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Shoujian Peng - One of the best experts on this subject based on the ideXlab platform.
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structural evolution characteristics of middle high rank Coal samples subjected to high voltage electrical pulse
Energy & Fuels, 2018Co-Authors: Jiang Xu, Yihan Wang, Xiangliang Zhang, Shoujian PengAbstract:High-voltage electrical pulse (HVEP) technology has been proposed to increase the gas production of low-permeability Coal reservoirs in recent years. In this study, we investigated the variation characteristics of the pore structure of Coal samples by combining scanning electrical microscopy with mercury intrusion porosimetry analysis, to better understand the structural evolution characteristics of middle–high rank Coal subjected to HVEP. Furthermore, changes in the chemical structure of the Coal samples before and after HVEP treatment were investigated by Fourier transform infrared spectroscopy analysis. The results show that, under the action of HVEP, both anthracite and bituminous Coal samples can be crushed into many small pieces. Because the conductivity of anthracite Coal samples is better than that of bituminous Coal samples, the average breakdown voltage of anthracite Coal samples is lower than that of bituminous Coal samples. It was found that the greater the breakdown voltage, the more the numb...
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Structural Evolution Characteristics of Middle–High Rank Coal Samples Subjected to High-Voltage Electrical Pulse
Energy & Fuels, 2018Co-Authors: Fazhi Yan, Xiangliang Zhang, Baiquan Lin, Wang Yihan, Shoujian PengAbstract:High-voltage electrical pulse (HVEP) technology has been proposed to increase the gas production of low-permeability Coal reservoirs in recent years. In this study, we investigated the variation characteristics of the pore structure of Coal samples by combining scanning electrical microscopy with mercury intrusion porosimetry analysis, to better understand the structural evolution characteristics of middle–high rank Coal subjected to HVEP. Furthermore, changes in the chemical structure of the Coal samples before and after HVEP treatment were investigated by Fourier transform infrared spectroscopy analysis. The results show that, under the action of HVEP, both anthracite and bituminous Coal samples can be crushed into many small pieces. Because the conductivity of anthracite Coal samples is better than that of bituminous Coal samples, the average breakdown voltage of anthracite Coal samples is lower than that of bituminous Coal samples. It was found that the greater the breakdown voltage, the more the numb...
Fazhi Yan - One of the best experts on this subject based on the ideXlab platform.
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Structural Evolution Characteristics of Middle–High Rank Coal Samples Subjected to High-Voltage Electrical Pulse
Energy & Fuels, 2018Co-Authors: Fazhi Yan, Xiangliang Zhang, Baiquan Lin, Wang Yihan, Shoujian PengAbstract:High-voltage electrical pulse (HVEP) technology has been proposed to increase the gas production of low-permeability Coal reservoirs in recent years. In this study, we investigated the variation characteristics of the pore structure of Coal samples by combining scanning electrical microscopy with mercury intrusion porosimetry analysis, to better understand the structural evolution characteristics of middle–high rank Coal subjected to HVEP. Furthermore, changes in the chemical structure of the Coal samples before and after HVEP treatment were investigated by Fourier transform infrared spectroscopy analysis. The results show that, under the action of HVEP, both anthracite and bituminous Coal samples can be crushed into many small pieces. Because the conductivity of anthracite Coal samples is better than that of bituminous Coal samples, the average breakdown voltage of anthracite Coal samples is lower than that of bituminous Coal samples. It was found that the greater the breakdown voltage, the more the numb...
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Effects of different conductive ions on pore-structure evolution of medium- and High-Rank Coal bodies induced by electric pulses
Fuel, 1Co-Authors: Wang Yihan, Baiquan Lin, Wei Yang, Fazhi YanAbstract:Abstract Electric pulse fracturing technology is a new type of Coal seam fracturing and permeability increasing technology based on high-pressure shock wave technology. Compared with conventional technology, electric pulse fracturing has the advantages of a higher energy efficiency, less environmental pollution, and a shorter fracturing time, but having the disadvantages of rapid energy loss and a small fracture radius. To reduce the energy loss of electric pulses and increase the fracture radius, the experimental system of high-voltage electric pulse was employed in this study. The effects of NaCl, CaCl2, and AlCl3 conductive ions on the evolution of the pore structure induced by electric pulses were examined for medium- and High-Rank Coal bodies. The experimental results indicated the adsorption capacity of Coal for ions was positively correlated with the valence of the cations and the soaking time, and the amount of ions adsorbed was larger when the solution was more alkaline. Amounts of ions adsorbed onto the Coal surface decreased in the following order Al3+ > Ca2+ > Na+. After the treatment, the conductivity of the Coal was significantly improved, making the plasma channel in the Coal body more fully developed in the process of high-voltage electric pulse impaction, thus reducing significantly the breakdown voltage of the Coal samples. Additionally, tthe total pore volume, total specific surface area, porosity, and average pore diameter of the treated Coal increased and that the percentages of macropores and mesopores increased, indicating that the pore structure of Coal samples is significantly improved.
Shuxun Sang - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of High-Rank Coal structure parallel and perpendicular to the bedding plane via NMR and X-ray CT
Petroleum Science, 2020Co-Authors: Shiqi Liu, Shuxun Sang, Huihuang FangAbstract:Pores and fractures and their connectivity play a significant role in Coalbed methane production. To investigate the growth characteristics and connectivity of pores and fractures in Coal parallel and perpendicular to the bedding plane, the pores and fractures of High-Rank Coal samples collected from the southern Qinshui Basin were measured by low-field nuclear magnetic resonance, X-ray-computed tomography and field emission scanning electron microscopy. Then, the determinants of their connectivity were further discussed. The results show that the High-Rank Coal samples have similar pore size distributions both parallel and perpendicular to the bedding plane. They primarily contain mesopores (2–50 nm in width), followed by macrospores (> 50 nm in width). The research indicated that the High-Rank Coal connectivity parallel to the bedding plane is significantly better than that perpendicular to the bedding plane. The connectivity of High-Rank Coal is mainly determined by throats, and the orientation of the pores and fractures. The two connectivity modes in High-Rank Coal are “pore connectivity,” in which the throats are mainly pores with a low coordination number, and “microfissure connectivity”, in which the throats are mainly microfissures with a high coordination number.
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Three-dimensional digitalization modeling characterization of pores in High-Rank Coal in the southern Qinshui basin
Geosciences Journal, 2018Co-Authors: Shiqi Liu, Shuxun Sang, Xin Wang, Tian WangAbstract:Pore connectivity is an important property of Coal. To explore the connectivity of pore-fractures in terms of macropores and mesopores in High-Rank Coal, two Coal samples collected from the Coal seam #3 in the southern Qinshui basin were selected. A pore-fracture network model of High-Rank Coal on the nanometer (10–100 nm) to micrometer (0.1–10 μm) scale is constructed, and key parameters are extracted using the 3D (three-dimensional) digital spatial characterization based on 3D scanning with FIB-SEM (Focused Ion Beam Scanning Electron Microscopy). Then, the connectivity of the pore-fractures and the contribution of pores with different genetic types to the connectivity of the High-Rank Coal are confirmed. The results show that the pores and throats of High-Rank Coal in Coal seam #3 in the southern Qinshui basin are very narrow, with predominant mesopores < 50 nm in width. The tortuosity of the Coal samples is low, and the cross-section is predominantly square and triangular in shape, which means that the capillary resistance is small. The connectivity of the pores is poor, and mesopores play an important role in the pore connectivity. Linear differential shrinkage pores are the main connected pores on the nanometer scale and communicate with irregularly rounded and elliptic differential shrinkage pores, secondary pores, and mineral pores. The types and contents of the minerals in Coals determine the morphological characteristics and degree of development of the differential shrinkage pores, and have an important influence on the pore connectivity in High-Rank Coal. The content of quartz determines the degree of development of the linear differential shrinkage pores, and is the primary reasons for the differences in the connectivity of the two samples.
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Experimental Study of the Reactions of Supercritical CO2 and Minerals in High-Rank Coal under Formation Conditions
Energy & Fuels, 2018Co-Authors: Shuxun Sang, Tian Wang, Shiqi Liu, Wang Wenfeng, Huihuang FangAbstract:This study investigates the influence of supercritical CO2 (scCO2) injection on minerals in High-Rank Coal under the temperature, pressure, and hydrologic conditions of a deep Coalbed. A typical High-Rank Coal reservoir in the Qinshui basin, the #3 Coal seam, is the focus of this research. A Coal–scCO2 geochemical reaction experiment is conducted to simulate the 2000 m burial depth of the Coal seam. Field emission scanning electron microscopy is used to determine the locations of specific minerals and observe the effects of scCO2–H2O on these minerals at the micrometer scale. These results are combined with X-ray diffraction and inductively coupled plasma-atomic emission spectrometry and mass spectrometry analysis results, and the effects of the scCO2–H2O fluid on minerals in the High-Rank Coal over a short period are discussed. In addition, the influence on Coal reservoir structure was studied based on intrusive mercury and liquid nitrogen adsorption experiment. The results suggest that instantaneous CO2...
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fib sem and x ray ct characterization of interconnected pores in high rank Coal formed from regional metamorphism
Journal of Petroleum Science and Engineering, 2017Co-Authors: Shuxun Sang, Geoff Wang, Yi Du, Wenfeng Wang, Tian WangAbstract:Pores in Coal and their connectivity are important properties of Coal, providing network or channels for gas storage and migration within Coal, e.g. during the Coalbed methane (CBM) recovery. To investigate the growth characteristics and genetic types of pores in Coal in terms of macropore and mesopore, the pores of a High-Rank Coal were measured by various techniques such as the mercury intrusion method, nitrogen adsorption, focused ion beam scanning electron microscopy (FIB-SEM), and X-ray micro-CT (Computed Tomography). Two High-Rank Coals formed from regional metamorphism collected from the southern Qinshui basin were selected. The FIB-SEM and X-ray micro-CT provides detailed experimental information for development of a three dimensional (3D) pore network model, which was further used to characterize the pore connectivity. Volume percent of pores of these High-Rank Coals are dominated by mesopores of approximately 10–50 nm in width, and then followed by micropores, along with the smallest volume percent of macropores. The connectivity within this High-Rank Coal was mesopore-dominated pore network. Electron microscopy observations further revealed there are Coalification-related pores and mineral-related pores in the High-Rank Coal. The Coalification-related pores can be classified as secondary gas pores in organic matter and shrinkage-induced pores around quartz and clay minerals; and the mineral-related pores are developed within minerals, and can be classified as dissolution-created pores and intercrystalline pores. The secondary gas pores are macropores and have poor connectivity. The mineral-related pores can be both macropores and mesopores, and have little influence on pore connectivity due to small content of carbonate minerals in these samples. Under electron microscopy, the shrinkage-induced pores are mainly mesopores. The regional metamorphism, with a high abnormal old thermal field in the research area, is the precondition of the formation of the shrinkage-induced pores. The quartz and clay minerals in the Coal provide different formation conditions and hence form different shapes of the shrinkage-induced pores. The Coal samples include a large number of shrinkage-induced pores that act as the interconnected pores in the Coal and exhibit good connectivity. The quartz and clay minerals play a significant role in developing the interconnected pores in the High-Rank Coal formed from regional metamorphism.
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growth characteristics and genetic types of pores and fractures in a high rank Coal reservoir of the southern qinshui basin
Ore Geology Reviews, 2015Co-Authors: Shuxun SangAbstract:Abstract In this paper, field investigations such as underground Coal wall observations and core log analyses have been conducted and combined with laboratory experiments such as the mercury intrusion method, the low-temperature liquid nitrogen adsorption method, photomicrography and scanning electron microscopy (SEM) to study the growth characteristics and genetic types of pores, micro-fractures and macro-fractures in Coal bed #3 of the southern Qinshui basin, and to analyze the connections between pores and fractures. The results show that this Coal bed prioritizes micropores and transition pores (i.e., intermolecular pores and residual gas pores), followed by macropores (i.e., plant tissue pores and intergranular pores). Mesopores (metamorphic gas pores) do not develop. Moreover, Coal bed #3 contains a considerable number of closed and semi-closed pores. It develops two groups of exogenous fractures and cleats (i.e., endogenous fractures) and the formation is controlled by a paleotectonic stress field. The cleats have a relatively small density and are usually filled by calcite and other minerals, which are harmful to the permeability of the Coal bed. Shrinkage micro-fissures, static pressure micro-fissures, structure micro-fissures and ultramicroscopic fissures are all widely developed and are not filled by minerals. Micro-fissures are important channels for the connections between pores and cleats. Ultramicroscopic fissures cut through some gas pores. These two types of fractures improve the permeability and connectivity of the Coal bed and are important links between different sizes of pores and fractures. There are three levels of connections between pores and fractures, namely, connections between ultramicrostructures and microstructures, connections between microstructures and cleats and connections between cleats and exogenous fractures.
Wang Yihan - One of the best experts on this subject based on the ideXlab platform.
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Structural Evolution Characteristics of Middle–High Rank Coal Samples Subjected to High-Voltage Electrical Pulse
Energy & Fuels, 2018Co-Authors: Fazhi Yan, Xiangliang Zhang, Baiquan Lin, Wang Yihan, Shoujian PengAbstract:High-voltage electrical pulse (HVEP) technology has been proposed to increase the gas production of low-permeability Coal reservoirs in recent years. In this study, we investigated the variation characteristics of the pore structure of Coal samples by combining scanning electrical microscopy with mercury intrusion porosimetry analysis, to better understand the structural evolution characteristics of middle–high rank Coal subjected to HVEP. Furthermore, changes in the chemical structure of the Coal samples before and after HVEP treatment were investigated by Fourier transform infrared spectroscopy analysis. The results show that, under the action of HVEP, both anthracite and bituminous Coal samples can be crushed into many small pieces. Because the conductivity of anthracite Coal samples is better than that of bituminous Coal samples, the average breakdown voltage of anthracite Coal samples is lower than that of bituminous Coal samples. It was found that the greater the breakdown voltage, the more the numb...
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Effects of different conductive ions on pore-structure evolution of medium- and High-Rank Coal bodies induced by electric pulses
Fuel, 1Co-Authors: Wang Yihan, Baiquan Lin, Wei Yang, Fazhi YanAbstract:Abstract Electric pulse fracturing technology is a new type of Coal seam fracturing and permeability increasing technology based on high-pressure shock wave technology. Compared with conventional technology, electric pulse fracturing has the advantages of a higher energy efficiency, less environmental pollution, and a shorter fracturing time, but having the disadvantages of rapid energy loss and a small fracture radius. To reduce the energy loss of electric pulses and increase the fracture radius, the experimental system of high-voltage electric pulse was employed in this study. The effects of NaCl, CaCl2, and AlCl3 conductive ions on the evolution of the pore structure induced by electric pulses were examined for medium- and High-Rank Coal bodies. The experimental results indicated the adsorption capacity of Coal for ions was positively correlated with the valence of the cations and the soaking time, and the amount of ions adsorbed was larger when the solution was more alkaline. Amounts of ions adsorbed onto the Coal surface decreased in the following order Al3+ > Ca2+ > Na+. After the treatment, the conductivity of the Coal was significantly improved, making the plasma channel in the Coal body more fully developed in the process of high-voltage electric pulse impaction, thus reducing significantly the breakdown voltage of the Coal samples. Additionally, tthe total pore volume, total specific surface area, porosity, and average pore diameter of the treated Coal increased and that the percentages of macropores and mesopores increased, indicating that the pore structure of Coal samples is significantly improved.
Baiquan Lin - One of the best experts on this subject based on the ideXlab platform.
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Structural Evolution Characteristics of Middle–High Rank Coal Samples Subjected to High-Voltage Electrical Pulse
Energy & Fuels, 2018Co-Authors: Fazhi Yan, Xiangliang Zhang, Baiquan Lin, Wang Yihan, Shoujian PengAbstract:High-voltage electrical pulse (HVEP) technology has been proposed to increase the gas production of low-permeability Coal reservoirs in recent years. In this study, we investigated the variation characteristics of the pore structure of Coal samples by combining scanning electrical microscopy with mercury intrusion porosimetry analysis, to better understand the structural evolution characteristics of middle–high rank Coal subjected to HVEP. Furthermore, changes in the chemical structure of the Coal samples before and after HVEP treatment were investigated by Fourier transform infrared spectroscopy analysis. The results show that, under the action of HVEP, both anthracite and bituminous Coal samples can be crushed into many small pieces. Because the conductivity of anthracite Coal samples is better than that of bituminous Coal samples, the average breakdown voltage of anthracite Coal samples is lower than that of bituminous Coal samples. It was found that the greater the breakdown voltage, the more the numb...
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Effects of different conductive ions on pore-structure evolution of medium- and High-Rank Coal bodies induced by electric pulses
Fuel, 1Co-Authors: Wang Yihan, Baiquan Lin, Wei Yang, Fazhi YanAbstract:Abstract Electric pulse fracturing technology is a new type of Coal seam fracturing and permeability increasing technology based on high-pressure shock wave technology. Compared with conventional technology, electric pulse fracturing has the advantages of a higher energy efficiency, less environmental pollution, and a shorter fracturing time, but having the disadvantages of rapid energy loss and a small fracture radius. To reduce the energy loss of electric pulses and increase the fracture radius, the experimental system of high-voltage electric pulse was employed in this study. The effects of NaCl, CaCl2, and AlCl3 conductive ions on the evolution of the pore structure induced by electric pulses were examined for medium- and High-Rank Coal bodies. The experimental results indicated the adsorption capacity of Coal for ions was positively correlated with the valence of the cations and the soaking time, and the amount of ions adsorbed was larger when the solution was more alkaline. Amounts of ions adsorbed onto the Coal surface decreased in the following order Al3+ > Ca2+ > Na+. After the treatment, the conductivity of the Coal was significantly improved, making the plasma channel in the Coal body more fully developed in the process of high-voltage electric pulse impaction, thus reducing significantly the breakdown voltage of the Coal samples. Additionally, tthe total pore volume, total specific surface area, porosity, and average pore diameter of the treated Coal increased and that the percentages of macropores and mesopores increased, indicating that the pore structure of Coal samples is significantly improved.