Method for quantitatively determining effectiveness of ultra-deep-layer compact sandstone crack

The invention provides a method for quantitatively determining effectiveness of an ultra-deep-layer compact sandstone crack. The method comprises the steps of performing rock core observation, performing system sampling on a typical rock core crack segment, and obtaining a sample; after preliminary treatment is performed on the sample, performing micrometer CT scanning and crack permeability determination, and obtaining a sample data packet; correspondingly storing the effective opening degree and permeability determination result of the crack according to the sample data packet, calibrating an electric imaging crack interpreting result, and compiling an effective crack characteristic chart; analyzing a full-shaft-segment crack effectiveness and crack extending direction according to the effective crack characteristic chart; determining the direction and magnitude of a current maximal principal stress, and determining the effect of the current maximal principal stress to crack effectiveness; and determining an effective crack distribution range and quantitatively analyzing crack permeability according to the full-shaft-segment crack effectiveness, the crack extending direction and the effect of the current maximal principal stress to crack effectiveness.