SUMMARY:

Nowadays, heavy oil resources are the world's great petroleum deposits worldwide. These reservoirs are typically poorly or unconsolidated formations and characterized by having deforming permanently under the influence of mechanical stresses. During plastic strain, reservoir can exhibit irreversible changes that could generate sand production, well instability, subsidence, and changes in petrophysical properties such as porosity and permeability or mechanical properties such as elastic modules, tension strength, uniaxial compressive strength (UCS), among others. To prevent these harmful events and in order to make assertive predictions of their occurrence, it is necessary to study the effect of the change in the rock properties during plastic strain using coupled reservoir simulation. This paper presents a review of the basic existing models in the literature, which predict the behavior of the angle of internal friction and cohesion of the rock under a plastic strain regime. It presents that most models propose mathematical expressions to describe the behavior of the properties in function of plastic strain. Each model incorporates different parameters to quantify the level of plastic strain. However, these parameters do not correlate with variables of direct measurement and apply only to certain tests. As a result, this work performs a comparative analysis between the parameters and their behavior with the studied properties. In addition, it conducts a simulation of elastic and plastic regimes of rock behavior using a progressive algorithm under the basic assumptions of the plasticity theory and the failure criteria of Mohr-Coulomb with a yield surface of bilinear behavior. This algorithm solves stresses and strains for each increment of axial displacement for a Triaxial Compressive Strength Test. The results of the simulation show that the accumulator parameters of plastic strain exhibit a similar behavior respect to friction angle and cohesion but these parameters differ in magnitude. Additionally, the yield surface mobilization during the softening and hardening regimes is similar to the mobilization described in the literature. Finally, this work intends to develop subsequent analysis and to generate accurate relationships to model the behavior of the friction angle and cohesion in the plastic region.

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