Shear Strength Parameters of Cretaceous Shales from the Cap-rock of the Longyearbyen CO2 Storage Pilot, Svalbard

This study presents results of a laboratory direct shear test program on shale samples from cap rock of the Longyearbyen CO2 storage pilot on Svalbard, Northern Norway. The objective is to determine frictional properties of fractured shale samples which are key elements in determining the maximum pressure a cap rock can sustain. Shale samples were drilled from borehole Dh6, depth interval of 367-384 m below surface. Three test specimens were prepared from Rurikfjellet shale core. Each specimen was splitted along the bedding plane, put together and mounted inside the direct shear box. The tests were run for three different normal and normal loads representing overburden conditions at the storage site. Results of the experiments show friction angle of 16 degrees and cohesion of about 3 MPa. The friction angle is much lower than that obtained from triaxial tests on other shale samples from the same well, at a slightly deeper interval. Possible reasons behind this discrepancy are the difference in testing conditions and the effect of shale strength anisotropy.