我国低渗煤层井下注气驱替增流抽采瓦斯技术进展及前景展望

Progress and prospect of gas extraction technology by underground gas injectiondisplacement for increasing flow in low-permeability coal seam in China

我国大部分矿区煤层渗透率较低,注气驱替增流抽采瓦斯技术是提高低渗煤层瓦斯抽采效率的有效方法之一。分类梳理了我国低渗煤层瓦斯赋存特征,总结概括出高资源储量、低含气饱和度、多储层压力并存、低渗透性和复杂分区性5个特点。利用差异置信法、灰色关联法、置信区间计算法,分析了我国煤层瓦斯对井下注气驱替增流抽采瓦斯技术的适用性,获得6个影响注气驱替瓦斯效果的直接因素,影响度依次为:煤体普氏系数>瓦斯压力>渗透率>灰分>瓦斯含量>朗格缪尔压力常数;建立了适用于井下注气驱替增流抽采瓦斯技术的煤层参数筛选评价方法。根据注气驱替煤体瓦斯增流机制的不同,从气体因素、注能改性两方面厘清了注气驱替煤体瓦斯增流机制,气体因素增流机制包括:充能携载、分压促解、稀释促扩散、竞争吸附;注能改性增流机制包括:充能扩孔、促解扩孔、充能拓孔、脉冲气流损伤孔隙结构/展布裂隙网络。总结了注气驱替气源、工艺参数对瓦斯驱替效果的影响规律,简要介绍了井下注气驱替增流抽采瓦斯关键技术与装备、应用模式及应用效果。展望了我国井下注气驱替增流抽采瓦斯技术的未来发展趋势,具体包括:多学科深化注气驱替增流抽采瓦斯理论、多方法协同注气驱替增流抽采瓦斯技术、注气驱替增流抽采瓦斯工艺参数精准化、注气驱替增流抽采瓦斯装备智能化、煤层注-抽-掘-采衔接布局协调化。

Most coal mining areas in China have a low coal seam permeability.Gas extraction technology by gas injection displacement for increasing flow is one of effective methods to improve the efficiency of gas extraction in low-permeability coal seams.In this study,the gas occurrence characteristics of low-permeability coal seam in China were reviewed and classified.Five characteristics were summarized,including high resource reserves,low gas saturation,coexistence of multiple reservoir pressures,low-permeability,and complex partitioning.Based on the method of difference confidence,grey correlation and confidence interval calculation,the applicability of coal seam gas in China to the gas extraction technology by underground gas injection displacement for increasing flow was analyzed.Six direct factors affecting the effect of gas injection displacement were obtained.The influence degree was as follows:Platts coefficient>Gas pressure>Permeability>Ash content>Gas content>Langmuir pressure constant.A screening and evaluation method of coal seam parameters was established which was suitable for the gas drainage technology by underground gas injection displacement for increasing flow.According to the different mechanisms of increasing gas flow in gas injection displacement,the gas flow increasing mechanism of gas injection displacement was clarified from two aspects:gas factor increasing flow(carry CH 4 with filling energy to increase flow,promote CH 4 desorption by sharing pressure to increase flow,promote CH 4 diffusion by diluting to increase flow,and competitive adsorption to increase CH 4 flow)and energy injection modification increasing flow(enlarge pores with filling energy to increase CH 4 flow,enlarge pores with promoting desorption to increase CH 4 flow,expand pores with promoting desorption to increase CH 4 flow,and damaged pore structure/spread fracture network by pulse gas flow to increase CH 4 flow).The influence of gas source and process parameters on the gas injection displacement effect was summarized.A brief introduction to the key technology and equipment,application mode and application effect of the underground gas extraction technology by gas injection displacement for increasing flow.The future development trend of the underground gas extraction technology by gas injection displacement for increasing flow in China was prospected,including multidisciplinary deepening the theory of gas extraction by gas injection displacement for increasing flow,multimethod collaborative the technology of gas extraction by gas injection displacement for increasing flow,precision of the parameters of gas extraction by gas injection displacement for increasing flow,intellectualization of the equipment of gas extraction by gas injection displacement for increasing flow,coordination of injection-pumping-excavation-mining connection layout in coal seam.