摘要
为解决艾维尔沟矿区碎软突出煤层瓦斯抽采难的问题,阐述了定向长钻孔水力压裂消突机理,建立数值模型研究了水力压裂渗流场和应力场耦合规律及水力压裂效果的影响因素。研究表明:煤层注水压裂过程中,渗流引起煤炭内部有效应力场改变、煤体骨架发生变形,改变了煤体的物理力学性质,又进一步影响了水的渗流过程,渗流场和应力场相互作用、相互影响;注水压裂时间、注水压力、地应力和渗透率对水力压裂效果都有明显影响;煤的浸润过程靠压裂孔中的高压水来支撑,注水压力越高,压裂初期孔隙压力增长速度越快,较长的压裂时间和较高的注水压力有助于提高煤体孔隙压力、降低有效应力;地应力的增大会导致煤体颗粒受到压迫、颗粒间隙变小、煤体渗透率降低,需要提高注水压力才能取得较好增透效果。现场应用过程中,4号煤层采取水力压裂措施抽采109 d后,预抽率达14.4%,残余瓦斯含量下降了5.2%~34.6%,水力压裂影响半径为20~25 m,有效影响半径为18~19 m。
In order to solve the difficult gas drainage problem in broken and soft outburst coal seams in Ewirgol mining area,the mechanism of outburst elimination by directional long borehole hydraulic fracturing was elaborated,and a numerical model was established to study the coupling law of hydraulic fracturing seepage field and stress field,as well as the influencing factors of hydraulic fracturing effect.The research shows that in the process of coal seam fracturing,seepage causes the change of effective stress field inside the coal and the deformation of the coal body skeleton,which changes the physical and mechanical properties of the coal body,and further affects the seepage process of water.The seepage field and stress field interacts.Water injection fracturing time,injection pressure,geostress and permeability coefficient have obvious influence on hydraulic fracturing effect.The coal infiltration process is supported by the high-pressure water in fracturing hole,the higher injection pressure is,the faster the pore pressure increases at the initial stage.A longer injection time and higher injection pressure will help increase the pore pressure of coal body and reduce the effective stress.The increase of geostress will lead to the compression of coal particles,the reduction of particle gap and coal permeability,and it is necessary to increase the injection pressure to achieve better permeability-increase effect.After 109 days of gas drainage with hydraulic fracturing measure in No.4 coal seam during the field application,the pre-drainage rate reaches 14.4%,the residual gas content decreased by 5.2%~34.6%,the influence radius of hydraulic fracturing is about 20~25 m,and the effective radius is about 18~19 m.
作者
王正帅
WANG Zhengshuai(CCTEG Chongqing Research Institute,Jiulongpo,Chongqing 400037,China)
出处
《中国煤炭》
2023年第6期46-52,共7页
China Coal
基金
“十三五”国家科技重大专项资助项目——新疆大倾角多煤组煤矿区煤层气开发利用技术(2016ZX05043-005)。
关键词
碎软突出煤层
水力压裂
煤体骨架
孔隙压力
渗流场
broken and soft outburst coal seams
hydraulic fracturing
coal body skeleton
pore pressure
seepage field
