Shear damage mechanism and early warning study of shale standard layer casing

Aiming at the problem of shear-induced casing damage caused by standard layer shale soaking water, the theory of rock mechanics is used to establish the fluid-solid coupling calculation model of the formation-cement ring-casing of the standard interval shale interbed. It allows obtaining the strain and deformation changes of casing shear damage, and it puts forward the casing logarithmic strain exacerbated area should prompt adoption of reasonable measures to slow down the casing damage. Three-level orthogonal numerical simulation experiments were carried out for the five factors affecting casing damage. The simulation results show the critical strain data of the casing damage and the true strain data of the casing under the influence of five factors. According to the statistical principle, the predictive mathematical model of the critical strain and true strain prediction of the casing is obtained by the multiple regression method. The prediction of the strain state of the casing under actual working conditions is realized, and then the casing damage early warning was also realized.