摘要
既要避免出现压裂空白带又要防止局部应力过度集中是煤矿井下水力压裂的难点,需要控制裂缝的扩展方向和压裂能量大小。基于诱导应力导控机理,利用RFPA2D-Flow模拟,分析了多孔同步压裂条件下诱导应力场对煤层水力裂缝的导控作用规律,提出水射流扩孔卸压与多孔水力压裂导向的联合卸压增透煤层技术并现场应用。结果表明:同步压裂各钻孔的水压主裂缝在扩展与延伸过程中会相互影响,先期产生的水力裂缝所产生的诱导应力场对后压裂缝的扩展和延伸具有诱导作用,使其附近区域内的最小主应力方向发生47.5°的偏转,偏转后的最小主应力方向基本垂直于2个钻孔水压主裂缝偏转点的连线;水射流扩孔对其附近水力裂缝的扩展具有偏向射流钻孔的诱导作用;采用水射流扩孔卸压与多孔水力压裂导控能避免应力过度集中的同时在一定程度上消除压裂空白带,瓦斯抽采效率显著提高。
It is necessary but difficult to avoid the occurrence of fracturing blind zone and to prevent the excessive concentration of local stress at the same time in hydraulic fracturing in coal mine. The difficulty lies in that it needs to make much more fractures while limiting the fracturing energy. Based on the mechanism of induced stress, the orientation and controlling role of the induced stress field on the hydraulic fractures in coal seam under the condition of multi-hole synchronous fracturing was analyzed by RFPA^2D-Flow simulation. A new technology, combined with the water injection for directional pressure relief and the multi-hole hydraulic fracturing for controlling the fractures propagation, was presented and applied in the field. The results show that： the hydro-fractures of all the simultaneously fracturing drilling-holes will be induced by each other; under the function of the induced stress field, the direction of the minimum principal stress in the vicinity of the later main hydro-fracture deflects about 47.5°,basically perpendicular to the connection line of the main hydro-fracturing deflection points of two drilling-holes; the water jet drilling expansion could induces the hydro-fractures near expanding to itself; the technology could, in a certain extent, eliminate fracturing blind zone, while avoiding excessive stress concentration, and it would significantly improve the gas drainage content.
作者
王耀锋
薛伟超
李艳增
许幸福
WANG Yaofeng;XUE Weichao;LI Yanzeng;XU Xingfu(Gas Safety Research Branch,China Coal Technology and Engineering Group Shenyang Research Institute,Shenyang 110016,China;State Key Laboratory of Coal Mine Safety Technology,Fushun 113122,China)
出处
《煤矿安全》
CAS
北大核心
2018年第11期10-15,19,共7页
Safety in Coal Mines
基金
"十二五"国家科技重大专项资助项目(2011ZX05041-003)
"十三五"国家科技重大专项资助项目(2016ZX05045004-001)
关键词
诱导应力
水射流
多孔压裂
导控作用
裂缝扩展
induced stress
water jet
multi-hole hydraulic fracturing
orientation and controlling role
fracture propagation
