Numerical simulation of Thick-Walled-Cylinder (TWC) test for study of Wellbore Instability Mechanism in Clayey Formation

Shallow oil reservoirs at depths less than 1,000 m are found within weak rock formations. Most of these formations are typically consisting of hard clays and soft shale. The stability of boreholes in shales is a major problem. In this paper, nonlinear elasto-plastic model are used to investigate the influence of strain rate and consolidation stress level on deformations of a Thick-walled hollow cylinder (TWC) of resedimented Boston blue clay (RBBC) during undrained shearing that have been performed to studywellbore instability mechanism under simulated wellbore in situ conditions in clayey formation. The investigation shows that the Modified Cam-Clay constitutive model can adequately predict the deformationin thick-walled hollow cylinders of shale in high pressure. Results indicate that for normally consolidated clays most of the change in cavity pressure occurs at volumetric strains less than 5% after which the borehole becomes unstable

کلیدواژه ها:

Wellbore Stability ، TWC test ، Modified Cam Clay ، 2D Simulation ، Clayey Formation