Changes in Pore Structure of Dry-hot Rock with Supercritical CO<sub>2</sub> Treatment

Li, Honglian; Zhou, Lei; Lu, Yiyu; Yan, Fazhi; Zhou, Jiankun; Tang, Jiren

doi:10.1021/acs.energyfuels.0c00250

Cited by 22 publications

(8 citation statements)

References 54 publications

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“…Adsorption in rocks mainly occurs in micropores and mesopores, while macropores are the main channels for gas migration. Therefore, according to the T 2 curves obtained from NMR tests, T 2 = 2.5 ms (corresponding to a pore size of 50 nm) is chosen as the demarcation point, and the fractal dimensions of shale adsorption pores and seepage pores are calculated using eq . − Figure and Table present the results of the calculations of fractal dimensions. D N 1 obtained from adsorption pores represents the fractal dimension of the pore area, which reflects the roughness and heterogeneity of the surface of shale adsorption pores, and its value is typically between 1 and 2.…”

Section: Resultsmentioning

confidence: 99%

Different Effect Mechanisms of Supercritical CO₂ on the Shale Microscopic Structure

Zhou

et al. 2020

ACS Omega

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To better understand how supercritical carbon dioxide (CO 2 ) enhances shale gas production, it is necessary to study the interaction of supercritical CO 2 with shale and its impact on shale microstructure. The different mechanisms by which supercritical CO 2 changes the shale pore structure were studied by X-ray diffraction analyses, scanning electron microscopy (SEM), nuclear magnetic resonance spectroscopy, and low-pressure nitrogen gas adsorption tests on shale samples before and after treatment with different pressures and gases (CO 2 and Ar). The results showed that after treatment with CO 2 , the mineral content of shale changed significantly, and in particular, the proportions of calcite and dolomite decreased. The mineral content of shale changed the most after treatment with supercritical CO 2 , and the microscopic pores were most observable by SEM. In a gaseous CO 2 environment, the effect of CO 2 adsorption on shale pores is greater than the effects of gas pressure and dissolution reactions. However, in a supercritical CO 2 environment, the changes in shale pore structures are mainly controlled by extraction and dissolution reactions. When shale is exposed to supercritical CO 2 , the fractal dimensions of adsorption pores and seepage pores decrease, indicating that the specific surface area and roughness of adsorption pores decrease. This implies that the adsorption capacity decreases, and that the complexity of the seepage pores declines, which is conducive for gas migration.

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Section: Resultsmentioning

confidence: 99%

Different Effect Mechanisms of Supercritical CO₂ on the Shale Microscopic Structure

Zhou

et al. 2020

ACS Omega

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“…When shale, granite and other rocks are exposed to supercritical CO 2 , the water molecules in rock minerals combine with the CO 2 to form carbonic acid and dissolve calcite, feldspar and other mineral particles (Cai et al, 2018;Zhou et al, 2019;Li et al, 2020a). It can be seen from Table 1 that the granite mineral composition changes significantly after supercritical CO 2 soaking, with a significant decrease in the calcite content.…”

Section: Xrd and Semmentioning

confidence: 99%

“…Combined with X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical electron microscopy (Li et al, 2020a), the influence of supercritical CO 2 on the failure mechanism of granite is explored in combination with changes in the mineral composition and microstructure of granite. This study will be of significance for the prediction of artificial earthquakes induced by the development of hot dry rock.…”

Section: Introductionmentioning

confidence: 99%

The effect of supercritical CO2 on failure mechanisms of hot dry rock

Jiang

et al. 2022

Adv. Geo-Energy Res.

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Hot dry rock is a clean, renewable resource of geothermal energy with good stability and a high utilization rate. Supercritical CO 2 has shown promising results for improving the permeability and heat exchange of hot dry rock. In order to demonstrate the effect of supercritical CO 2 on the failure mechanism of granite, the acoustic emission of granite during its failure process were studied in addition to X-ray diffraction, scanning electron microscopy, and optical electron microscopy investigations. The experimental results showed that for granite without supercritical CO 2 treatment, as it approached failure, there were many acoustic emission events with a waiting time less than 0.0001 s, and that the power law exponent of the acoustic emission energy distribution decreased. The failure mechanisms were a combination of fracture and friction, with fracturing dominant. After immersion in supercritical CO 2 , new cracks and pores appeared in the granite due to the dissolution of minerals, but friction was also a factor evidenced in particle crumbing. Generally, the acoustic emission statistical distributions of granite before and after supercritical CO 2 soaking conformed to the seismic statistical distribution law. This study is conducive to increasing the understanding of artificial earthquakes induced by the development of hot dry rock.

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“…9 In addition, it can be used to enhance coalbed methane, 10−12 shale gas 13,14 and oil recovery, 15,16 improve heat extraction from an enhanced geothermal system, 17 and facilitate rock fracturing. 18−22 Large-scale storage of CO 2 in deep formations, which involves thermo−hydro−mechanical− chemical processes, may damage the microstructure 23 of the rock formation, causing considerable fluid pressure perturbation, altering the in situ stresses, and then increasing the leakoff risk. 24,25 The damage induced by CO 2 storage to sandstone can be attributed to physical and chemical factors.…”

Section: Introductionmentioning

confidence: 99%

Microscale Damage Induced by CO₂ Storage on the Microstructure of Sandstone Coupling Hydro–Mechanical–Chemical Processes

Nie

Zhang

et al. 2022

Energy Fuels

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A good understanding of CO2–brine–rock interactions that cause microscale damage to the microstructure of sandstone, affecting pore fluid transport and reservoir stability, is important for studying storage efficiency during CO2 storage. In this study, the equipment is first designed to saturate rock samples using CO2–brine under in situ conditions and then the homogeneous and heterogeneous sandstone samples are saturated for 30 days with and without the confining pressure (20 MPa). Through scanning electron microscopy (SEM) observation and analysis, it is found that the confining pressure reduces the degree of damage in various scales from micrometer to millimeter, such as reducing the mineral dissolution, decreasing the induced swelling of the bedding planes, and causing some pores to collapse. The nuclear magnetic resonance results show that the change in porosity is mainly caused by the increase in the number of relatively small-sized (characterized in terms of fluid relaxation time T 2 < 10–3 s) pores after CO2–brine saturation. In addition, the alterations of the pore system in homogeneous and heterogeneous sandstones are different, such as a larger increase in the porosity of homogeneous sandstone (by 5.29%). In heterogeneous sandstone, the effect of mineral dissolution induced by chemical reactions on damaging the microstructure is more obvious than mineral swelling. In addition, it is found that the CO2–brine saturation decreases the fractal dimension of the sandstone by nearly 2%, increasing the pore connectivity. This study is helpful for understanding the evolution of the sandstone microstructure under geological conditions during the long-term CO2 storage process.

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Changes in Pore Structure of Dry-hot Rock with Supercritical CO₂ Treatment

Cited by 22 publications

References 54 publications

Different Effect Mechanisms of Supercritical CO₂ on the Shale Microscopic Structure

Different Effect Mechanisms of Supercritical CO₂ on the Shale Microscopic Structure

The effect of supercritical CO2 on failure mechanisms of hot dry rock

Microscale Damage Induced by CO₂ Storage on the Microstructure of Sandstone Coupling Hydro–Mechanical–Chemical Processes

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Changes in Pore Structure of Dry-hot Rock with Supercritical CO2 Treatment

Cited by 22 publications

References 54 publications

Different Effect Mechanisms of Supercritical CO2 on the Shale Microscopic Structure

Different Effect Mechanisms of Supercritical CO2 on the Shale Microscopic Structure

The effect of supercritical CO2 on failure mechanisms of hot dry rock

Microscale Damage Induced by CO2 Storage on the Microstructure of Sandstone Coupling Hydro–Mechanical–Chemical Processes

Contact Info

Product

Resources

About

Changes in Pore Structure of Dry-hot Rock with Supercritical CO₂ Treatment

Different Effect Mechanisms of Supercritical CO₂ on the Shale Microscopic Structure

Different Effect Mechanisms of Supercritical CO₂ on the Shale Microscopic Structure

Microscale Damage Induced by CO₂ Storage on the Microstructure of Sandstone Coupling Hydro–Mechanical–Chemical Processes