A method and device for calculating the amount of water that can be drained from a coal seam roof aquifer

Abstract

The present invention relates to the field of coal mine water prevention and control, and discloses a method and device for calculating the amount of water that can be drained from a coal seam roof aquifer, which makes full use of logging data in the coal resource exploration stage, establishes a relationship between logging curves and aquifer porosity, and is used to calculate the porosity of unmeasured aquifer areas, calculate the amount of water that can be drained from aquifers, reduce the number of porosity tests and the amount of drilling and geophysical exploration projects, and reduce the cost of coal mine water prevention and control. The present invention calculates the amount of water that can be drained from the main aquifer of the coal seam roof, and compared with the relative water richness in the past, it can efficiently guide the drainage of roof water.

Description

Technical Field

[0001] The invention relates to the field of coal mine water prevention and control, and in particular to a method and equipment for calculating the amount of water that can be drained from a coal seam roof aquifer. Background Art

[0002] Coal seam roof water hazard is an important factor affecting mine safety production. With the gradual increase in coal mining depth, the hydrogeological conditions of the coal seam roof aquifer are becoming more and more complex. The problem of coal seam roof water hazard is becoming increasingly prominent, threatening the lives of miners and causing significant economic losses to the mine. Therefore, carrying out efficient prevention and control of coal seam roof water hazard has important practical significance and great social significance.

[0003] At present, the conventional practice for coal seam roof water hazard prevention and control is to explore the hydrogeological conditions in the coal resource exploration stage. In the production stage, the first is to use geophysical exploration methods to explore the abnormal water-rich areas of the aquifer, the second is to use geostatistics, mathematical geology, multi-source geoscience information fusion and other methods to predict the strong water-rich areas of the coal seam roof aquifer, and the third is to use the size of the unit water inflow of the borehole to circle the strong water-rich areas of the coal seam roof aquifer. Then, according to whether the water-conducting fracture zone communicates with the abnormal water-rich and strong water-rich areas after coal seam mining, the roof drainage borehole is designed and constructed to drain the water from the roof aquifer to ensure the safe recovery of the coal seam. Among them, the determination of abnormal water-rich areas and strong water-rich areas of the coal seam roof aquifer is an important part of coal mine water prevention and control work. At present, the determination of abnormal water-rich areas and strong water-rich areas of the roof aquifer has the following problems:

[0004] (1) Since there are multiple solutions when using geophysical exploration methods to interpret the abnormal water-rich areas in aquifers, the reliability of the abnormal water-rich areas in aquifers is reduced;

[0005] (2) There are many factors that affect the water-richness of aquifers, and the influencing mechanism is complex. Under different geological and hydrogeological conditions, the factors affecting the water-richness of aquifers are different, and the prediction indicators are selected differently. There may be a certain correlation between the prediction indicators of water-richness of various aquifers. It is difficult to select typical water-richness prediction indicators when predicting the strong water-rich area of ​​the coal seam roof aquifer using methods such as geostatistics, mathematical geology, and multi-source geoscience information fusion, which affects the accuracy of the prediction results of water-richness of aquifers.

[0006] (3) Although the borehole unit water yield is the most direct and accurate means to evaluate the water richness of aquifers, the borehole unit water yield is obtained by conducting pumping tests in boreholes. It is expensive, has limited data, and is distributed in a point-like manner, making it difficult to reflect the spatial water richness of aquifers.

[0007] (4) The current methods for predicting the water richness of aquifers are all qualitative evaluations of the water richness of aquifers, which have little guiding significance for top plate drainage. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a method and device for calculating the amount of water that can be drained from a coal seam roof aquifer.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for calculating the amount of water that can be drained from a coal seam roof aquifer comprises the following steps:

[0011] Step 1, determine the main aquifers that affect coal mining;

[0012] Step 2, taking core samples of the main aquifer to determine the porosity and permeability lower limit of the main aquifer;

[0013] Step 3, determining the porosity and permeability of the main aquifer through porosity and permeability testing experiments;

[0014] Step 4, establishing the relationship between porosity and acoustic wave time difference;

[0015] Step 5, using the acoustic time difference curve to obtain the porosity of the main aquifer whose porosity has not been measured;

[0016] Step 6, using the water saturation formula to calculate the water saturation of the main aquifer;

[0017] Step 7, calculating the amount of water that can be drained in the area where the porosity of the main aquifer is greater than the lower limit of porosity and permeability and the water-conducting fracture zone communicates;

[0018] Step 8, using the water-rich abnormal area exploration and the unit water yield of the borehole to correct the calculation results of the drainable water volume.

[0019] Preferably, in step 1, hydrogeological data from the coal resource exploration stage are collected and the main aquifers that affect coal seam mining are determined based on the aquifer division and its main hydrogeological characteristics, and the development of water-conducting fracture zones in coal seam mining, wherein the hydrogeological data from the coal resource exploration stage include hydrological borehole drilling columns, hydrological borehole pumping experiment results, hydrogeological comprehensive columnar diagrams, geological exploration reports, and hydrogeological supplementary exploration reports.

[0020] Furthermore, the conditions for determining the main aquifer include:

[0021] A. The unit water yield of the boreholes in the main aquifer is large;

[0022] B. The thickness of the main aquifer is large;

[0023] C. After coal seam mining, the water-conducting fracture zone develops highly and communicates with the main aquifer in part or all of the area.

[0024] Preferably, in step 2, a core displacement experiment is used to determine the lower limits of the porosity and permeability of the main aquifer, that is, when the porosity and permeability are greater than or equal to the lower limits, water in the aquifer will be released when the coal seam mining water-conducting fracture zone communicates with the main aquifer.

[0025] Preferably, in step 3, the porosity is the ratio of the connected pore space to the total volume of the rock, and the porosity is ≥5%.

[0026] Preferably, in step 4, the porosity is combined with the acoustic time difference logging curve to construct a fitting relationship between the porosity and the acoustic time difference, and the relationship is as follows:

[0027] y=Ax+B

[0028] Where: y is the effective porosity %; x is the acoustic wave time difference data μs / s; A and B are constants.

[0029] Preferably, in step 6, a rock sample of the main aquifer is taken, a rock-electricity experiment of the main aquifer is carried out, and the relevant coefficients of the calculation formula of the water saturation of the main aquifer are determined. The specific formula is as follows:

[0030]

[0031] Among them, S W is water saturation; n is saturation index; a, m are coefficients related to lithology and pore structure; R W is the pore water resistivity; R t is the rock resistivity; is the porosity.

[0032] Preferably, in step 7, the amount of water that can be drained in the area where the porosity of the main aquifer is greater than the lower limit of the porosity and permeability and the water-conducting fracture zone is connected is calculated using the following formula:

[0033] E=S w ×h

[0034] Where E is the amount of water that can be drained from the aquifer; S W is the water saturation; h is the thickness of the aquifer.

[0035] A device for calculating the amount of water that can be drained from a coal seam roof aquifer, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned method for calculating the amount of water that can be drained from a coal seam roof aquifer when executing the computer program.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] The present invention provides a method for calculating the amount of water that can be drained from a coal seam roof aquifer, which makes full use of well logging data in the coal resource exploration stage, establishes a relationship between the well logging curve and the porosity of the aquifer, and is used to calculate the porosity of an unmeasured aquifer area, calculate the amount of water that can be drained from the aquifer, reduces the number of porosity tests and the amount of drilling and geophysical exploration projects, and reduces the cost of water prevention and control in coal mines.

[0038] Furthermore, the present invention calculates the drainable water volume of the main aquifer in the coal seam roof, which can efficiently guide the roof water drainage work compared with the previous relative water richness. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a flow chart of the method for calculating the amount of water that can be drained from the coal seam roof aquifer in the present invention;

[0040] Figure 2 is a correlation diagram between sonic logging and porosity in the present invention;

[0041] Figure 3 This is a regional distribution map for calculating the amount of water that can be drained from the aquifer in the present invention. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0045] See also Figure 1In one embodiment of the present invention, a method for calculating the amount of water that can be drained from a coal seam roof aquifer is provided, comprising the following steps:

[0046] Step 1, determine the main aquifers that affect coal mining;

[0047] Specifically, hydrogeological data are collected during the coal resource exploration stage and the main aquifers that affect coal seam mining are determined based on the division of aquifers (impermeable) layers and their main hydrogeological characteristics, and the development of water-conducting fracture zones in coal seam mining. The hydrogeological data during the coal resource exploration stage include hydrological borehole drilling columns, hydrological borehole pumping experiment results, hydrogeological comprehensive column charts, geological exploration reports and hydrogeological supplementary exploration reports.

[0048] The conditions for determining the main aquifer are as follows:

[0049] A. The unit water yield of the boreholes in the main aquifer is large;

[0050] B. The thickness of the main aquifer is large;

[0051] C. After coal seam mining, the water-conducting fracture zone develops highly and communicates with the main aquifer in part or all of the area.

[0052] Step 2, taking core samples of the main aquifer to determine the porosity and permeability lower limit of the main aquifer;

[0053] Among them, in step 2, a core displacement experiment is used to determine the lower limit of the porosity and permeability of the main aquifer, that is, when the porosity and permeability are greater than or equal to this lower limit, the water in the aquifer will be released when the coal seam mining water-conducting fracture zone communicates with the main aquifer.

[0054] In the present invention, the principle of core displacement experiment is: according to the displacement mechanism and similarity principle, the stratum is designed in similar proportions, and the physical simulation test is carried out under the conditions of simulated formation pressure and temperature with the help of the latest achievements of modern science and technology, such as computer technology, advanced sensor technology, automatic control technology, etc. It is mainly used to simulate the flow displacement process of water in simulated rock samples under different temperatures, pressures and formation conditions. Determine the critical porosity and permeability, that is, the porosity and permeability when the normal formation pressure is equal to the injection water pressure. If it is greater than this value, the aquifer water will be released, which can provide a basis for the subsequent calculation of the amount of water that can be drained from the main aquifer.

[0055] The core displacement test rock sample is cylindrical, with a core diameter of 2-20 cm and a height of 5-30 cm. The core is placed in a thermostat at a high temperature of 70-90°C for 10-12 hours to fully dry. The test environment temperature is 10-30°C, the ambient humidity is ≤80%RH, and the ground is flat without strong vibration. The displacement pressure is 30-60MPa, and the confining pressure is 40-70MPa.

[0056] Step 3, determining the porosity and permeability of the main aquifer through porosity and permeability testing experiments;

[0057] Specifically, the porosity and permeability test experiments of the main aquifer are carried out to obtain the porosity and permeability of the main aquifer. Porosity is the ratio of the pore volume in the rock to the total volume of the rock in the natural state, including all pores in the rock, regardless of whether they are connected. The porosity tested in the present invention is the ratio of the connected pore space to the total volume of the rock, and the porosity is ≥5%.

[0058] Step 4, establishing the relationship between porosity and acoustic wave time difference;

[0059] Specifically, the porosity is combined with the acoustic time difference logging curve to construct a fitting relationship between porosity and acoustic time difference, which is as follows:

[0060] y=Ax+B

[0061] Where: y is the effective porosity %; x is the acoustic wave time difference data μs / s; A and B are constants.

[0062] Step 5, using the acoustic time difference curve to obtain the porosity of the main aquifer whose porosity has not been measured;

[0063] Step 6, using the water saturation formula to calculate the water saturation of the main aquifer;

[0064] Specifically, take rock samples from the main aquifer, carry out rock-electricity experiments on the main aquifer, and determine the relevant coefficients of the calculation formula for the water saturation of the main aquifer. The specific formula is as follows:

[0065]

[0066] Among them, S W is water saturation; n is saturation index; a, m are coefficients related to lithology and pore structure; R W is the pore water resistivity; R t is the rock resistivity; is the porosity.

[0067] Step 7, calculating the amount of water that can be drained in the area where the porosity of the main aquifer is greater than the lower limit of porosity and permeability and the water-conducting fracture zone communicates;

[0068] Specifically, the amount of water that can be drained in the area where the porosity of the main aquifer is greater than the lower limit of porosity and permeability and the water-conducting fracture zone is connected is calculated using the following formula:

[0069] E=S w ×h

[0070] Where E is the amount of water that can be drained from the aquifer; S Wis the water saturation; h is the thickness of the aquifer.

[0071] Step 8, using the water-rich abnormal area exploration and the unit water yield of the borehole to correct the calculation results of the drainable water volume.

[0072] Collect water-richness evaluation reports such as transient electromagnetic and direct current detection and the unit water yield of boreholes obtained from hydrological borehole pumping tests, and compare and analyze the accuracy of the calculation of the amount of water that can be drained from the main aquifers, focusing on correcting the calculation results of the amount of water that can be drained from the aquifers according to the size of the unit water yield of the boreholes. Guide the drainage design and construction based on the calculation results of the amount of water that can be drained.

[0073] Example

[0074] A coal mine is mining No. 2 coal seam, which is 5.2m thick and 380m deep. It is a nearly horizontal coal seam. The coal seam is overlain by the Yan'an Formation, Zhiluo Formation, Anding Formation, and Luohe Formation sandstone aquifers. The thickness of the roof sandstone is about 300m, and the water-richness is uneven. Currently, the 31123 working face is being mined. Before mining, the following steps are used to calculate the amount of water that can be drained from the roof sandstone, which provides scientific guidance for the drainage of roof water.

[0075] Step 1: Determine that the main aquifer affecting coal seam mining is the Zhiluo Formation aquifer. Collect coal mine geological exploration reports, hydrogeological supplementary exploration reports, borehole column charts, hydrological borehole pumping test results and other information, and combine the measured data of the mine's water-conducting fracture zone to determine the main aquifer as follows:

[0076] (1) The unit water yield of the Zhiluo Formation aquifer in the pumping test was 1.2-1.5 L / (s·m), which was larger than that of the Yan'an Formation, Anding Formation, and Luohe Formation aquifers;

[0077] (2) The thickness of the Yan'an aquifer is 60-100 m, the Zhiluo aquifer is 150-200 m, the Anding aquifer is 50-80 m, and the Luohe aquifer is 30-70 m. The Zhiluo aquifer is the thickest.

[0078] (3) After the mining of the No. 2 coal seam, the height of the water-conducting fracture zone is 23 times the mining height, and the height of the water-conducting fracture zone is 119.6 m. After the mining of the No. 2 coal seam, the water-conducting fracture zone communicates with the Yan'an Formation aquifer and partially communicates with the Zhiluo Formation aquifer.

[0079] Step 2: Determine that the lower limit of the porosity of the main aquifer is 8%, and the lower limit of the permeability is 120mD. Take the core of the Zhiluo Formation aquifer at the 31123 working face. The core diameter is 3cm and the height is 10cm. Place the core in a constant temperature box at a high temperature of 80℃ for 11 hours and fully dry. The test environment temperature is 24℃, the environment is moderately 75%RH, and the ground is flat without strong vibration. The displacement pressure is 35MPa and the confining pressure is 45MPa. The porosity is greater than 8% and the permeability is greater than 120mD. The water in the aquifer in the area where the coal seam mining water-conducting fracture zone communicates with the Zhiluo Formation aquifer is released immediately, providing a basis for calculating the amount of aquifer that can be drained after the top plate drainage drilling construction.

[0080] Step 3: Determine the porosity of the Zhiluo Formation aquifer at the 31123 working face. Take 10 cores of the Zhiluo Formation aquifer to conduct porosity and permeability test experiments on the Zhiluo Formation aquifer to obtain the porosity of the main aquifer. The porosity is as follows:

[0081]

[0082] Step 4: Establish the relationship between porosity and acoustic time difference. Collect the borehole acoustic time difference logging data in the exploration stage, combine it with the porosity tested in step 3, and construct the porosity and acoustic time difference fitting relationship ( Figure 2 ), as follows:

[0083] y=0.0215x+3.4728 (1)

[0084] R 2 =0.9094

[0085] Where: y is the effective porosity (%); x is the acoustic time difference data (μs / s); R 2 is the correlation coefficient.

[0086] Step 5: Use the porosity and acoustic time difference fitting relationship (1) in step 4 to calculate the porosity of the Zhiluo Formation aquifer in the 31123 working face where the porosity has not been tested, as follows: Figure 2 The calculation results are shown in the following table:

[0087] Table 2 Porosity calculation results of the unmeasured porosity area of ​​the working face

[0088] Serial number Porosity(%) Acoustic time difference (μs / s) Serial number Porosity(%) Acoustic time difference (μs / s) 1 7.7728 (removed) 200 9 8.0523 213 2 8.0523 213 10 8.5253 235 3 8.6973 243 11 8.6328 240 4 7.8803 (removed) 205 12 7.9878 (removed) 210 5 8.0953 215 13 8.0738 214 6 8.2028 220 14 8.2028 220 7 8.4178 230 15 8.8048 248 8 8.2888 224 16 8.1598 218

[0089] Step 6: Calculate the water saturation of the Zhiluo Formation aquifer using the water saturation formula. Take rock samples from the Zhiluo Formation aquifer and conduct rock-electric experiments to determine the relevant coefficients in the water saturation calculation formula. The coefficients include saturation index, coefficients related to lithology and pore structure, pore water resistivity, rock formation resistivity, etc. After experiments, it was finally determined that the saturation index n is 2, the coefficient a related to lithology and pore structure is 0.7, m is 1.9, and the pore water resistivity R is 1.9. W The rock resistivity R t is 1.3Ω·m, and the pore water resistivity R W It is 0.5Ω·m.

[0090] Step 7: Calculate the amount of water that can be drained from the Zhiluo Formation aquifer. Select the areas in Steps 3 and 5 where the porosity is greater than 8%, the permeability is greater than 120mD, and the water-conducting fracture zone connects to the Zhiluo Formation aquifer, and calculate the amount of water that can be drained according to the following formula:

[0091]

[0092] Where: E is the amount of water that can be drained from the aquifer; n is the data that meets the conditions; S Wi is water saturation; h i is the thickness of the aquifer.

[0093] After screening the data, it was calculated that the amount of water that can be drained from the Zhiluo Formation aquifer is 25,000 m 3 .

[0094] Step 8: Use the water-rich abnormal area exploration and the unit water yield of the borehole to correct the calculation results of the drainable water volume, such as Figure 3 As shown. Collect water-richness evaluation reports such as transient electromagnetic and direct current electrical detection and the unit water yield of boreholes obtained from hydrological borehole pumping tests, and compare and analyze the accuracy of the calculation of the amount of water that can be drained from the main aquifers, focusing on correcting the calculation results of the amount of water that can be drained from the aquifers according to the size of the unit water yield of the boreholes. Guide the drainage design and construction based on the calculation results of the amount of water that can be drained.

[0095] The method for calculating the amount of drainable water in the coal seam roof aquifer in the present invention is implemented by a device for calculating the amount of drainable water in the coal seam roof aquifer. The device for calculating the amount of drainable water in the coal seam roof aquifer includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method for calculating the amount of drainable water in the coal seam roof aquifer as described above is implemented.

[0096] In summary, the present invention makes full use of the logging data in the coal resource exploration stage, establishes the relationship between the logging curve and the porosity of the aquifer, and uses it to calculate the porosity of the unmeasured aquifer area, calculates the drainable water volume of the aquifer, reduces the number of porosity tests and the amount of drilling and geophysical exploration projects, and reduces the cost of water prevention and control in coal mines; the present invention calculates the drainable water volume of the main aquifer in the roof of the coal seam, and compared with the relative water richness in the past, it can efficiently guide the roof water drainage work.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for calculating the amount of water that can be drained from a coal seam roof aquifer, characterized in that: The steps include: Step 1, determine the main aquifers that affect coal mining; Step 2, taking core samples of the main aquifer to determine the porosity and permeability lower limit of the main aquifer; The core displacement experiment is used to determine the lower limits of the porosity and permeability of the main aquifer, that is, when the porosity and permeability are greater than or equal to this lower limit, the water in the aquifer will be released when the coal seam mining water-conducting fracture zone connects the main aquifer; Step 3, determining the porosity and permeability of the main aquifer through porosity and permeability testing experiments; Step 4, establishing the relationship between porosity and acoustic wave time difference; The porosity and acoustic time difference logging curves are combined to construct the porosity and acoustic time difference fitting relationship, which is as follows: y =A x +B Where: y is the effective porosity%; x is the acoustic time difference data µs / s; A and B are constants; Step 5, using the acoustic time difference curve to obtain the porosity of the main aquifer whose porosity has not been measured; Step 6, using the water saturation formula to calculate the water saturation of the main aquifer; Take rock samples from the main aquifer, carry out rock-electricity experiments on the main aquifer, and determine the relevant coefficients of the calculation formula for water saturation of the main aquifer. The specific formula is as follows: ； Among them, S W is water saturation; n is saturation index; a, m are coefficients related to lithology and pore structure; R W is the pore water resistivity; R t is the rock resistivity; is the porosity; Step 7, calculating the amount of water that can be drained in the area where the porosity of the main aquifer is greater than the lower limit of the porosity, the permeability of the aquifer is greater than the lower limit of the permeability and the water-conducting fracture zone is connected; Step 8, using the water-rich abnormal area exploration and the unit water yield of the borehole to correct the calculation results of the drainable water volume.

2. The method for calculating the amount of water that can be drained from a coal seam roof aquifer according to claim 1, characterized in that: In step 1, hydrogeological data in the coal resource exploration stage are collected and the main aquifers that affect coal seam mining are determined based on the aquifer division and its main hydrogeological characteristics, and the development of water-conducting fracture zones in coal seam mining. The hydrogeological data in the coal resource exploration stage include hydrological borehole drilling columns, hydrological borehole pumping experiment results, hydrogeological comprehensive columnar diagrams, geological exploration reports, and hydrogeological supplementary exploration reports.

3. The method for calculating the amount of water that can be drained from a coal seam roof aquifer according to claim 2, characterized in that: The conditions for determining the main aquifer include: A. The unit water yield of the boreholes in the main aquifer is large; B. The thickness of the main aquifer is large; C. After coal seam mining, the water-conducting fracture zone develops highly and communicates with the main aquifer in part or all of the area.

4. The method for calculating the amount of water that can be drained from a coal seam roof aquifer according to claim 1, characterized in that: In step 3, the porosity is the ratio of the connected pore space to the total volume of the rock, and the porosity is ≥5%.

5. A device for calculating the amount of water that can be drained from a coal seam roof aquifer, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method for calculating the amount of drainable water in the coal seam roof aquifer as described in any one of claims 1 to 4 is implemented.

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