废弃矿井遗煤吸附瓦斯储量计算模型及注液促采机制

There are abundant reserves gas resources in abandoned coal mines, In addition, the exploitation and utilization of abandoned coal mines gas resource not only has good economic effectiveness, but also has good environmental and safety effectiveness, at the same time, it is also a new direction for the secondary exploration of the coal mines which have already closed or coal resources are going to dry up. However, the exploitation and utilization of mine gas resources in abandoned mines is still in the preliminary exploration stage at present, because the model for accurate assessment of gas resources and the promoting gas production mechanism have not completely conquered yet. For this reason, the project aims at the problem of inaccurate assessment of gas resources and the mechanism of promoting gas production by liquid injection not clear enough in abandoned coal mines, intend to start with the environmental(ambient gas pressure, bearing stress and temperature)evolution law of residual coal, research the influence of the key environmental parameters on the adsorbed gas and the effect of promoting gas production by liquid injection through the test of coal adsorbing gas under the conditions of different ambient gas pressure, temperature and loading condition and promoting gas production by liquid injection, combined with the properties of coal properties, pore structure and related theories, establish the calculation model of adsorbed gas reserves in abandoned coal mine and study on the mechanism of promoting gas production by liquid injection, make firm or stable a theoretical support for the exploitation and utilization of gas resources in abandoned coal mines.

废弃矿井瓦斯资源储量丰富，对废弃矿井瓦斯资源开发利用不但具有较好的经济效益，还具有良好的环境效益和安全效益，同时亦是当前已关闭煤矿及煤炭资源即将枯竭矿井二次开发利用的新方向。但由于瓦斯资源量精准评估模型和遗煤吸附态瓦斯资源促采机制尚未完全攻克，使得目前我国废弃矿井瓦斯资源开发利用仍处于初步探索阶段。为此，项目针对废弃矿井瓦斯资源开采利用存在的资源量评估不精准、注液促采机制不够明确的问题，拟从遗煤所处环境（环境气体压力、承载应力以及温度）演变规律入手，通过开展不同环境气体压力、温度、载荷条件下遗煤吸附瓦斯试验和外液对遗煤吸附态瓦斯促采效应试验，研究遗煤关键环境参数对吸附瓦斯特性影响和外液对遗煤吸附态瓦斯促采效应，结合遗煤物性参数、孔隙结构和相关理论，构建废弃矿井遗煤吸附态瓦斯储量计算模型和研究注液对吸附态瓦斯促采机制，为废弃矿井瓦斯资源开发利用奠定理论支撑。

在诸多因素的影响下，我国较大数量煤矿被关停，数量庞大的废弃矿井蕴藏了丰富的资源，据估计，废弃矿井中赋存的瓦斯资源量近5000亿m3，储量巨大。但遗憾的是，由于废弃矿井瓦斯资源量精准评估模型不够完善，使得目前我国废弃矿井瓦斯资源开发利用仍处于初步探索阶段。为此，针对遗煤吸附态瓦斯资源储量评估不精准、注液促采机制不够明确的问题，以晋城矿区3号煤层为研究对象，分析了废弃矿井遗煤所处环境气体压力、温度、载荷的演变过程，研究了遗煤所处环境气体压力、温度、载荷变化对遗煤吸附瓦斯特性影响效应，研究结果表明：环境气体压力越高，达到相同吸附率所用时间越短。煤样甲烷初始吸附速率随环境气体压力的升高而增大，在相同的时间段内环境气体压力低的煤样甲烷吸附速率相对衰减较快，随着环境气体压力的升高，阶段甲烷吸附量呈现降低趋势；温度对煤的孔隙结构具有改造效应，随着煤样处理温度的增高，煤中的大孔孔体积增加，孔隙结构复杂，大孔孔隙发育良好，有助于煤中瓦斯解吸出来，煤孔隙微孔的比表面积减小，使煤体吸附瓦斯气体的能力减弱。煤样的平衡甲烷吸附量随着温度的升高呈现出减小的趋势，且环境温度越高，甲烷吸附量减小的越快；煤样甲烷吸附量随着轴向载荷的增大出现先增大后减小的趋势。载荷对遗煤吸附瓦斯特性具有一定程度的影响，但较于温度和环境气体压力可忽略不计，在建立废弃矿井遗煤吸附态瓦斯储量模型时，应将遗煤所处环境气压和温度环境因素考虑在内。在此基础上，结合吸附势理论，构建了包含温度和环境气体压力的遗煤吸附瓦斯储量模型。煤样注水后，水分置换出煤中的吸附瓦斯，随着外加水分的增加，瓦斯的置换量随之增加。添加外加水分后，无烟煤分子结构对甲烷的吸附量、吸附热均明显降低，而且随着外加水分含量增大，甲烷的吸附量、吸附热越低，揭示了外加水促进煤中瓦斯解吸机制。