Visualization and Quantification of Thermally Induced Porosity Alteration of Immature Source Rock Using X-ray Computed Tomography

Glatz, Guenther; Castanier, L.M.; Kovscek, Anthony R.

doi:10.1021/acs.energyfuels.6b01430

Cited by 25 publications

(18 citation statements)

References 31 publications

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“…Moreover, organic rich specimens that have been thermally decomposed under confinement in the laboratory, or natural samples studied by microstructural analyses [Kalani et al, 2015], have revealed fractures filled with mobile organic matter. Laboratory experiments also suggested that kerogen transformation leads to the formation of fractures whose propagation direction (predominantly sub-parallel to the bedding plane) are controlled by the anisotropic stress and rock mechanical properties (strength and toughness), and by the orientation of kerogen patches in the source rock [Vernik, 1994;Kobchenko et al, 2011;Glatz et al, 2016]. In comparison with a previous study [Panahi et al, 2012], the rate of temperature increase, before the sample was held at a constant temperature, was slower.…”

Section: Mechanisms Of Primary Migrationmentioning

confidence: 93%

In-situ imaging of fracture development during maturation of an organic-rich shale: Effects of heating rate and confinement

Panahi

Kobchenko

Meakin

et al. 2018

Marine and Petroleum Geology

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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.

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Section: Mechanisms Of Primary Migrationmentioning

confidence: 93%

In-situ imaging of fracture development during maturation of an organic-rich shale: Effects of heating rate and confinement

Panahi

Kobchenko

Meakin

et al. 2018

Marine and Petroleum Geology

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“…Certain experiments, however, stand to benefit greatly from increased exposure times as noise is decreased. The noise reduction gives rise to better statistics if, for example, porosity is to be estimated in combination with a non-wetting radio contrast agent [ 9 ]. Similarly, core flood experiments necessitate the presence of a vessel to maintain temperatures and pressures resulting in attenuation of the X-rays.…”

Section: Introductionmentioning

confidence: 99%

Deep Learning Driven Noise Reduction for Reduced Flux Computed Tomography

Alsamadony

Yildirim

Glatz

et al. 2021

Sensors

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Deep neural networks have received considerable attention in clinical imaging, particularly with respect to the reduction of radiation risk. Lowering the radiation dose by reducing the photon flux inevitably results in the degradation of the scanned image quality. Thus, researchers have sought to exploit deep convolutional neural networks (DCNNs) to map low-quality, low-dose images to higher-dose, higher-quality images, thereby minimizing the associated radiation hazard. Conversely, computed tomography (CT) measurements of geomaterials are not limited by the radiation dose. In contrast to the human body, however, geomaterials may be comprised of high-density constituents causing increased attenuation of the X-rays. Consequently, higher-dose images are required to obtain an acceptable scan quality. The problem of prolonged acquisition times is particularly severe for micro-CT based scanning technologies. Depending on the sample size and exposure time settings, a single scan may require several hours to complete. This is of particular concern if phenomena with an exponential temperature dependency are to be elucidated. A process may happen too fast to be adequately captured by CT scanning. To address the aforementioned issues, we apply DCNNs to improve the quality of rock CT images and reduce exposure times by more than 60%, simultaneously. We highlight current results based on micro-CT derived datasets and apply transfer learning to improve DCNN results without increasing training time. The approach is applicable to any computed tomography technology. Furthermore, we contrast the performance of the DCNN trained by minimizing different loss functions such as mean squared error and structural similarity index.

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“…Many researchers have studied the variation of macroscopic rock properties after high-temperature heat treatment and achieved some progress. Regarding the pore structure, various experimental techniques, including CT scanning electron microscope (CT-SEM) [15], mercury intrusion porosimetry (MIP) [16][17][18][19][20], micro-CT [21,22], field emission scanning electron microscopy (FE-SEM) [23,24], low-field nuclear magnetic resonance (NMR) [25], photoacoustic spectrometry (PAS) [26], ultrasonic velocity measurement (UVM) [27], etc., were used to study the high-temperature effects on the porosity, pore size, and pore morphology of various materials such as calcareous sediments [21], coal [15,25], concrete [16], shale [22][23][24], granite [28,29], sandstone [18,19,28], limestone [17,20], and carbonate [27]. Almost all of the above studies have shown that thermal damage and microcracks are induced by high temperature and the rock porosity and permeability gradually increase with temperature, while the pore fractal dimension decreases.…”

Section: Introductionmentioning

confidence: 99%

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

et al. 2019

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In deep geoengineering, including geothermal development, deep mining, and nuclear waste geological disposal, high temperature significantly affects the mineral properties of rocks, thereby changing their porous and mechanical characteristics. This paper experimentally studied the changes in mineral composition, pore structure, and mechanical characteristics of pyroxene granite heated to high temperature (from 25 °C to 1200 °C). The results concluded that (1) the high-temperature effect can be roughly identified as three stages: 25–500 °C, 500–800 °C, 800–1200 °C. (2) Below 500 °C, the maximum diffracted intensities of the essential minerals are comparatively stable and the porous and mechanical characteristics of granite samples change slightly, mainly due to mineral dehydration and uncoordinated thermal expansion; additionally, the failure mechanism of granite is brittle. (3) In 500–800 °C, the diffraction angles of the minerals become wider, pyroxene and quartz undergo phase transitions, and the difference in thermal expansion among minerals reaches a peak; the rock porosity increases rapidly by 1.95 times, and the newly created pores caused by high heat treatment are mainly medium ones with radii between 1 μm and 10 μm; the P-wave velocity and the elastic modulus decrease by 62.5% and 34.6%, respectively, and the peak strain increases greatly by 105.7%, indicating the failure mode changes from brittle to quasi-brittle. (4) In 800–1200 °C, illite and quartz react chemically to produce mullite and the crystal state of the minerals deteriorate dramatically; the porous and mechanical parameters of granite samples all change significantly and the P-wave, the uniaxial compressive strength (UCS), and the elastic modulus decrease by 81.30%, 81.20%, and 92.52%, while the rock porosity and the shear-slip strain increase by 4.10 times and 11.37 times, respectively; the failure mechanism of granite samples transforms from quasi-brittle to plastic, which also was confirmed with scanning electron microscopy (SEM).

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Visualization and Quantification of Thermally Induced Porosity Alteration of Immature Source Rock Using X-ray Computed Tomography

Cited by 25 publications

References 31 publications

In-situ imaging of fracture development during maturation of an organic-rich shale: Effects of heating rate and confinement

In-situ imaging of fracture development during maturation of an organic-rich shale: Effects of heating rate and confinement

Deep Learning Driven Noise Reduction for Reduced Flux Computed Tomography

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

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