineering and the equipment conditions available on the engineering site are combined, and the test equipment used in the test is shown in the table 2.
Table 2 summary of drilling water injection test equipment
| Type of device | Name (R) |
| Water supply equipment | Watering lorry for mine (with short distance water pipeline) |
| Measuring equipment | Water meter, ultrasonic flowmeter, stopwatch, meter ruler, etc |
| Water level meter | Electric measuring water level meter |
Drilling holes by a drilling machine, setting a casing pipe to a preset depth, and strictly forbidding using slurry for drilling. The thickness of the sediment at the bottom of the hole is less than or equal to 10cm, and the test soil layer is prevented from being disturbed.
Secondly, before the water injection test is carried out, underground water level observation is carried out and used as a basis for calculating the zero line by pressure. In the test, the underground water level is roughly measured by adopting the measuring clock when the well washing is finished in the drilling process, and no water exists in the hole.
And thirdly, due to the limitation of the drilling process, the water injection test is carried out by using a disposable full-section water injection method, and the measured data is the permeability of the water storage medium at the average depth of the floral tube.
And fourthly, injecting clear water into the sleeve by using a water injection pipe or a measuring cylinder with a flowmeter, keeping the water level in the sleeve to the orifice and keeping the water level constant, observing the injection flow, simultaneously measuring the water injection amount by using the water meter and the ultrasonic flowmeter to reduce the test error, and measuring the time by using a stopwatch in the test process.
According to the drilling water injection test rule, the flow observation interval is 5min for 5 times, and the flow is observed once every 20min and at least twice; when the difference between the two continuous observed flows is not more than 10%, the test can be finished, and the last injection flow is taken as a calculated value. And when the water leakage amount of the test section is larger than the water supply capacity, recording the maximum water supply amount. The water injection test of the refuse dump drill hole is characterized in that water is continuously injected by a sprinkler, a flow valve is adjusted to keep the water level in the drill hole to be flush with an orifice, the injection flow is measured by a water meter, a stopwatch and an ultrasonic electromagnetic flowmeter, and the injection quantity q (L/min) in unit time is calculated by the ratio of the injection quantity of clean water to the injection time.
(3) Determination of water storage coefficient
The water level in the holes is measured by using a clock measuring method after the well is washed, and 3#, 1# and 5# drill holes are dry holes, namely the test soil layer is positioned above the underground water level. According to the drilling water injection test rule, when a test soil layer is positioned above the underground water level, the following formula is adopted for calculating the permeability coefficient:
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); and r is the borehole radius (cm).
The water storage medium of the underground reservoir in the west precious coal district is artificially constructed sandstone, is made of the same material, and has the same or higher similarity of internal pore structures. However, because of different elevations, the water storage medium is in different stress environments, and the water storage medium in different compaction states has different permeability. From the analysis, the medium elevation, namely the overlying load, has the largest influence on the water storage medium permeability and is basically the only influence factor, so that the relation between the water storage medium permeability and the elevation can be fitted through a statistical induction method.
There is no necessary functional relationship between permeability and porosity for conventional materials, but for the same material or materials with similar internal spatial structure, there is a greater correlation between porosity and permeability, i.e., the greater the permeability, the greater the porosity of the material. For the underground reservoir in the western region, the water storage medium is the reconstructed sandstone which is basically the same material or a material with a similar internal space structure, so that the necessary relation exists between the permeability and the porosity. Geologists, oil engineers, civil engineers and soil scientists have developed a variety of relationships between fluid flow properties and the surface area of natural porous media such as sandstone, and many scientists have studied the relationship between the porosity and permeability of bulk medium deposits and aquifers, particularly in order to derive a well-defined formula. Wherein the comparison of equations for determining subsurface fluid flow with the kozen and kalman are known. The formula is as follows:
in the formula: k is the permeability coefficient; eta is the dynamic viscosity coefficient of water; ρ is the density of water; g is the acceleration of gravity;
porosity (expressed in decimal numbers); spIs the surface area per unit pore volume; c is determined by the degree of cementation and other factorsA fixed constant.
In order to ensure the accuracy of the calculation result, the value of the layering thickness should be as small as possible, the layering thickness is 5m in the calculation by combining contour line information of the underground reservoir in the western region, and the calculation result is shown in table 3. As can be seen from the table, the total water storage capacity of the underground reservoir in the western region is 126 ten thousand meters3。
TABLE 3 Western region underground reservoir storage capacity calculation table
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. A method for determining the water storage coefficient of an underground reservoir of an open pit coal mine is characterized by comprising the following steps:
the method comprises the following steps: according to the construction range of the open pit coal mine underground reservoir, the position of a water injection well and possible stratum conditions, a plurality of water injection drill holes are uniformly distributed on the ground surface of the open pit coal mine underground reservoir, and the final hole of each drill hole is positioned at the bottom of the underground reservoir or below the underground reservoir;
step two: determining the properties of the reconstructed soil layer of the waste dump by combining drilling and adopting an acoustic detection technology;
step three: in the drilling process, a drilling television is arranged, and the porosity of the rock stratum is measured;
step four: carrying out a drilling water injection test on the basis of drilling, measuring the layered permeability of the water storage medium, and calculating the layered porosity of the water storage medium;
step five: and (4) layering along the elevation based on contour line information of the underground reservoir, calculating the water storage capacity of each layer, and calculating the total water storage capacity of the underground reservoir through accumulation.
2. The method for determining the water storage coefficient of the underground reservoir of the open coal mine according to claim 1, wherein in the first step, when a drilling machine drills holes to a preset depth, a casing pipe is put, and the thickness of sediment at the bottom of the hole is less than or equal to 10 cm; and arranging a filtering perforated pipe when drilling construction is carried out to a layer needing water injection.
3. The method for determining the water storage coefficient of the underground reservoir of the opencast coal mine according to claim 1, wherein the method for determining the properties of the reconstructed soil layer of the refuse dump in the second step comprises the following steps:
s1, detecting the underground reservoir of the coal mine through a sound wave detection technology to preliminarily obtain the porosity of each layer of water storage medium of the refuse dump;
and S2, preliminarily evaluating the physical and mechanical properties and the water physical properties of each reconstructed rock stratum by combining the sound wave detection result and the drill core analysis, and obtaining the porosity of the water storage medium.
4. The method for determining the storage coefficient of the underground reservoir of the open coal mine according to claim 1, wherein a drilling television is arranged in the third step to measure the porosity of the rock stratum, and the method comprises the following steps:
s1, in the process of drilling on site, detecting the drilled hole by using a drilling television, and reconstructing lithology and porosity of the rock stratum through inversion of image data of the drilling television;
s2, further analyzing the basic properties of each reconstructed rock stratum by combining the coring condition of the drill hole and the detection result of the acoustic wave;
and S3, analyzing the result obtained in the second step, and finally determining the mechanical property, the hydraulic mechanical parameter and the porosity of the reconstructed rock stratum.
5. The method for determining the water storage coefficient of the underground reservoir of the open coal mine according to claim 1, wherein the water injection test of the drill hole in the fourth step comprises the following steps:
s1, observing the underground water level as a basis for calculating the zero line of the pressure; the water level observation interval is 5min, and when the amplitude of the observation data for two consecutive times is less than 5cm/min, the water level observation can be finished;
s2, performing a water injection test by using a disposable full-section water injection method, wherein the measured data is the permeability of the water storage medium at the average depth of the filtering floral tube;
s3, injecting clear water into the sleeve by using a water injection pipe or a measuring cylinder with a flowmeter, keeping the water level in the sleeve higher than the underground water level by a certain height or to an orifice and keeping the water level constant, and observing the injection flow; adopt water table and ultrasonic flowmeter simultaneous measurement water injection volume in order to reduce experimental error, adopt the stopwatch to measure time interval in the testing process.
6. The method for determining the water storage coefficient of the underground reservoir of the opencast coal mine according to claim 5, wherein in S3, according to the drilling water injection test regulation, the flow rate observation interval is 5min at the beginning, and the flow rate observation interval is observed once every 20min and at least twice; when the difference between the two continuous observed flows is less than or equal to 10%, the test can be ended, and the last injection flow is taken as a calculated value; when the water leakage amount of the test section is larger than the water supply capacity, recording the maximum water supply amount; the injection flow rate q (L/min) per unit time was calculated in accordance with the time interval measured by the stopwatch.
7. The method for determining the storage coefficient of the underground reservoir of the opencast coal mine according to claim 5, wherein the permeability of the test horizon water storage medium is calculated by the following formula:
when the test soil layer is positioned below the underground water level, calculating the permeability coefficient of the test soil layer by adopting a formula (1):
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); a is the shape factor (cm);
when the test soil layer is located above the underground water level, calculating the permeability coefficient of the test soil layer by adopting a formula (2):
in the formula: k is the permeability coefficient (cm/s) of the test soil layer; q is the injection flow (L/min); h is the test head (cm); and r is the borehole radius (cm).
8. The method for determining the storage coefficient of the opencast coal mine underground reservoir according to claim 7, wherein the method for calculating the total storage capacity of the opencast coal mine underground reservoir comprises the following steps:
s1, generalizing the discharged materials at the same elevation of the waste dump into the same material, wherein the discharged materials at the same elevation are in the same stress environment and compaction state;
s2, calculating the permeability coefficient based on the 2 or more groups of drilling water injection tests, calculating the functional relation between the permeability and the elevation of the water storage medium by adopting a statistical induction method, and calculating the layered permeability of the water storage medium;
the S3, based on the kozen and kalman formula calculates the stratified porosity of the water storage media, the formula of which is as follows:
in the formula: k is the permeability coefficient; eta is the dynamic viscosity coefficient of water; ρ is the density of water; g is the acceleration of gravity;
porosity (expressed in decimal numbers); spIs the surface area per unit pore volume; c is a constant dependent on the degree of cementation and other factors；
S4, on the basis that the water storage medium is well layered and the porosity of each layer is known, calculating the water storage capacity of each layer through a layer summation method, and then summing all the layers to calculate the water storage coefficient of the underground reservoir:
in the formula: q is the water storage capacity of the underground reservoir;
the porosity of the ith layer of the water storage medium of the underground reservoir; h isiThe layering thickness of the ith layering of the water storage medium of the underground reservoir; siThe water storage area of the ith layer of the underground reservoir; n is the number of layers.
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