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3D Micro-imaging of fracture networks using micro-computed tomography: Upscaling of porosity and permeability of a fractured reservoir (Hauptdolomit)

2 PhD positions granted by the OMV Exploration and Production GmbH, Austria

Principal Investigator: Ulrike Exner

Co-applicants: Bernhard Grasemann, Marcel Frehner, Kurt Decker

Project duration: 2010 - 2014

Project homepage: Fracture networks

This project was approved when I still was a Research Associate/Lecturer in Vienna and I acted as one of the principal investigators. However, after I left Vienna I had to resign from that role. Today, I am taking the role of external collaborator.

Description

The late Triassic Hauptdolomit in the Pre-Neogene basement of the Vienna Basin (Austria) contains a dense, multiscale fracture network caused by its deformation history. This property makes the Hauptdolomit a suitable gas reservoir, from which production is successfully ongoing. Standard (laboratory) methods for measuring porosity and permeability are however not always suitable for fractured reservoir rocks, whereas these properties are of great importance in assessing a reservoir.

We conduct micro-Computed Tomography (ÁCT) measurements on Hauptdolomit drill core samples provided by OMV LEP-FC. ÁCT provides radiograms, which by reconstruction can provide a 3D-Model and visualize the fracture network (hence the porosity), without destroying the samples. The measurements are performed on differently sized samples, with different parameters, to ensure the most complete information and best spatial resolution. With the reconstruction and proper calibration, it is possible to quantify and visualize the porosity and permeability using analysis software packages (Amira, ImageJ, Petrel, MATLAB). In addition, the microstructural features of the fractures and veins are investigated, using the Scanning Electron Microscope (SEM) and Cathodoluminescence (CL). These additional analytical methods provide important information about the deformation mechanisms and mineral growth, and the chemical composition of the cements filling part of the fractures.

In a next step, the porosity and permeability data acquired from ÁCT measurements are calibrated and compared with data from standard laboratory measurements on sample plugs (e.g. helium porosity and gas permeability experiments). The final goal is to get a 3D view of the porosity and permeability of various Hauptdolomit samples, on various scales (Ám to dm), which can serve as an input for upscaling permeability to the reservoir scale.