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The porous structure of oil shale plays a vital role in heat transfer and mass transport of its pyrolysis, particularly for the flow behavior of shale oil and gas during in-situ conversion. It is essential to clarify the pore evolution and give a mathematical description of the complex pyrolysis. In this study, the effect of temperature (100–800°C) on Huadian oil shale pyrolysis, and the creation...
Various types of lithospheric geological reservoirs are available for the safe and long-term storage of CO2. The phase of CO2 transitions between liquid and supercritical (mostly supercritical for depths greater than 800m) when injected into the subsurface. This high-density super-critical phase prevents CO2 molecules from upward diffusion toward the surface. Many questions arise in the context of...
Liquid nitrogen (LN2), a non-aqueous medium, has attracted attention in recent years as a fluid for fracturing in the petroleum/energy industry. This study proposes a freeze-thaw method using LN2 to improve coal permeability for the production of coal bed methane. Experiments were conducted using nuclear magnetic resonance (NMR) to explore the physical properties of frozen-thawed coal. The coal samples...
A constant suction negative pressure is used in coal mines owing to a lack of research on the effects of diffusion and suction negative pressure on methane extraction, resulting in the low methane concentration and utilization rate. In this study, Comsol Multiphysics is used to conduct a numerical solution of a gas–solid coupling model considering pseudo-steady diffusion in coal matrix, seepage in...
Permeability values measured for low-permeability (tight) rocks by commercial and research laboratories may exhibit an unacceptably large variability even when measured using samples subjected to similar experimental conditions. One cause of this variability is that, for a particular measurement method, laboratories utilize different experimental configurations with instrumental components that have...
The evolution of the petrophysical properties (porosity/permeability) of lignite, subbituminous and high-volatile bituminous coals (LSBC) and the effects of the first coalification jump on the pore-cleat physical properties are still poorly understood. We investigated the pore-cleat heterogeneity, volume, aperture, connectivity and pore-contributed porosity/permeability with increasing coal ranks...
Coal permeability has been identified as one of the key factors affecting coalbed methane (CBM) extraction. CBM drainage and hydraulic fracturing usually lead to coal fines output. Some of these coal fines passed through wellbore discharged of coal bed, and some of them were compacted in fractures during the closing of fractures (or cleats) under the confining pressure. The pore distribution and seepage...
Oil shales are organic-rich mudstones that generally have little porosity and permeability until kerogen is transformed into oil and gas. A simple mathematical model is reported for how porosity and permeability values for the Green River Formation change during retorting under confinement. Unlike when retorted unconstrained, during which numerous fractures occur due to the limited tensile strength...
Liquid carbon dioxide (LCO2) fracturing technology has been applied in the enhanced coalbed methane recovery (ECBM), and it has made some progress in the physical experiments and field applications. However, the freeze phenomenon during the injection process might induce coal matrix shrinkage, hindering the fracturing efficiency. A multiple cycle LCO2 fracturing technology is proposed, and the feasibility...
Permeability is a crucial macroscopic parameter in characterizing fluid flow and mass transfer behavior in porous media. A great theoretical basis for permeability estimation has been provided by many traditional and recently presented fractal models. However, since the influence of overlying sediments, the low-permeability porous media such as natural rock and coal generally have lower permeability...
The methane found in coal is regarded as one of the clean energy resources. Methane forms inside coal beds according to geological conditions through coalification. The lifecycle of coalification and source of coal formation directly affect macerals. Coal is classified based on its maceral content. In this study, firstly macerals were identified in coal samples from two different mines. Then, the...
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