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贵州省低渗薄煤层水力增渗模拟及地面抽采试验以山脚树矿YP-7井为例

Surface permeability improvement and gas control extraction test of low permeability thin coal seam in Guizhou province——Taking the YP-7 well of Shanjiaoshu Mine as an example

  • 摘要: 贵州省多薄煤层发育,龙潭组煤系地层1.5 m以下薄煤层占煤层总数50%以上,针对薄煤层开采的地面瓦斯治理技术,目前没有成功的单一薄煤层地面瓦斯治理案例可供借鉴。基于此,以贵州省山脚树矿YP-7井为例,利用数值模拟软件对单一薄煤层的压裂液及支撑剂参数变化对改造效果的影响进行分析,为低渗薄煤层煤层气井的地面压裂工艺优化提供指导,提高瓦斯抽采及治理效果。模拟研究及工程试验表明:压裂泵注的排量及砂比对储层改造效果的影响较显著;在压裂工艺上,采用活性水+KCL的压裂液体系减小煤层伤害,采取大液量、中高排量、高砂量、中高砂比、段塞加砂的方式提高薄煤层改造效果,压裂改造后煤层的渗透率提高6 070倍;在排采制度上,与煤矿采动卸压相结合,实行控制产粉、快速降压的方式,提高低渗薄煤层的压裂液返排率及扩大解吸半径,开抽6个月解吸范围内煤层吨煤瓦斯下降4.49 m3/t,预计开抽2 a后压裂缝网范围内煤层瓦斯含量将降低至8 m3/t以下,对应范围内的煤层气采收率达到51.53%。结果表明:YP-7井压裂施工过程中压力相对稳定,出现石英砂轻微堆积造成压力上升,但中高排量能够迅速解堵,排采过程连续稳定,未出砂出粉,日产气量达到900 m3以上。根据该井地面压裂与采动卸压的综合治理瓦斯研究与实践,为贵州省薄煤层瓦斯综合治理工程实践提供指导。

     

    Abstract: Multiple and thin coal seams develop in Guizhou province, and the thin coal seams below 1.5 m in the coal measures of Longtan Formation account for more than 50% of the total coal seams. As for the surface gas control technology of thin coal seam mining, there is no single successful surface gas control case of thin coal seam for reference. Based on this, taking YP-7 well in Shanchushu Mine, Guizhou Province as an example, numerical simulation software was used to analyze the influence of fracturing fluid and proppant parameter changes of a single thin coal seam on the reconstruction effect, providing guidance for the optimization of surface fracturing technology of low-permeability thin coal seam gas Wells, and improving the gas extraction and treatment effect. Simulation studies and engineering tests show that fracturing pump displacement and sand ratio have significant effects on reservoir reconstruction. In the fracturing process, the fracturing liquid system of active water +KCL is used to reduce coal seam damage, and the transformation effect of thin coal seam is improved by large liquid volume, medium and high discharge, high sand volume, medium and high sand ratio, slug plus sand, and the permeability of coal seam after fracturing is increased by 6 070 times. In terms of drainage system, combined with mining pressure relief in coal mine, the method of controlling powder production and rapid pressure reduction is implemented to improve the fracturing fluid return rate of low permeability thin coal seam and expand the desorption radius. Within the desorption range of coal seam tons of coal gas decreased by 4.49 m3/t within 6 months of opening and pumping, and it is expected that the coal seam gas content within the pressure fracture network range will be reduced to less than 8 m3/t after opening and pumping for 2 years. The recovery rate of coalbed methane in the corresponding range reached 51.53%. The results show that the pressure is relatively stable during the fracturing process of YP-7 well, and the slight accumulation of quartz sand causes the pressure to rise. However, the plugging can be quickly solved with medium and high displacement, the drainage and production process is continuous and stable, and no sand and powder are produced, and the daily gas volume reaches more than 900 m3. According to the research and practice of comprehensive gas control of surface fracturing and mining pressure relief in this well, it provides guidance for the comprehensive gas control engineering practice of thin coal seam in Guizhou Province.

     

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