瓦斯抽采上行钻孔钻屑自封孔性能实验研究

发布时间：2018-07-20 11:14

【摘要】：保护层开采是煤层群开采条件下区域性防治煤与瓦斯突出最有效的技术手段。被保护层卸压不明显时,通常需要由底抽巷向上方煤层打穿层钻孔进行瓦斯抽放,此类上行钻孔数量众多。上行钻孔的有效封孔是井下钻孔瓦斯抽放的技术关键,封孔材料和方法直接影响瓦斯抽采效果。本文致力于研究一种低成本、高效率的新型上行钻孔钻屑自封孔方法,取得的主要研究成果如下:采用FLAC3D软件模拟了钻孔周边应力场和塑性区分布,分析了上行钻孔密封段的泄漏方式,明确了上行钻孔封孔失效机制:上行钻孔封孔过程中存在3种漏气方式,即材料漏气、界面漏气和裂隙漏气,有效封堵这3种漏气通道是防止上行钻孔封孔失效的关键。在此基础上提出了上行钻孔钻屑自封孔方法,该方法利用打钻形成的钻屑自动封堵钻孔,实现钻孔、封孔一体化。采用上行钻孔钻屑自封孔模拟实验系统研究了干钻工况下上行钻孔钻屑自封孔密封机理,包括钻屑颗粒粒度分布和运动过程观测实验。实验结果表明:大多数钻屑颗粒间空隙很小,钻屑沉降后存在压实过程,堆积致密,透气性差;钻屑颗粒会以较大的速度进入钻孔周围煤体破碎区和塑性区的裂隙群内,填充裂隙空间,阻隔巷道内的空气通过钻孔周围煤体裂隙流入钻孔内;钻屑堆积过程中,堆积角呈现增大的趋势,直至钻屑堆满钻孔的横截面,且比例高的细颗粒与钻孔壁接触的机会更多,钻屑与钻孔壁接触严密。钻屑自封孔方法能够有效封堵上行钻孔漏气通道,保证封孔效果。研究了水钻工况下,水和钻屑混合颗粒运动规律对钻孔密封的促进作用:水屑耦合颗粒在喷出钻孔后在钻孔空间内的运动过程中,可以触碰到大钻孔钻孔壁横断面的各个方向,并进入钻孔周围煤岩体裂隙内;水屑混合物在钻孔壁运移的过程中,水具有向钻孔周围煤岩体裂隙渗流的趋势,从而引导钻屑进入裂隙,填充裂隙空间,封堵裂隙漏气通道。钻进过程中,水屑混合物能够在钻孔内不断的堆积,并且当两相流到达水屑堆积体时,水裹挟着钻屑从堆积体的表面斜向上运动,导致堆积体的堆积角增大,直至堆满整个钻孔横截面;封孔完成后,部分残余水填充在钻屑和钻孔壁的界面,形成固-液-固耦合的稳定状态,抑制了钻孔通过界面漏气。固液两相流携带较大的能量沿钻孔壁向下运动冲击堆积在钻孔封孔段的水屑混合物,对钻屑堆积的形态起塑造作用,促进钻屑致密堆积,从而抑制了钻屑材料自身的漏气。采用NMR测试系统测试了固结的水屑混合物的透气性及其影响因素:钻屑颗粒粒度越大,水屑混合物中大孔、裂隙所占的比例越高,总孔隙度越大(其中小孔、中孔孔隙度越小),渗透率越大,致密性越低,透气性越好。水屑混合物随着固化时间的增加,孔隙度会降低,渗透能力变差,透气性也会变差,密封效果进一步增强。研究了干钻和水钻工况下钻屑自封孔密封效果影响因素。干钻工况下,上行钻孔的角度越大、钻杆钻进速度越快以及上行钻孔直径越大时,密封效果越好;水钻工况下,上行钻孔角度越大、水流速度越大以及钻进速度越大时,密封效果越好。对比了相同影响因素下和不同影响因素下两种工况的密封效果:水钻工况下上行钻孔钻屑自封孔密闭气室负压大,负压衰减速度慢,密封性能比干钻工况要好。研究结果对于降低钻孔封孔成本、提高瓦斯抽采效率和促进保护层开采具有一定的科学价值和实际意义。
[Abstract]:The protection layer mining is the most effective technical means to prevent the coal and Gas Outburst under the condition of coal seam group mining. When the pressure relief of the protected layer is not obvious, the gas drainage is usually needed from the bottom seam to the top coal seam. The number of such upper boreholes is numerous. The effective sealing hole of the uplink hole is the technology of gas drainage in the borehole. The key, sealing material and method directly affects the gas extraction effect. This paper is devoted to the study of a new type of low cost and high efficiency self sealing hole drilling hole drilling method. The main research results are as follows: FLAC3D software is used to simulate the stress field and plastic distribution around the borehole, and the leakage mode of the sealing section of the uplink is analyzed. It is true that the sealing failure mechanism of the upper bore hole: there are 3 kinds of air leakage in the process of sealing the hole, that is material leakage, the leakage of the interface and the leak of the crack. The key to prevent the 3 kinds of air leakage effectively is the key to prevent the failure of the hole sealing. On this basis, the self sealing hole method of the drilling cuttings is put forward, which uses the drilling cuttings formed by drilling drilling. The sealing mechanism of the self sealing hole of the drilling cuttings under the working conditions of the drills, including the particle size distribution of the debris particles and the observation experiments of the movement process, is studied by using the simulation experiment system of the self sealing hole of the drilling cuttings in the working condition of the drills. The compaction process has a tight accumulation and poor permeability, and the drilling debris particles will enter the fractured zone of the coal body around the borehole and the fracture group in the plastic zone at a large speed, and fill in the fissure space, and the air inside the roadway flows into the borehole through the cracks in the coal body around the borehole, and the accumulation angle increases in the process of drilling, until the drilling chips are filled with drilling holes. The cross section and the high proportion of fine particles have more opportunities to contact the borehole wall, and the drilling cuttings have close contact with the borehole wall. The self sealing hole method of the drilling chip can effectively block the air leakage channel of the upper drilling hole and ensure the sealing effect. The effect of the movement law of the mixed particles of water and drilling chips on the drilling seal under the working condition of the drill is studied. During the movement of the drill hole in the drilling space, the drilling hole can touch all directions of the cross section of the borehole wall and enter the cracks in the coal rock surrounding the borehole. In the course of the movement of the borehole wall, the water mixture has the trend of seepage to the fracture of the coal rock mass around the borehole, thus guiding the drilling debris into the fissure and filling the void. In the process of drilling, the mixture of water debris can accumulate in the drilling hole, and when the two-phase flow reaches the water debris accumulation, the water is forced to move upward from the surface of the accumulation body, causing the accumulation angle of the accumulation to increase until the whole cross section is piled; after the sealing is completed, some residual water filling is filled. The solid liquid solid coupling stable state is formed at the interface of the drilling and drilling hole wall, which inhibits the hole leakage through the interface. The solid and liquid two phase flow carries a large amount of energy along the borehole wall to pile up the water debris mixture in the borehole sealing section, and makes the formation of the drilled debris form to promote the compact accumulation of the drills, thus restraining the drilling debris. The air leakage of the material itself is tested by the NMR test system. The permeability of the consolidated water chip mixture and its influencing factors are tested. The larger the particle size of the drilled particles is, the higher the pore size of the water debris mixture, the higher the proportion of the fracture, the larger the total porosity is, the smaller the pore and the porosity of the mesopore, the greater the permeability, the lower the density and the better the permeability. The better the permeability is, the mixture of water and debris is better. With the increase of the curing time, the porosity will decrease, the permeability becomes worse, the permeability will become worse and the sealing effect is further enhanced. The influence factors of the sealing effect of the self sealing hole in the drills and the drills are studied. The greater the angle of the drill hole, the faster the drilling rod drilling speed and the larger the diameter of the uplink hole. The better sealing effect is, the greater the angle of the drill hole, the greater the angle of the upstream drilling, the greater the flow speed and the greater the drilling speed, the better the sealing effect. The sealing effect of the two operating conditions under the same influence factors and the different influence factors is compared: the negative pressure of the self sealing chamber of the drilling cuttings under the working condition of the drills is large, the attenuation speed of the negative pressure is slow and the seal is sealed. The performance is better than that of dry drill. The research results have certain scientific and practical significance for reducing the cost of drilling hole sealing, improving the gas extraction efficiency and promoting the protection layer mining.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.6

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