Abstract
The evaluation of rock strength from geophysical well logs is fundamental to engineering problems associated with wellbore stability, sand control and hydraulic fracture containment. Meaningful inversion of geophysical data for rock strength requires a better understanding of how intrinsic rock properties affect rock strength as well as new models to capture this understanding. A study of the relationships between compressive strength and rock composition and texture was conducted on cores from the Travis Peak formation. Travis Peak lithologies vary from mudstones to quartz arenites, and porosities range from 5.5% to 8.5%. After identifying the dominant composition and texture elements controlling strength variations in the Travis Peak formation, we explain our results in terms of micromechanical deformation mechanisms. A simple predictive model of rock strength is developed, based on measurable quantities physically linked to the governing deformation mechanisms. We show that the most accurate strength models include explicit information on both extrinsic and intrinsic rock properties. Our method suggests a new approach to quantifying rock strength from well logs.
