【作者】 郭涛；

【导师】 司鹄；

【作者基本信息】 重庆大学 ， 安全技术及工程， 2010， 硕士

【摘要】 煤炭是我国的主要能源之一。在煤炭的生产过程中,由瓦斯产生的灾害事故严重影响着煤矿的安全生产。同时,煤矿瓦斯又是一种热值非常高的宝贵能源。我国煤层瓦斯储量较大,其储量大致与天然气的储量相当。如何利用好治理好煤矿瓦斯是世界各国研究的重点。钻孔抽放瓦斯技术是利用和治理瓦斯最主要的方法和途径。瓦斯在煤层中运移规律是煤矿瓦斯抽放或者瓦斯灾害防治研究领域中的基础问题之一,其对瓦斯的抽放等具有重要的理论和工程指导作用。本文根据含瓦斯煤岩具有的特点,利用流固耦合、有限元分析相关理论,运用数值模拟的方法,对煤层瓦斯运移和钻孔抽放瓦斯进行了深入系统的研究,得到了一些有益的研究成果:①阐述了含瓦斯煤岩相关物理特性。从煤的变形机制出发,根据孔隙率的基本定义,考虑到钻孔抽放瓦斯的过程中,游离瓦斯压力变化较剧烈并对煤岩体产生变形的影响,建立了含瓦斯煤岩孔隙率的表达式。利用一系列假设和Terzaghi有效应力理论,建立了含瓦斯煤岩体变形控制方程。论述了瓦斯运移的相关参数。通过Carman-Kozeny方程推导出了含瓦斯煤渗透率的数学表达式。基于以往的假设和质量守恒定律得出了瓦斯流固耦合控制方程。②对不同条件下单孔抽放瓦斯运移变化的规律进行了研究。在瓦斯抽放初期,瓦斯压力变化较大,瓦斯压力梯度较大。随着抽放时间的推移,抽放范围逐渐扩大,有效应力逐渐增加,煤层孔隙率和渗透率逐渐减小,抽放难度加大。分析了不同埋藏深度条件下和不同抽放负压条件下,瓦斯压力、孔隙率以及渗透率的变化和分布。通过对不同钻孔半径条件下抽放瓦斯的分析,得出了不同钻孔半径条件下,有效抽放半径与时间的关系图。分析了不同的初始渗透率对抽放瓦斯的影响,初始渗透率越大,瓦斯越易抽放。③分析了在顺层多个钻孔抽放瓦斯条件下,瓦斯运移规律。随着抽放时间的延长,各个钻孔的抽放范围不断扩大,钻孔之间产生相互影响。对于不同钻孔间距,间距越小,钻孔之间的影响作用加强,煤层瓦斯压力降低较快。④同时对两种不同的钻孔方式(倾斜(向上)、水平钻孔)抽放瓦斯进行了模拟分析。在相同的时间内,倾斜(向上)对煤层瓦斯影响较大。相同抽放条件下,利用倾斜钻孔抽放瓦斯,瓦斯压力减小速度较快。更多还原

【Abstract】 Coal is the primary energy source in China. In the process of coal production, the disasters of gas have seriously affected the safety. Meanwhile, the coal gas is a kind of precious resource with very high calorific value. In our country, the reserve of coal gas is as large as natural gas reserve .How to make good use of coal mine gas is the focus of the world study. Gas drainage from boreholes is a main method of utilization and management of coal seam gas.The law of gas in the coal seam is the basic problem in the research of mine gas drainage and prevention of disaster caused by gas, and it provides important theoretical and engineering guidance for gas drainage. Based on the characteristics of the coal rock , by using the theory of Fluid-structure interaction,Finite element and Numerical simulation method, this paper conducted the research systematically into seam gas migration on the coal and gas drainage from boreholes. The main research results are followed:①The basic physical properties of the coal rock are described. Based on the deformation mechanism of coal mine and the definition of the porosity, the equation of porosity in coal rock containing gas is deduced. By using the effective stress in porous media theory( (Terzaghi effective stress theory) and a series of assumptions,the deformation equations of coal rock is derived, and the relevant parameters of gas migration are discussed. The mathematical expression of the permeability is derived based on Carman-Kozeny equation. Based on a series of basic assumptions of gas migration and the principle of conservation of mass, the equation of gas migration is derived.②The analysis and research have been conducted to the law of the variation of gas migration under different conditions of single-hole drainage. Early in the gas drainage, the change of underground pressure is greater and gas pressure gradient is larger. With the advance of gas drainage, the area of gas drainage is gradually expanded; the effective stress is increasing; porosity and permeability of coal decreases, gas drainage is more difficult. The analysis and research have been conducted to the changes and distribution of gas pressure, porosity and permeability under the conditions of different burial depth and different negative pressure. The diagram of effective drainage radius and time is obtained by the analysis of gas drainage under different drainage radius conditions. The analysis has been conducted to the impact of different initial permeability on gas drainage, and the result is that the larger the initial, permeability, the more easily gas drainage is.③The law of gas migration under gas drainage in a number of boreholes along coal seam is analyzed. With the drainage time going on, the drainage areas of each drilling hole expanded and the interaction between boreholes is created. For different spacing of boreholes, the smaller the spacing, the stronger mutual influence between boreholes is created and the more quickly gas pressure is reduced .④Two different gas drainage drilling methods which are the tilt (up) and horizontal drilling method, respectively, have been simulated and analyzed. Within the same time slot, the tilt (up) method has a greater impact on the coal seam gas. Under the same drainage conditions, gas pressure decreases faster using the tilt (up) method.更多还原