A three-dimensional simulation of triaxial test on Mancos Shale using peridynamics and the microplane constitutive model (M7)

As the petroleum industry aligns its vision with that of the fourth industrial revolution, modeling and simulation of traditional laboratory experiments may have a significant impact on process optimization and cutting costs. Therefore, this thesis aims to simulate the triaxial test, a crucial experiment in geomechanics laboratories that helps with understanding rocks’ properties and for constitutive model calibration. Once calibrated, a geomechanical constitutive model can be used in designing hydraulic fracturing operations or for wellbore stability analysis. Hydraulic fracture completions are typically used in unconventional reservoir rocks for the production of oil and natural gas, like Mancos Shale, whose rock samples are chosen to be a subject in these simulations due to its anisotropy and heterogeneity. This thesis provides a methodology to create a model that simulates the triaxial test using the microplane constitutive model (M7) paired with peridynamics as a simulation technology. We use the Peridigm code, a massively-parallel peridynamics analysis software for simulation of fracturing and fragmentation. The simulations are partially validated by analytical solutions and calibrated against triaxial experiments. After additional development of the software with a few additional algorithms, it was able to run as if a triaxial test was being conducted, allowing the user to freely adjust parameters such as confining pressure and axial loads. As a part of this project, stress versus strain plots are generated using post-processing scripts in order to calculate the error between simulation data and literature data utilizing an objective function, hence supporting the calibration process of the model. In this thesis, several important aspects are discussed, such as the significant role of natural gas in the future energy landscape, the quantification of anisotropy in Mancos Shale, the mechanics of triaxial test apparatus, the theory of peridynamics, and the microplane constitutive model (M7).