页岩气高效开采的可压裂度和射孔簇间距预测

页岩储层的可压裂性是影响页岩气产量的关键因素. 本文基于断裂力学理论, 以高围压下岩石层理弱面的剪切破坏为主要研究对象, 依据岩石抗拉强度和层理弱面抗剪强度的比值关系, 首先提出了可压裂度的概念, 给出了无量纲的定性曲线图, 涵盖了岩石脆性矿物质含量, 粘性主导和韧性主导裂缝尖端流体压强、射孔簇分布间距的综合地质与工程因素. 接着提出了一种新的表征高围压下页岩可压裂度的无量纲参数, 在保证达到充分解吸附的最小压裂间距前提下, 依据该参数可计算水平井压裂中的射孔簇间距, 可作为工程参考指标. 本文将断裂力学理论结合水力压裂高效开采页岩气工程, 具有力学理论意义和工程应用前景. 

FRACTURING DEGREE AND PREDICTION OF PERFORATION CLUSTER SPACING FOR EFFICIENT EXPLOITATION OF SHALE GAS

The fracturing property of shale reservoirs is a key factor affecting shale gas production. Based on fracture mechanics theory, taking the shear failure of rock bedding weak plane under high confining pressure as the main research object, the concept of fracturing degree is proposed according to the ratio between tensile strength of rock and shear strength of bedding plane. The dimensionless qualitative curve is given, which covers the comprehensive geological and engineering factors of brittle mineral content, viscosity-dominated and toughness-dominated fracture tip fluid pressure and perforation cluster distribution spacing. Then, a new dimensionless parameter is proposed to characterize the fracturing degree of shale under high confining pressure, which can be used as a reference index for engineering. In this paper, fracture mechanics theory is combined with hydraulic fracturing for efficient shale gas production, which has mechanics theoretical significance and engineering application prospects.