Maya Kobchenko

• Johnson, James Ronald; Kobchenko, Maya; Johnson, Andrew Charles; Mondol, Nazmul Haque & Renard, Francois (2022). Experimental modelling of primary migration in a layered, brittle analogue system. Tectonophysics. ISSN 0040-1951. 840. doi: 10.1016/j.tecto.2022.229575. Full text in Research Archive Show summary

  A 2D Hele-Shaw cell was built to study microfracture nucleation, growth, and network formation during internal fluid production. Fluid is slowly produced into a low permeability solid, which leads to a local fluid pressure increase that controls the nucleation of microfractures that grow and then connect to create flow pathways. This process occurs during the primary migration of hydrocarbons in source rocks, which is the main topic of our study. It may also occur in other geological systems, such as the expulsion of water during dehydration of clay-rich sediments in sedimentary basins or serpentinite rocks in subduction zones and the transport of magmatic melts. Our system consists of a transparent, brittle gelatin material mixed with yeast and sugar. The consumption of sugar by yeast leads to CO2 formation, resulting in microfracture nucleation and growth. We varied three parameters, (1) anisotropy (i.e., number of layers), (2) lateral sealing, and (3) rate of fluid production. We tracked fluid movement through the opening and closing of microfractures within the system. Microfracture nucleation density is similar in a layered system to previous studies (0.45 microfracture per cm2). However, we observed that lateral confinement (0.31 microfracture per cm2) and rate of expulsion (0.99 microfracture per cm2) affect nucleation density and the geometrical characteristics of the microfracture network. The size, extent, and geometry of the microfracture network are dependent on all three parameters investigated, where lateral confinement and a higher rate of expulsion result in greater microfracture network connectivity. Layers control the angle of intersection between microfractures. Furthermore, layering and sealing have an impact on fracture topology. Results also show that the microfracture pattern significantly influences the fluid expulsion rate. Our results have direct applications to understanding how fluid migration occurs in low-permeability rocks through the development of a connected microfracture network produced by internal fluid generation.

• Johnson, James Ronald; Kobchenko, Maya; Mondol, Nazmul Haque & Renard, Francois (2022). Multiscale synchrotron microtomography imaging of kerogen lenses in organic-rich shales from the Norwegian Continental Shelf. International Journal of Coal Geology. ISSN 0166-5162. 253. doi: 10.1016/j.coal.2022.103954. Full text in Research Archive Show summary

  Kerogen lens shape and size distribution control how organic-rich shales may behave as either source or seal rocks. Prior to thermal conversion, kerogen is a brittle, load-bearing constituent of the shale matrix. During thermal maturation, kerogen lenses become more ductile, and hydrocarbon expulsion may lead to the creation of microfractures, a process controlled not only by temperature and pressure but also by the size and shape of kerogen lenses and their total content in the rock. Here, we use high-resolution multiscale synchrotron microtomography imaging of centimeter-scale shale rock samples collected in two boreholes at different depths in the North Sea and the Barents Sea, respectively. From these three-dimensional microtomography data, we quantify the various shapes of kerogen lenses and discuss how each step of a kerogen lens's life-cycle (i.e. original biological structure, deposition, degradation, and diagenesis) impacted its shape before catagenesis. We quantify the relationship between kerogen volume and the number of kerogen lenses in a given rock volume. The relationship between total organic carbon (TOC) content and the average kerogen lens volume is also measured. For a given rock volume, results show that organic content increases with the number of kerogen lenses up to a point (~8–12 wt% TOC) above which TOC continues to increase, but the number of kerogen lenses decreases. These results combined with kerogen lens orientation may control microfracturing during kerogen maturation.

• Panahi, Hamed; Kobchenko, Maya; Meakin, Paul; Dysthe, Dag Kristian & Renard, Francois (2019). Fluid expulsion and microfracturing during the pyrolysis of an organic rich shale. Fuel. ISSN 0016-2361. 235, p. 1–16. doi: 10.1016/j.fuel.2018.07.069. Full text in Research Archive Show summary

  During progressive burial, low permeability organic-rich shale rocks evolve chemically and physically as the temperature and stress increase and organic matter matures. The transformation of organic matter into hydrocarbon, followed by its expulsion into secondary migration pathways along which it is conveyed into reservoirs rocks, is a coupled process that involves chemical reactions, changes in volume and stress leading to the nucleation and growth of microfractures, the opening and closing of these microfractures, and fluid transport through them. Primary migration was studied using an experimental setup that was designed to measure changes in fluid pressure, which are correlated with organic matter maturation and hydrocarbon expulsion. The setup consisted of a pressurized autoclave which was externally heated. Shale samples were confined, under an initially low confining pressure and an applied differential stress (0.18 MPa), and heated to temperatures of 210–320 °C. Changes in temperature, static pressure (pressure measured using a linear response transducer) and dynamic fluid pressures (measured using a piezoelectric differential transducer) in the autoclave chamber were monitored and recorded during each experiment. In the higher part of the temperature range, fluid produced by kerogen maturation and the concomitant formation of microfractures increased volumetric expansion of the shale. Power spectral densities of the fluid pressure signals were calculated and a conceptual model is proposed to explain the dynamics of fluid expulsions. While a power law distribution of frequencies of pressure burst amplitudes was identified, the frequencies of time intervals between successive expulsion events (waiting times) decrease monotonically with increasing waiting time. Co-generation of gas and liquid hydrocarbon was evidenced. Several samples were imaged after kerogen maturation using X-ray microtomography, and the data confirm the existence of a percolating network of microfracture that controls the primary migration of hydrocarbons.

• Renard, Francois; McBeck, Jessica Ann; Cordonnier, Benoit; Zheng, Xiaojiao; Kandula, Neelima & Sanchez, Jesus Rodriguez [Show all 12 contributors for this article] (2019). Dynamic In Situ Three-Dimensional Imaging and Digital Volume Correlation Analysis to Quantify Strain Localization and Fracture Coalescence in Sandstone. Pure and Applied Geophysics (PAGEOPH). ISSN 0033-4553. 176, p. 1083–1115. doi: 10.1007/s00024-018-2003-x. Full text in Research Archive Show summary

  Advances in triaxial compression deformation apparatus design, dynamic X-ray microtomography imaging, data analysis techniques, and digital volume correlation analysis provide unparalleled access to the in situ four-dimensional distribution of developing strain within rocks. To demonstrate the power of these new techniques and acquire detailed information about the micromechanics of damage evolution, deformation, and failure of porous rocks, we deformed 3-cm-scale cylindrical specimens of low-porosity Fontainebleau sandstone in an X-ray-transparent triaxial compression apparatus, and repeatedly recorded three-dimensional tomograms of the specimens as the differential stress was increased until macroscopic failure occurred. Experiments were performed at room temperature with confining pressure in the range of 10–20 MPa. Distinct grayscale subsets, indicative of density, enabled segmentation of the three-dimensional tomograms into intact rock matrix, pore space, and fractures. Digital volume correlation analysis of pairs of tomograms provided time series of three-dimensional incremental strain tensor fields throughout the experiments. After the yield stress was reached, the samples deformed first by dilatant opening and propagation of microfractures, and then by shear sliding via grain rotation and strain localization along faults. For two samples, damage and dilatancy occurred by grain boundary opening and then a sudden collapse of the granular rock framework at failure. For the third sample, a fault nucleated near the yield point and propagated in the sample through the development of transgranular microfractures. The results confirm findings of previous experimental studies on the same rock and provide new detailed quantifications of: (1) the proportion of shear versus dilatant strain in the sample, (2) the amount of dilatancy due to microfracture opening versus pore opening when a fault develops, and (3) the role of grain boundaries and pore walls in pinning microfracture propagation and slowing down the rate of damage accumulation as failure is approached. Our study demonstrates how the combination of high-resolution in situ dynamic X-ray microtomography imaging and digital volume image correlation analysis can be used to provide additional information to unravel brittle failure processes in rocks under stress conditions relevant to the upper crust.

• McBeck, Jessica Ann; Kobchenko, Maya; Hall, Stephen; Tudisco, Erika; Cordonnier, Benoit & Meakin, Paul [Show all 7 contributors for this article] (2018). Investigating the Onset of Strain Localization Within Anisotropic Shale Using Digital Volume Correlation of Time-Resolved X-Ray Microtomography Images. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 123(9), p. 7509–7528. doi: 10.1029/2018JB015676. Full text in Research Archive Show summary

  Digital volume correlation analysis of time‐resolved X‐ray microtomography scans acquired during in situ triaxial compression of Green River shale cores provided time series of 3‐D incremental strain fields that elucidated evolving deformation processes by quantifying microscopic strain localization. With these data, we investigated the impact of mechanical anisotropy on microscopic strain localization culminating in macroscopic shear failure. We conducted triaxial compression experiments with the maximum compressive stress, σ1, aligned perpendicular and parallel to lamination planes in order to investigate end‐member stress states that arise within sedimentary basins. When the preexisting laminations were perpendicular to σ1, a lamination‐parallel region with high axial compaction developed within the macroscopically linear deformation phase of the experiment and then thickened with increasing applied differential stress. Scanning electron microscopy images indicate that this axial compaction occurred within a lower density lamination and that more axial compaction occurred within the center of the core than near its sides. Boundary element method simulations suggest that this compacting volume promoted shear fracture development within the upper portion of the shale. When the laminations were parallel to σ1, lamination‐parallel dilation bands formed, thickened, and intensified in dilation. Population densities of the distributions of incremental shear strain, radial dilation, and axial contraction calculated by digital volume correlation analysis enabled quantification of the evolving overall impact of, and interplay between, these various deformation modes.

• Panahi, Hamed; Kobchenko, Maya; Meakin, Paul; Dysthe, Dag Kristian & Renard, Francois (2018). In-situ imaging of fracture development during maturation of an organic-rich shale: Effects of heating rate and confinement. Marine and Petroleum Geology. ISSN 0264-8172. 95, p. 314–327. doi: 10.1016/j.marpetgeo.2018.05.002. Full text in Research Archive Show summary

  The statistics and dynamics of fractures formed during the accelerated maturation of kerogen-rich shale was investigated by heating Green River Shale (R-8 unit, Piceance Basin, northwestern Colorado) core samples while 3D X-ray microtomographic images were acquired. Previous studies have shown that, when there was no confining stress, fractures formed while the kerogen contained in the shale matured, and the produced hydrocarbon was expelled through these fractures. In the present study, X-ray tomographic scans at multiple voxel sizes were conducted on similar samples during heating. In one experiment, the shale sample was tightly fitted in a non-porous ceramic tube to confine it while it was heated. Three unconfined samples were heated and then held at different final temperatures to investigate the effects of the gas production rate on fracturing. 3D image processing was used to survey fracture network development, and time-lapse 2D digital image correlation analysis was used to monitor the development of the displacement and strain fields. The results revealed that fracturing is strongly dependent on the heating rate and the final heating temperature. While most of the fractures were oriented more-or-less parallel to the bedding plane, some were strongly inclined relative to the bedding plane. The formation of inclined fractures is attributed primarily to the shape and orientation of a minority of the flake-like kerogen patches, and also to the effective stress field and fractured zones of weakness. A conceptual model is proposed to explain the dynamics of fluid expulsion and the associate fracturing behavior.

• Pluymakers, Anne Marie Henriette; Kobchenko, Maya & Renard, Francois Marie Paul L (2017). How microfracture roughness can be used to distinguish between exhumed cracks and in-situ flow paths in shales. Journal of Structural Geology. ISSN 0191-8141. 94, p. 87–97. doi: 10.1016/j.jsg.2016.11.005. Full text in Research Archive Show summary

  Flow through fractures in shales is of importance to many geoengineering purposes. Shales are not only caprocks to hydrocarbon reservoirs and nuclear waste or CO2 storage sites, but also potential source and reservoir rocks for hydrocarbons. The presence of microfractures in shales controls their permeability and transport properties. Using X-ray micro-tomography and white light interferometry we scanned borehole samples obtained from 4 km depth in the Pomeranian shales in Poland. These samples contain open exhumation/drying cracks as well as intact vein-rock interfaces plus one striated slip surface. At micron resolution and above tensile drying cracks exhibit a power-law roughness with a scaling exponent, called the Hurst exponent H, of 0.3. At sub-micron resolution we capture the properties of the clay interface only, with H = 0.6. In contrast, the in-situ formed veins and slip surface exhibit H = 0.4–0.5, which is deemed representative for in-situ fractures. These results are discussed in relation to the shale microstructure and linear elastic fracture mechanics theory. The data imply that the Hurst roughness exponent can be used as a microstructural criterion to distinguish between exhumation and in-situ fractures, providing a step forward towards the characterization of potential flow paths at depth in shales.

• Renard, Francois; Cordonnier, Benoit; Kobchenko, Maya; Kandula, Neelima; Weiss, Jérôme & Zhu, Wenlu (2017). Microscale characterization of rupture nucleation unravels precursors to faulting in rocks. Earth and Planetary Science Letters. ISSN 0012-821X. 476, p. 69–78. doi: 10.1016/j.epsl.2017.08.002. Full text in Research Archive Show summary

  Precursory signals, manifestations of microscale damage that precedes dynamic faulting, are key to earthquake forecasting and risk mitigation. Detections of precursors have primarily relied on measurements performed using sensors installed at some distance away from the rupture area in both field and laboratory experiments. Direct observations of continuous microscale damage accumulated during fault nucleation and propagation are scarce. Using an X-ray transparent triaxial deformation apparatus, we show the first quantitative high resolution three-dimensional (3D) information about damage evolution of rocks undergoing brittle failure. The dynamic microtomography images documented a spectrum of damage characteristics and different fault growth patterns. The interplay between various deformation mechanisms can result in either a positive, negative, or constant net volume change. Consequently, changes in rock density and acoustic wave velocities before faulting are expected to vary in different tectonics settings, hence making failure forecasting intrinsically dependent on rock type at depth.

• Jamtveit, Bjørn; Krotkiewski, Marcin; Kobchenko, Maya; Renard, Francois Marie Paul L & Angheluta, Luiza (2014). Pore-space distribution and transport properties of an andesitic intrusion. Earth and Planetary Science Letters. ISSN 0012-821X. 400, p. 123–129. doi: 10.1016/j.epsl.2014.05.042. Full text in Research Archive
• Hafver, Andreas; Jettestuen, Espen; Kobchenko, Maya; Dysthe, Dag Kristian; Meakin, Paul & Malthe-Sørenssen, Anders (2014). Classification of fracture patterns by heterogeneity and topology. Europhysics letters. ISSN 0295-5075. 105(5). doi: 10.1209/0295-5075/105/56004. Full text in Research Archive
• Kobchenko, Maya; Hafver, Andreas; Jettestuen, Espen; Renard, Francois Marie Paul L; Galland, Olivier & Jamtveit, Bjørn [Show all 8 contributors for this article] (2014). Evolution of a fracture network in an elastic medium with internal fluid generation and expulsion. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 90(5). doi: 10.1103/PhysRevE.90.052801. Full text in Research Archive
• Panahi, Hamed; Meakin, Paul; Renard, Francois Marie Paul L; Kobchenko, Maya; Scheibert, Julien & Mazzini, Adriano [Show all 9 contributors for this article] (2013). A 4D Synchrotron X-Ray-Tomography Study of the Formation of Hydrocarbon-Migration Pathways in Heated Organic-Rich Shale. SPE Journal. ISSN 1086-055X. 18(2), p. 366–377. doi: 10.2118/162939-PA. Full text in Research Archive
• Kobchenko, Maya; Hafver, Andreas; Jettestuen, Espen; Galland, Olivier; Renard, Francois Marie Paul L & Meakin, Paul [Show all 8 contributors for this article] (2013). Drainage fracture networks in elastic solids with internal fluid generation. Europhysics letters. ISSN 0295-5075. 102(6). doi: 10.1209/0295-5075/102/66002. Full text in Research Archive
• Jamtveit, Bjørn; Kobchenko, Maya; Austrheim, Håkon Olav; Malthe-Sørenssen, Anders; Røyne, Anja & Svensen, Henrik (2011). Porosity evolution and crystallization-driven fragmentation during weathering of andesite. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 116. doi: 10.1029/2011JB008649. Full text in Research Archive
• Kobchenko, Maya; Panahi, Hamed; Renard, Francois Marie Paul L; Dysthe, Dag Kristian; Malthe-Sørenssen, Anders & Mazzini, Adriano [Show all 9 contributors for this article] (2011). 4D imaging of fracturing in organic-rich shales during heating. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 116(12). doi: 10.1029/2011JB008565. Full text in Research Archive

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• Golla, Archana; Pieschnik, Sophia; Kobchenko, Maya; Reiten, Ingrid; Chatzopoulos, Serafeim & Rojas, César Parra [Show all 16 contributors for this article] (2026). Building an Integrated Scientific Knowledge Graph for Neuroscience: Enhancing Research Impact Analysis and Optimizing Data Curation. doi: 10.5281/ZENODO.18864403. Full text in Research Archive Show summary

  The Neuroscience pilot of the EU-funded SciLake project seeks to tackle the complexities of fragmented and disorganized open research data. This initiative has united partners with expertise in knowledge management with curators from EBRAINS (RRID: SCR_019260), an open research infrastructure focused on brain-related studies. The innovative Scientific Knowledge Graph (SKG) (https://bip.imsi.athenarc.gr/search/neuroscience-pilot) created through this pilot serves as a cohesive framework for data integration while enabling the use of value-added services provided by SciLake. The developed SKG combines curated datasets from EBRAINS with extensive neuroscience research products from the OpenAIRE neuroscience gateway (https://neuroscience.openaire.eu/). The SKG incorporates controlled terms from openMINDS (RRID: SCR_023173) as nodes and utilizes an entity recognition model to classify and map these terms in relevant texts, enriching the connections among research products. Additionally, the SciLake services deploy language models to extract mentions of research artifacts (RAs) and enhance the interlinking of research products. Fully integrated with impact-driven discovery and reproducibility tools and leveraging the analytical capabilities of SciLake, the SKG serves as a powerful resource for contextualizing curation efforts and exploring research trends, ultimately optimizing curation processes in the neuroscientific landscape.

• Johnson, James Ronald; Kobchenko, Maya; Mondol, Nazmul Haque & Renard, François (2021). Multiscale synchrotron X-ray microtomography imaging of organic material in shales in the context of primary migration. Full text in Research Archive
• Kobchenko, Maya; Pluymakers, Anne Marie Henriette; Benoit, Cordonnier; Mondol, Nazmul Haque & Renard, François (2021). Time-lapse synchrotron X-ray imaging of deformation modes in organic-rich Green River Shale heated under confinement. Full text in Research Archive
• Johnson, James Ronald; Kobchenko, Maya; Mondol, Nazmul Haque & Renard, François (2021). Analogue modelling of primary migration in shales using organic-rich and organic-poor layered gel. Full text in Research Archive
• Dysthe, Dag Kristian; Kobchenko, Maya; Hafver, Andreas; Panahi, Hamed; Jamtveit, Bjørn & Renard, Francois Marie Paul L (2014). Temporal and spatial characteristics of drainage fracture networks in elastic media with internal fluid generation. Full text in Research Archive
• Kobchenko, Maya (2013). Fracturing of tight rocks during internal fluid production: implications for primary migration. Universitetet i Oslo. Full text in Research Archive Show summary

  This thesis presents a study of fracture formation in low permeability rocks induced by generation of fluid or gas during chemical reaction. In nature, primary migration of hydrocarbons, i.e. generation of oil and gas from tight source rock and its expulsion to more permeable reservoirs, is driven by formation of microfractures in the heated organic-rich shale. The tomographic 3D imaging of the rocks samples during heating showed that micro-cracks develop in the shale due to internal pore pressure build-up. Generation of hydrocarbons drives fracture formation until a drainage network sufficient for expulsion is developed. Experiments were also conducted on analogue material, where gelatine was fractured during fermentation of yeast and sugar. Studies of the gel confined in Hele-Shaw cell showed that CO2 generation leads to formation of a drainage network which topology represents a new class of networks, intermediate between hierarchical fracture pattern and river\tree network. When CO2 escapes via fracture network, individual cracks open and close in intermittent manner. The variation of fracture opening in time exhibits a universal frequency distribution with 1/f and 1/f2 noise. These results have implication for understanding how the generated fluids escape from hydraulic fractures. The methods can be applied in studying dehydration of sediments, formation of mud volcanoes, methane hydrate exploration and assessment, geological sequestration of carbon dioxide CO2, hydraulic fracturing of unconventional reservoirs, hydrothermal energy.

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