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利用自行研制的煤岩体水力压裂试验系统,开展了配比型煤与原煤水力压裂试验,测试并分析了水力压裂过程中压裂孔孔壁应变-水压曲线,并基于孔壁应变的发展规律,分析了压裂孔的三阶段起裂特征。结果表明,在压裂孔起裂过程中,钻孔孔壁呈现拉伸与压缩应变两种类型,并呈现拉伸破裂区与压缩变形区,其中压缩型应变具有较好的可恢复性,其应变恢复比远大于拉伸型应变;钻孔起裂过程分为3个阶段,即水气作用诱导微损伤形成阶段,孔壁内形成气流通道并产生初始损伤;局部损伤带形成阶段,孔壁形成拉伸破裂区和压缩变形区;试件失稳破坏阶段,裂缝不断延伸直至试件破裂,拉伸破裂区依然保持拉伸变形并较好地保持残余变形,而压缩变形区则由于作用力转向而得到一定程度恢复。研究成果对于揭示钻孔起裂行为及能量的演化规律具有重要理论意义。
Based on the self-developed hydraulic fracturing test system of coal and rock mass, the hydraulic fracturing test of matching coal and raw coal was carried out. The strain-hydraulic curve of fractured pore wall in hydraulic fracturing was tested and analyzed. Strain development law, analyzed the fracturing hole three-phase initiation characteristics. The results show that during the fracture initiation process, the hole wall of the borehole exhibits two types of tensile and compressive strains, and presents the tensile rupture zone and the compressive deformation zone. The compressive strain has good recoverability, The strain recovery ratio is much larger than the tensile strain. The initiation process of drilling is divided into three stages, namely the formation of micro-damage induced by water vapor, the formation of airflow passage and the initial damage in the pore wall, the formation stage of the local damage zone, Forming the tensile rupture zone and the compressive deformation zone. During the failure of the test piece, the cracks extend continuously until the test piece ruptures. The tensile rupture zone still maintains the tensile deformation and keeps the residual deformation well. However, Turn to get a certain degree of recovery. The research results have important theoretical significance for revealing the initiation behavior of drilling and energy evolution.