Evaluation of lost gas in the borehole drilling stage: Implication for the direct method of coalbed methane content determination

Wang, Youpai; Kang, Jianhong; Zhou, Fang; Yuan, Liang; Pan, Zhejun

doi:10.1016/j.jngse.2022.104711

Cited by 14 publications

(11 citation statements)

References 39 publications

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“…Based on the ideal gas law, the gas density and the gas density under standard conditions can be obtained as follows , ρ normalg = M normalg R T 1 p ρ ga = M normalg R T normala p normala where P a is the gas pressure (Pa) and T a is the temperature (K) under standard conditions.…”

Section: Controlling Equationsmentioning

confidence: 99%

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Ultrasonic-Assisted Coalbed Methane Recovery: A Coupled Acoustic–Thermal–Mechanical–Hydrological Model

Yang

Wang

et al. 2023

Energy Fuels

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Ultrasonic propagation in coal seams is accompanied by heat transfer, which has the potential to increase coal seam permeability, enhance coalbed methane (CBM) recovery, and prevent coal and gas outbursts. Therefore, it is important to analyze the effects of heat transfer by ultrasonic vibration on CBM recovery and evaluate the prospects of engineering applications of ultrasonic heating technology. In this study, the factors affecting heat transfer by ultrasonic vibration were analyzed theoretically; then, CBM recovery under the condition of ultrasonic heating was simulated by establishing a coupled acoustic–thermal–mechanical–hydrological model. The correctness of acoustic–thermal model was validated by matching simulated data with experimental data. And the accuracy of the gas flow model was verified by comparing the production data from CBM extraction boreholes with the simulated data. The research results were as follows: heat transfer by ultrasonic vibration was affected by frequency and sound pressure. When the ultrasonic frequency varied from 30 to 40 kHz and the sound pressure varied from 0.1 to 0.12 MPa, the lower the frequency, the higher the sound pressure, and the better the ultrasonic vibration heat transfer effect. In addition, the thermal expansion volumetric strain of the coal matrix caused by the ultrasonic heating of coal seams was weaker than the shrinkage volumetric strain of the coal matrix caused by gas desorption, improving the porosity and permeability of the coal seams. Furthermore, the gas drainage standard area increased by 20.8 m2 after 720 days of CBM recovery when replacing conventional CBM recovery with ultrasonic-assisted CBM recovery. With a production time of 720 days, the maximum production of CBM after ultrasonic excitation at a frequency of 40 kHz and a sound pressure of 0.10 MPa increases from 3744 to 9740 m3/day compared to conventional excitation. Our fully coupled acoustic–thermal–mechanical–hydrological model can improve current understandings of heat and mass transfer in thermal simulation of ultrasonic-enhanced CBM recovery.

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Section: Controlling Equationsmentioning

confidence: 99%

“…Based on the ideal gas law, the gas density and the gas density under standard conditions can be obtained as follows 30,31…”

Section: Gas Flow Andmentioning

confidence: 99%

Ultrasonic-Assisted Coalbed Methane Recovery: A Coupled Acoustic–Thermal–Mechanical–Hydrological Model

Yang

Wang

et al. 2023

Energy Fuels

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“…Compared with the direct method, the parameters measured by the indirect method are all measured values, including the gas pressure in the coal seam, and as there are fewer influencing factors in the process of measurement, the measurement error is small, and the measured data has higher credibility. The values measured by direct method are often lower than the actual values, whereas the values measured by indirect method in many mines are often closer to the actual values (Li et al, 2020;Wang et al, 2022). However, the indirect method has its deficiencies-the measurement of gas adsorption constant needs to be done in laboratory and the measurement of coal-seam gas pressure needs to be done in the pit.…”

Section: Introductionmentioning

confidence: 99%

Prediction of coal seam gas content based on the correlation between gas basic parameters and coal quality indexes

et al. 2023

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The measurement of gas content in coal seam by means of indirect method involves heavy workload, long period, high cost and complicated operation and a proneness of negative values in the process of measuring gas absorption constant. To address these problems, the gas basic parameters and coal quality indexes of 90 coal samples from 90 coal mines in 13 provinces of China are determined experimentally in this paper. The intrinsic relationship between gas adsorption constant a and atmospheric adsorption capacity Q0-initial velocity index of gas emission Δp, gas adsorption constant b and volatile Vdaf - apparent density ARD is analyzed, and a prediction model of coal seam gas content based on gas basic parameters and coal quality index is established. The results show that the effect of Q0-Δp correlation on a is mainly caused by the change of specific surface area and gas pressure of coal, while the effect of Vdaf-ARD correlation on b is mainly caused by the change of pore volume of coal. By comparing the predicated value from the prediction model of coal seam gas content with the measured value, it is found that the average absolute error rate of predicted value is 8.15%. This method is proven to be effective and feasible in routine gas content predictions, and can provide a reference for coal seam gas content prediction in China.

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“…Fractures serve as important channels for gas transport, while the matrix provides the main site for the storage and diffusion of adsorbed gas . During coal-bed methane (CBM) extraction, gas in the matrix is continuously transported to the fracture system through the pore channels, which ensures stabilized production of gas wells . In the later stage of extraction, almost all free gas in the fracture system comes from the matrix. , Therefore, clarifying the mechanism of gas transport and migration within the coal matrix is of great significance for CBM development, mine gas control, and CO 2 geological sequestration.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Gas Emission under Pressure from the Coal Matrix: Understanding Gas Transport Patterns from an Engineering Scale

Lin

Liu

et al. 2023

Energy Fuels

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Gas transport within the coal matrix is key to realizing mass exchange between the fracture and matrix systems. However, considerable controversy remains regarding gas transport within the coal matrix system. In this study, the applicability of several typical models was evaluated based on the proposed criteria, mainly through gas emission under pressure experiments, and it is found that the Darcy seepage model describes gas transport behavior within the coal matrix more scientifically. Subsequently, the validity of the seepage model was re-evaluated through pore structure analysis, and the gas transport patterns and underlying mechanisms of the dual-porosity and dualpermeability models were discussed. The results suggest that gas transport within the matrix is dominated by the Fick diffusion flow only when methane molecules within the coal matrix are located in the micropore filling section. When the pore size is located in the outer pore section, gas within the matrix will be transported outward in a free state driven by pressure. In addition, the proposed gas transport model and field data were used to validate the analysis. It is concluded that in view of the low efficiency of gas transport in the micropore filling section, the dual-porosity and doublepermeability models can be used to simplify gas transport in coal seams.

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Evaluation of lost gas in the borehole drilling stage: Implication for the direct method of coalbed methane content determination

Cited by 14 publications

References 39 publications

Ultrasonic-Assisted Coalbed Methane Recovery: A Coupled Acoustic–Thermal–Mechanical–Hydrological Model

Ultrasonic-Assisted Coalbed Methane Recovery: A Coupled Acoustic–Thermal–Mechanical–Hydrological Model

Prediction of coal seam gas content based on the correlation between gas basic parameters and coal quality indexes

Experimental Study on Gas Emission under Pressure from the Coal Matrix: Understanding Gas Transport Patterns from an Engineering Scale

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