Structural characterization of the Longyearbyen CO2 Lab reservoir-caprock succession

This baseline study on fracture populations affecting the Mesozoic sedimentary succession of central Spitsbergen (Svalbard) has been performed to characterize the reservoir-caprock system explored for potential subsurface CO2 storage by the Longyearbyen CO2 Lab project. Integrating structural and stratigraphie analyses of outcrop and borehole data, we identified recurrent litho-structural and structural units (LSUs and SUs, respectively) on the basis of their fracture associations, lithologies and dominant sedimentary facies. A principal fracture settrending approximately E-W (J1) and a subordinate fracture set trending approximately N-S (J2) have been recognized. Subordinate systems of shear fractures (SI) trending roughly NE-SW and NW-SE, and a secondary low-angle, fracture set (S2) striking E-W to NW-SE have been observed. Their origin is interpreted as related to the far-field stress of the Paleogene West Spitsbergen fold-and-thrust Belt. The identified units are thought to influence the local hydrogeologic regime due to the intrinsic variations in the matrix and fracture network properties. The architecture of the reservoir-caprock succession is segmented, with the vertical alternation of intervals characterized by 1) fracture porosity and permeability, 2) microfracturing- related matrix porosity, and 3) preferential subsurface fluid flow pathways.