Experimental And Numerical Simulation Of Deformation And Failure Characteristics Of Anisotropic Shale

Due to the developed fractures,low porosity and permeability,shale shows obvious anisotropy,which plays an important role on the effect of stability of borehole.In addition,it also decreases the extraction efficiency of shale gas,causing difficulties and potential safety hazard for engineering practice.Consequently,this paper carried out researches to investigate the anisotropy of shale,analyzed its mechanical and failure characteristics based on the physical experiments and numerical simulation,so as to ensure the safe operation during well drilling and improve the extraction efficiency of shale gas.The main researches in this paper are as following:(1)Physical experiments were carried out to investigate the anisotropic mechanical characteristics and failure mechanism of the shale based on the combination of the three-dimensional non-contact measurement system(Aramis)and uniaxial compression.The strength,elastic modulus and failure characteristics of shale were obtained,as well as the change law of the major strain and displacement along with the bedding dip.The change law of strength of shale with different bedding dip was obtained by numerical simulation.And the results was consistent with physical experiment.At the same time,it confirmed the effectiveness of RFPA2D to simulate uniaxial compression experiment.(2)Based on rock damage mechanism,the influence of bedding space,bedding strength,elastic modulus and Poisson's ratio on strength and failure mode of shale was studied by the finite element simulation.And obtained the change law of strength and failure characteristics of shale under different condition.(3)Based on the fracture mechanics,the variation law of the strength and failure form of shale with the initial crack angle,the crack length and the inclination and length of the rock bridge under the condition of single fracture and double fracture are studied.The results of this article are helpful for further understanding of the nature of shale strength.Besides,it also provides theoretical guidance for drilling and fracturing exploit of shale gas.