A Study On The Impact Of Slick-water On Deformation And Damage Characteristics Of Shale

Hydraulic fracturing technology is the core of shale gas development technology to increase production and the key to realize it is to select the easily fractured well intervals.Based on this,the paper carries out rock mechanics experiment with the gas-bearing shale and surface outcrop of Lower Silurian Series Longmaxi Group in the South of China.The specific research methods and conclusions are as follows:Using MiniFlex II desktop X-ray diffractometer,ZEISS SIGMA field emission scanning electron microscope,the MTS-816 and MTS Insight TM-30 KN servo testing machine,the paper studies the relationship between the shale mineral composition,microstructure,single triaxial strength,tensile strength,fracture toughness,stress intensity factor and crack propagation rate.By measuring the basic mechanic parameters of the shale under different fluid state,combined with the CCNBD testing method proposed by International Society for Rock Mechanics(ISRM),the paper measures the mode I fracture toughness of the samples under different fluid state and analyzes the relationship between mode I fracture toughness and the tensile strength of the shale.With double torsion experiment method,this paper carries out an experiment on the subcritical crack growth propagation of the shale under both dry and saturated fluids condition and analyzes the law.The result indicates that the stress intensity factor and crack propagation rate has good linear rule and with the increase of stress intensity factor,the crack propagation is accelerated.Under the same condition,the fluids that the rate of crack propagates in descending order are distilled water,slick-water and no water,which indicates that the water rock interaction is obvious.