深部开采条件下压力水对煤体瓦斯解吸特性影响研究及应用

As coal mines are gradually entering the stage of deep mining in China, the situation of coal and gas outburst prevention is becoming more serious.In works of coal seam infusion to prevent outburst and coal seam gas drainage, there are three - phase coupling effects of pressure water with coal and gas, which make influences to gas desorption characteristics of coal body.In response to the scientific problem, this project uses the combination of theoretical analysis and experimental study as the method, and does the following researches:With seepage theory of porous media and molecular adsorption theory, the mechanical mechanism is to be explored that how pressure water affects coal gas desorption in pores;By applying overburden pressure to simulate the deep mining condition, and pumping high pressure water into the coal samples with water injection pump, the simulation test device of pressure water influencing coal gas desorption characteristics in deep mining is to be established;with the device, the competitive adsorption of water and gas on coal is to be demonstrated by testing changes of homothermic adsorption pressure in the experiments tank after water injected; wiht the device, the influences of overburden pressure, water injection pressure, water quantity and water infiltration time to coal gas desorption characteristics is to be tested;Combined the results of theoretical analysis and experimental researches, the mechanism of three - phase coupling effects of pressure water with coal and gas in deep mining, and coal gas desorption mechanism under this influence is studied.the research results can be used in optimization of coal seam infusion to prevent outburst and engineering design to improve the effect of coal seam gas drainage.

我国煤矿正逐步进入深部开采阶段，煤与瓦斯突出灾害防治形势比较严峻。在煤层注水防突和煤层气抽采工作中，均存在压力水与煤体、瓦斯的三相耦合作用并影响煤体瓦斯解吸特性的问题。针对这一问题，本项目采用理论分析和实验研究相结合的方法，进行如下研究：采用多孔介质渗流理论和分子吸附理论，探讨压力水在煤体孔隙中影响瓦斯解吸的力学作用机理；通过施加覆压作用模拟深部开采条件，采用注水泵向预先吸附瓦斯的煤样注入高压水，建立深部开采条件下压力水对煤体瓦斯解吸特性影响的模拟测试装置；采用该装置测试注水后实验罐内恒温吸附压力的变化，论证水与瓦斯的竞争吸附作用；测试覆压、注水压力、注水量及注水后浸润时间对瓦斯解吸特性的影响；结合理论分析和实验研究的成果，探讨深部开采条件下压力水与煤体、瓦斯的三相耦合作用及其影响煤体瓦斯解吸的机制。研究成果可广泛用于煤层注水防突方案优化和提高煤层气抽采效果的工程设计中。

在生产实践中，煤层注水、水力压裂、水力冲孔、煤层水力排采过程中均会出现压力水侵入煤层并影响煤层瓦斯解吸的问题，本项目研究了深部开采条件下压力水对煤体瓦斯解吸影响机制。.项目具体研究内容包括：（1）压力水影响瓦斯解吸的机理：理论上提出了压力水影响瓦斯的三个必要条件，先天条件是煤的多孔介质特性；后天条件是压力水侵入煤层；受力条件是的根源，毛管阻力和贾敏效应产生的阻力是抑制解吸效应产生的根本原因。（2）压力水影响煤体瓦斯解吸的机制研究：构建了压力水影响煤体瓦斯解吸特性的实验装置和实验方法；证实了水分与瓦斯的竞争吸附作用可使约10%的吸附瓦斯转化为游离瓦斯；证实了在覆压作用下瓦斯解吸速度增加，但注入水分会降低瓦斯解吸速度，在覆压作用下合理注水量取决于煤质和覆压大小；验证了在同样注水量条件下较低注水压力有利于降低瓦斯解吸速度；通过研究注水后瓦斯解吸特性提出通过第一分钟瓦斯解吸速度、第一分钟瓦斯解吸率、120分钟瓦斯解吸率和残存瓦斯含量计算合理注入水分的方法，合理注入水分受注水压力、煤质和瓦斯吸附量影响；提出煤层注水合理浸润时间的确定方法，并确定了超化、古汉山和寺河煤样的合理浸润时间。（3）提出了包括注水过程中的渗流驱替过程和注水后水分对瓦斯抑制解吸过程的压力水影响瓦斯解吸的数值模型，模拟得出注水后瓦斯涌出量降低、煤层中残存瓦斯含量增高，残存量随时间的变化速度明显变慢。.项目研究成果是对现有理论进行了补充、完善，在煤层注水防治瓦斯领域，有利于进一步认清煤层注水的防突机理，优化煤层注水防治瓦斯的工艺方案。