摘要
为充分揭示采动影响下地面井抽采瓦斯运移的主要影响因素,实现地面井瓦斯的高效抽采,在建立含瓦斯煤体的多物理场的耦合数学模型的基础上,推导出煤体应力及渗流方程,进而得出孔隙率及渗透率与应变、瓦斯压力等参数之间相互关系。以山西某矿为工程背景,利用COMSOL Multiphysics软件对地面井瓦斯抽采实践进行模拟,并确立了数值模拟的初始和边界条件,分析不同地应力条件、不同的初始渗透率及不同初始瓦斯压力对钻井抽采产量及效率的影响。结果显示:地面钻井瓦斯抽采速率及抽采量受地应力、瓦斯压力、渗透率影响明显,其中渗透率是其决定性参数,但渗透率主要受到了地应力的影响。在一定地应力条件下,孔隙率及渗透率随着抽采时间的增加先行减小,而后增大,存在着一个临界残余瓦斯压力点;而初始渗透率对地面井瓦斯抽采影响明显,初始值越大,瓦斯压力下降越显著,抽采速率和抽采量同时变大。因而在地面井进行抽采时,提高煤层初始渗透率不失为实现钻井高效抽采的一种方法。通过采动地面井现场实际试验表明,受到采动充分卸压以及渗透率的提高影响,抽采浓度及纯量皆有阶跃式地增长,极大地提升了地面井抽采效率。
In order to reveal the main influencing factors of gas migration in surface wells under the influence of mining and realize efficient gas extraction in surface wells,the stress and seepage equations of coal body were deduced,based on the multi-physical field coupling mathematical model of coal body containing gas,and then the relationship between the porosity and permeability and the parameters such as strain and gas pressure was obtained.Finally,with a mine in Shanxi Province as the engineering background,COMSOL Multiphysics software was used to simulate the surface well gas extraction practice,the initial and boundary conditions of numerical simulation are established,and the influences of different in-situ stress conditions,different initial permeability and different initial gas pressure on drilling production and efficiency were analyzed.The result shows:The gas extraction rate and quantity of surface drilling are obviously affected by ground stress,gas pressure and permeability,among which permeability is the decisive parameter,but permeability is mainly affected by ground stress.Under certain in-situ stress conditions,porosity and permeability decrease first and then increase with the increase of extraction time,and there is a critical residual gas pressure point;Initial permeability has an obvious influence on surface well gas extraction.The larger the initial value is,the more significant the gas pressure drops,and the higher the extraction rate and quantity simultaneously.Therefore,increasing the initial permeability of coal seam can be regarded as a way to realize efficient extraction in surface wells.The field test of mining surface well shows that the extraction concentration and pure quantity increase step by step under the influence of full mining pressure relief and permeability increase,which greatly improves the extraction efficiency of surface well.
作者
唐建平
李日富
TANG Jianping;LI Rifu
出处
《中国矿山工程》
2023年第4期30-36,61,共8页
China Mine Engineering
基金
山西省科技重大专项(20201102001)。
关键词
地面井
瓦斯运移
抽采效率
模拟
渗透率
the ground well
gas migration
extraction efficiency
simulate
permeability
