Quantitative Descriptions of Faults and Microfractures from Surface Outcrops of a Fractured Dolomite Reservoir

The outcrop study focuses on the qualitative and quantitative assessment of fractures of different scale (subseismic faults, slickensides, microfractures) in Late Triassic dolomite of the Austroalpine Calcareous Alps. Outcrops are regarded surface analogues of deep oil and gas fields in the subcrop of the Vienna Basin with respect to lithology, lithostratigraphy and deformation history. Results include assessments of the fractured matrix (microfractures, joints) carrying most of the fracture porosity, faults, and fault rocks. The latter form marked discontinuities in the fractured host rock. All structures are quantitatively described with respect to their abundance, geometry and the properties of fracture fill and fault rocks. Depth extrapolation of the surface-derived fault data to reservoir depth (about 3 km) is enabled by a regionally consistent deformation model and the genetic classification of faults to well-defined and dated deformation events.