井下直接法测定煤层瓦斯压力数值模拟研究及工程指导

发布时间：2018-05-23 12:19

本文选题：直接法 + 煤层瓦斯压力　；参考：《华北科技学院》2017年硕士论文

【摘要】：煤层瓦斯压力作为矿井瓦斯最重要的基础参数之一,其准确测定对于防治瓦斯灾害、保证煤矿安全生产和巩固煤炭能源基础地位具有重要意义。通过对以前相关研究成果总结和分析,提出了一些研究内容作为补充和延伸。以瓦斯在煤层中流动的物理模型、瓦斯在煤层中流动的数学模型、多物理场耦合数值仿真软件COMSOL Multiphysics作为桥梁,采用数值模拟手段开展了一些有益的探讨,得出以下结论,并对现场测压工作提供了一定的工程指导。(1)在一定的数学模型指导下,研究不同因素对瓦斯压力平衡时间的影响规律,表明并不是钻孔影响范围越大,瓦斯压力平衡时间越长,依具体情况而定。在钻孔暴露时间、渗透率、孔隙率、钻孔直径相同的条件下,煤层原始瓦斯压力越大,钻孔影响范围就越大,但是瓦斯压力平衡时间并不会因此而增加;在钻孔暴露时间、煤层原始瓦斯压力、孔隙率、钻孔直径相同的条件下,煤层渗透率越大,钻孔影响范围越大,但是瓦斯压力平衡时间并不会因此而增加;在煤层原始瓦斯压力、渗透率、孔隙率、钻孔直径相同的条件下,钻孔暴露时间越长,钻孔影响范围越大,瓦斯压力平衡时间越长,验证了前人的结论;在煤层原始瓦斯压力、渗透率、孔隙率、钻孔暴露时间相同的条件下,钻孔直径越大,钻孔影响范围越大,瓦斯压力平衡时间越长。(2)考虑滑脱效应以后,在封孔生效阶段,随着钻孔暴露时间的增加,钻孔周围处任意一点处的瓦斯渗透率都在增加,并且随着距钻孔壁的距离增加,这种增加效应逐渐减小甚至没有。因此在一定条件下,考虑滑脱效应时,封孔过程中钻孔周边任意一点处的煤层瓦斯压力值比不考虑滑脱效应的煤层瓦斯压力值低,表明在封孔过程中滑脱效应的存在不利于测压;在封孔后压力恢复阶段,由于滑脱效应的存在,使得煤层渗透率始终大于煤层初始渗透率,瓦斯更易在煤层中流动。这也间接表明在封孔之后滑脱效应的存在有利于瓦斯压力恢复。(3)考虑煤与瓦斯流固耦合以后,封孔生效前钻孔周边任意一点的瓦斯压力值比非耦合模型的瓦斯压力值高,即煤与瓦斯的耦合作用减小了钻孔周围的煤层瓦斯压力损失,但随着封孔时间的增大,耦合模型与非耦合模型的瓦斯压力值相差不大,这种优势将减小;传统的单场分析只能考虑封孔生效阶段内在钻孔周围形成的压降漏斗,但是考虑煤与瓦斯耦合作用之后,还会在钻孔周围形成煤层孔隙率和煤层渗透率漏斗,在封孔生效之前,随着钻孔暴露时间的增大,钻孔周围孔隙率和渗透率都不断减小,并且这种减小速度会越来越慢;从使测压钻孔周边的煤层孔隙率和渗透率降低的角度出发,得出煤层埋藏深度越深,越不利于测压;在封孔生效后的初始阶段,瓦斯压力上升速度较快,这也使得孔隙率和渗透率增加较快,很快接近煤层初始孔隙率和渗透率,又由于煤与瓦斯的耦合作用减小了钻孔周围的煤层瓦斯压力损失,所以测压时间比非耦合条件下的短。(4)突破传统数值模拟分析的局限,分别建立了穿层钻孔测压模拟App、考虑滑脱效应的穿层钻孔测压模拟App以及考虑煤与瓦斯耦合作用的顺层钻孔测压模拟App,实现了快速仿真。(5)结合数值模拟结果和工程试验研究,对现场测压工作提供了一定的工程指导,为了减少测压钻孔暴露时间,一方面需要提高测压人员的操作技能,提前备好封孔材料,以保证在见煤后及时封孔,另一方面可以选择采用能够较快封孔的技术和方法,比如黄泥-聚氨酯封孔法和胶囊-聚氨酯封孔法;测压钻孔直径宜为65~95mm;可以采用封孔段大孔口配合测压气室小孔口测压技术,比如先按照《煤矿井下煤层瓦斯压力的直接测定方法》(AQ/T 1047—2007)中要求的钻孔直径65~95mm开孔20m,然后从20m的位置一直到煤层采用小钻头来开孔等。
[Abstract]:Coal seam gas pressure is one of the most important basic parameters of mine gas, its accurate determination is of great significance for preventing gas disaster, ensuring coal mine safety production and consolidating coal energy basic status. By summarizing and analyzing the previous related research results, some research contents are put forward as supplement and extension. Gas is used in coal seam. The mathematical model of the flow in the medium, the mathematical model of gas flow in the coal seam, the multi physical field coupling numerical simulation software COMSOL Multiphysics as the bridge, using the numerical simulation method to carry out some useful discussions, draw the following conclusions, and provide a definite engineering guidance for the field pressure measurement work. (1) under the guidance of a certain mathematical model, The influence of different factors on the time of gas pressure balance shows that the greater the borehole influence range is, the longer the gas pressure balance time is, the more the borehole exposure time, permeability, porosity and borehole diameter are the same, the bigger the original gas pressure is, the larger the borehole influence range is, but the gas is bigger. The pressure balance time does not increase; under the conditions of the borehole exposure time, the coal seam original gas pressure, the porosity and the diameter of the borehole, the greater the permeability of the coal seam, the greater the influence range of the borehole, but the gas pressure balance time will not increase, and the original gas pressure, permeability, porosity and borehole diameter are the same in the coal layer. Under the condition of the longer exposure time, the greater the influence range of borehole and the longer the balance time of gas pressure, the longer the balance of gas pressure, the longer the pressure, the permeability, the porosity and the exposure time of the borehole are the same, the bigger the diameter of the borehole, the larger the borehole influence range, the longer the balance time of the gas pressure. (2) consideration of the slippage effect. In the future, the gas permeability at any point around the hole increases with the increase of the exposure time of the borehole, and with the increase of distance from the borehole wall, the effect of this increase gradually decreases or not. Therefore, under certain conditions, when the slipping effect is considered, any point around the hole around the hole is closed. The pressure value of coal seam gas is lower than that of coal seam gas pressure without taking off effect, which indicates that the existence of slipping effect is not conducive to pressure measurement in the process of sealing, and the coal seam permeability is always larger than the initial permeability of coal seam, and the gas is more easily flowing in the coal seam after sealing the hole, and the gas is more easily flowing in the coal seam. After the sealing of the hole, the existence of slippage effect is beneficial to the recovery of gas pressure. (3) considering the coupling of coal and gas flow, the value of gas pressure at any point around the borehole before the sealing is effective is higher than that of the non coupled model, that is, the coupling effect of coal and gas reduces the loss of gas pressure in the coal seam around the drilling hole, but with the sealing hole. With the increase of time, the difference of gas pressure between the coupling model and the non coupling model is small, and this advantage will be reduced. The traditional single field analysis can only consider the pressure drop funnel formed around the hole in the effective phase of the hole, but after the coupling of coal and gas, the porosity and permeability funnel of the coal seam can be formed around the drilling hole. Before the opening of the hole, the porosity and permeability around the borehole are decreasing with the increase of the exposure time, and this decrease speed will be more and more slow. From the angle of reducing the porosity and permeability of the coal seam surrounding the borehole, the deeper the depth of the coal seam is, the more unfavorable the pressure measurement. At the stage, the gas pressure rises faster, which also increases the porosity and permeability faster, quickly approaches the initial porosity and permeability of the coal seam, and reduces the loss of gas pressure in the coal seam around the borehole because of the coupling effect of coal and gas, so the time of pressure measurement is shorter than that under the non coupling condition. (4) breakthrough the traditional numerical simulation analysis. Limited, we have set up the simulation App of the penetrating hole pressure measurement, the simulation App of the drill hole and the simulation App considering the coupling effect of coal and gas, which consider the coupling effect of coal and gas. (5) combining the numerical simulation results and the engineering experiment research, it provides some engineering guidance for the current field pressure measurement work, in order to reduce the pressure. On the one hand, it is necessary to improve the operating skills of the manometer and prepare the sealing material in advance to ensure the timely sealing of the hole, and on the other hand, the technology and methods, such as the yellow mud polyurethane sealing method and the capsule - polyurethane sealing method, can be used to seal holes in time, and the diameter of the pressure drilling hole is 65~95mm. The small hole pressure measurement technology of the pressure chamber is used in combination with the opening of the hole and the hole. For example, the hole diameter 65~95mm required by the direct measurement method of the coal seam gas pressure in the coal mine (AQ/T 1047 - 2007) is used to open the hole 20m, and then from the position of the 20m to the coal seam to use a small bit to open the hole.
【学位授予单位】：华北科技学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712.3

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