Frictional properties of natural and induced fractures in two types of shales

Abstract

This paper presents results of direct shear tests on two types of shales; Rurikfjellet from Svalbard, Arctic Norway and Draupne from Ling Depression, the North Sea. Rurikfjellet formation is part of a caprock system for the proposed CO2 storage site at Svalbard. Draupne shale forms the caprock for deep hydrocarbon reservoirs and also the primary seal for Smeaheia, a candidate site for CO2 storage in the North Sea. Four specimens from Rurikfjellet and one specimen from Draupne were tested. Results of the tests shows that the peak friction coefficient for fractures in Rurikfjellet specimens varies between 0.26 and 0.29 while the residual friction coefficient ranges from 0.19 to 0.25. For Draupne shale, peak and residual friction coefficients were equal; i.e. 0.25. Simulation of friction coefficient was performed using the Barton-Bandis model and showed relatively good results in the post-peak and residual parts. The results of these tests provide reliable input data to support analytical and numerical models for assessing stability of fractures and faults under various loading conditions.