Three-dimensional cleat scale modelling of gas transport processes in deformable fractured coal reservoirs

Chen, Min; Masum, Shakil; Thomas, Hywel Rhys

doi:10.1016/j.jgsce.2023.204901

Cited by 6 publications

(3 citation statements)

References 45 publications

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“…More attempts are required for an accurate representation of multiscale fractures in fluid flow. In this study, the coal deformation was assumed to be linearly elastic, however, recent work by Chen et al [50] indicates that nonlinear deformation of fractured coal can also affect the stress field of coal seams. Thus, the nonlinearity of coal deformation should be taken into account in future studies.…”

Section: Discussionmentioning

confidence: 99%

Hydromechanical Impacts of CO2 Storage in Coal Seams of the Upper Silesian Coal Basin (Poland)

et al. 2023

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Deep un-mineable coal deposits are viable reservoirs for permanent and safe storage of carbon dioxide (CO2) due to their ability to adsorb large amounts of CO2 in the microporous coal structure. A reduced amount of CO2 released into the atmosphere contributes in turn to the mitigation of climate change. However, there are a number of geomechanical risks associated with the commercial-scale storage of CO2, such as potential fault or fracture reactivation, microseismic events, cap rock integrity or ground surface uplift. The present study assesses potential site-specific hydromechanical impacts for a coal deposit of the Upper Silesian Coal Basin by means of numerical simulations. For that purpose, a near-field model is developed to simulate the injection and migration of CO2, as well as the coal-CO2 interactions in the vicinity of horizontal wells along with the corresponding changes in permeability and stresses. The resulting effective stress changes are then integrated as boundary condition into a far-field numerical model to study the geomechanical response at site-scale. An extensive scenario analysis is carried out, consisting of 52 simulation runs, whereby the impacts of injection pressures, well arrangement within two target coal seams as well as the effect of different geological uncertainties (e.g., regional stress regime and rock properties) is examined for operational and post-operational scenarios. The injection-induced vertical displacements amount in maximum to 3.59 cm and 1.07 cm directly above the coal seam and at the ground surface, respectively. The results further demonstrate that neither fault slip nor dilation, as a potential consequence of slip, are to be expected during the investigated scenarios. Nevertheless, even if fault integrity is not compromised, dilation tendencies indicate that faults may be hydraulically conductive and could represent local pathways for upward fluid migration. Therefore, the site-specific stress regime has to be determined as accurately as possible by in-situ stress measurements, and also fault properties need to be accounted for an extensive risk assessment. The present study obtained a quantitative understanding of the geomechanical processes taking place at the operational and post-operational states, supporting the assessment and mitigation of environmental risks associated with CO2 storage in coal seams.

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Section: Discussionmentioning

confidence: 99%

Hydromechanical Impacts of CO2 Storage in Coal Seams of the Upper Silesian Coal Basin (Poland)

et al. 2023

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“…The results of the laboratory tests and numerical modeling activities [45][46][47][48][49][50][51][52][53] provided useful insights into potential scenarios of the in situ CO 2 injection operation. These helped to determine the final location and position of the wells, and the results suggested that the maximum migration of the injected CO 2 during the experiment was approximately a dozen meters.…”

Section: Injection Systemmentioning

confidence: 99%

CO2 Injection via a Horizontal Well into the Coal Seam at the Experimental Mine Barbara in Poland

Stańczyk,

Hildebrandt,

Chećko

et al. 2023

Energies

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This study, conducted as part of the ROCCS project, investigates the potential of coal seams for CO2 sequestration through in situ tests. The in situ tests, performed at Experimental Mine Barbara in Mikołów, Poland, involved injecting CO2 through a horizontal well into a coal seam, with variable well lengths and injection parameters. The experiments included monitoring for CO2 leakage and migration within the coal seam. The objective was to examine the correlation between the CO2 injection rate and the coal–CO2 contact area, monitoring for any potential leakage. The total mass of CO2 injected was about 7700 kg. Significant leakage, probably due to the formation of preferential pathways, prevented pressure buildup in the injection well. The results provide insights into challenges regarding CO2 injection into coal seams, with implications for the design of commercial-scale CO2 storage installations.

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“…The adsorbed gas in micropores can account for ∼90% of the total gas content, and the remaining ∼10% free gas is stored as compressed state defined by equation of state (EOS). , For sorbed gas, three staged gas transport mechanisms are involved, namely, desorption, diffusion, and seepage, to be produced from the wellbore. For coal seam with either low diffusivity or permeability or both combined, the production of gas can be disappointing due to the limited gas deliverability. − The cleat/fracture system plays the key role on the coal permeability, which is the most important parameters for effective gas drainage. − In the United States, coal seam with permeability less than 1.0 millidarcy (mD) is considered as a low quality CBM reservoir for the potential commercial production for vertical CBM wells. , However, it is found that more than 70% of the coal reservoir permeability is below 1.0 mD in China. , Reservoir stimulation aiming at permeability enhancement has been the major technological challenge for CBM exploitation and gas drainage. − …”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Permeability Enhancement of Anthracite by High Pressure Nitrogen Injection and Soaking

Shi,

Cao,

et al. 2024

Energy Fuels

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Nitrogen treatment is a widely used coalbed methane (CBM) recovery technique for low permeability CBM reservoirs. We conducted a series of experiments to investigate the nitrogen injection and soaking (NI-n-S) induced coal structure alteration and, thus, the permeability variations. Two sets of experimental variations were investigated, which are the treatment pressure and the treatment duration. The experiments were carried out with nitrogen pressures of 6, 9, 12, and 15 MPa for 2, 12, 24, and 36 h, respectively. The core-scale permeability was employed as an indication of the gas flow enhancement capability and effectiveness. Both X-ray CT and field emission scanning electron microscopy (FESEM) were used for the imaging analyses for cross-comparison before and after NI-n-S treatments. The permeability of the coal samples after NI-n-S has shown a significant increase by 13.6−524.1%, with an average of 98.5%. The permeability increase ratio positively correlates with nitrogen treatment pressure; high-pressure nitrogen produced six types of damage modes on microfractures. The main mode is improving the microfracture opening width, and it increased by 4.4−166.7% (mean 45.1%) of the coal specimen with NI-n-S.

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Three-dimensional cleat scale modelling of gas transport processes in deformable fractured coal reservoirs

Cited by 6 publications

References 45 publications

Hydromechanical Impacts of CO2 Storage in Coal Seams of the Upper Silesian Coal Basin (Poland)

Hydromechanical Impacts of CO2 Storage in Coal Seams of the Upper Silesian Coal Basin (Poland)

CO2 Injection via a Horizontal Well into the Coal Seam at the Experimental Mine Barbara in Poland

Experimental Study on Permeability Enhancement of Anthracite by High Pressure Nitrogen Injection and Soaking

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