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

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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Biogeochemistry and the associated redox signature of co-produced water from coalbed methane wells in the Shizhuangnan block in the southern Qinshui Basin, China

Energy Exploration & Exploitation ◽

10.1177/0144598720911107 ◽

2020 ◽

Vol 38 (4) ◽

pp. 1034-1053

Author(s):

Yang Li ◽

Shuheng Tang ◽

Songhang Zhang ◽

Zhaodong Xi ◽

Pengfei Wang

Keyword(s):

Coalbed Methane ◽

Produced Water ◽

Dissolved Inorganic Carbon ◽

Gas Production ◽

Redox Conditions ◽

Effective Parameters ◽

Production Rates ◽

Qinshui Basin ◽

Southern Qinshui Basin ◽

Biogeochemical Parameters

To meet the global energy demands, the exploitation of coalbed methane has received increasing attention. Biogeochemical parameters of co-produced water from coalbed methane wells were performed in the No. 3 coal seam in the Shizhuangnan block of the southern Qinshui Basin (China). These biogeochemical parameters were firstly utilized to assess coal reservoir environments and corresponding coalbed methane production. A high level of Na+ and HCO3– and deuterium drift were found to be accompanied by high gas production rates, but these parameters are unreliable to some extent. Dissolved inorganic carbon (DIC) isotopes δ13CDIC from water can be used to distinguish the environmental redox conditions. Positive δ13CDIC values within a reasonable range suggest reductive conditions suitable for methanogen metabolism and were accompanied by high gas production rates. SO42–, NO3– and related isotopes affected by various bacteria corresponding to various redox conditions are considered effective parameters to identify redox states and gas production rates. Importantly, the combination of δ13CDIC and SO42– can be used to evaluate gas production rates and predict potentially beneficial areas. The wells with moderate δ13CDIC and negligible SO42– represent appropriate reductive conditions, as observed in most high and intermediate production wells. Furthermore, the wells with highest δ13CDIC and negligible SO42– exhibit low production rates, as the most reductive environments were too strict to extend pressure drop funnels.

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Geological Controls of the Coalbed Methane (CBM) Enrichment in the Zhengzhuang Coal Zone, Southern Qinshui Basin, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.616-618.234 ◽

2012 ◽

Vol 616-618 ◽

pp. 234-239 ◽

Cited By ~ 2

Author(s):

Jun Qian Li ◽

Da Meng Liu ◽

Yan Bin Yao ◽

Yi Dong Cai ◽

Xiao Qain Guo ◽

...

Keyword(s):

Coal Seam ◽

Coalbed Methane ◽

Adsorptive Capacity ◽

Qinshui Basin ◽

Coalbed Gas ◽

Southern Qinshui Basin ◽

Exploration And Development

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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Geological and hydrological controls on the accumulation of coalbed methane within the No. 3 coal seam of the southern Qinshui Basin

International Journal of Coal Geology ◽

10.1016/j.coal.2017.09.008 ◽

2017 ◽

Vol 182 ◽

pp. 94-111 ◽

Cited By ~ 34

Author(s):

Junyan Zhang ◽

Dameng Liu ◽

Yidong Cai ◽

Zhejun Pan ◽

Yanbin Yao ◽

...

Keyword(s):

Coal Seam ◽

Coalbed Methane ◽

Qinshui Basin ◽

Southern Qinshui Basin

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Comprehensive Analysis of Factors Affecting Coalbed Methane Productivity: A Case Study of Southern Qinshui Basin

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.962-965.21 ◽

2014 ◽

Vol 962-965 ◽

pp. 21-28

Author(s):

Bei Liu ◽

Wei Hua Ao ◽

Wen Hui Huang ◽

Qi Lu Xu ◽

Juan Teng

Keyword(s):

Coalbed Methane ◽

Gas Production ◽

Gas Content ◽

Burial Depth ◽

Reservoir Pressure ◽

Factors Affecting ◽

Qinshui Basin ◽

Geological Conditions ◽

Geological Factors ◽

Southern Qinshui Basin

Coalbed methane (CBM) productivity is influenced by various factors. Based on field production data and test data of southern Qinshui Basin, factors including geological factors, engineering factors and drainage factors that affect CBM productivity are analyzed. Analytic hierarchy process (AHP) is introduced to calculate the contribution of each parameter to CBM productivity. A three-level model for evaluating CBM productivity based on AHP is established. The results show that average daily gas production of single well in southern Qinshui Basin increases with gas content, coal seam thickness, permeability, porosity, gas saturation, critical desorption pressure. Filling minerals in pores and fractures of coal can decrease gas content, porosity and permeability of coal reservoir. When burial depth is deeper than 500m or reservoir pressure is greater than 2MPa and burial depth is shallower than 1000m or reservoir pressure is less than 10MPa, CBM productivity is relatively high. According to the calculation, the weight of geological factors, engineering factors and drainage factors are 50%, 25% and 25%, respectively. Reservoir physical properties, geological conditions, fracturing technology and drainage process have the most impact, the weight of which are 33.33%, 16.67%, 11.79%, and 15.00%, respectively.

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Quantify Coal Macrolithotypes of a Whole Coal Seam: A Method Combing Multiple Geophysical Logging and Principal Component Analysis

Energies ◽

10.3390/en14010213 ◽

2021 ◽

Vol 14 (1) ◽

pp. 213

Author(s):

Chao Cui ◽

Suoliang Chang ◽

Yanbin Yao ◽

Lutong Cao

Keyword(s):

Principal Component Analysis ◽

Coal Seam ◽

Coalbed Methane ◽

Principal Component ◽

Component Analysis ◽

Gas Production ◽

Index Model ◽

Geophysical Logging ◽

The Relationship ◽

Observation Results

Coal macrolithotypes control the reservoir heterogeneity, which plays a significant role in the exploration and development of coalbed methane. Traditional methods for coal macrolithotype evaluation often rely on core observation, but these techniques are non-economical and insufficient. The geophysical logging data are easily available for coalbed methane exploration; thus, it is necessary to find a relationship between core observation results and wireline logging data, and then to provide a new method to quantify coal macrolithotypes of a whole coal seam. In this study, we propose a L-Index model by combing the multiple geophysical logging data with principal component analysis, and we use the L-Index model to quantitatively evaluate the vertical and regional distributions of the macrolithotypes of No. 3 coal seam in Zhengzhuang field, southern Qinshui basin. Moreover, we also proposed a S-Index model to quantitatively evaluate the general brightness of a whole coal seam: the increase of the S-Index from 1 to 3.7, indicates decreasing brightness, i.e., from bright coal to dull coal. Finally, we discussed the relationship between S-Index and the hydro-fracturing effect. It was found that the coal seam with low S-Index values can easily form long extending fractures during hydraulic fracturing. Therefore, the lower S-Index values indicate much more favorable gas production potential in the Zhengzhuang field. This study provides a new methodology to evaluate coal macrolithotypes by using geophysical logging data.

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