| dc.description.abstract | The triaxial test is a technique commonly used to determine the failure stress of rocks in compression. Typically, a series of triaxial tests are needed to establish a failure envelope. Unfortunately, the practical constraint on the number of available samples prohibits a multitude of tests from core recovered from reservoirs. Furthermore, if multiple samples are taken they are offset in depth which introduces geological variability.
This thesis presents the mechanics of a multistage triaxial test (Pagoulatos, 2004) as a more efficient technique to determine the mechanical properties at multiple stress states. Each multistage experiment provides the failure envelope and the pressure dependence of elastic moduli using a single sample. Previous work indicates that there is a static offset between the conventional testing results and the multistage testing results. Thus, a simple rescaling recovers the multi–sample equivalent failure envelope.
In this study, we explore the pore fluid dependence of the mechanical behavior of conventional rocks by testing samples of Berea, Bandera, Lyons, and Tennessee sandstones under drained multistage triaxial tests. Moreover, we extend the scope of the multistage triaxial test to unconventional rocks by testing eight samples from the Eagle Ford and Woodford shales. The effect of preexisting weakness planes remains to be the biggest limitation for multistage testing on shales. | en_US |
