The Experts below are selected from a list of 84321 Experts worldwide ranked by ideXlab platform
Jake J Grossman - One of the best experts on this subject based on the ideXlab platform.
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standardization of electrolyte leakage data and a novel Liquid Nitrogen control improve measurements of cold hardiness in woody tissue
Plant Methods, 2021Co-Authors: Alisson Pacheco Kovaleski, Jake J GrossmanAbstract:BACKGROUND A variety of basic and applied research programs in plant biology require the accurate and reliable determination of plant tissue cold hardiness. Over the past 50 years, the electrolyte leakage method has emerged as a popular and practical method for quantifying the amount of damage inflicted on plant tissue by exposure to freezing temperatures. Numerous approaches for carrying out this method and analyzing the resultant data have emerged. These include multiple systems for standardizing and modeling raw electrolyte leakage data and multiple protocols for boiling or autoclaving samples in order to maximize leakage as a positive control. We compare four different routines for standardization of leakage data and assess a novel control method-immersion in Liquid Nitrogen in lieu of traditional autoclaving-and apply them to woody twigs collected from 12 maple (Acer) species in early spring. We compare leakage data from these samples using each of four previously published forms of data analysis and autoclaving vs. Liquid Nitrogen controls and validate each of these approaches against visual estimates of freezing damage and differential thermal analysis. RESULTS Through presentation of our own data and re-analysis of previously published findings, we show that standardization of raw data against estimates of both minimum and maximum attainable freezing damage allows for reliable estimation of cold hardiness at the species level and across studies in diverse systems. Furthermore, use of our novel Liquid Nitrogen control produces data commensurate across studies and enhances the consistency and realism of the electrolyte leakage method, especially for very cold hardy samples. CONCLUSION Future leakage studies that relativize data against minimum and maximum leakage and that employ our updated Liquid Nitrogen control will contribute generalizable, repeatable, and realistic data to the existing body of cold hardiness research in woody plants. Data from studies conducted using a Liquid Nitrogen (and not an autoclaving) control can still be compared to previously published data, especially when raw data are standardized using the best-performing approach among those we assessed. Electrolyte leakage of woody twigs emerges as a useful technique for quickly assessing the probability of tissue death in response to freezing in dormant plants. Differential thermal analysis may provide different and complementary information on cold hardiness.
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standardization of electrolyte leakage data and a novel Liquid Nitrogen control improve measurements of cold hardiness in woody tissue
Plant Methods, 2021Co-Authors: Alisson Pacheco Kovaleski, Jake J GrossmanAbstract:A variety of basic and applied research programs in plant biology require the accurate and reliable determination of plant tissue cold hardiness. Over the past 50 years, the electrolyte leakage method has emerged as a popular and practical method for quantifying the amount of damage inflicted on plant tissue by exposure to freezing temperatures. Numerous approaches for carrying out this method and analyzing the resultant data have emerged. These include multiple systems for standardizing and modeling raw electrolyte leakage data and multiple protocols for boiling or autoclaving samples in order to maximize leakage as a positive control. We compare four different routines for standardization of leakage data and assess a novel control method—immersion in Liquid Nitrogen in lieu of traditional autoclaving—and apply them to woody twigs collected from 12 maple (Acer) species in early spring. We compare leakage data from these samples using each of four previously published forms of data analysis and autoclaving vs. Liquid Nitrogen controls and validate each of these approaches against visual estimates of freezing damage and differential thermal analysis. Through presentation of our own data and re-analysis of previously published findings, we show that standardization of raw data against estimates of both minimum and maximum attainable freezing damage allows for reliable estimation of cold hardiness at the species level and across studies in diverse systems. Furthermore, use of our novel Liquid Nitrogen control produces data commensurate across studies and enhances the consistency and realism of the electrolyte leakage method, especially for very cold hardy samples. Future leakage studies that relativize data against minimum and maximum leakage and that employ our updated Liquid Nitrogen control will contribute generalizable, repeatable, and realistic data to the existing body of cold hardiness research in woody plants. Data from studies conducted using a Liquid Nitrogen (and not an autoclaving) control can still be compared to previously published data, especially when raw data are standardized using the best-performing approach among those we assessed. Electrolyte leakage of woody twigs emerges as a useful technique for quickly assessing the probability of tissue death in response to freezing in dormant plants. Differential thermal analysis may provide different and complementary information on cold hardiness.
Zhongwei Huang - One of the best experts on this subject based on the ideXlab platform.
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non contaminating cryogenic fluid access to high temperature resources Liquid Nitrogen fracturing in a lab scale enhanced geothermal system
Renewable Energy, 2021Co-Authors: Ruiyue Yang, Chunyang Hong, Wei Liu, Tianyu Wang, Zhongwei HuangAbstract:Abstract Hot dry rock (HDR) geothermal energy exploitation is essential to meet the energy demand and achieve low-carbon solutions. Creation of complex fracture networks in HDR by hydraulic fracturing to enhance the thermodynamic efficiency and heat production is significant. However, the economic and environmental burden of freshwater sourcing, transportation, and treatment raises concerns. Here, we investigate Liquid Nitrogen, an environmental-friendly and super-cooling fluid, as an alternative fracturing fluid for potential applications in Enhanced Geothermal System. We studied the fracturing performances of Liquid Nitrogen in high-temperature granites under true triaxial-confining stresses. Cryo-scanning electron microscopy and 3D X-ray micro-computed tomography were applied to illuminate the fracture-network patterns. Results show that Liquid Nitrogen fracturing exhibits the lowest breakdown pressure compared with water fracturing and Nitrogen gas fracturing. The fracture morphology displays a 3-D volumetric pattern comprised of branched fractures and thermally-stimulated zones. Higher fluid-rock temperature difference and lower stress anisotropy cause more complex fracture networks. This study, for the first time, shows potential benefits of Liquid Nitrogen fracturing in high-temperature crystalline rocks, paving the road towards waterless fracturing in Enhanced Geothermal System. It is expected to provide a viable alternative for the sustainable development of deep geothermal resources in an efficient and clean way.
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experimental study of thermal crack characteristics on hot dry rock impacted by Liquid Nitrogen jet
Geothermics, 2018Co-Authors: Shikun Zhang, Tianyu Wang, Zhongwei Huang, Hongyuan Zhang, Zhaoquan Guo, Chengcheng Zhang, Chao XiongAbstract:Abstract Liquid Nitrogen jet fracturing is a novel stimulation technology, which is expected to be suitable for hot dry rock (HDR) reservoirs. Due to the large temperature difference between hot rock and cryogenic fluid, a great number of thermal cracks would be created during fracturing process, which is conductive to improve the penetration capacity of formation. In this study, a set of experiments were conducted to investigate the characteristics of thermal cracks. In these experiments, granite specimens with temperatures ranging from 200 ℃ to 300 ℃ were impacted by the low-pressure Liquid Nitrogen jet. The complexity and connectivity of cracks were quantitatively analyzed by a fractal method. The permeability and ultrasonic velocity of the granite specimens were tested in order to evaluate the damage conditions caused by thermal stress. Additionally, scanning electron microscope was adopted to analyze the microscopic characteristics of the thermal cracks. The results show that the heating process has a slight effect on thermal-crack generation compared with the Liquid-Nitrogen impact. The cracks mainly concentrate in the region near the impingement surface, due to the large temperature gradient there. The impacted rock breaks as the effects of tensile stress and shear stress. With an increase of initial rock temperature, the number of thermal cracks increases, and a more complex crack-network is formed in each specimen. Transient pulse evaluation and ultrasonic velocity measurements indicate that the impact of Liquid Nitrogen jet can improve the permeability and cause the damage of hot rock noticeably. This study demonstrates the important effect of thermal stress on crack generation during Liquid Nitrogen jet fracturing for HDR reservoirs, and the results shed light on the exploitation of HDR energy.
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evaluation of coal damage and cracking characteristics due to Liquid Nitrogen cooling on the basis of the energy evolution laws
Journal of Natural Gas Science and Engineering, 2016Co-Authors: Gensheng Li, Zhongwei HuangAbstract:Abstract Liquid Nitrogen used as fracturing fluid can significantly reduce reservoir temperature and cause damage and cracking effect on rock because of its extremely cryogenic characteristic. To investigate the cryogenic damage and cracking characteristics of Liquid Nitrogen on coal, coal samples were cool-treated with Liquid Nitrogen. Then, uniaxial compression tests were conducted on the cool-treated coal samples and intact samples (not cool-treated). The energy evaluation laws of intact and cool-treated samples during deformation and failure were compared. Results showed that Liquid Nitrogen cooling was able to improve the initial damage degree of coal, thereby leading to a significant effect on the energy evolution laws of coal. The elastic energy, dissipated energy, and absorbed energy of cool-treated samples were less than those of intact samples when the samples ruptured. During the initial loading stage, the ratio of dissipated energy of cool-treated samples was greater than that of intact samples. However, as the coal samples were about to rupture, the ratio of dissipated energy of intact samples was greater than that of cool-treated samples. The change in energy evolution laws of coal was mainly caused by the growth of micro-cracks inside coal, which can reflect the damage characteristics due to Liquid Nitrogen cooling. After Liquid Nitrogen cooling, the amount of micro-cracks inside coal increased, resulting in the deterioration of mechanical properties and the improvement of the fracturing performance in coalbed methane.
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experiment of coal damage due to super cooling with Liquid Nitrogen
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Chengzheng Cai, Zhongwei Huang, Shouceng Tian, Zhonghou ShenAbstract:Abstract The most distinct feature of Liquid Nitrogen fracturing is the sharp reduction in temperature around the rock when Liquid Nitrogen comes in contact with the reservoir. This condition induces thermal stress inside rocks, which then become damaged. To investigate the effect of Liquid Nitrogen super-cooling on coal damage, permeability tests were conducted on the same coal samples before and after cooling. Meanwhile, uniaxial compression tests were performed on intact and cool-treated coal samples. Experimental results showed that Liquid Nitrogen super-cooling not only induces thermal cracks on coal surface, but also causes coal cracking along macro-fractures on the surface of samples. Coal permeability was increased by 48.89%–93.55% because of Liquid Nitrogen super-cooling. The compressive strength of cool-treated coal samples decreased by 16.18%–33.74% compared with intact samples, and the former presented more obvious brittle failure characteristics. In the uniaxial compression tests, the numbers of points in which stress induced a sharp decrease in the stress–strain curves of cool-treated samples were more than those in the intact samples, which indicates enhanced micro-fracturing in the cool-treated samples. Thus, we can conclude that Liquid Nitrogen super-cooling may cause coal damage and fracture failure, consequently promoting the formation of fracture networks and improving stimulation performance because of the generation of thermal fractures.
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experimental study of the effect of Liquid Nitrogen cooling on rock pore structure
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Chengzheng Cai, Zhongwei Huang, Shouceng Tian, Zhonghou Shen, Jiangwei WeiAbstract:Abstract As Liquid Nitrogen brings about thermal damage to rock when it comes into contact with a reservoir, it can be used as a fracturing fluid under proper engineering conditions. To investigate the effects of Liquid Nitrogen cooling on rock pore structure, sandstone, marble, and shale samples were cooled with Liquid Nitrogen under dried and saturated conditions, respectively. The samples were examined before and after treatment using scanning electron microscopy and nuclear magnetic resonance. The results show that there are three main changes in the rock pore structure when the samples were cooled by Liquid Nitrogen: (i) a reduction in the number and volume of the pores, (ii) an expansion of the micro-fissures (micro-pores), and (iii) an increase in the pore scale. More specifically, the pore structure of dry sandstone showed a reduction in the number and volume of pores; dry and saturated marble and shale presented expansion of their micro-fissures (micro-pores); and the pore scale was increased in the saturated sandstone (to the extent that macro-cracks were observable in the surface). The changes in the rock pore structures were mainly caused by thermal stress and frost force, and the characteristics of the variations were influenced by the type of rock and water content. Liquid Nitrogen cooling increased the fracture degree inside the rocks, especially for shale samples. Cracks appeared along the joints, which were effective in producing micro-cracks on the walls of major fractures. This therefore increased the stimulation reservoir volume during the fracturing process.
Alisson Pacheco Kovaleski - One of the best experts on this subject based on the ideXlab platform.
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standardization of electrolyte leakage data and a novel Liquid Nitrogen control improve measurements of cold hardiness in woody tissue
Plant Methods, 2021Co-Authors: Alisson Pacheco Kovaleski, Jake J GrossmanAbstract:BACKGROUND A variety of basic and applied research programs in plant biology require the accurate and reliable determination of plant tissue cold hardiness. Over the past 50 years, the electrolyte leakage method has emerged as a popular and practical method for quantifying the amount of damage inflicted on plant tissue by exposure to freezing temperatures. Numerous approaches for carrying out this method and analyzing the resultant data have emerged. These include multiple systems for standardizing and modeling raw electrolyte leakage data and multiple protocols for boiling or autoclaving samples in order to maximize leakage as a positive control. We compare four different routines for standardization of leakage data and assess a novel control method-immersion in Liquid Nitrogen in lieu of traditional autoclaving-and apply them to woody twigs collected from 12 maple (Acer) species in early spring. We compare leakage data from these samples using each of four previously published forms of data analysis and autoclaving vs. Liquid Nitrogen controls and validate each of these approaches against visual estimates of freezing damage and differential thermal analysis. RESULTS Through presentation of our own data and re-analysis of previously published findings, we show that standardization of raw data against estimates of both minimum and maximum attainable freezing damage allows for reliable estimation of cold hardiness at the species level and across studies in diverse systems. Furthermore, use of our novel Liquid Nitrogen control produces data commensurate across studies and enhances the consistency and realism of the electrolyte leakage method, especially for very cold hardy samples. CONCLUSION Future leakage studies that relativize data against minimum and maximum leakage and that employ our updated Liquid Nitrogen control will contribute generalizable, repeatable, and realistic data to the existing body of cold hardiness research in woody plants. Data from studies conducted using a Liquid Nitrogen (and not an autoclaving) control can still be compared to previously published data, especially when raw data are standardized using the best-performing approach among those we assessed. Electrolyte leakage of woody twigs emerges as a useful technique for quickly assessing the probability of tissue death in response to freezing in dormant plants. Differential thermal analysis may provide different and complementary information on cold hardiness.
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standardization of electrolyte leakage data and a novel Liquid Nitrogen control improve measurements of cold hardiness in woody tissue
Plant Methods, 2021Co-Authors: Alisson Pacheco Kovaleski, Jake J GrossmanAbstract:A variety of basic and applied research programs in plant biology require the accurate and reliable determination of plant tissue cold hardiness. Over the past 50 years, the electrolyte leakage method has emerged as a popular and practical method for quantifying the amount of damage inflicted on plant tissue by exposure to freezing temperatures. Numerous approaches for carrying out this method and analyzing the resultant data have emerged. These include multiple systems for standardizing and modeling raw electrolyte leakage data and multiple protocols for boiling or autoclaving samples in order to maximize leakage as a positive control. We compare four different routines for standardization of leakage data and assess a novel control method—immersion in Liquid Nitrogen in lieu of traditional autoclaving—and apply them to woody twigs collected from 12 maple (Acer) species in early spring. We compare leakage data from these samples using each of four previously published forms of data analysis and autoclaving vs. Liquid Nitrogen controls and validate each of these approaches against visual estimates of freezing damage and differential thermal analysis. Through presentation of our own data and re-analysis of previously published findings, we show that standardization of raw data against estimates of both minimum and maximum attainable freezing damage allows for reliable estimation of cold hardiness at the species level and across studies in diverse systems. Furthermore, use of our novel Liquid Nitrogen control produces data commensurate across studies and enhances the consistency and realism of the electrolyte leakage method, especially for very cold hardy samples. Future leakage studies that relativize data against minimum and maximum leakage and that employ our updated Liquid Nitrogen control will contribute generalizable, repeatable, and realistic data to the existing body of cold hardiness research in woody plants. Data from studies conducted using a Liquid Nitrogen (and not an autoclaving) control can still be compared to previously published data, especially when raw data are standardized using the best-performing approach among those we assessed. Electrolyte leakage of woody twigs emerges as a useful technique for quickly assessing the probability of tissue death in response to freezing in dormant plants. Differential thermal analysis may provide different and complementary information on cold hardiness.
Chengzheng Cai - One of the best experts on this subject based on the ideXlab platform.
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Numerical Investigation into the Distributions of Temperature and Stress around Wellbore during the Injection of Cryogenic Liquid Nitrogen into Hot Dry Rock Reservoir
'Hindawi Limited', 2021Co-Authors: Keda Ren, Chengzheng CaiAbstract:Cryogenic Liquid Nitrogen fracturing is expected to provide an effective stimulation method for hot dry rock reservoirs to increase heat production. This paper establishes a three-dimensional model to calculate the distributions of temperature and stress of the reservoir rock when Liquid Nitrogen is injected into the wellbore. The sensitivity of different parameters and water fracturing to the stress state is studied. The results indicate that when Liquid Nitrogen is injected into the bottom of well, a huge heat exchange occurs on the rock surface, which generates great thermal stress on the fluid-solid interface, and the value of thermal stress exceeds the tensile strength of rock. For the effect of parameters, the primitive temperature of the rock has a significant impact on the value of maximum principal stress. The pressure drop and ambient pressure affect the thermal stress slightly. At the same time, a series of experiments are conducted to validate the effect of thermal stress induced by Liquid Nitrogen injection on the rock fracture. As the temperature rises, the shale samples are broken more severely at the action of thermal stress. Thus, the study of Liquid Nitrogen fracturing provides a scientific and effective method for geothermal exploitation
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Experimental research on rock fracture failure characteristics under Liquid Nitrogen cooling conditions
Elsevier, 2018Co-Authors: Feng Gao, Chengzheng Cai, Yugui YangAbstract:As Liquid Nitrogen is injected into a wellbore as fracturing fluid, it can rapidly absorb heat from warmer rock and generate cryogenic condition in downhole region. This will alter the physical conditions of reservoir rocks and further affect rock failure characteristics. To investigate rock fracture failure characteristics under Liquid Nitrogen cooling conditions, the fracture features of four types of sandstones and one type of marble were tested on original samples (the sample without any treatment) and cryogenic samples (the samples just taken out from the Liquid Nitrogen), respectively. The differences between original samples and cryogenic samples in load-displacement curves, fracture toughness, energy evolution and the crack density of ruptured samples were compared and analyzed. The results showed that at elastic deformation stage, cryogenic samples presented less plastic deformation and more obvious brittle failure characteristics than original ones. The average fracture toughness of cryogenic samples was 10.47%–158.33% greater than that of original ones, indicating that the mechanical strength of rocks used were enhanced under cooling conditions. When the samples ruptured, the cryogenic ones were required to absorb more energy and reserve more elastic energy. In general, the fracture degree of cryogenic samples was higher than that of original ones. As the samples were entirely fractured, the crack density of cryogenic samples was about 536.67% at most larger than that of original ones. This indicated that under Liquid Nitrogen cooling conditions, the stimulation reservoir volume is expected to be improved during fracturing. This work could provide a reference to the research on the mechanical properties and fracture failure of rock during Liquid Nitrogen fracturing. Keywords: Liquid Nitrogen, Fracturing, Cooling conditions, Rock, Fracture failur
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experiment of coal damage due to super cooling with Liquid Nitrogen
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Chengzheng Cai, Zhongwei Huang, Shouceng Tian, Zhonghou ShenAbstract:Abstract The most distinct feature of Liquid Nitrogen fracturing is the sharp reduction in temperature around the rock when Liquid Nitrogen comes in contact with the reservoir. This condition induces thermal stress inside rocks, which then become damaged. To investigate the effect of Liquid Nitrogen super-cooling on coal damage, permeability tests were conducted on the same coal samples before and after cooling. Meanwhile, uniaxial compression tests were performed on intact and cool-treated coal samples. Experimental results showed that Liquid Nitrogen super-cooling not only induces thermal cracks on coal surface, but also causes coal cracking along macro-fractures on the surface of samples. Coal permeability was increased by 48.89%–93.55% because of Liquid Nitrogen super-cooling. The compressive strength of cool-treated coal samples decreased by 16.18%–33.74% compared with intact samples, and the former presented more obvious brittle failure characteristics. In the uniaxial compression tests, the numbers of points in which stress induced a sharp decrease in the stress–strain curves of cool-treated samples were more than those in the intact samples, which indicates enhanced micro-fracturing in the cool-treated samples. Thus, we can conclude that Liquid Nitrogen super-cooling may cause coal damage and fracture failure, consequently promoting the formation of fracture networks and improving stimulation performance because of the generation of thermal fractures.
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experimental study of the effect of Liquid Nitrogen cooling on rock pore structure
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Chengzheng Cai, Zhongwei Huang, Shouceng Tian, Zhonghou Shen, Jiangwei WeiAbstract:Abstract As Liquid Nitrogen brings about thermal damage to rock when it comes into contact with a reservoir, it can be used as a fracturing fluid under proper engineering conditions. To investigate the effects of Liquid Nitrogen cooling on rock pore structure, sandstone, marble, and shale samples were cooled with Liquid Nitrogen under dried and saturated conditions, respectively. The samples were examined before and after treatment using scanning electron microscopy and nuclear magnetic resonance. The results show that there are three main changes in the rock pore structure when the samples were cooled by Liquid Nitrogen: (i) a reduction in the number and volume of the pores, (ii) an expansion of the micro-fissures (micro-pores), and (iii) an increase in the pore scale. More specifically, the pore structure of dry sandstone showed a reduction in the number and volume of pores; dry and saturated marble and shale presented expansion of their micro-fissures (micro-pores); and the pore scale was increased in the saturated sandstone (to the extent that macro-cracks were observable in the surface). The changes in the rock pore structures were mainly caused by thermal stress and frost force, and the characteristics of the variations were influenced by the type of rock and water content. Liquid Nitrogen cooling increased the fracture degree inside the rocks, especially for shale samples. Cracks appeared along the joints, which were effective in producing micro-cracks on the walls of major fractures. This therefore increased the stimulation reservoir volume during the fracturing process.
Zhonghou Shen - One of the best experts on this subject based on the ideXlab platform.
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experiment of coal damage due to super cooling with Liquid Nitrogen
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Chengzheng Cai, Zhongwei Huang, Shouceng Tian, Zhonghou ShenAbstract:Abstract The most distinct feature of Liquid Nitrogen fracturing is the sharp reduction in temperature around the rock when Liquid Nitrogen comes in contact with the reservoir. This condition induces thermal stress inside rocks, which then become damaged. To investigate the effect of Liquid Nitrogen super-cooling on coal damage, permeability tests were conducted on the same coal samples before and after cooling. Meanwhile, uniaxial compression tests were performed on intact and cool-treated coal samples. Experimental results showed that Liquid Nitrogen super-cooling not only induces thermal cracks on coal surface, but also causes coal cracking along macro-fractures on the surface of samples. Coal permeability was increased by 48.89%–93.55% because of Liquid Nitrogen super-cooling. The compressive strength of cool-treated coal samples decreased by 16.18%–33.74% compared with intact samples, and the former presented more obvious brittle failure characteristics. In the uniaxial compression tests, the numbers of points in which stress induced a sharp decrease in the stress–strain curves of cool-treated samples were more than those in the intact samples, which indicates enhanced micro-fracturing in the cool-treated samples. Thus, we can conclude that Liquid Nitrogen super-cooling may cause coal damage and fracture failure, consequently promoting the formation of fracture networks and improving stimulation performance because of the generation of thermal fractures.
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experimental study of the effect of Liquid Nitrogen cooling on rock pore structure
Journal of Natural Gas Science and Engineering, 2014Co-Authors: Chengzheng Cai, Zhongwei Huang, Shouceng Tian, Zhonghou Shen, Jiangwei WeiAbstract:Abstract As Liquid Nitrogen brings about thermal damage to rock when it comes into contact with a reservoir, it can be used as a fracturing fluid under proper engineering conditions. To investigate the effects of Liquid Nitrogen cooling on rock pore structure, sandstone, marble, and shale samples were cooled with Liquid Nitrogen under dried and saturated conditions, respectively. The samples were examined before and after treatment using scanning electron microscopy and nuclear magnetic resonance. The results show that there are three main changes in the rock pore structure when the samples were cooled by Liquid Nitrogen: (i) a reduction in the number and volume of the pores, (ii) an expansion of the micro-fissures (micro-pores), and (iii) an increase in the pore scale. More specifically, the pore structure of dry sandstone showed a reduction in the number and volume of pores; dry and saturated marble and shale presented expansion of their micro-fissures (micro-pores); and the pore scale was increased in the saturated sandstone (to the extent that macro-cracks were observable in the surface). The changes in the rock pore structures were mainly caused by thermal stress and frost force, and the characteristics of the variations were influenced by the type of rock and water content. Liquid Nitrogen cooling increased the fracture degree inside the rocks, especially for shale samples. Cracks appeared along the joints, which were effective in producing micro-cracks on the walls of major fractures. This therefore increased the stimulation reservoir volume during the fracturing process.