Enhancing SEM Grayscale Images through Pseudocolor Conversion: Examples from Eagle Ford, Haynesville, and Marcellus Shales

Camp, Wayne K.

doi:10.1190/urtec2013-240

Cited by 4 publications

(7 citation statements)

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“…Segmentation of AFM elastic moduli maps into organic and inorganic components was carried out through comparison to backscattered electron scanning electron microscopy (BSE), and EDX images of the same sample regions. The methodology of Camp and Wawak (2013) was applied to BSE images to produce pseudo-greyscale images for thresholding. Four greyscale classes were identified, and comparison with EDX element maps showed that these can be interpreted as organic carbon, carbonate, aluminosilicate + quartz, and 'heavy' phases (pyrite, apatite, etc.).…”

Section: Mechanical Segmentation and Data Analysismentioning

confidence: 99%

Geomechanical characterisation of organic-rich calcareous shale using AFM and nanoindentation

et al. 2020

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The geomechanical integrity of shale overburden is a highly significant geological risk factor for a range of engineering and energy-related applications including CO$$_2$$ 2 storage and unconventional hydrocarbon production. This paper aims to provide a comprehensive set of high-quality nano- and micro-mechanical data on shale samples to better constrain the macroscopic mechanical properties that result from the microstructural constituents of shale. We present the first study of the mechanical responses of a calcareous shale over length scales of 10 nm to 100 $$\upmu$$ μ m, combining approaches involving atomic force microscopy (AFM), and both low-load and high-load nanoindentation. PeakForce quantitative nanomechanical mapping AFM (PF-QNM) and quantitative imaging (QI-AFM) give similar results for Young’s modulus up to 25 GPa, with both techniques generating values for organic matter of 5–10 GPa. Of the two AFM techniques, only PF-QNM generates robust results at higher moduli, giving similar results to low-load nanoindentation up to 60 GPa. Measured moduli for clay, calcite, and quartz-feldspar are $$22 \pm 2\,\hbox { GPa}$$ 22 ± 2 GPa , $$42 \pm 8\,\hbox { GPa}$$ 42 ± 8 GPa , and $$55 \pm 10\,\hbox { GPa}$$ 55 ± 10 GPa respectively. For calcite and quartz-feldspar, these values are significantly lower than measurements made on highly crystalline phases. High-load nanoindentation generates an unimodal mechanical response in the range of 40–50 GPa for both samples studied here, consistent with calcite being the dominant mineral phase. Voigt and Reuss bounds calculated from low-load nanoindentation results for individual phases generate the expected composite value measured by high-load nanoindentation at length scales of 100–600 $$\upmu$$ μ m. In contrast, moduli measured on more highly crystalline mineral phases using data from literature do not match the composite value. More emphasis should, therefore, be placed on the use of nano- and micro-scale data as the inputs to effective medium models and homogenisation schemes to predict the bulk shale mechanical response.

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Section: Mechanical Segmentation and Data Analysismentioning

confidence: 99%

Geomechanical characterisation of organic-rich calcareous shale using AFM and nanoindentation

et al. 2020

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“…The residual data are then checked for a maximum value of organic matter Young's modulus, achieved by comparing the AFM QI™ scans with their equivalent SEM scan and EDX data obtained. This was undertaken first by enhancing the SEM through color thresholding using the method proposed by Camp (2013). The pixel values of the enhanced SEM are then manually compared with visible values for organic matter and porosity.…”

Section: Methodsmentioning

confidence: 99%

The Assessment of Organic Matter Young's Modulus Distribution With Depositional Environment and Maturity

et al. 2020

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Quantification of risk to seal integrity in CCS, or gas extraction from hydraulic fracturing, is directly affected by the accessibility of organic pores within organic rich mudrocks. Knowledge of the host organic matter's mechanical properties, which are influenced by depositional environment and thermal maturity, are required to reduce operational risk. In this study we address the effect of both depositional environment and maturity on organic matter Young's modulus by means of Atomic Force Microscopy Quantitative Imaging TM , which is a nondestructive technique capable of nanomechanical measurements. Shales from varying marine depositional environments covering kerogen Types II (Barnett), IIS (Tarfaya), and II/III (Eagle Ford/ Bowland) are analyzed to capture variance in organic matter. The findings show organic matter has a Young's modulus ranging between 0.1 and 24 GPa. These marine shales have a bimodal distribution of Young's modulus to some degree, with peaks at between 3-10 and 19-24 GPa. These shales exhibit a trend with maturity, whereby Young's modulus values of <10 GPa are dominant in immature Tarfaya shale, becoming similar to the proportion of values above 15 GPa within the oil window, before the stiffer values dominate into the gas window. These peaks most likely represent soft heterogeneous aliphatic rich kerogen and stiff ordered aromatic rich kerogen, evidenced by the increase in the stiffer component with maturity and correlated with 13 C NMR spectrocopy. These findings enable increased realism in microscale geomechanical fracture tip propagation models and may allow direct comparison between Young's modulus and Rock-Eval parameters. Plain Language Summary Gas recovery from hydraulic fracturing and validating the top-seal integrity for carbon capture and storage require knowledge of key mechanical properties of the associate mudrock. One key property is elasticity (Young's modulus), which is relatively well constrained for each component of a shale, except for the organic matter. This has historically been due to the difficulties in analyzing elasticity at the resolution of organic matter particles, which can be <1 micron in diameter. Here we use a new technique to measure elasticity at a spatial resolution of between 10 and 50 nm. Organic matter elasticity measurements have been undertaken on a range of shales from marine and lacustrine depositional environments and a range of thermal maturities. The marine-derived organic matter exhibits a bimodal distribution with a peak at around 3-10 and 19-22 gigapascals (GPa). When comparing the shale samples with maturity, a clear bimodal trend is observed within the marine-derived organic matter, which becomes increasingly dominated by a stiffer (higher Young's modulus) peak with maturity.

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“…The resulting signals, which are secondary electrons (SE), backscattered electrons (BSE), or X-rays can be used to image the sample (Curtis et al, 2010). Both backscattered electron and secondary electron images are produced by assigning grayscale values to represent signal intensity measurements (Camp et al, 2013). Secondary electrons (SE) are low voltage electrons arising from the inelastic interactions between the primary electron beam and the sample (Nanakoudis, 2019).…”

Section: Motivation and Problem Statementmentioning

confidence: 99%

“…Secondary electrons (SE) are low voltage electrons arising from the inelastic interactions between the primary electron beam and the sample (Nanakoudis, 2019). Secondary electron images are useful to study the topography of the sample surface, including rock fabric, texture, and mineral, pore, and microfossil morphology (Camp et al, 2013, Nanakoudis, 2019. These images also make it possible to evaluate near-surface negative aberrations such as pores and cracks from polished or ion-milled surfaces (Camp et al, 2013).…”

Section: Motivation and Problem Statementmentioning

confidence: 99%

“…Secondary electron images are useful to study the topography of the sample surface, including rock fabric, texture, and mineral, pore, and microfossil morphology (Camp et al, 2013, Nanakoudis, 2019. These images also make it possible to evaluate near-surface negative aberrations such as pores and cracks from polished or ion-milled surfaces (Camp et al, 2013). The negative aberrations are represented as low intensity (dark) regions on the image (Camp et al, 2013).…”

Section: Motivation and Problem Statementmentioning

confidence: 99%

See 1 more Smart Citation

Do We Really Need Deep Learning? A Study on Play Identification using SEM Images

Zhang¹,

Kasumov²,

Devegowda³

et al. 2021

Proceedings of the 9th Unconventional Resources Technology Conference

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Enhancing SEM Grayscale Images through Pseudocolor Conversion: Examples from Eagle Ford, Haynesville, and Marcellus Shales

Cited by 4 publications

References 1 publication

Geomechanical characterisation of organic-rich calcareous shale using AFM and nanoindentation

Geomechanical characterisation of organic-rich calcareous shale using AFM and nanoindentation

The Assessment of Organic Matter Young's Modulus Distribution With Depositional Environment and Maturity

Do We Really Need Deep Learning? A Study on Play Identification using SEM Images

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