μCT on narrowly fractured natural rock samples from a hydrocarbon reservoir

Micro-Computed Tomography (μCT) is used for imaging narrowly fractured natural rocks from the subsurface of the Vienna Basin, Austria. The dolomites from the Hauptdolomit Formation represent a successfully producing reservoir for hydrocarbons (mainly gas). However, the heterogeneity of the rocks and their fracture networks make conventional predictions on economically viable exploration of the reservoir difficult. μCT can provide a better insight on the internal fracture network of these rocks, and the porosity and permeability that go along with it. 3 cm diameter plugs from various locations of these rocks prove to be suitable for scanning by μCT with sufficient quality. After obtaining proper datasets, a segmentation step is required for further analysis. Segmentation by techniques often used for geological datasets does not provide reasonable results for narrow fractures. We therefore apply a technique termed multiscale Hessian filtering to extract the fractures from the datasets. This multiscale Hessian filter is an adaptation of a technique from the field of medical sciences, called Frangi Filtering, which is used for the extraction of blood vessels. The multiscale Hessian filter runs on a full 3D dataset using the public domain software ImageJ, on a desktop computer. After the segmentation routine and successive improvement of the results, the porosity distribution and the fracture network orientations can be extracted, and the permeability can be modelled. Eventually, results from different techniques and samples will be integrated, to improve the knowledge on the studied reservoir.