低渗煤层定向多簇气相压裂瓦斯治理技术研究与实践

摘要

为解决低渗透煤层瓦斯抽采难题,在潞安矿区5 a多的研究和规模化现场试验基础上,提出了一种低渗透煤层CO2气相定向多簇压裂瓦斯综合治理技术.该技术是应用改进后的CARDOX装置系统所产生的高压CO2气体在煤层中进行定向多簇造缝,实现煤层的卸压和增透,均化和改善局部地应力集中和瓦斯含量/压力的异常分布状态,提高瓦斯抽采效率.研究表明,在气相压裂试验区段,瓦斯突出危险性降低,煤层渗透率提高1～2个数量级,瓦斯抽采浓度和流量提高1个数量级,抽采达标时间由原来的720 d减少到210 d,实现了高瓦斯煤层的安全掘采协调生产.%With the progressive increase of the mining depth,gas related mine hazards are getting worse since gas content and gas pressure naturally elevates.In the study,a novel methane control technology namely CO2 gas fracturing (CO2-Frac),has been proposed and investigated in Luan coal mine field.The CO2-Frac is achieved by directional multiple stage CO2 gas fracturing with a newly renovated CARDOX system.The key mechanism of CO2-Frac is to reduce local stress and gas pressure,and increase permeability effectively.Mine-scale tests on CO2-Frac have been conducted in five coal mines in Luan mine field from 2011 to 2015.It was observed that gas outburst tendency was reduced,permeability and methane drainage effectiveness (concentration and flow rate) in the CO2-Frac boreholes were significantly improved,and drainage time was shortened to 210 days from 720 days.The CO2-Frac is confirmed as the best technology to control coalmine gas disaster in this low permeability coal seams in Luan mine field,and it can be effectively applied in the gassy coalmines with similar geology conditions cross the county.This paper delineates the key research findings of this five year project including the CO2 Frac procedure,the fracture initiation and prorogation mechanism,methane drainage results,and how to optimize fracturing direction.