A Framework for Fracture Network Formation in Overpressurised Impermeable Shale: Deformability Versus Diagenesis

TitleA Framework for Fracture Network Formation in Overpressurised Impermeable Shale: Deformability Versus Diagenesis
Publication TypeJournal Article
Year of Publication2017
AuthorsS Alevizos, T Poulet, M Sari, M Lesueur, K Regenauer-Lieb, and M Veveakis
JournalRock Mechanics and Rock Engineering
Volume50
Issue3
Start Page689
Pagination689 - 703
Date Published03/2017
Abstract

© 2016, Springer-Verlag Wien. Understanding the formation, geometry and fluid connectivity of nominally impermeable unconventional shale gas and oil reservoirs is crucial for safe unlocking of these vast energy resources. We present a recent discovery of volumetric instabilities of ductile materials that may explain why impermeable formations become permeable. Here, we present the fundamental mechanisms, the critical parameters and the applicability of the novel theory to unconventional reservoirs. We show that for a reservoir under compaction, there exist certain ambient and permeability conditions at which diagenetic (fluid-release) reactions may provoke channelling localisation instabilities. These channels are periodically interspersed in the matrix and represent areas where the excess fluid from the reaction is segregated at high velocity. We find that channelling instabilities are favoured from pore collapse features for extremely low-permeability formations and fluid-release diagenetic reactions, therefore providing a natural, periodic network of efficient fluid pathways in an otherwise impermeable matrix (i.e. fractures). Such an outcome is of extreme importance the for exploration and extraction phases of unconventional reservoirs.

DOI10.1007/s00603-016-0996-y
Short TitleRock Mechanics and Rock Engineering