The Effects of Physical and Geometrical Properties on Rock Brittleness Index Based on Numerical Modeling
Farhan Hamid Lubis (a*), Fatkhan (a), Umar Fauzi (b)

a) Geophysical Engineering, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia
*farhanhamidlubis[at]gmail.com
b) Physics of Earth and Complex Systems, Bandung Institute of Technology, Jalan Ganesha 10, Bandung 40132, Indonesia

Abstract

Rock brittleness is a key parameter to quantify and evaluate the brittle nature of rock. A better estimating technique of rock brittleness is crucial for acquiring an efficient simulation of unconventional shale gas reservoir such as hydraulic fracturing. One way to predict rock brittleness index is by using rock elastic moduli. This physical properties are highly depends on complexity of the micro-structure, fluid content and mineral composition. Micro CT imaging provides a tool for describing an accurate image of pore geometry in a rock. In this study, rock brittleness index estimation was carried out based on elastic properties on numerical models and digital rock images using finite element method. We then evaluate the effect of physical and geometrical properties (pore aspect ratio, mineral composition, and water saturation) in determining the rock brittleness characteristic. The results indicate that there was an increase in Young modulus along with increasing pore aspect ratio to 1 which in turn increasing the rock brittleness. Fluid saturation in this case water saturation cause brittleness to be reduced. The rock mineral composition such as abundant quartz and carbonates content yield high brittleness values, while high clay content and porosity lower the rock brittleness. Overall, the results imply that pore geometry, fluid saturation and mineral composition significantly alters the rock strength parameters.

Keywords: Digital Rock Images- Finite Element Method- Effective Ellastic Modulus- Brittleness Index

Topic: Earth and Planetary Sciences