【摘要】 在多薄层状产层组压裂过程中,水力裂缝的起裂扩展行为受到层间应力差、岩性差异、界面性质等因素的影响,使得人工裂缝的起裂扩展规律认识不清。基于此,采用改进的室内真三轴水力压裂物理模拟系统,开展3层介质水力压裂模拟试验,研究岩性差异、界面性质对水力裂缝起裂扩展的影响。试验结果表明:在上覆压力为10 MPa条件下,当层间界面未胶结时,水力裂缝沿层间起裂扩展,对应的泵注压力最低;当层间界面存在弱胶结时,水力裂缝先从强度最低的岩样起裂,在裂缝扩展过程中遇到层间弱胶结面时,水力裂缝发生转向,沿弱胶结面扩展;当层间界面强胶结时,按照岩石抗拉强度的大小关系,水力裂缝在各岩样介质中先后起裂,最终导致3层介质的整体性破坏,裂缝中的压裂液呈现非对称扩展。更多还原

【Abstract】 When multi-laminated thin formation is fractured as a whole,it is hard to know fracture initiation and propagation morphology because of stress contrast,lithology difference,interfacial property and some other factors. In this paper,a model of three-layer hydraulic fracturing was designed and an improved large-scale tri-axial fracturing device was used to observe the fracture initiation and propagation. The effects of rock strength and interfacial property on the hydraulic fracture initiation and propagation were studied. It was observed from the experimental results that an unbonded and smooth interface inside rocks would induce a shear slippage at a low fracturing pressure under overburden pressure of 10 MPa. And the fracture would firstly be induced from a layer of low rock strength and then turned to propagate through the weak bonded interface when interlayer cement strength was small. However,large interlayer cement strength would cause sequential fracturing in all layers with low strength layer fractured first. In addition,asymmetric distribution of fracturing fluid in fracture was observed directly.更多还原