Continental shale generally consists of layers with varying components

including clay

felsic minerals

and calcite. During hydraulic fracturing stimulation of shale fracture network structure

the interfacial transition zone (ITZ) forms

significantly influencing crack propagation direction and morphology. Currently

effective quantitative methods for determining the ITZ distribution range in shale layers are lacking. This study focuses on the discrete characteristics of shale micro-mechanical parameter curves and employs confidence ellipses to calibrate discrete data within the ITZ range. Linear fitting and the projection length of confidence ellipse intersections are introduced as a new method for quantifying the ITZ in shale layers. Scanning electron microscopy and a mineral quantitative evaluation system were used to obtain shale surface morphology and mineral distribution

analyzing mineral damage forms after scratch experiment. Nano scratch experiment results were used to determine mineral distribution lengths from various rock types via fracture toughness

compared with scanning electron microscopy findings. Results show that plastic minerals such as illite show a damage pattern of debris accumulation on both sides during the scratch test

while brittle minerals such as albite and quartz show jagged damage or point-like chipping. The presence of ITZ causes the distribution length of plastic minerals identified by scanning electron microscopy to exceed the quantitative results from fracture toughness curves. The friction coefficient method is affected by surface roughness

resulting in lower fitting confidence and higher quantitative results. Compared to the friction coefficient method

the fracture toughness method offers higher data continuity and fitting confidence

though it considers relatively fewer factors. Non-dimensional parameters comprehensively account for fracture toughness

hardness

friction coefficient

and scratch depth

reducing curve dispersion and fitting errors. Compared to traditional methods for identifying individual mechanical parameters

the accuracy of ITZ distribution range quantification based on dimensionless parameters is greatly enhanced.