Application of Mechanical and Mineralogical Rock Properties to Identify Fracture Fabrics in the Devonian Duvernay Formation in Alberta (original) (raw)

Proceedings of the 3rd Unconventional Resources Technology Conference, 2015

Abstract

Mechanical rock properties, along with in situ stresses and pore pressure, play critical roles in forming fractures in reservoir rocks. As part of a regional geomechanical analysis of the Duvernay resource play, several Duvernay cores were analyzed in detail, including the identification of different types of natural and induced fractures. The observed natural fractures include uncategorized natural fractures and polished slip faces (PSF) with rare presence of cleavage. Coring-induced fractures included petal and petal-centreline fractures and bed parallel parting (BPP). Comparison of the presence of the different fracture fabrics with mechanical and mineralogical properties of the rock revealed strong correlations between rock properties and fracture types. Such correlations may be efficiently implemented for characterization of fracture fabrics in the rock using wireline logs or seismic surveys. The observed natural and induced fractures in the cores have also been utilized to revisit and verify the concept of rock brittleness. The analyses show that, as a result of high clay content and overpressuring, the conventional mineralogical and mechanical brittleness indices do not adequately describe the variability of the Duvernay Formation stratigraphic units. Alternative indices developed for this study (i.e., plane-strain Young’s modulus and clay-based brittleness index) seem to be able to represent the mechanical behaviour of rock much more precisely. This study suggests that using natural and induced fracture fabrics observed on image logs and in cores, along with mineralogical and mechanical rock properties, is a more practical approach to assist with identifying sweet spots in unconventional plays.

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