WO2019184148A1 - 一种低渗透性煤层高效注水方法 - Google Patents

一种低渗透性煤层高效注水方法 Download PDF

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Publication number
WO2019184148A1
WO2019184148A1 PCT/CN2018/095832 CN2018095832W WO2019184148A1 WO 2019184148 A1 WO2019184148 A1 WO 2019184148A1 CN 2018095832 W CN2018095832 W CN 2018095832W WO 2019184148 A1 WO2019184148 A1 WO 2019184148A1
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coal
coal seam
pressure
borehole
gas injection
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PCT/CN2018/095832
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English (en)
French (fr)
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孟祥豹
张延松
刘博�
杜文州
王相
徐翠翠
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山东科技大学
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Publication of WO2019184148A1 publication Critical patent/WO2019184148A1/zh
Priority to ZA2020/05910A priority Critical patent/ZA202005910B/en

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/20—Displacing by water
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E21B43/261—Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/25—Methods for stimulating production
    • E21B43/26—Methods for stimulating production by forming crevices or fractures
    • E21B43/263—Methods for stimulating production by forming crevices or fractures using explosives
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
    • E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
    • E21F17/18—Special adaptations of signalling or alarm devices
    • E21F17/185—Rock-pressure control devices with or without alarm devices; Alarm devices in case of roof subsidence

Definitions

  • the invention relates to the technical field of coal seam water injection, in particular to a high-efficiency water injection method for a low permeability coal seam.
  • Coal still plays a pivotal role in China's energy consumption structure.
  • coal consumption accounted for 62.6%, which is expected to be around 60% in 2017.
  • the increasing scale of coal mining and the rapid development of related production activities have caused the safety of coal mine production to become increasingly prominent and urgently to be resolved.
  • Coal seam water injection technology is one of the effective measures to prevent coal and gas outburst, prevent impact pressure and prevent spontaneous combustion.
  • coal seam water injection is also a complex project subject to many factors.
  • the coal seam water injection benefit is affected and affected by many factors such as the physical and mechanical properties of the coal seam, the depth of burial, the degree of coal seam voids and fissures, and the characteristics of coal voids.
  • China's coal seams are generally low-permeability coal seams.
  • coal seam permeability is generally 2-3 orders of magnitude smaller.
  • Low permeability has caused many mines in China to cause frequent earthquake pressure accidents, coal and gas outburst accidents, and at the same time
  • the low permeability coal seam is injected with water and the water injection effect is poor. These problems have seriously hindered the efficient and safe mining of coal mines in China.
  • Coal mine low permeability coal seam is also called low permeability coal seam. In order to ensure efficient intensive mining and safe production of low permeability coal seam, it is necessary to study the high efficiency water injection method of low permeability coal seam.
  • the pre-cracking and anti-reflection measures for low-permeability coal seams mainly include deep-hole loose blasting, hydraulic fracturing, hydraulic punching, mining liberation layer, and hydraulic kerf.
  • deep hole loose blasting makes the coal seam near the borehole be broken, but the pre-cracking effect is slightly decreased from the farther point of the borehole, the pre-cracking radius is small, the effect is not good, and the explosion of coal mine explosives is also caused. The distance is small.
  • the on-site construction needs the detonating cord connection. Therefore, the construction on site is troublesome; then the pre-cracking of the explosive may cause the gas explosion in the area through the crack to be unsafe.
  • Hydraulic punching is to flush the borehole by hydraulic expansion, and to enlarge the diameter of the borehole while flushing the pulverized coal in the borehole wall, so that the borehole wall has better permeability. Because the method has little effect on improving the permeability of the coal seam, it is basically not at present. Adopt again.
  • the mining liberation layer is often close to the liberation layer with small thickness, difficult to mine, or poor coal quality, no mining value, and even many coal seams are not adjacent to the liberation layer, making the technology unusable.
  • the hydraulic kerf is limited by the equipment, making the implementation process of this technology complicated and difficult to promote and apply on the spot.
  • the object of the present invention is to provide a high-efficiency water injection method for a low-permeability coal seam, which solves the technical problem that the current low-permeability coal seam gas extraction radius is small and the effect is poor.
  • the invention provides a high-efficiency water injection method for a low permeability coal seam, comprising the following steps:
  • Step 1 Determination of mechanical properties of coal
  • Step 2 determine the highest gas injection pressure of high pressure gas injection
  • Step three drilling the coal body
  • Explosives are loaded into the borehole using a non-coupling charge
  • Step 5 Reserve high pressure pipeline in the borehole
  • a high-pressure pipeline is reserved in the borehole, and the length of the high-pressure pipeline in the borehole is 0.5 to 0.6 times the depth of the borehole, and the end of the high-pressure pipeline extends out of the borehole;
  • the hole is sealed and sealed with cement material.
  • the length of the cement sealing hole is 0.2 to 0.3 times of the drilling depth, and the length of the cement sealing hole is greater than the depth of the coal body pressing band;
  • the high-pressure gas is injected into the borehole through the high-pressure pipeline, and the pressure of the injected high-pressure gas is gradually increased to the highest gas injection pressure and maintained.
  • the highest gas injection pressure is determined by the second step, and the flow rate of the injected high-pressure gas is significantly reduced and remains high after being stabilized.
  • the gas injection pressure is several hours, the high pressure gas is a mixed gas of propane and air, and the volume fraction of propane in the mixed gas is 5%;
  • the high-pressure pipeline is connected to the water injection pipeline to perform water injection operation on the coal seam to be mined.
  • the horizontal spacing of the adjacent boreholes is 20 m, and the drilling distance closest to the coal mining face is 10 m, and the diameter of the borehole is 96 mm.
  • the charge of the explosive is 0.5 to 0.7 times the length of the drilled hole.
  • the end of the high-pressure pipeline protrudes from the borehole by a length of 0.5 m to 1 m.
  • step 6 the ratio of cement to water in the cement material is 1:0.2 to 1:0.5.
  • the flow rate of the injected high pressure gas is significantly reduced and the maximum gas injection pressure is maintained for 6 hours after being stabilized.
  • the low permeability coal seam high efficiency water injection method of the invention has the following characteristics and advantages:
  • the high-efficiency water injection method of the low-permeability coal seam of the invention is safe and reliable in construction, reasonablely arranged drilling holes in the coal seam to be mined, and injecting high-pressure gas (mixed gas of propane and air) to realize synergy between propane and explosive detonation, greatly increasing
  • high-pressure gas mixed gas of propane and air
  • the porosity of the coal seam is mined, the pre-cracking radius is large, and the effect is good.
  • the water injection radius of the low permeability coal seam is large, which greatly improves the effect of water injection in the low permeability coal seam.
  • FIG. 1 is a flow chart of a method for efficiently injecting water into a low permeability coal seam according to an embodiment of the present invention
  • FIG. 2 is a drilling arrangement diagram of an efficient water injection method for a low permeability coal seam according to an embodiment of the present invention
  • coal mining face 1, track along the trough, 3, tape along the trough, 4, coal seam to be mined, 5, drilling.
  • the embodiment provides a method for efficiently injecting water into a low permeability coal seam, comprising the following steps:
  • Step one the determination of the mechanical properties of the coal
  • Step 2 determine the highest gas injection pressure of high pressure gas injection
  • the compressive strength of the coal body is divided by 1.5 as the highest gas injection pressure for subsequent high pressure gas injection.
  • Step three drilling the coal body
  • the hole is drilled horizontally to the coal seam 4 to be mined.
  • the depth of the hole 5 is 0.3 times the length of the coal face 1 and the vertical height of the hole 5 is coal.
  • the working face 1 is 0.5 times the height.
  • the horizontal spacing of the adjacent boreholes 5 is 20 m, and the borehole 5 closest to the coal mining face 1 is 10 m from the coal mining face 1 and the bore diameter is 96 mm.
  • Explosives are loaded into the borehole 5 by means of a non-coupling charge.
  • the charge of the explosive is 0.5 to 0.7 times the length of the borehole 5.
  • Step 5 Reserve high pressure pipeline in the borehole 5
  • a high-pressure pipeline is reserved in the borehole 5, and the length of the high-pressure pipeline in the borehole 5 is 0.5 to 0.6 times the depth of the borehole 5.
  • the end of the high-pressure pipeline extends out of the borehole 5, and the end of the high-pressure pipeline extends out.
  • the length of the hole 5 is 0.5 m to 1 m.
  • the hole is sealed with 5 holes and sealed with cement material.
  • the ratio of cement to water in the cement material is 1:0.2 to 1:0.5.
  • the length of the cement sealing hole is 0.2 to 0.3 times the depth of the drilling hole 5, and the length of the cement sealing hole is greater than the depth of the coal body pressing band.
  • the high pressure gas is injected into the borehole 5 through the high pressure pipeline, and the pressure of the injected high pressure gas is gradually increased to the highest gas injection pressure and maintained.
  • the highest gas injection pressure is determined by the second step, and the flow rate of the injected high pressure gas is significantly reduced and remains after the stabilization.
  • the maximum gas injection pressure is 6 hours.
  • the high pressure gas is a mixture of propane and air.
  • the volume fraction of propane in the mixed gas is 5%.
  • the explosive in the borehole 5 is detonated to pre-crack and enhance the coal seam.
  • the high pressure pipeline is connected to the water injection pipeline, and the coal seam 4 to be treated is filled with water.
  • the high-efficiency water injection method for the low-permeability coal seam of the present embodiment achieves the purpose of high-efficiency water injection by increasing the cracks, small cracks, pores, micro-pores, and semi-closed pores of the coal seam 4 to be mined, and increases the gas permeability of the coal seam 4 to be mined.
  • the key to the success of the example is the role of high pressure gas in the borehole and the synergistic principle of high pressure propane and explosive detonation in the following six aspects.
  • the high-pressure propane enters the cracks, small cracks, pores, micropores, and semi-closed pores in the coal seam 4 to be mined, and the expansion work is performed, so that the small cracks expand and connect into a large crack, and at the same time, the pores,
  • the microporous and semi-closed pores expand into fissures and larger pores, so that the primary fissures, regenerated fissures, pores and the like are interconnected to form a gas permeable network, and the gas permeability of the coal seam 4 to be mined is improved.
  • the high-pressure gas is continuously injected for 6 hours, so that the high-pressure gas passes through the static pressure action, and can better act on the coal seam cracks and pores of the joint and the unconnected coal seam.
  • the micro-porosity and semi-closed pores further develop the coal seam fissure and the pore network communication network, and improve the gas permeability of the coal seam 4 to be mined.
  • the charging method is uncoupling charge
  • the detonation wave generated by the explosion of the explosive causes radial cracks to form inside the coal seam, and the high-pressure gas and the high-pressure gas in the borehole 5 penetrate into the radial crack and act as a gas wedge.
  • Increasing the tensile stress in the coal at the front end of the fracture can further develop the fracture and pore communication network in the coal seam 4 to be mined, and improve the gas permeability of the coal seam 4 to be mined.
  • the high temperature and high pressure generated can detonate the high-pressure propane with a volume fraction of 5% in the borehole 5, and strengthen the explosion to expand the fracture and pore network of the borehole and its surrounding communication, and improve the waiting
  • the gas permeability of the coal seam 4 is mined.
  • the porosity of the coal seam 4 to be mined can be greatly increased, which is beneficial to the efficient water injection of the low permeability coal seam.
  • the high-efficiency water injection method of the low-permeability coal seam of the present embodiment is safe and reliable in construction, and the drilling hole 5 is reasonably arranged in the coal seam 4 to be mined, and the effect of high-pressure gas in the borehole and the detonation synergy of propane and explosive greatly increase.
  • the porosity of the coal seam to be mined, the pre-cracking anti-transmission radius is significantly increased, about 15 to 20 meters, and the deep-hole loosening blasting of the most commonly used explosives in coal mines has a relatively small pre-cracking anti-reflection radius of about 3 to 5 meters. .
  • the deep hole loose blasting of the most commonly used explosives in coal mines requires encrypted borehole 5 to achieve the same anti-reflection effect.
  • the high-water injection method of low-permeability coal seam has a moisture content of 8.230% and a water increase of 2.128%. Compared with the common water injection method, the moisture content of the coal seam is increased by 88.9%, and the moisture increase of coal seam is increased by 88.8. %, the high-efficiency water injection method of low permeability coal seam shows better water injection effect.

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Abstract

一种低渗透性煤层高效注水方法，包括以下步骤：步骤一、煤体力学性质测定；步骤二、确定高压气体注气的最高注气压力；步骤三、煤体钻孔；步骤四、不耦合装药；步骤五、钻孔内预留高压管路；步骤六、钻孔封孔；步骤七、高压气体注气；步骤八、引爆炸药预裂增透；步骤九、煤层注水。通过注入高压气体，实现丙烷和炸药爆轰协同，增加待开采煤层的孔隙率，提高注水效果。

Description

一种低渗透性煤层高效注水方法 技术领域
本发明涉及煤层注水技术领域，特别是涉及一种低渗透性煤层高效注水方法。
背景技术
煤炭在我国能源消费结构中仍然占有举足轻重的地位，2016年，煤炭消费比重为62.6％，预计2017年约为60％左右。煤矿开采规模的日益增大及相关生产活动的高速发展，造成煤矿生产的安全问题日益突出，亟待解决。煤层注水技术是防治煤与瓦斯突出、防治冲击地压以及防自燃等煤矿安全问题的有效措施之一。然而，煤层注水亦是一项受制于众多因素影响的复杂工程，煤层注水效益受煤层自身物理力学性质、埋藏深度、煤层空隙和裂隙程度、煤体空隙特征等诸多因素制约和影响。但是我国煤层普遍为低渗透率煤层，相比国外，我国煤层渗透性普遍要小2-3个数量级，低渗透性造成了我国许多煤矿冲击地压事故、煤与瓦斯突出事故频发，同时对低渗透性煤层进行注水，注水效果差，这些问题都严重阻碍了我国煤矿高效安全开采。煤矿低渗透率煤层也称为低透气性煤层，为保障低透气性煤层高效集约化开采和安全生产，需要对低渗透性煤层高效注水方法进行研究。
目前，低透气性煤层预裂增透措施主要包括深孔松动爆破、水压致裂、水力冲孔、开采解放层、水力割缝等方法。其中深孔松动爆破使得钻孔附近的煤层被炸的很碎，但对离钻孔稍远的地方预裂效果迅速下降，预裂半径较小，效果不好；另外由于煤矿用炸药的殉爆距离较小，为防止拒爆，现场施工需要导爆索联结，因此，现场施工麻烦；再就是炸药预裂，有可能引起通过裂隙导通的区域瓦斯爆炸，不安全。水力压裂若水压小，裂隙扩张有限，预裂效果不好；若水压大，高压水会从较大的裂隙中流出，预裂不均匀，效果不好；且高压水在煤层中的流动不可控制。水力冲孔是通过水力冲刷钻孔，扩大钻孔直径的同时冲洗钻孔壁的煤粉，使钻孔壁有更好的渗透性，由于该方法对于提高煤层透气性效果甚小，目前基本不再采用。开采解放层由于煤层赋存条件的限制，往往临近解放层厚度很小，难于开采，或者煤质较差，没有开采价值，甚至许多煤层没有临近解放层，使得该技术无法使用。水力割缝受设备的限制，使得该项技术的实施工艺复杂，难以在现场推广应用。
发明内容
本发明的目的在于提供一种低渗透性煤层高效注水方法，解决目前低渗透性煤层瓦斯抽采半径小且效果较差的技术问题。
本发明提供一种低渗透性煤层高效注水方法，包括以下步骤：
步骤一、煤体力学性质测定
在待开采煤层中取煤样，测定煤体的抗压强度，确定待开采煤层靠近轨道顺槽、胶带顺 槽部位煤体压酥带深度；
步骤二、确定高压气体注气的最高注气压力
将煤体的抗压强度除以1.5作为后续高压气体注气的最高注气压力；
步骤三、煤体钻孔
分别沿轨道顺槽、胶带顺槽的延伸方向向待开采煤层中等间距水平钻孔，钻孔的深度为采煤工作面长度的0.3倍，钻孔的垂直高度为采煤工作面高度的0.5倍；
步骤四、不耦合装药
采用不耦合装药方式向钻孔内装入炸药；
步骤五、钻孔内预留高压管路
钻孔内预留高压管路，高压管路位于钻孔内的长度为钻孔深度的0.5至0.6倍，高压管路的末端伸出钻孔；
步骤六、钻孔封孔
将钻孔封孔，采用水泥材料封孔，水泥封孔的长度为钻孔深度的0.2至0.3倍，水泥封孔的长度要大于煤体压酥带深度；
步骤七、高压气体注气
通过高压管路向钻孔内注入高压气体，注入高压气体的压力逐渐增大到最高注气压力并保持，最高注气压力由步骤二中确定，注入高压气体流量明显变小且稳定后依然保持最高注气压力数个小时，高压气体为丙烷和空气的混合气体，混合气体中丙烷的体积分数为5％；
步骤八、引爆炸药预裂增透
在注入高压气体保持最高注气压力的时间内，引爆钻孔内的炸药，对煤层进行预裂增透；
步骤九、注水
将高压管路连接注水管路，对待开采煤层进行注水作业。
进一步的，步骤三中，相邻钻孔的水平间距为20m，距离采煤工作面最近的钻孔距离采煤工作面为10m，钻孔直径为96mm。
进一步的，步骤四中，炸药的装药长度为钻孔长度的0.5至0.7倍。
进一步的，步骤五中，高压管路的末端伸出钻孔的长度为0.5m至1m。
进一步的，步骤六中，水泥材料中水泥与水的比例为1:0.2至1:0.5。
进一步的，步骤七中，注入高压气体流量明显变小且稳定后依然保持最高注气压力6个小时。
与现有技术相比，本发明的低渗透性煤层高效注水方法及具有以下特点和优点：
本发明的低渗透性煤层高效注水方法，施工安全、可靠，在待开采煤层中合理布置钻孔， 注入高压气体(丙烷和空气的混合气体)，实现丙烷和炸药爆轰协同，极大增加待开采煤层的孔隙率，预裂增透半径大、效果好，对低渗透性煤层注水半径大，极大提高低渗透性煤层注水的效果。
结合附图阅读本发明的具体实施方式后，本发明的特点和优点将变得更加清楚。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本发明实施例低渗透性煤层高效注水方法的流程图；
图2为本发明实施例低渗透性煤层高效注水方法的钻孔布置图；
其中，1、采煤工作面，2、轨道顺槽，3、胶带顺槽，4、待开采煤层，5、钻孔。
具体实施方式
如图1、图2所示，本实施例提供一种低渗透性煤层高效注水方法，包括以下步骤：步
骤一、煤体力学性质测定
在待开采煤层4中取煤样，测定煤体的抗压强度，确定待开采煤层4靠近轨道顺槽2、胶带顺槽3部位煤体压酥带深度。
步骤二、确定高压气体注气的最高注气压力
将煤体的抗压强度除以1.5作为后续高压气体注气的最高注气压力。
步骤三、煤体钻孔
分别沿轨道顺槽2、胶带顺槽3的延伸方向向待开采煤层4中等间距水平钻孔，钻孔5的深度为采煤工作面1长度的0.3倍，钻孔5的垂直高度为采煤工作面1高度的0.5倍。相邻钻孔5的水平间距为20m，距离采煤工作面1最近的钻孔5距离采煤工作面1为10m，钻孔直径为96mm。
步骤四、不耦合装药
采用不耦合装药方式向钻孔5内装入炸药，炸药的装药长度为钻孔5长度的0.5至0.7倍。
步骤五、钻孔5内预留高压管路
钻孔5内预留高压管路，高压管路位于钻孔5内的长度为钻孔5深度的0.5至0.6倍，高压管路的末端伸出钻孔5，高压管路的末端伸出钻孔5的长度为0.5m至1m。
步骤六、钻孔5封孔
将钻孔5封孔，采用水泥材料封孔，水泥材料中水泥与水的比例为1:0.2至1:0.5。水泥封孔的长度为钻孔5深度的0.2至0.3倍，水泥封孔的长度要大于煤体压酥带深度。
步骤七、高压气体注气
通过高压管路向钻孔5内注入高压气体，注入高压气体的压力逐渐增大到最高注气压力并保持，最高注气压力由步骤二中确定，注入高压气体流量明显变小且稳定后依然保持最高注气压力6个小时，高压气体为丙烷和空气的混合气体，混合气体中丙烷的体积分数为5％。
步骤八、引爆炸药预裂增透
在注入高压气体保持最高注气压力的时间内，引爆钻孔5内的炸药，对煤层进行预裂增透。
步骤九、注水
将高压管路连接注水管路，对待开采煤层4进行注水作业。
本实施例的低渗透性煤层高效注水方法，通过增加待开采煤层4的裂隙、小裂隙、孔隙、微孔隙、半封闭孔隙，达到高效注水目的，增加待开采煤层4的透气性，是本实施例成功的关键，其高压气体在钻孔内的作用及高压丙烷和炸药爆轰协同增透原理体现在以下六个方面。
一是高压丙烷注入钻孔5中后，高压丙烷进入待开采煤层4中裂隙、小裂隙、孔隙、微孔隙、半封闭孔隙的同时膨胀做功，使得小裂隙扩张联通成较大裂隙，同时孔隙、微孔隙、半封闭孔隙扩展变为裂隙和较大孔隙，使得原生裂隙、再生裂隙、孔隙等相互联通形成透气性网络，提高待开采煤层4的透气性。
二是在原生裂隙、再生裂隙、孔隙等相互联通形成的透气性网络中，高压丙烷改变待开采煤层4中甲烷的赋存状态(吸附/解吸)，使钻孔、原生裂隙、再生裂隙、孔隙中游离甲烷的量变小，进而使待开采煤层中的甲烷浓度低于其爆炸极限，提高安全性。
三是钻孔5中注入高压气体流量明显变小且相对稳定后，持续注入高压气体6个小时，使得高压气体通过静压作用，能更好的作用于联通和未联通的煤层裂隙、孔隙、微孔隙、半封闭孔隙，使煤层裂隙、孔隙网联通网络进一步发展，提高待开采煤层4的透气性。
四是由于装药方式为不耦合装药，炸药爆炸产生的爆轰波使煤层内部形成径向裂隙，钻孔5中的高压气体和爆生高压气体渗入径向裂隙，起着气楔作用，增大裂隙前端煤体内的拉应力，可以使待开采煤层4中的裂隙、孔隙联通网络进一步发展，提高待开采煤层4的透气性。
五是炸药爆炸时，爆炸初期产生的大量爆生高压气体，与钻孔5中已有高压气体通过静压作用于待开采煤层4中联通和未联通的煤层裂隙、孔隙、微孔隙、半封闭孔隙，使煤层裂隙、孔隙网联通网络进一步发展，提高待开采煤层4的透气性。
六是钻孔5中炸药起爆后，产生的高温高压可以引爆钻孔5中体积分数5％的高压丙烷共同爆炸，强化爆炸对钻孔及其周边联通的裂隙、孔隙网络的扩展作用，提高待开采煤层4的透气性。
通过以上原理过程，能极大地增加待开采煤层4的孔隙率，有利于低渗透性煤层高效地注水。
本实施例的低渗透性煤层高效注水方法，施工安全、可靠，在待开采煤层4中合理布置钻孔5，通过高压气体在钻孔内的作用以及丙烷和炸药的爆轰协同，极大增加待开采煤层的孔隙率，预裂增透半径显著提升，约为15至20米，而煤矿最常用的炸药深孔松动爆破，其预裂增透影响半径相对较小，约为3至5米。采用煤矿最常用的炸药深孔松动爆破，若要达到相同的增透效果，需要加密钻孔5，有时为了获得较好的增透效果，还需要实施大量的控制钻孔，意味着劳动强度的增大和劳动效率的降低，同时还要加大爆破炸药用量，意味着效率较低。本实施例针对某相邻两个工作面，进行注水后煤层湿润程度的考察，其一采面采用普通注水方法，另一采面采用高效注水方法，对在工作面范围内的5架、25架、45架、65架、85架、105架液压支架六个点，取煤样进行含水量的测定，并与注水前煤层的含水量进行对比，从而求得水分增量，对比两种注水方法的注水效果。
表1.不同煤层注水工艺水分增量对比
Figure PCTCN2018095832-appb-000001
从表1可以看出，应用低渗透性煤层高效注水方法煤层含水率达到8.230％，水分增量达到2.128％，对比普通注水方法，使煤层含水率增加了88.9％，煤层水分增量增加了88.8％，低渗透性煤层高效注水方法表现出较好的注水效果。
当然，上述说明并非是对本发明的限制，本发明也并不仅限于上述举例，本技术领域的技术人员在本发明的实质范围内所做出的变化、改型、添加或替换，也应属于本发明的保护范围。

Claims (6)

  1. 一种低渗透性煤层高效注水方法，其特征在于，包括以下步骤：
    步骤一、煤体力学性质测定
    在待开采煤层中取煤样，测定煤体的抗压强度，确定待开采煤层靠近轨道顺槽、胶带顺槽部位煤体压酥带深度；
    步骤二、确定高压气体注气的最高注气压力
    将煤体的抗压强度除以1.5作为后续高压气体注气的最高注气压力；
    步骤三、煤体钻孔
    分别沿轨道顺槽、胶带顺槽的延伸方向向待开采煤层中等间距水平钻孔，钻孔的深度为采煤工作面长度的0.3倍，钻孔的垂直高度为采煤工作面高度的0.5倍；
    步骤四、不耦合装药
    采用不耦合装药方式向钻孔内装入炸药；
    步骤五、钻孔内预留高压管路
    钻孔内预留高压管路，高压管路位于钻孔内的长度为钻孔深度的0.5至0.6倍，高压管路的末端伸出钻孔；
    步骤六、钻孔封孔
    将钻孔封孔，采用水泥材料封孔，水泥封孔的长度为钻孔深度的0.2至0.3倍，水泥封孔的长度要大于煤体压酥带深度；
    步骤七、高压气体注气
    通过高压管路向钻孔内注入高压气体，注入高压气体的压力逐渐增大到最高注气压力并保持，最高注气压力由步骤二中确定，注入高压气体流量明显变小且稳定后依然保持最高注气压力数个小时，高压气体为丙烷和空气的混合气体，混合气体中丙烷的体积分数为5％；
    步骤八、引爆炸药预裂增透
    在注入高压气体保持最高注气压力的时间内，引爆钻孔内的炸药，对煤层进行预裂增透；
    步骤九、注水
    将高压管路连接注水管路，对待开采煤层进行注水作业。
  2. 根据权利要求1所述的低渗透性煤层高效注水方法，其特征在于：步骤三中，相邻钻孔的水平间距为20m，距离采煤工作面最近的钻孔距离采煤工作面为10m，钻孔直径为96mm。
  3. 根据权利要求1所述的低渗透性煤层高效注水方法，其特征在于：步骤四中，炸药的装药长度为钻孔长度的0.5至0.7倍。
  4. 根据权利要求1所述的低渗透性煤层高效注水方法，其特征在于：步骤五中，高压管路的末端伸出钻孔的长度为0.5m至1m。
  5. 根据权利要求1所述的低渗透性煤层高效注水方法，其特征在于：步骤六中，水泥材料中水泥与水的比例为1:0.2至1:0.5。
  6. 根据权利要求1所述的低渗透性煤层高效注水方法，其特征在于：步骤七中，注入高压气体流量明显变小且稳定后依然保持最高注气压力6个小时。
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