EGU21-5585
https://doi.org/10.5194/egusphere-egu21-5585
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Time-lapse synchrotron X-ray imaging of deformation modes in organic-rich Green River Shale heated under confinement 

Maya Kobchenko1, Anne Pluymakers2, Benoit Cordonnier1, Nazmul Mondol1, and Francois Renard1
Maya Kobchenko et al.
  • 1University of Oslo, Njørd center, Oslo, Norway
  • 2Civil Engineering and Geosciences TU Delft

Shales are layered sedimentary rocks, which can be almost impermeable for fluids and act as seals and cap-rocks, or if a shale layer hosts a fracture network, it can act as a fluid reservoir and/or conduit. Organic-rich shales contain organic matter - kerogen, which can transform from solid-state to oil and gas during burial and exposure to a suitable temperature. When hydrocarbons are expelled from the organic matter due to maturation, pore-pressure increases, which drives the propagation of hydraulic fractures, a mechanism identified to explain oil and gas primary migration. Density, geometry, extension, and connectivity of the final fracture network depend on the combination of the heating conditions and history of external loading experienced by the shale. Here, we have performed a series of rock physics experiments where organic-rich shale samples were heated, under in situ conditions, and the development of microfractures was imaged through time. We used the high-energy X-ray beam produced at the European Synchrotron Radiation Facility to acquire dynamic microtomography images and monitor different modes of shale deformation in-situ in 3D. We reproduced natural conditions of the shale deformation processes using a combination of axial load, confining pressure, and heating of the shale samples. Shales feature natural sedimentary laminations and hydraulic fractures propagate parallel to these laminae if no overburden stress is applied. However, if the principal external load becomes vertical, perpendicular to the shale lamination, the fracture propagation direction can deviate from the horizontal one. Together horizontal and vertical fractures form a three-dimensional connected fracture network, which provides escaping pathways for generated hydrocarbons. Our experiments demonstrate that tight shale rocks, which are often considered impermeable, could host transient episodes of micro-fracturing and high permeability during burial history.

How to cite: Kobchenko, M., Pluymakers, A., Cordonnier, B., Mondol, N., and Renard, F.: Time-lapse synchrotron X-ray imaging of deformation modes in organic-rich Green River Shale heated under confinement , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5585, https://doi.org/10.5194/egusphere-egu21-5585, 2021.