Responses of multi-scale microstructures, physical-mechanical and hydraulic characteristics of roof rocks caused by the supercritical CO2-water-rock reaction

Cao, Liwen; Wang, Qizhi; Wang, Wei; Chang, Jiangfang; Chen, Mingyi; Wang, Haichao; Cai, Nian; Li, Fan

doi:10.1016/j.energy.2021.121727

Cited by 47 publications

(24 citation statements)

References 56 publications

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“…If CBM development is planned in this area, some methods of hydraulic fracturing (Cao et al, 2021), CO 2 /N 2 enhanced coalbed methane recovery (CO 2 -ECBM, N 2 -ECBM, etc.) (Niu et al, 2021b(Niu et al, , 2022Wang et al, 2021aWang et al, , 2021b) should be considered.…”

Section: Analysis Of Evaluation Results For Deep Coalbed Methane Reco...mentioning

confidence: 99%

Evaluation of deep high-rank coal seam gas content and favorable area division based on GIS: A case study of the South Yanchuan block in Ordos Basin

Cao

Cui³

et al. 2022

Energy Exploration & Exploitation

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The South Yanchuan block is the deepest developed high-rank coalbed methane (CBM) field in China, the geological conditions in this block are complex and the main controlling factors of CBM content are various. Thus, a decision-making model of the potential of deep high-rank coalbed methane resource based on geographical information system (GIS) and weighted linear combination (WLC) is established, the influence of geological conditions on CBM content is analyzed, the favorable areas of CBM potential are divided. Results show that the buried depth, coal rank and hydrodynamic condition in the coal seam are dominant factors that control the gas content on a block scale, while the gas content has a weak correlation with maceral composition, coal thickness and the effective thickness of the overlying strata. The study area is divided into five units according to the natural breaks method, i.e., the extramely favourable area, the favourable area, the relatively favourable area, the normally favourable area and the unfavourable area, which account for 14.23%, 22.23%, 24.77%, 25.08% and 13.70% in area, respectively. The extramely favourable area is located in the northwestern of the South Yanchuan block, which is considered to be the key exploration and development area. The study will deepen the understanding of the control of CBM potential in south Yanchuan Block, and is of practical significance for CBM recovery in this area.

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Section: Analysis Of Evaluation Results For Deep Coalbed Methane Reco...mentioning

confidence: 99%

Evaluation of deep high-rank coal seam gas content and favorable area division based on GIS: A case study of the South Yanchuan block in Ordos Basin

Cao

Cui³

et al. 2022

Energy Exploration & Exploitation

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“…As reported by Guo et al, the gas adsorption amount is nonlinearly correlated with the volume strain of coal; in this work, the relationships between the swelling/shrinkage strain and the adsorption/desorption amount are analogous and can be fitted by the binomial expression. CO 2 is a kind of strong plasticizer and has a strong adsorption affinity, which can dramatically decrease the surface free energy of the coal matrix and has a significant softening effect on the mechanical property of coal. , The result is that the coal matrix becomes more relaxed and is easily affected by the CO 2 circulating injection and pumping. The volume deformation is then measured by the experiment in this work.…”

Section: Discussionmentioning

confidence: 99%

“…CO 2 is a kind of strong plasticizer 58 and has a strong adsorption affinity, which can dramatically decrease the surface free energy of the coal matrix and has a significant softening effect on the mechanical property of coal. 59,60 The result is that the coal matrix becomes more relaxed and is easily affected by the CO 2 circulating injection and pumping. The volume deformation is then measured by the experiment in this work.…”

Section: Swelling and Shrinkage Characteristics Of Coalsmentioning

confidence: 99%

CO₂ Adsorption/Desorption, Induced Deformation Behavior, and Permeability Characteristics of Different Rank Coals: Application for CO₂-Enhanced Coalbed Methane Recovery

et al. 2022

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To understand and evaluate the CO2 injectivity in different coal seams, low-, middle-, and high-rank coals from Shanxi Province of China were collected to conduct CO2 adsorption/desorption, induced swelling/shrinkage, and permeability experiments. Results show that the adsorption/desorption amount, swelling/shrinkage deformation, and permeability depend on the coal rank. The CO2 adsorption/desorption amount of high-rank coal is the largest, followed by middle-rank coal, and that of low-rank coal is the smallest. The swelling/shrinkage strain and initial permeability of coals follow the sequence middle-rank coal > low-rank coal > high-rank coal. The percentage reductions of permeability of low-rank coal, middle-rank coal, and high-rank coal are 57.46, 48.50, and 71.17% when CO2 adsorption reaches the equilibrium state, indicating that the permeability of high-rank coal is more sensitive for the CO2 adsorption swelling. The swelling and shrinkage deformation presents obvious three-dimensional anisotropic characteristics; the deformation in the vertical bedding plane direction (VBD) is the maximum, the second is that in the parallel face cleat direction (PFD), and the deformation in the parallel butt cleat direction (PBD) is the maximum. The developmental characteristics of cleats and the distribution of macerals in coal contribute largely to the anisotropic deformation of coal induced by CO2 adsorption–desorption. The permeability of coal shows a U-shaped change trend of first decreasing and then increasing after CO2 adsorption because the permeability of coal is first dominated by the CO2 adsorption swelling and then is dominated by the reduction of effective stress. The swelling behavior and permeability attenuation of coal seams after CO2 injection are unavoidable; adopting the reservoir stimulation methods to produce more complex fracture networks is the key to improving CO2 injectivity. Combining the reservoir stimulation methods with CO2-ECBM technology may be an important development direction of the CCUS in coal seams.

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“…The pore–fissure systems of coal reservoirs have ternary features that consist of cleats, microcracks, and pores . The change in the stress field state during the mining process, including the axial and radial loading–unloading, affects the pore–fissure structure and permeability. , The in situ stress compresses the coal matrix and pore–fissures, and the coal permeability decreases exponentially with the increase of effective stress. , Nevertheless, the failure deformation formed in TDC reservoirs when stress is released can help to expand fissures and improve reservoir permeability. , In fact, the engineering practices of reservoir depressurization and permeability enhancement are widely applied for CBM extraction in TDC reservoirs, such as Huainan coalfield and Tiefa coalfield in China. − …”

Section: Introductionmentioning

confidence: 99%

Permeability Response Characteristics of Primary Undeformed Coal and Tectonically Deformed Coal under Loading–Unloading Conditions in Huainan Coalfield, China

Zhang

Sang

et al. 2022

ACS Omega

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Reservoir pressure relief is a practical method to enhance permeability for coalbed methane (CBM) extraction in tectonically deformed coal (TDC) reservoirs. To explore the coal permeability response to stress changes, the primary undeformed coal (PUC) and TDC from the same coal seam were sampled for the pore–fissure structure analysis, mechanical property test, and permeability experiments under different stress loading–unloading methods in this study. The experimental results demonstrated that the coal permeability is more sensitive to the changes in confining pressure (perpendicular to airflow) than axial stress (parallel to airflow). Coal permeability decreases negatively exponentially as the confining pressure increases, and its change process with increased axial pressure can be divided into five stages in this study. The pore structures and mechanical properties of coal samples affected their permeability response to stress changes. Under the stress loading condition, the coal matrix and fractures of PUC samples were compressed simultaneously, and the permeability was regulated by the pore–fissure structures in the coal matrix. Due to the deformation and displacement of coal particles, the permeability of the TDC sample is predominantly dependent on changes in intergranular pores. At the initial stress unloading stage, the fissure recovery and expansion lead to a rapid increase in permeability, but the permeability cannot rereach the original value when the stress is fully released. Furthermore, the influencing factors of coal permeability in response to stress loading–unloading also include confining pressure conditions and coal matrix adsorption swelling. Research on the permeability response characteristics of the stress loading–unloading process can provide some clarifications for the reservoir depressurization and permeability enhancement of CBM extraction in the TDC reservoir.

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Responses of multi-scale microstructures, physical-mechanical and hydraulic characteristics of roof rocks caused by the supercritical CO2-water-rock reaction

Cited by 47 publications

References 56 publications

Evaluation of deep high-rank coal seam gas content and favorable area division based on GIS: A case study of the South Yanchuan block in Ordos Basin

Evaluation of deep high-rank coal seam gas content and favorable area division based on GIS: A case study of the South Yanchuan block in Ordos Basin

CO₂ Adsorption/Desorption, Induced Deformation Behavior, and Permeability Characteristics of Different Rank Coals: Application for CO₂-Enhanced Coalbed Methane Recovery

Permeability Response Characteristics of Primary Undeformed Coal and Tectonically Deformed Coal under Loading–Unloading Conditions in Huainan Coalfield, China

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Responses of multi-scale microstructures, physical-mechanical and hydraulic characteristics of roof rocks caused by the supercritical CO2-water-rock reaction

Cited by 47 publications

References 56 publications

Evaluation of deep high-rank coal seam gas content and favorable area division based on GIS: A case study of the South Yanchuan block in Ordos Basin

Evaluation of deep high-rank coal seam gas content and favorable area division based on GIS: A case study of the South Yanchuan block in Ordos Basin

CO2 Adsorption/Desorption, Induced Deformation Behavior, and Permeability Characteristics of Different Rank Coals: Application for CO2-Enhanced Coalbed Methane Recovery

Permeability Response Characteristics of Primary Undeformed Coal and Tectonically Deformed Coal under Loading–Unloading Conditions in Huainan Coalfield, China

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CO₂ Adsorption/Desorption, Induced Deformation Behavior, and Permeability Characteristics of Different Rank Coals: Application for CO₂-Enhanced Coalbed Methane Recovery