Pore-fracture alteration of different rank coals: Implications for CO2 sequestration in coal

Zhang, Guanglei; Ranjith, P.G.; Fu, Xuehai; Li, Xin

doi:10.1016/j.fuel.2020.119801

Cited by 48 publications

(15 citation statements)

References 57 publications

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“…In general, long-term scCO 2 –H 2 O exposure decreases the coal mesoporosity. The changing mesopore structure parameters of coals after scCO 2 exposure are greatly relevant to the mineral dissolution. ,,, As previously stated, the quartz content of coals significantly decreases after long-term scCO 2 –H 2 O exposure. Quartz is classified as a skeleton mineral .…”

Section: Resultsmentioning

confidence: 78%

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Zhang

et al. 2021

Energy Fuels

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Regarding CO2 geologic sequestration in the coal seam, injected CO2 in the coal reservoir at an optimum depth often presents as supercritical fluid (scCO2), which is capable of changing the physicochemical properties of coal and further affecting its CO2 storage capacity. Aiming to better explore the aforementioned influences, we conducted a long-term scCO2–H2O–coal static interaction in the laboratory. The influences of scCO2 exposure on the pore structure characteristics, the main oxygenic functional groups, and the high-pressure CO2 adsorption and desorption capabilities of four rank coals were explored. The results show that long-term scCO2–H2O exposure has minor effects on the coal micropore surface area and volume. On the contrary, it remarkably decreases the mesopore of all of the coals. The alterations in the coal pore structure parameters are mainly relevant to coal matrix swelling and mineral dissolution due to long-term scCO2–H2O exposure. In general, long-term scCO2–H2O exposure increases the Neimark fractal dimension of coals, further implying an elevated pore surface roughness and a more complex pore structure. Moreover, the main oxygenic functional groups, including C–O, CO, and −COOH, of coals after long-term scCO2 exposure are reduced. The aforementioned changes in the physicochemical properties of coals further affect their CO2 adsorption and desorption capabilities. In particular, the maximum CO2 adsorption capacity of high-rank coals decreases after exposure, whereas that of low-rank coals increases. Furthermore, the CO2 adsorption and desorption hystereses of coals become pronounced after long-term scCO2–H2O exposure, implying more stable CO2 sequestration in the coal seam. In conclusion, the implementation of CO2 sequestration in the coal seam should focus on the long-term scCO2–H2O–coal interaction.

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Section: Resultsmentioning

confidence: 78%

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Zhang

et al. 2021

Energy Fuels

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“…Following the Chinese National Standard GB/T19587-2004, the low-temperature liquid nitrogen adsorption (LTLNA) analysis was carried out with a Quadrawin SI automated specific surface area and pore size analyzer (Quantachrome, USA) at 77 K. , Both adsorption and desorption isotherms were measured at a relative pressure ( P / P 0 ) range from 0.01 to 0.99, and the SSA, PV, and PSD were, respectively, calculated by the Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) models. , On the basis of the Chinese National Standard GB/T 21650.1-2008, the MIP was performed by using the Autopore 9505 mercury injection apparatus at 0–228.00 MPa. During the calculation of MIP, the pores in coal are idealized as cylindrical pores of different sizes, and the PV and SSA were obtained by the methods mentioned in previously published literature. , …”

Section: Samples and Methodsmentioning

confidence: 99%

“…During the calculation of MIP, the pores in coal are idealized as cylindrical pores of different sizes, 55 and the PV and SSA were obtained by the methods mentioned in previously published literature. 56,57 The SEM-EDS analysis of samples was performed at the Advanced Analysis & Computation Center of China University of Mining and Technology using the Quanta TM 250 instrument manufactured by the FEI Company of USA. The accelerating voltage of the SEM ranges from 0.2 to 30 kV, and the magnification reaches 6−100 million times.…”

Section: Samples and Methodsmentioning

confidence: 99%

Changes of Multiscale Surface Morphology and Pore Structure of Mudstone Associated with Supercritical CO₂-Water Exposure at Different Times

et al. 2021

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CO2 enhanced coalbed methane recovery (CO2-ECBM) has been confirmed as an effective technology to improve coalbed methane (CBM) production; however, the injected CO2 and the reservoir water can react with the caprock of the coal seam, which changes its internal structure and increases the risk of CO2 leakage. To clarify the CO2–water–rock reaction process and the structural responses of the caprock, the roof mudstone samples of coal seams from Qinshui Basin were first selected to conduct the geochemical reaction experiment; then, scanning electron microscopy (SEM), N2 adsorption, and mercury intrusion porosimetry were adopted to monitor the multiscale structure alteration of the samples. The results show that the rock sample has progressively deteriorated during the CO2–water–rock reaction process, and this effect is aggravated with the increase of the reaction time. The dissolution process consists of three stages: (1) lots of isolated and shallow holes are developed; (2) holes are connected and formed to the dissolution grooves; (3) dissolution grooves are widened, and the dissolution zone is expanded until all the soluble minerals immerse into the reaction solution. The pore volume (PV) and specific surface area (SSA) of small pores are reduced, while those of large pores are increased, which can be attributed to the pore-blocking effect caused by clay mineral swelling and mineral precipitation and the pore-enlarging effect caused by mineral dissolution, respectively. Additionally, the ScCO2–water–rock reaction varies the pore structure distribution and makes the PV distribution more heterogeneous and the SSA distribution more homogeneous. The changes in the internal structure of the roof mudstone promote gas diffusion and seepage, which may increase the potential threat of CO2 leakage during the long-term CO2-ECBM process to a certain degree. This study will provide an essential basis for the investigation and evaluation of the security of CO2-ECBM in Qinshui Basin, China.

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“…18 The medium and large pores are well developed in low-rank coal, while high-rank and mid-rank coal have well-developed cracks. 19 The methane adsorption capacity of high-rank coal (anthracite) is stronger than that of low-rank coal (lignite). 20,21 The permeability of coal decreases with increasing coal metamorphism, which is the same trend as the change of coal porosity.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Effect of Coal Particle Size on the Mechanics, Pore Structure, and Permeability of Coal-like Materials for Low-Rank Coalbed Methane Reservoir Simulation

Zheng

Zhai

et al. 2021

Energy Fuels

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Coal-like materials have been widely used to simulate low-rank coalbed methane (CBM) reservoirs to develop fracturing stimulation technology since the transportation and preparation of low-rank coal produce easily secondary damages, causing large dispersion of test results. However, the coal particle sizes have a significant effect on the performance of coal-like materials among many factors. Hence, to accurately simulate lowrank CBM reservoirs for promoting the development of reservoir stimulation technologies, cement, gypsum, pulverized coal, and sand were selected as similar materials to make coal-like samples with different coal particle sizes to study the influence law of coal particle size on the mechanics, pore structure, and permeability of samples. The ultrasonic wave velocity, dynamic parameters, uniaxial compressive strength, elastic modulus, and uniaxial tensile strength of samples increased with increasing coal particle size in the range of 0−2 mm. However, these parameters suddenly decreased when the coal particle size increased to 2−3 mm. The porosity and permeability of the samples exhibited an opposite trend compared to the above parameters. The fracture occurred in cementing materials, and the crack extension direction was affected by the coal particle sizes. The fracture complexity of the coal-like samples decreased with increasing particle size under uniaxial compressive testing. The failure mode was mainly a tensile failure, supplemented by shear failure. The coal-like materials can well meet the performance requirements of low-rank CBM reservoirs.

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Pore-fracture alteration of different rank coals: Implications for CO2 sequestration in coal

Cited by 48 publications

References 57 publications

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Changes of Multiscale Surface Morphology and Pore Structure of Mudstone Associated with Supercritical CO₂-Water Exposure at Different Times

Experimental Study on the Effect of Coal Particle Size on the Mechanics, Pore Structure, and Permeability of Coal-like Materials for Low-Rank Coalbed Methane Reservoir Simulation

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Pore-fracture alteration of different rank coals: Implications for CO2 sequestration in coal

Cited by 48 publications

References 57 publications

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Impacts of Long-Term Exposure to Supercritical Carbon Dioxide on Physicochemical Properties and Adsorption and Desorption Capabilities of Moisture-Equilibrated Coals

Changes of Multiscale Surface Morphology and Pore Structure of Mudstone Associated with Supercritical CO2-Water Exposure at Different Times

Experimental Study on the Effect of Coal Particle Size on the Mechanics, Pore Structure, and Permeability of Coal-like Materials for Low-Rank Coalbed Methane Reservoir Simulation

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Changes of Multiscale Surface Morphology and Pore Structure of Mudstone Associated with Supercritical CO₂-Water Exposure at Different Times