Method and device for determining interval transit time after casing

The embodiment of the invention discloses a post-casing interval transit time determination method and device, and the method comprises the steps: calculating a first cement bond index at each depth position, and a first ratio of the stratum longitudinal wave amplitude to the casing wave amplitude according to the first array sound wave full wave train data of a cased well; respectively processing the first array sound wave full-wave train data by using two sound wave time difference extraction modes to obtain two post-sleeving sound wave time difference results; analyzing the accuracy of two post-casing interval transit time results under different first cement bond indexes and different first ratios to obtain an accuracy analysis result, and further dividing the optimal index chart into two optimal index intervals; and according to the two optimal index intervals, determining a corresponding target interval transit time extraction mode for each depth well section in the second array sound wave full wave tra