中文摘要：

裂缝网络是页岩气有效开发的基础,为研究页岩裂缝渗透率在有效应力作用下的变化规律,选取具有代表性的四川盆地龙马溪组页岩样品,通过实验考察了基质、微裂缝和人工裂缝渗透率对应力的敏感程度,总结了孔渗幂指数模型、Gangi模型和Walsh模型对裂缝渗透率的拟合和修正结果,并探讨了支撑裂缝和裂缝滑移降低应力敏感性的作用机理。研究结果表明,微裂缝和人工无填充裂缝的渗透率的应力敏感最强,随着有效应力的增加呈指数式递减,Gangi模型和Walsh模型的拟合精度都在97%以上,参数分析结果表明可通过增加裂缝面的粗糙度和向裂缝加入支撑剂来降低其应力敏感系数。有支撑和滑移裂缝的应力敏感性最低,仅仅在一定应力范围内满足Walsh模型。高应力状态下,优选强度较高、耐压性好的陶粒支撑剂有利于提高裂缝的导流能力,而裂缝滑移在一定程度上比裂缝支撑剂更能增加裂缝渗透率,因此在水力压裂模型中应该考虑设计裂缝滑移来降低裂缝的应力敏感性。

英文摘要：

Fracture network is the foundation of effective development of shale reservoir.In order to investi- gate the change of fracture permeability under different effective stress,the typical shale core sample from Silurian Longmaxi Group in Sichuan Basin was selected.Firstly,the stress sensitivity coefficient of matrix, micro fracture and artificial fracture was evaluated through experiment, then the experimental data were fitted and corrected by exponential model,Gangi model and Walsh model.At last,the mechanism of prop- pant and shear displacement on decreasing stress sensitivity coefficient was discussed.The results show that the permeability of micro fracture and artificial fracture are more sensitive to the effective stress,and expo- nentially decline with the stress.The fitting accuracy of Gangi and Walsh models is more than 97%.And it also demonstrates that the stress sensitivity coefficient can he reduced by increasing the fracture roughness and proppant.The proppant and shear displacement fracture have the lowest stress sensitivity coefficient, and the result is only fitting the Walsh model in a certain range of stress.The ceramic proppant with high strength and pressure resistance can improve the fracture conductivity in high stress condition formation. The slip of fracture surface can increase the fracture roughness and aperture, which enhance the fracture permeability more effectively than proppant.Therefore it is suggested that hydraulic simulations should be designed to induce shear displacement to decrease the stress sensitivity of fractured permeability.