Micro-CT characterization on pore structure evolution of low-permeability sandstone under acid treatment

Liu, Sinan; Zhang, Liwei; Su, Xuebin; Zhao, Lixin; Wang, Yan

doi:10.1016/j.apgeochem.2023.105633

Cited by 14 publications

(5 citation statements)

References 37 publications

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“…For instance, medical and dental CTscan techniques are applied for the porosity determination of 20 core samples collected from the Persian Gulf coastal zone and Zagros basin in order to compare with routine porosity measurement technique [30]. The results showed a considerable agreement between CT-scan techniques and average routine porosity method [31,32]. In addition, many scholars have reproduced the flow process of fluids in sandstone pore structures through numerical simulation methods, revealing the influence mechanism of pore structures on the macroscopic permeability of sandstone [33][34][35].…”

Section: Introductionmentioning

confidence: 99%

3D Characterization of Pore Structure and Pore Scale Seepage Simulation of Sandstone Based on Computational Tomography

Zhu,

Li,

et al. 2024

Water

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The microscopic pore structure of sandstone determines its macroscopic permeability. Based on computer tomography (CT) technology, CT scans were performed on three different types of sandstone pore structures, namely coarse sandstone, medium sandstone, and fine sandstone. And the three-dimensional microscopic structure of sandstone pores was reconstructed. Furthermore, based on the Navier–Stokes equations, the fluid flow process in the pore structure of sandstone was simulated, and the effective permeability of sandstone was obtained. By extracting the pore structure from sandstone CT images, the average porosity of coarse sandstone, medium sandstone, and fine sandstone was 16.43%, 12.03%, and 11.64%, respectively. And the porosity of unconnected pores is less than 0.5%. The porosity and permeability of coarse sandstone are higher than those of medium sandstone and fine sandstone with an average value of 1.7 D. The porosity of medium sandstone and fine sandstone is relatively similar. However, the average pore radius and pore throat radius of medium sandstone are larger than those of fine sandstone. More importantly, although the permeability and porosity of sandstone are generally linearly related, when the porosity is low, the data show a large dispersion, and auxiliary indicators such as pore structure characteristic parameters such as pore throat radius should be adopted to evaluate the permeability of sandstone. The flow trajectory of fluid in the pore structure of sandstone is revealed through the streamline of fluid in the pore structure, revealing the mechanism of fluid flow.

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Section: Introductionmentioning

confidence: 99%

3D Characterization of Pore Structure and Pore Scale Seepage Simulation of Sandstone Based on Computational Tomography

Zhu,

Li,

et al. 2024

Water

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“…Most of the time, two methods are required to describe pore structures accurately. The first type is direct imaging, which includes field emission scanning electron microscopy (FE-SEM) [5][6][7], the focused ion beam-scanning electron microscope system (FIB-SEM) [8][9][10], and computed tomography (CT) technology [11][12][13][14], which can obtain the microscopic morphology of pores. The second type comprises fluid injection methods, such as CO 2 and N 2 adsorption experiments [4,[15][16][17], high-pressure mercury intrusion (MIP) [18][19][20], and low-field nuclear magnetic resonance (NMR) [3,21], which can quantify the pore volume, specific surface area, and pore size distribution (PSD) of rock samples.…”

Section: Introductionmentioning

confidence: 99%

Application of Multifractal Theory for Determination of Fluid Movability of Coal-Measure Sedimentary Rocks Using Nuclear Magnetic Resonance (NMR)

et al. 2023

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A precise evaluation of the fluid movability of coal sedimentary rock is crucial to the effective and secure utilization of coal measures gas reserves. Furthermore, its complex pore structure and diverse mineral components impact the flow properties of fluids in pore structures, causing accurate evaluation of fluid mobility to be extremely challenging. Nuclear magnetic resonance (NMR) technology is currently a prevalent technique to assess unconventional reservoirs due to its capacity to acquire abundant reservoir physical property data and determine fluid details. The free-fluid volume index (FFI) is a crucial factor in assessing fluid movability in the application of NMR technology, which can only be derived through intricate NMR saturation and centrifugation experiments This research utilized nuclear magnetic resonance (NMR) tests on 13 classic coal-measure sedimentary rock samples of three lithologies to reveal the FFI value. Moreover, the association between mineral components, pore structure parameters, and FFI was then extensively analyzed, and a prediction model for FFI was constructed. The results indicate that the T2 spectra of sandstone and shale own a bimodal distribution, with the principal point between 0.1 and 10 ms and the secondary peak between 10 and 100 ms. The majority of the T2 spectra of mudstone samples provide a unimodal distribution, with the main peak distribution range spanning between 0.1 and 10 ms, demonstrating that the most of the experimental samples are micropores and transition pores. The calculated results of the FFI range from 7.65% to 18.36%, and depict evident multifractal properties. Porosity, the content of kaolinite, multifractal dimension (Dq), and the FFI are linearly positively correlated. In contrast, the content of chlorite, illite, multifractal dimension subtraction (Dmin − Dmax), multifractal dimension proportion (Dmin/Dmax), and singularity strength (Δα) possess a negative linear correlation with the FFI, which can be further used for modeling. On the basis of the aforementioned influencing factors and the FFI experimental values of eight core samples, an FFI prediction model was constructed through multiple linear regression analysis. The accuracy of the prediction model was validated by utilizing this approach to five samples not included in the model development. It was revealed that the prediction model produced accurate predictions, and the research findings may serve as a guide for the classification and estimation of fluid types in coal reservoirs.

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“…Therefore, the pore and crack structure is the key aspect in the study of the low-temperature cyclic fracturing technique using liquid nitrogen and liquid CO2 as the freezing medium. At present, the pores and cracks of coal after freezing are mainly studied in three areas: firstly, the research is conducted with a single experimental method, which includes four main experiments; ①Based on nuclear magnetic resonance technology, the pore structure has been analyzed from six aspects, such as pore size distribution and pore fluidity (Guo et al, 2023;Zhang et al, 2022;Liu et al, 2023). based on the CT scanning and three-dimensional reconstruction technology, the spatial distribution characteristics of the pore structure were investigated under the aspects of porosity, pore size, and coordination number (Liu et al, 2023;Quan et al, 2022;Jozef et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

“…At present, the pores and cracks of coal after freezing are mainly studied in three areas: firstly, the research is conducted with a single experimental method, which includes four main experiments; ①Based on nuclear magnetic resonance technology, the pore structure has been analyzed from six aspects, such as pore size distribution and pore fluidity (Guo et al, 2023;Zhang et al, 2022;Liu et al, 2023). based on the CT scanning and three-dimensional reconstruction technology, the spatial distribution characteristics of the pore structure were investigated under the aspects of porosity, pore size, and coordination number (Liu et al, 2023;Quan et al, 2022;Jozef et al, 2022). based on mercury intrusion and nitrogen adsorption experiments at low temperatures, the pore structure was investigated from the aspects of adsorption isotherm, pore volume, specific pore surface area, and pore size distribution (Qi et al, 2022;Yuan et al, 2022b).…”

Section: Introductionmentioning

confidence: 99%

Study on evolution law of pore characteristics of freeze-thaw coal based on fractal theory

Yuan,

Chen,

Wang

et al. 2023

Preprint

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To investigate the characteristics of pore structure change of coal under freeze-thaw cycles, the surface and internal pore structure distribution of coal samples with long flame and different freeze-thaw times were measured by scanning electron microscopy (SEM) and low-temperature nitrogen adsorption method, and the law of pore structure change of coal after freeze-thaw was analyzed by fractal theory. The results of scanning electron microscopy experiments show that after freeze-thaw, the phenomenon of crack pore enlargement on the surface of coal samples occurs to different extents, and the phenomenon of crack pore enlargement on the surface of coal samples increases with the duration of freeze-thaw; at the same time, the porosity and fractal dimension DS of microcracks on the surface increased by 214.2% and 8.8%, respectively, corresponding to the change of macrocracks. The low-temperature nitrogen adsorption results show that the freezing and thawing changes the internal pore structure from simple to complex, and the maximum nitrogen adsorption capacity, specific surface area and pore volume in the pore parameters increase by 67.57%, 49.12% and 35.55%, respectively, compared with those before freezing and thawing. After freezing and thawing, the fractal dimension of the pores decreased to different degrees in the high-pressure and low-pressure stages. It decreased by 6.6% in the high pressure stage and by 8.9% in the low pressure stage. The change in fractal dimension DL in the low-pressure stage is greater than that of fractal dimension DH in the high-pressure stage, and the difference between the two decreases with increasing number of freeze-thaw cycles.

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Micro-CT characterization on pore structure evolution of low-permeability sandstone under acid treatment

Cited by 14 publications

References 37 publications

3D Characterization of Pore Structure and Pore Scale Seepage Simulation of Sandstone Based on Computational Tomography

3D Characterization of Pore Structure and Pore Scale Seepage Simulation of Sandstone Based on Computational Tomography

Application of Multifractal Theory for Determination of Fluid Movability of Coal-Measure Sedimentary Rocks Using Nuclear Magnetic Resonance (NMR)

Study on evolution law of pore characteristics of freeze-thaw coal based on fractal theory

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