The invention discloses a shale
cement damage quantitative evaluation method based on an
acoustic wave velocity test and relates to the technical field of
unconventional oil-gas exploration and development. The method comprises the following steps of
drying drilled rock samples, screening out at least three rock samples with similar longitudinal and
transverse wave velocities to form a
rock sample group, calculating the initial average longitudinal and
transverse wave velocity and density of the
rock sample group, and calculating an initial
dynamic elastic modulus; soaking the
rock sample group, taking out the rock sample group every time t, and calculating the
water content and the
dynamic elastic modulus of the soaked rock sample; calculating a damage variable of the rock sample group; and fitting by adopting a nonlinear fitting method to obtain a shale
water content evolution equation and a shale hydration damage evolution equation. According to the method, the influence of rock
sample quality change caused by
free water invasion on hydration damage is considered, meanwhile, the influence of drilling shaft pressure and shaft temperature is also considered, defects of an existing method are overcome, the shale hydration damage process can be reflected more truly, and the method is simpler, more convenient, more economical and more practical.