Bounding Surface Plasticity Concept and its Application in Modeling Cyclic Loading

Rocks around petroleum wells are subjected to cyclic loading due to repeated changes in the effective stresses in the rock. It may experience many loading cycles via injection start-up and shut-in cycles and injection/production rate fluctuations. Every cycle of unloading-reloading gives rise to energy dissipation and thus plastic deformation which leads to the degradation of cementation bonds. A constitutive model is required to address stress-strain behavior and mechanical degradation of soft sandstone in the course of cyclic loading. First, different types of cyclic loading (namely slow and fast cyclic loadings, which both can occur during wellbore operation) and their differences are discussed. Then famous elastoplastic theories, which are usually used for simulation of cyclic loading, and their effectiveness in describing cyclic loading are reviewed. Ultimately, a methodology is proposed to come up with a suitable constitutive model that can be employed for replicating the cyclic behavior of weakly cemented sands.

کلیدواژه ها:

Slow cyclic loading ، Dynamic cyclic loading ، Classical plasticity theory ، Bounding surface plasticity ، Radial mapping