Advantageous Seepage Channel in Coal Seam and its Effects on the Distribution of High-yield Areas in the Fanzhuang CBM Block, Southern Qinshui Basin, China

For finding out favorable coalbed methane development districts, the evaluation of geological controls of CBM distribution and accumulation is essential during CBM exploration and development. In this paper, the No. 3 coal seam in the Zhengzhuang coal zone located at southern Qinshui Basin, China, was selected as a focus for comprehensively evaluating geological controls of CBM. The findings of this study are: (1) Coalbed gas contents increase with increasing mudstone roof thickness (ranging from 0-9 m), and will always be as high as 20 m3/t in the coal reservoirs with the mudstone roof thickness greater than about 9 m. (2) The weak transmission and stagnant coalbed water are favorable for CBM accumulation in coal reservoirs resulting from the typical hydraulic preservation of CBM. (3) High coalbed gas contents will commonly occur in vitrinite-rich and low-ash yield coals with high CH4 adsorptive capacity.

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Geological controls on prediction of coalbed methane of No. 3 coal seam in Southern Qinshui Basin, North China

International Journal of Coal Geology ◽

10.1016/j.coal.2011.08.009 ◽

2011 ◽

Vol 88 (2-3) ◽

pp. 101-112 ◽

Cited By ~ 166

Author(s):

Yidong Cai ◽

Dameng Liu ◽

Yanbin Yao ◽

Junqian Li ◽

Yongkai Qiu

Keyword(s):

Coal Seam ◽

Coalbed Methane ◽

North China ◽

Qinshui Basin ◽

Southern Qinshui Basin

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Numerical analysis of drainage rate for multilayer drainage coalbed methane well group in Southern Qinshui basin

Energy Exploration & Exploitation ◽

10.1177/0144598720946494 ◽

2020 ◽

Vol 38 (5) ◽

pp. 1535-1558

Author(s):

Qiujia Hu ◽

Shiqi Liu ◽

Shuxun Sang ◽

Huihuang Fang ◽

Ashutosh Tripathy ◽

...

Keyword(s):

Pressure Drop ◽

Coal Seam ◽

Coalbed Methane ◽

Gas Production ◽

Hydraulic Pressure ◽

Qinshui Basin ◽

Well Production ◽

Drainage Rate ◽

Southern Qinshui Basin ◽

Cbm Production

Multilayer drainage is one of the important technologies for coalbed methane (CBM) production in China. In this study, a multi-field fully coupled mathematical model for CBM production was established to analyze the multilayer drainage of CBM well group in southern Qinshui basin. Based on the numerical simulation results, the characteristics of CBM well production under different drainage rates and key factors influencing the CBM production were further discussed. The results show that the effect of an increased drainage rate on gas production of CBM wells and CBM recovery of No.3 coal seam is not significant. However, it significantly improved the gas production of CBM wells and CBM recovery of No.15 coal seam. After a long period of production, the CBM content in No.3 coal seam has reduced to a low level and the pressure drop potential of No.3 coal seam is insignificant, which are important reasons for the insignificant increase of CBM production even under a drainage rate of 2 to 7 times. Conversely, No.15 coal seam has larger residual CBM content and increasing the drainage rate can significantly improve the pressure drop and superimposed well interference of No.15 coal seam, which means No.15 coal seam has greater production potential than No.3 coal seam. Therefore, it is recommended to improve the gas production and CBM recovery in No.15 coal seam by increasing the drainage rate, and the average hydraulic pressure drop should be 0.018–0.031 MPa/day. The influence of effective stress is weak in No.3 and No.15 coal seam, and the coal seam permeability is largely influenced by the shrinkage of coal matrix caused by CBM desorption. This indicates the feasibility of increase in gas production from CBM wells by increasing the drainage rate.

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Permeability Prediction in Deep Coal Seam: A Case Study on the No. 3 Coal Seam of the Southern Qinshui Basin in China

The Scientific World JOURNAL ◽

10.1155/2013/161457 ◽

2013 ◽

Vol 2013 ◽

pp. 1-10 ◽

Cited By ~ 9

Author(s):

Pinkun Guo ◽

Yuanping Cheng

Keyword(s):

Coal Seam ◽

Effective Stress ◽

Axial Stress ◽

Gas Pressure ◽

Coal Bed ◽

Stress And Strain ◽

Qinshui Basin ◽

Coal Permeability ◽

Permeability Prediction ◽

Southern Qinshui Basin

The coal permeability is an important parameter in mine methane control and coal bed methane (CBM) exploitation, which determines the practicability of methane extraction. Permeability prediction in deep coal seam plays a significant role in evaluating the practicability of CBM exploitation. The coal permeability depends on the coal fractures controlled by strata stress, gas pressure, and strata temperature which change with depth. The effect of the strata stress, gas pressure, and strata temperature on the coal (the coal matrix and fracture) under triaxial stress and strain conditions was studied. Then we got the change of coal porosity with strata stress, gas pressure, and strata temperature and established a coal permeability model under tri-axial stress and strain conditions. The permeability of the No. 3 coal seam of the Southern Qinshui Basin in China was predicted, which is consistent with that tested in the field. The effect of the sorption swelling on porosity (permeability) firstly increases rapidly and then slowly with the increase of depth. However, the effect of thermal expansion and effective stress compression on porosity (permeability) increases linearly with the increase of depth. The most effective way to improve the permeability in exploiting CBM or extracting methane is to reduce the effective stress.

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