碎软低渗煤层穿层钻孔水力压裂瓦斯抽采技术研究

Research on hydraulic fracturing gas drainage technology of through layer drilling in broken soft and low permeability coal seams

碎软低渗煤层透气性差是制约煤层瓦斯治理效果的关键因素,水力压裂技术能够改善煤岩层透气性,提高瓦斯抽采效果。通过理论分析和数值模拟,发现碎软煤层水力压裂无法形成有效裂缝,而是通过高压水在碎软煤层中不断地挤胀和穿刺,使煤体发生位移,达到煤层增容、增透目的。在此基础上,以淮北矿区某矿山西组10号煤层为研究对象,开展了现场工程试验。结果显示,压裂过程中,目标煤层发生了多次的挤胀和穿刺作用,压裂影响范围超过25 m,压裂区域预抽钻孔平均瓦斯抽采浓度为63.45%,压裂区域百米煤孔瓦斯抽采纯量是未压裂区域的2.62倍,压裂区域抽采效果较未压裂区域显著提升。研究结果可为碎软低渗煤层瓦斯高效抽采提供借鉴。

The poor permeability of broken soft and low permeability coal seams is a key factor restricting the effectiveness of coal seam gas control,hydraulic fracturing technology can improve the permeability of coal and rock strata and improve the effective of gas drainage.Through theoretical analysis and numerical simulation,it was found that hydraulic fracturing in broken and soft coal seams can not form effective fractures.Instead,high-pressure water continuously expands and penetrates the broken soft coal seam,causing displacement of the coal body and achieving the goal of increasing coal seam capacity and permeability.On this basis,on-site engineering tests were conducted on the No.10 coal seam in Shanxi Group of a certain mine in Huaibei mining area.The results showed that the target coal seam experienced multiple squeezing and puncture effects during the fracturing process,with a fracturing impact range of over 25 m.The average gas extraction concentration from pre drilled holes in the fracturing area was 63.45%,and the pure gas extraction amount from coal holes in the fracturing area was 2.62 times that of the non fracturing area.The extraction effect in the fracturing area has significantly improved compared to the non fracturing area.The research results can provide reference for efficient gas extraction in fractured soft and low permeability coal seams.