Thick-walled (TWC) cylinder triaxial as well as uniaxial compressive strength tests are commonly used experimental techniques for determining the potential for sand production. Industry-wide, the most commonly used analytical and empirical models use the results of these tests as inputs and as a measure of rock resistance to shear failure, which is a necessary condition for sand production. Both triaxial and thick-wall cylinder testing measure rock strength properties; however, thick-wall cylinder testing is the best representative laboratory model of a wellbore perforation in subsurface conditions. Plasticity and scale effects are implicitly incorporated in the TWC strength. Besides analytical methods, finite element methods are increasingly used to model near wellbore stresses, strains, and rock failure for sanding prediction analysis. This work illustrates the need for calibrating the finite element model to thick wall testing results and reproducing them for a realistic simulation of sand production phenomenon. The paper presents a workflow that achieves the best match between laboratory test results and finite element model simulation results. It includes the experimentally observable curves of thick-walled cylinder testing, such as volumetric strain vs. hydrostatic stress. A finite element model of the same test is developed and the material strength and plasticity properties are calibrated to match test results. The paper demonstrates that the Mohr Coulomb failure criterion with the Menetrey-Willam plastic flow model is able to satisfactorily match experimental results and discusses the importance of calibrating post-failure hardening vs. softening parameters. Once the numerical test matches the experimental results, the critical equivalent plastic strain can be estimated and the threshold for failure determined. The calibrated rock properties can then be used to simulate near wellbore failure during fluid production using the correct equivalent plastic strain threshold for failure. This workflow allows for more accurate sanding production prediction analysis providing the link between experiments and numerical modeling.
The thick-walled cylinder (TWC) test and advanced thick-walled cylinder (ATWC) test, as well as triaxial and uniaxial compressive strength (UCS) tests are commonly used experimental techniques for determining the potential for sand production of reservoir rocks during production. A sand production prediction analysis is performed to determine the type of completion method and to establish drawdown and reservoir depletion limits on production.