Advanced X-ray and neutron imaging of fractured and porous rocks

In the subsurface, fractures can act as fast conduits for fluid transport, where the geometry of the void space (most notably wall roughness and aperture) determines the transport properties. The project ARGUS has developed time-resolved X-ray and neutron imaging applications to unravel geological processes related to flow in rocks. Understanding the interactions between fluid flow and rock deformation has numerous fundamental applications in geosciences: groundwater movement, displacement of contaminants, geothermal energy, hydrocarbon exploration and subsurface storage of waste (such as processed water, CO2, or nuclear waste), and enhanced oil and gas recovery. We have performed advanced time-lapse X-ray in situ three-dimensional microtomography to image the fracturing of solid rock under pressure/temperature conditions representative for hydrocarbon reservoirs. This project has used several large-scale facilities, the European Synchrotron Radiation Facility (Grenoble, France) and the neutron imaging beamlines at the Institut Laue Langevin (Grenoble, France) and the Paul Scherrer Institute (Villigen, Switzerland), Using our knowledge from X-ray imaging, we have adapted and developed 2-D and 3-D neutron imaging for flow in fractures. Developing in situ experiments and data processing routines helps us to build up towards usage of the new neutron imaging capacities currently being installed in Scandinavia. In 2029-2020, we have developed a unique series of neutron experiments where the transport of cadmium, a pollutant in soils, was imaged in three-dimensions. We have also developed new machine learning algorithms to characterize fractures in rocks.

The outcomes and impacts (9 publications) are well-beyond the expected results (see attached report), lending confidence that the Oslo rock physics group is a world leader in neutron and X-ray imaging of rock processes.

In the subsurface, fractures can act as fast conduits for fluid transport, where the geometry of the void space (most notably wall roughness and aperture) determines the transport properties. However, flow-through of a reactive fluid may affect this, coupling flow rate, transport of dissolved species, and stress in the solid. The project ARGUS will develop time-resolved X-ray and neutron imaging applications to unravel geological processes related to flow in rocks. Understanding the interactions between fluid flow and rock deformation has numerous fundamental applications in geosciences: groundwater movement, displacement of contaminants, geothermal energy, hydrocarbon exploration and subsurface storage of waste (such as processed water, CO2, or nuclear waste), and enhanced oil and gas recovery. Moreover, the transport of fluid in fault zones is also related to earthquakes, and how transport controls the occurrence of local chemical reactions and metamorphism at depth. We will perform advanced time-lapse X-ray 3-D tomography to image the fracturing of solid rock under pressure/temperature conditions representative for hydrocarbon reservoirs. Using our knowledge from X-ray imaging, we will adapt and develop 2-D and 3-D neutron imaging for flow in fractures. Furthermore, tomography data image processing to date is dependent on the operator, where user bias decreases reproducibility and may introduce errors. Therefore, we propose to apply innovative segmentation routines, based on machine-learning algorithms, to quantitatively describe the 3D morphology of the growing crack network and the flow, and to minimize errors. Developing in situ experiments and data processing routines will help us to build up towards usage of the new neutron imaging capacities currently being installed in Scandinavia. We aim to collect a database of reference samples and images of fractures and flow patterns in rocks that can be used for comparison between various X-rays and neutron sources.