Advances in stress-strain constitutive models for rock failure: Review and new dynamic constitutive failure (DCF) model using core data from the Tarim Basin (China)

Abstract

A wide range of constitutive models exists to quantify how the applied forces will lead to breakdown of rock samples. This paper reviews the mechanical models that have been developed to capture the full stress-strain curve for rocks deforming first elastically and then failing by fracturing after an elastic limit has been reached. Existing models are poorly suited for application to rock samples subjected to extreme physical conditions, such as the mechanical behavior of rocks under high temperature and high stress as encountered in ultra-deep oil and gas wells. First, conventional triaxial rock mechanics experiments were carried out on core collected from a 7000 m deep reservoir in the Tarim Basin (China); the effects of temperature and confining pressure on rock mechanical properties were analyzed. After a review of existing stress-strain curve models, it was concluded that none of the current rock constitutive models can accurately describe the stress-strain curve of rocks under high temperature and high pressure. Therefore, a new constitutive model was developed to (1) describe the characteristics of pre-peak and post-peak failure curves, and (2) predict the full stress-strain curve at different temperatures and confining pressure. The model was calibrated with the experimental data from the Tarim well. A new constitutive model was obtained by assigning variables to the parameters of a dynamic constitutive failure (DCF) model, which can be used in other scenarios, such as compression failure of rock under cyclical loading, plastic deformation, and rock creep. The dynamic constitutive failure model first presented here provides a useful reference for future modeling attempts.