A method of accurate pressure water injection along the seam based on the calculation of hydraulic gradient between coal seams

Abstract

The present invention discloses a method for accurate pressure water injection along the layer based on the measurement of hydraulic gradient of intervals in coal seams, and relates to the technical field of mine disaster prevention. The method comprises: firstly, taking the water injection borehole as the center, setting pressure measuring holes on both sides of the water injection borehole, and setting a monitoring device to measure the stress in the pressure measuring hole in real time; then, in the process of water injection in the coal seam, obtaining the pressure change in the water injection hole and each pressure measuring hole in real time, and timing the pressure change nodes of the pressure measuring holes at different positions, calculating the interval hydraulic gradient during the water injection process, and obtaining the dynamic loss of the pressure water along the process; finally, according to the pressure difference change within different water injection influence radius ranges, and the pressure change nodes of the pressure measuring holes, in the process of water injection in the same coal seam, at the corresponding time node, timely increase the coal seam water injection pressure. The method of the present invention can not only effectively avoid the water leakage phenomenon caused by excessive pressure in the initial stage of water injection, but also compensate for the pressure water dynamic damage to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of mine disaster prevention, and in particular to a method for accurate pressure water injection along a coal seam based on calculation of hydraulic gradients of coal seam intervals. Background Art

[0002] At present, coal is one of the most abundant, widely distributed and economical energy resources in the world. For a long time, coal resources, as the most important basic energy and industrial raw materials, have made important contributions to ensuring national energy security and stable social and economic development. However, with the increase in the depth and intensity of coal mining in my country, the coal structure, coal seam temperature, and ground stress state have undergone significant changes. The risk of high-concentration dust disasters in mines is getting higher and higher, seriously restricting the safe and efficient production of coal. Since coal seam water injection technology can significantly reduce the ground stress of the coal body and increase the water content to inhibit the generation of coal dust, coal seam water injection technology has become a commonly used source dust reduction method in most mining areas in my country. However, during the on-site implementation of coal seam water injection, there are problems such as low-pressure water injection is difficult to effectively initiate cracking, and high-pressure water injection is prone to water leakage, which will limit the on-site dust reduction effect of coal seam water injection.

[0003] In order to avoid the influence of water leakage on the disaster prevention effect of coal seam water injection, a pressure-stabilizing water injection system is usually used in the prior art to stabilize the water injection pressure. The present invention provides a new method, which can achieve accurate control of the pressure during coal seam water injection without the need for a pressure-stabilizing water injection system. Summary of the invention

[0004] The purpose of the present invention is to provide a method for precise pressurized water injection along the coal seam based on the measurement of the hydraulic gradient of coal seam intervals. This method is different from the prior art and overcomes the defect that the water injection pressure is difficult to effectively control in the prior art. The method of the present invention can meet the needs of different mining areas for coal seam water injection disaster prevention operations along the coal seam, and provide scientific guidance for improving the effect of coal seam water injection in preventing and controlling coal mine disasters.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam intervals comprises the following steps in sequence:

[0007] Step 1: Based on the on-site basic data that the effective water invasion radius of the coal seam water injection process is within 5m, two pressure measuring holes are constructed on both sides of the water injection borehole with the water injection borehole as the center. The distances between the two pressure measuring holes on the left and the water injection borehole are 2m and 4m respectively, and the distances between the two pressure measuring holes on the right and the water injection borehole are 3m and 5m respectively;

[0008] Step 2: The water injection borehole is sealed by two blocking and one injection; then each pressure measuring hole is sealed by cement grouting, and the stress change in each pressure measuring hole is monitored by a monitoring device;

[0009] Step 3: Before water injection into the coal seam, record the initial pressure value in each pressure measuring hole, and then start water injection; during the water injection process, obtain the pressure change in the water injection hole and each pressure measuring hole in real time, and time the pressure change nodes of the pressure measuring holes at different positions. According to the pressure difference and distance between the water injection hole and the pressure measuring hole, and the difference between the initial pressure in the pressure measuring hole and the pressure when the pressure in the pressure measuring hole reaches stability after the water injection starts, calculate the interval hydraulic gradient during the water injection process, and obtain the dynamic loss of the pressure water along the way;

[0010] Step 4: According to the pressure difference changes within different water injection influence radius ranges and the pressure change nodes of the pressure measuring holes, the coal seam water injection pressure is increased in a timely manner at the corresponding time nodes during the same coal seam water injection process.

[0011] In the above-mentioned method of precise pressure water injection along the layer based on the measurement of the hydraulic gradient of coal seam intervals, in step 2, the sealing length of the water injection borehole is that the hole mouth of the water injection borehole is more than 5m away from the bottom of the hole; the sealing length of each pressure measuring hole is within 10m from the bottom of the pressure measuring hole.

[0012] The above-mentioned method of precise pressure water injection along the layer based on the measurement of hydraulic gradient of coal seam intervals, the monitoring device includes a stress strain gauge and a stress display instrument, the stress display instrument is located near the orifice of the pressure measuring hole, and a stress strain gauge is arranged in each pressure measuring hole. The stress strain gauge transmits the stress changes in each monitoring hole to the stress display instrument.

[0013] The above-mentioned method of precise pressure water injection along the layer based on the measurement of hydraulic gradient of coal seam intervals is characterized in that: in step one, the construction bottom position of each pressure measuring hole is 5 meters deeper than the bottom of the water injection hole.

[0014] The above-mentioned method of precise pressure water injection along the layer based on the measurement of hydraulic gradient of coal seam intervals, in step 4, increases the coal seam water injection pressure to avoid water leakage caused by excessive pressure in the initial stage of water injection, and is also used to compensate for pressure water dynamic damage.

[0015] In the above-mentioned method of precise pressure water injection along the coal seam based on the measurement of hydraulic gradient of coal seam intervals, the stress strain gauge is pasted in each pressure measuring hole.

[0016] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0017] (1) In the process of constructing coal seam water injection drilling holes and pressure measuring holes, the method of the present invention selects the water injection drilling hole as the center and arranges two pressure measuring holes on both sides of the water injection drilling hole, wherein the interval between the pressure measuring hole on one side and the water injection drilling hole is 2 meters and 4 meters, and the interval between the pressure measuring hole on the other side and the water injection drilling hole is 3 meters and 5 meters. This arrangement is equivalent to the field basic data that the effective water invasion radius of the coal seam water injection process is within 5 meters, and the interval between the water injection drilling hole and the pressure measuring hole is 2 meters, 3 meters, 4 meters, and 5 meters respectively. Compared with the prior art, this construction method can effectively reduce the construction workload and efficiently perform coal seam water injection pressure measurement.

[0018] (2) During the coal seam water injection process, the method of the present invention obtains the pressure changes in the water injection holes and the pressure measuring holes in real time, and times the pressure change nodes of the pressure measuring holes at different positions. According to the pressure difference between the water injection holes and the pressure measuring holes at different distances, the dynamic loss of the pressurized water along the way is calculated. The measurement method is simple and easy.

[0019] (3) The method of the present invention adjusts the injection pressure at the corresponding time point during the coal seam water injection process based on the pressure change in the pressure measuring hole during the coal seam water injection process - the distance curve between the pressure measuring hole and the water injection hole and the water injection time. This can compensate for the pressure hydrodynamic damage to a certain extent and further increase the coal seam water injection infiltration range, thereby providing technical guidance for improving the disaster prevention effect of coal seam water injection, while reducing the power and energy loss during the coal seam water injection process and promoting sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings:

[0021] Figure 1 This is the construction layout diagram of the coal seam water injection drilling hole and the pressure measuring hole of the present invention;

[0022] Figure 2 The principle diagram of precise pressure water injection along the layer;

[0023] Among them, 1-coal seam, 2-pressure measuring hole, 3-two plugging and one injection sealing hole, 4-water injection hole, 5-cement grouting sealing hole. DETAILED DESCRIPTION

[0024] The present invention proposes a method for accurate pressure water injection along the coal seam based on the measurement of hydraulic gradient of coal seam intervals. In order to make the advantages and technical solutions of the present invention clearer and more specific, the present invention is further described below in conjunction with specific embodiments.

[0025] like Figure 1The figure shows the layout of the coal seam water injection borehole and pressure measuring hole construction of the present invention, which respectively shows the coal seam 1, the pressure measuring hole 2, the two-blocking and one-injection sealing hole 3, the water injection hole 4 and the cement grouting sealing hole 5. The present invention has made improvements in the arrangement of the water injection hole and the pressure measuring hole, that is, based on the field basic data that the effective water invasion radius of the coal seam water injection process along the layer is within 5m, two pressure measuring holes are arranged on both sides of the water injection borehole with the water injection borehole as the center, and the two pressure measuring holes on the left side are 2 meters and 4 meters apart from the water injection borehole, respectively, and the two pressure measuring holes on the right side are 3 meters and 5 meters apart from the water injection borehole, respectively; such a design can ensure that the intervals between the water injection borehole and the pressure measuring hole are 2 meters, 3 meters, 4 meters, and 5 meters, respectively, further reducing the construction workload. In addition, the interval design of the pressure measuring holes and the water injection boreholes can pave the way for the subsequent interval hydraulic gradient measurement.

[0026] The water injection borehole is sealed by two plugging and one injection, and the sealing length is the position where the mouth of the water injection borehole is 5m away from the bottom of the hole. Each pressure measuring hole is sealed by cement grouting, and the sealing length is: within 10 from the bottom of the pressure measuring hole. A stress strain gauge is set in each pressure measuring hole. Specifically, the stress strain gauge can be set on the inner wall of the pressure measuring hole by pasting. A stress display instrument is set at the mouth of each pressure measuring hole. The stress strain gauge is connected to the stress display instrument, and the stress in the pressure measuring hole is observed through the stress display instrument.

[0027] Later, during the coal seam water injection process, the pressure changes in the water injection holes and pressure measuring holes can be obtained in real time through stress strain gauges and stress displays, and the pressure change nodes of the pressure measuring holes at different positions (such as the two pressure measuring holes on the left side of the water injection borehole and the two pressure measuring holes on the right side of the water injection borehole) can be timed. According to the pressure difference and distance between the water injection hole and the pressure measuring hole, and the difference between the initial pressure in the pressure measuring hole and the pressure when the pressure in the pressure measuring hole reaches stability after the start of water injection, the interval hydraulic gradient during the water injection process is calculated to obtain the dynamic loss of pressurized water along the way.

[0028] Finally, according to the changes in pressure difference within the influence radius of different water injections and the pressure change nodes of the pressure measuring holes, the coal seam water injection pressure is increased in time at different time nodes during the water injection process in the same coal seam. This can not only effectively avoid the water leakage caused by excessive pressure in the initial stage of water injection, but also compensate for the pressure hydrodynamic damage to a certain extent, and further increase the coal seam water injection infiltration range, thereby providing technical guidance for improving the disaster prevention effect of coal seam water injection.

[0029] The following is a detailed description of the method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam intervals of the present invention, which specifically includes the following steps:

[0030] Step 1: During the construction phase of the coal seam water injection drilling site, the coal seam water injection borehole is first designed. Based on the on-site basic data that the effective water invasion radius of the coal seam water injection process along the seam is within 5m, with the water injection borehole as the center, pressure measuring holes are constructed at intervals of 2m and 4m on one side of the water injection borehole and 3m and 5m on the other side. The pressure measuring holes are equipped with stress strain gauges and the orifices are connected to stress display instruments to achieve real-time measurement of stress in the hole. In order to further measure the water invasion in the annular area centered on the bottom of the water injection borehole, the bottom of the pressure measuring hole is designed to be 5m deeper than the bottom of the water injection hole.

[0031] Step 2: During the process of drilling and sealing, the water injection borehole is sealed by two plugging and one injection, and the sealing length is 5m from the borehole mouth to the bottom of the hole. The pressure measuring hole is sealed by cement grouting, and the length is within 10m from the bottom of the hole. A stress strain gauge is built in, and the hole mouth is connected to a stress display instrument to realize real-time measurement of stress in the hole;

[0032] Step 3: During the coal seam water injection process, the pressure changes in the water injection holes and pressure measuring holes are obtained in real time, and the pressure change nodes of the pressure measuring holes at different positions are timed. According to the pressure difference and distance between the water injection holes and the pressure measuring holes, the hydraulic gradient of the intervals during the water injection process is calculated to obtain the dynamic loss of the pressure water along the way;

[0033] Step 4. According to the pressure difference changes within the different water injection influence radius and the pressure change nodes of the pressure measuring holes, the coal seam water injection pressure is increased in time at the corresponding time nodes during the same coal seam water injection process. This can not only effectively avoid the water leakage caused by excessive pressure in the initial stage of water injection, but also compensate for the pressure hydrodynamic damage to a certain extent, and further increase the coal seam water injection infiltration range, thereby providing technical guidance for improving the disaster prevention effect of coal seam water injection.

[0034] The present invention will be further described below in conjunction with specific embodiments.

[0035] Embodiment 1:

[0036] The application of the method of precise pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam intervals in a certain mine is further explained.

[0037] The specific steps are as follows:

[0038] Step 1: During the construction phase of the coal seam water injection drilling site, first design the coal seam water injection borehole, and then construct pressure measuring holes with the water injection borehole as the center, at intervals of 2 meters and 4 meters on one side and at intervals of 3 meters and 5 meters on the other side. In order to further measure the water intrusion in the annular area centered on the bottom of the water injection borehole, the bottom of the pressure measuring holes is designed to be 5 meters deeper than the bottom of the water injection hole.

[0039] Step 2: During the process of drilling and sealing, the water injection borehole is sealed by two plugging and one injection, and the sealing length is 5m from the borehole mouth to the bottom of the hole. The pressure measuring hole is sealed by cement grouting, and the length is within 10m from the bottom of the hole. A stress strain gauge is built into each pressure measuring hole, and a stress display instrument is connected to the hole mouth of the pressure measuring hole to realize real-time measurement of stress in the pressure measuring hole.

[0040] Step 3: Before water injection into the coal seam, record the initial pressure value in each pressure measuring hole, and then start water injection; during the water injection process, obtain the pressure changes in the water injection hole and the pressure measuring hole in real time, and time the pressure change nodes of the pressure measuring holes at different positions. According to the pressure difference and distance between the water injection hole and the pressure measuring hole, and the difference between the initial pressure in the pressure measuring hole and the pressure when the pressure in the pressure measuring hole reaches stability after the water injection starts, calculate the interval hydraulic gradient during the water injection process, and obtain the dynamic loss of the pressure water along the way, such as Figure 2 As shown, T represents the time from the start of water injection to the time when water flows to each pressure measuring hole, the vertical axis ΔP represents the difference between the initial pressure in the pressure measuring hole and the pressure when the pressure in the pressure measuring hole reaches stability after the start of water injection, and the horizontal axis represents the distance between the water injection hole and the pressure measuring hole.

[0041] Step 4: According to the pressure difference changes within different water injection influence radius ranges and the pressure change nodes of the pressure measuring holes, during the same coal seam water injection process, the coal seam water injection pressure is increased in a timely manner at the corresponding time nodes, such as Figure 2 As shown, when the coal seam water injection time reaches T1, the pressure change in the pressure measuring hole 2 meters away from the water injection hole is ΔP1. At this time, the pressure of the coal seam water injection should be increased by |ΔP1|. When the coal seam water injection time reaches T2, the pressure change in the pressure measuring hole 3 meters away from the water injection hole is ΔP2. At this time, the pressure of the coal seam water injection should be increased by |ΔP2|. When the coal seam water injection time reaches T3, the pressure change in the pressure measuring hole 4 meters away from the water injection hole is ΔP3. At this time, the pressure of the coal seam water injection should be increased by |ΔP3|. When the coal seam water injection time reaches T4, the pressure change in the pressure measuring hole 5 meters away from the water injection hole is ΔP4. At this time, the pressure of the coal seam water injection should be increased by |ΔP4|.

[0042] The coal seam interval hydraulic gradient calculation method and the layer-by-layer precise pressure water injection technology overcome the defects of existing technologies such as the difficulty in effectively controlling the water injection pressure. The calculated data can provide a reference for the coal seam water injection process under the same geological conditions, further improve the coal seam water injection infiltration range, and thus provide technical guidance for improving the disaster prevention effect of coal seam water injection.

[0043] The working principles of the stress strain gauge and the stress display instrument described in the present invention can be realized by referring to the existing technology.

[0044] Parts not described in the present invention can be implemented by referring to the existing technology.

[0045] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of protection claimed in the present application.

Claims

1. A method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam intervals, characterized in that: The following steps are included in sequence: Step 1: Based on the on-site basic data that the effective water invasion radius of the coal seam water injection process is within 5m, two pressure measuring holes are constructed on both sides of the water injection borehole with the water injection borehole as the center. The distances between the two pressure measuring holes on the left and the water injection borehole are 2m and 4m respectively, and the distances between the two pressure measuring holes on the right and the water injection borehole are 3m and 5m respectively; Step 2: The water injection borehole is sealed by two blocking and one injection; then each pressure measuring hole is sealed by cement grouting, and the stress change in each pressure measuring hole is monitored by a monitoring device; Step 3: Before water injection into the coal seam, record the initial pressure value in each pressure measuring hole, and then start water injection; during the water injection process, obtain the pressure change in the water injection hole and each pressure measuring hole in real time, and time the pressure change nodes of the pressure measuring holes at different positions. According to the pressure difference and distance between the water injection hole and the pressure measuring hole, and the difference between the initial pressure in the pressure measuring hole and the pressure when the pressure in the pressure measuring hole reaches stability after the water injection starts, calculate the interval hydraulic gradient during the water injection process, and obtain the dynamic loss of the pressure water along the way; Step 4: According to the pressure difference changes within different water injection influence radius ranges and the pressure change nodes of the pressure measuring holes, the coal seam water injection pressure is increased in a timely manner at the corresponding time nodes during the same coal seam water injection process.

2. The method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam interval according to claim 1, characterized in that: In step 2, the sealing length of the water injection borehole is 5 meters from the hole mouth of the water injection borehole to the bottom of the hole; the sealing length of each pressure measuring hole is within 10 meters from the bottom of the pressure measuring hole.

3. The method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam interval according to claim 1, characterized in that: The monitoring device includes a stress strain gauge and a stress display instrument. The stress display instrument is located near the orifice of the pressure measuring hole. A stress strain gauge is arranged in each pressure measuring hole. The stress strain gauge transmits the stress change in each pressure measuring hole to the stress display instrument.

4. The method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam interval according to claim 1, characterized in that: In step 1, the bottom of each pressure measuring hole is 5 meters deeper than the bottom of the water injection hole.

5. The method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam interval according to claim 1, characterized in that: In step 4, the coal seam water injection pressure is increased to avoid water leakage caused by excessive pressure in the initial stage of water injection, and it is also used to compensate for pressure water dynamic damage.

6. The method for accurate pressure water injection along the coal seam based on the calculation of hydraulic gradient of coal seam interval according to claim 3, characterized in that: The stress strain gauge is pasted in each pressure measuring hole.

Images