Influence of Temperature on the Structure of Pore–Fracture of Sandstone
Abstract
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Subsidence caused by mining can lead to serious waterlogging problems. In this study, numerical simulation was used to predict both subsidence and waterlogging in a coal-mining area. Changes in the phreatic surface and the area of waterlogging caused by mining subsidence were estimated for various mining scenarios using field measurements and simulation analysis. The results of the numerical simulation for the area of waterlogging caused by existing mining subsidence agreed well with the measure...
The physical, mechanical and morphological properties of a rock undergo substantial change when exposed to the extreme temperatures that are encountered in processes such as nuclear waste disposal, underground coal gasification (UCG) and building fires. An attempt has been made in this article to study the different physical and morphological changes that occur within Indian sandstone due to thermal treatment. Tests were performed on a thermally treated air-cooled and non-cooled set of samples i...
Pore characterization and clay bound water assessment in shale with a combination of NMR and low-pressure nitrogen gas adsorption
Abstract Pore size distribution (PSD) and the volume of clay bound water (CBW) are crucial parameters for gas shale reservoirs formation evaluation. Low-field nuclear magnetic resonance (LF-NMR) has been extensively applied to characterize petrophysical properties of reservoirs. However, limited understanding remains for unconventional shales. Defining NMR T2 cutoff to differentiate CBW from free water is a challenge in shales since conventional approach, such as using centrifuge, is not feasibl...
Abstract Tight sandstone reservoirs typically contain a wide pore throat sizes ranging from the nano-scale to micro-scale, and have complex pore geometry and pore throat structure. Microscopic pore throat structures are the most important factors affecting the macroscopic reservoir quality and fluid flow in tight sandstones. Evaluation and characterization quantitatively the microscopic pore structures, including pore geometry, pore size distribution, and pore connectivity, are of great importan...
Abstract Understanding the pore structure characteristics of tight gas sandstones is the primary purpose of reservoir evaluation and efforts to characterize tight gas transport and storage mechanisms and their controls. Due to the various pore types and multi-scale pore sizes in tight reservoirs, it is essential to combine several techniques to characterize pore structure. Scanning electron microscopy (SEM), nitrogen gas adsorption (N2GA), mercury intrusion porosimetry (MIP) and nuclear magnetic...
Abstract To study the fracture toughness of sandstone, this study investigated the influence of temperature on the mixed-mode (I + II) and mode-II fracture toughness of sandstone using semi-circular bend (SCB) specimens. The results showed that temperatures above 500 °C significantly influenced mixed-mode (I + II) and mode-II fracture behavior. A comparison of experimental results with pure mode-I fracture toughness showed that the impact of temperature variations on the mixed-mode (I + II) and ...
Influence of fluid exposure on surface chemistry and pore-fracture morphology of various rank coals: implications for methane recovery and CO2 storage
The surface chemistry and pore-fracture morphology of coals are critical to the process of CO2 sequestration in coal seams with enhanced coalbed methane (CH4) recovery (CO2-ECBM). To assess the influence of deionized water–CO2 mixture (DH2O–CO2) exposure on these properties, the interaction of DH2O–CO2 with three rank coals, i.e., sub-bituminous coal (SBC), high volatile bituminous coal (HVBC), and anthracite, was conducted on a dynamic supercritical fluid extraction system with a temperature of...
Type and Size Distribution of Nanoscale Pores in Tight Gas Sandstones: A Case Study on Lower Cretaceous Shahezi Formation in Songliao Basin of NE China
Experimental investigation on triaxial mechanical and permeability behavior of sandstone after exposure to different high temperature treatments
Abstract Geothermal energy offers great advantages in cost, reliability and environmental friendliness compared with conventional fossil fuels; geothermal energy is recommended and has been identified as a renewable and alternative energy source. Two of the pre-requisites for the exploitation of geothermal energy are reservoir and cap rock, and the mechanical properties and permeability behavior of reservoir and cap rock have a great influence on the exploitation of geothermal energy. This study...
Comparisons of SEM, Low-Field NMR, and Mercury Intrusion Capillary Pressure in Characterization of the Pore Size Distribution of Lacustrine Shale: A Case Study on the Dongying Depression, Bohai Bay Basin, China
This work investigates the use of scanning electron microscopy (SEM), low-field nuclear magnetic resonance (NMR) relaxation, and mercury intrusion capillary pressure (MICP) to reveal the pore size distribution (PSD) characteristics of shales. The comparisons were conducted using six shale samples from the Dongying Depression, Bohai Bay Basin, China. The results show that SEM can effectively reveal the PSD of shale but cannot detect micropores (<100 nm in diameter) smaller than the imaging resolu...
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Abstract null null A detailed understanding of permeability in fractured granite after exposure to high-temperature treatments under different confining pressures is critical for deep resource exploitation and underground space utilization. Along with the mechanical behaviour deterioration resulting from geologic and engineering effects, thermal stress leads to a permeability variation. In this research, uniaxial compression tests are performed on granite after exposure to a high-temperature tre...
In deep rock engineering, the rock mass can be subjected to thermal stress caused by sudden changes in temperature, which is referred to as thermal shock (TS). To study the effect of TS on heated sandstone, three cooling methods are used to provide different cooling rates. Then the coupled dynamic and static loading tests are carried out on the heated sandstone by means of a modified split Hopkinson pressure bar (SHPB) system. The test results show that as the heating level increases, the dry de...
Numerical methods are the most popular tools in computational mechanics and have been used to tackle various practical engineering problems. However, the most common programming languages used for implementing numerical methods do not effectively balance the demands of productivity and efficiency. To address the most computationally intensive areas of numerical computing with the increased abstraction and productivity provided by a high-level language, the Julia language was released by the Mass...
Analyzing variations in rock pore structure under high-temperature thermal cycles is of great significance for the development of deep resource. In this paper, red sandstone from Linyi, Shandong Province, was heated to 200 °C, 400 °C, 500 °C, and 600 °C, followed by five cold thermal cycles. The transverse relaxation times (T2) of red sandstone treated at various temperatures were observed using nuclear magnetic resonance (NMR), and the porosity and the characteristics of the pore structure were...
During the underground coal gasification process, a large amount of heat will be released, causing the surrounding rock in the goaf to undergo a high-temperature baking process. Therefore, it is essential to study the pyrolysis characteristics and mechanism of rocks. In this paper, the red sandstone in Linyi city of China is taken as an example. According to the results of thermogravimetric analysis in argon and air, the thermokinetic parameters are calculated by non isothermal pyrolysis kinetic...
Effect of ground surface surcharge on deformational performance of tunnel in spatially variable soil
High temperature and pore structure are important factors affecting the emission rate of radon in rocks. This study mainly focused on the correlation between radon emission rate and temperature in red sandstone. The results showed that in the temperature range of 25-400 °C, as the temperature increased, the connectivity of the internal pores of the sample became better, resulting in a significantly increased radon emission rate. The radon emission rate at 400 °C was 2.86 times the original. To e...
High-temperature baked sandstone is widely distributed in the north of Shaanxi, China. The lithology of these rocks has a significant impact on the mining of underground resources such as coal. To understand changes in its physical properties after heat treatment, yellow sandstone was heated for two hour at a constant temperature of 25, 800, 1000, 1100 or 1250 °C. Data on the glossiness, hardness and colour brightness, and surface micrographs, were obtained to study the relationship between surf...
High temperatures affect the physical properties of red sandstone seriously, especially the pores. Understanding its mechanism is of great significance in coal mining following underground gasification, geothermal energy utilization, and the deep burial of nuclear waste. Nuclear magnetic resonance (NMR) was used to detect pore structure characteristics, and scanning electron microscopy (SEM) and polarizing light microscopy (PLM) were used to mechanism of change. The transverse relaxation time (T...