Petrophysics characteristics of coalbed methane reservoir: A comprehensive review

Jia, Qifeng; Liu, Dameng; Cai, Yidong; Fang, Xianglong; Li, Lijing

doi:10.1007/s11707-020-0833-1

Cited by 26 publications

(18 citation statements)

References 62 publications

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“…In recent years, an increased number of studies of coal pore structure characteristics with different metamorphic degrees and structural types have been carried out, − and the effects of changes in the coal macromolecular structure on the pore structure have been investigated . The main studies and review papers on coal pore research in recent years are systematically sorted, ,− and it is found that it is difficult to obtain complete pore development and connectivity characteristics due to the complex genetic types of coal pores, the wide range of pore size distributions, and strong heterogeneity; observation technology for pores with sizes below 10 nm must be improved. − Although many methods are used to characterize coal pores, measurements of pores below 10 nm using indirect characterization methods, such as X-ray or fluid intrusion methods, remain limited. − , The characterization and determination of the connectivity of multiscale pores in coal represent scientific problems in CBM geology and engineering that must be urgently addressed. Further, previous reviews have mainly focused on the lithological development characteristics of coal samples with different coal ranks and types, the relationship between coal seams and CBM development, and the application of the pore measurement methods (Table ), ,− resulting in a lack of comprehensive sorting and summary of coal pore-related factors.…”

Section: Introductionmentioning

confidence: 99%

Coal Pores: Methods, Types, and Characteristics

et al. 2021

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Coal pores are the locations of coalbed methane occurrence and enrichment and the main storage space targeted in CO2 sequestration. The systematic investigation of the coal pore structure and its development is of great significance to provide insights into coalbed methane generation, coal mine gas outburst mechanisms, and coal seam CO2 sequestration. In this study, coal pore testing technologies and methods, pore classification methods, and coal pore structure characteristics and their main control factors were systematically investigated and summarized. The results show that direct test methods, indirect fluid injection test methods, and X-ray and spectroscopic methods have been used for the quantitative characterization of the pore structure. However, each testing method has limitations. Therefore, a comprehensive method for the quantitative characterization of the full-scale pore structure must be developed, especially for the accurate quantitative characterization of closed pores in coal. The in situ measurement of pores in coal is one of the future research trends. Classification methods of pores in coal mainly include the classification of the genetic pore type, pore size, and pore morphology. Metamorphism, tectonic deformation, and macerals are the main internal factors affecting the pore distribution in coal. The effect of tectonic deformation on the macromolecular structure and micro- and ultramicropores of coal must be further studied. In addition, molecular mechanics simulations, molecular dynamics simulations, and quantum chemistry calculations of the dynamic response of the macromolecular structure and micro- and ultramicropores during gas adsorption and desorption must be carried out.

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Section: Introductionmentioning

confidence: 99%

Coal Pores: Methods, Types, and Characteristics

et al. 2021

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“…Coal is extremely sensitive to temperature and pressure changes during geological evolution. Under different geothermal-pressure conditions, coals take on various structures indicated by significant changes in their stratified state, macromolecular structure, and optical characteristics. ,,, Ground stress refers to the stress state in the Earth’s crust, and gravitiy stress and tectonic stress are the main sources . Tectonic stress affects the physical characteristics of coals with different coal structures, such as density, porosity, pore structure, and permeability .…”

Section: Tectonic Controls On Coal Structurementioning

confidence: 99%

Coal Structure and Its Implications for Coalbed Methane Exploitation: A Review

Liu

Cai

et al. 2020

Energy Fuels

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Coal structure refers to the internal structural characteristics of coals including the degree of macroscopic and microscopic deformation, pore structure, and mechanical properties after various geothermal and geological stresses, which have substantial impacts on coal mining safety and coalbed methane (CBM) exploitation. The coal structure is an indicator of coal mechanical strength, which determines the petrophysical properties of CBM reservoirs and gas extraction or CBM production efficiency from coals. Coals with different structures are divided into primary coals and tectonically deformed coals (TDCs). To explore the macro- and microscopic petrophysics of TDCs, a wide range of techniques including geophysical logging, seismic inversion, amplitude variation with offset (AVO), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and Fourier transform infrared spectroscopy (FTIR) have been employed. From a macroscopic perspective, the geological and geophysical methods are generally used to distinguish the degree of deformation of whole coal seams. Microscopic methods including SEM, NMR, and FTIR, are normally used to investigate the internal petrophysics (e.g., pore and fracture, macromolecular structure, and fluid performance) of TDCs. Herein, the macro- and micro-petrophysical properties of TDCs and their impacts on CBM exploration and exploitation are systematically reviewed and potential opportunities of future directions are recommended. Extensive studies have shown that the development zone of TDCs in the brittle series, notably cataclastic coals, has high potential for CBM exploration and exploitation, while that of TDCs in the ductile series is a dangerous region for coal mining and subject to gas outbursts. This review aims to provide background on the coal structure, summarize evaluation methods, highlight its geological drivers, and explain its significance in CBM exploitation. We will end with proposals for future research directions.

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“…The occurrence states of gas in coal are mainly the adsorption state and the free state, and the principal occurrence area is the coal pore structure. The existing research shows that the adsorbed gas in coal pores can reach 80% and above [ 6 , 7 , 8 ]. Many researchers have studied the pore size distribution of coal based on experimental measurements and other methods.…”

Section: Introductionmentioning

confidence: 99%

Molecular Simulation on Competitive Adsorption Differences of Gas with Different Pore Sizes in Coal

et al. 2022

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Micropores are the primary sites for methane occurrence in coal. Studying the regularity of methane occurrence in micropores is significant for targeted displacement and other yield-increasing measures in the future. This study used simplified graphene sheets as pore walls to construct coal-structural models with pore sizes of 1 nm, 2 nm, and 4 nm. Based on the Grand Canonical Monte Carlo (GCMC) and molecular dynamics theory, we simulated the adsorption characteristics of methane in pores of different sizes. The results showed that the adsorption capacity was positively correlated with the pore size for pure gas adsorption. The adsorption capacity increased with pressure and pore size for competitive adsorption of binary mixtures in pores. As the average isosteric heat decreased, the interaction between the gas and the pore wall weakened, and the desorption amount of CH4 decreased. In ultramicropores, the high concentration of CO2 (50–70%) is more conducive to CH4 desorption; however, when the CO2 concentration is greater than 70%, the corresponding CH4 adsorption amount is meager, and the selected adsorption coefficient SCO2/CH4 is small. Therefore, to achieve effective desorption of methane in coal micropores, relatively low pressure (4–6 MPa) and a relatively low CO2 concentration (50–70%) should be selected in the process of increasing methane production by CO2 injection in later stages. These research results provide theoretical support for gas injection to promote CH4 desorption in coal pores and to increase yield.

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Petrophysics characteristics of coalbed methane reservoir: A comprehensive review

Cited by 26 publications

References 62 publications

Coal Pores: Methods, Types, and Characteristics

Coal Pores: Methods, Types, and Characteristics

Coal Structure and Its Implications for Coalbed Methane Exploitation: A Review

Molecular Simulation on Competitive Adsorption Differences of Gas with Different Pore Sizes in Coal

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