Theoretical solution of casing loads in rheological formation in tectonic stress field

Based on the elasticity viscoelasticity correspondence theory and the acquired elastic solution, assuming the formation obey the Kelvin viscoelastic constitutive relation, the theoretical solution of casing loads in rheological formation in tectonic field and the analytic expression of relaxation time are obtained. The results indicate that the casing load in tectonic field changes with time and it exists a critical time in which the casing load has the most value. The viscoelastic solution is coincidence with corresponding elastic solution when the time is long enough. The casing tectonic stress load defined by elastic solution is slightly less than the maximum pressure subjected by casing pipe in rheological formation. Therefore, the elastic computation load or safety coefficient should be increased properly in design to ensure the safety of the casing pipe.EI0111-164