Quantification of Gas and Water Transfer Between Coal Matrix and Cleat Network During Drainage Process

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Mingjun Zou ◽  
Chongtao Wei ◽  
Miao Zhang ◽  
Xiaochun Lv
Keyword(s):  
Coalbed Methane ◽  
Gas Production ◽  
Water Transfer ◽  
Gas Transfer ◽  
Critical Porosity ◽  
Coal Matrix ◽  
Gas Desorption ◽  
Southern Qinshui Basin ◽  
Fluid Transfer

Mathematical models were developed in this study to quantify the gas and water transfer between coal matrix and cleat network during coalbed methane (CBM) drainage, which can be helpful to achieve some useful findings on features of fluid migration within coal reservoirs during drainage process. A typical CBM well located at southern Qinshui basin of China was selected as the case study. The ineffective critical porosity was defined and was used to acquire fluid transfer as a key parameter of the established model. Results showed that both the gas and water transfer controlled the drainage performances. Water drained from cleat was found to be the main reason for the decrease in the reservoir pressure at the early drainage stage, while the water transfer became significantly more important with the continuation of the drainage process. The first peak of gas production was controlled by gas desorption, and the subsequent peaks were influenced by the gas transfer.

scholarly journals A Comprehensive Coal Reservoir Classification Method Base on Permeability Dynamic Change and Its Application

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 644 ◽  
Author(s):  
Xinlu Yan ◽  
Songhang Zhang ◽  
Shuheng Tang ◽  
Zhongcheng Li ◽  
Yongxiang Yi ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Dynamic Change ◽  
Initial Permeability ◽  
Gas Production ◽  
Gas Desorption ◽  
Reservoir Permeability ◽  
Geological Conditions ◽  
Production Stages ◽  
Productivity Potential ◽  
Coal Reservoir

Due to the unique adsorption and desorption characteristics of coal, coal reservoir permeability changes dynamically during coalbed methane (CBM) development. Coal reservoirs can be classified using a permeability dynamic characterization in different production stages. In the single-phase water flow stage, four demarcating pressures are defined based on the damage from the effective stress on reservoir permeability. Coal reservoirs are classified into vulnerable, alleviative, and invulnerable reservoirs. In the gas desorption stage, two demarcating pressures are used to quantitatively characterize the recovery properties of permeability based on the recovery effect of the matrix shrinkage on permeability, namely the rebound pressure (the pressure corresponding to the lowest permeability) and recovery pressure (the pressure when permeability returns to initial permeability). Coal reservoirs are further classified into recoverable and unrecoverable reservoirs. The physical properties and influencing factors of these demarcating pressures are analyzed. Twenty-six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were examined as a case study, showing that there is a significant correspondence between coal reservoir types and CBM well gas production. This study is helpful for identifying geological conditions of coal reservoirs as well as the productivity potential of CBM wells.

Log evaluation of a coalbed methane (CBM) reservoir: a case study in the southern Qinshui basin, China

2014 ◽  
Vol 11 (1) ◽  
Author(s):  
Hou Jie ◽  
Zou Changchun ◽  
Huang Zhaohui ◽  
Xiao Liang ◽  
Yang Yuqing ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Qinshui Basin ◽  
Southern Qinshui Basin

scholarly journals Modeling and prediction for gas production during coalbed methane drainage based on two indirect reservoir parameters

2018 ◽  
Vol 36 (6) ◽  
pp. 1424-1437 ◽  
Author(s):  
Mingjun Zou ◽  
Xiaochun Lv ◽  
Zhiquan Huang ◽  
Simin Wei ◽  
Miao Zhang ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Good Accuracy ◽  
Simulated Data ◽  
Gas Production ◽  
Methane Drainage ◽  
Modeling And Prediction ◽  
Cubic Polynomial ◽  
Southern Qinshui Basin ◽  
Two Parameters ◽  
Gas Production Prediction

Two indirect parameters influencing coalbed methane (CBM) drainage performances are proposed in this paper, which are effective desorption radius and difference between reservoir pressure and critical desorption pressure (DRPCDP). Variations of the two parameters during CBM drainage are investigated, which shows that they have a linear relationship. By using formula derivations, a theoretical model for gas production prediction is built. It suggests that the cumulative gas production is a product of square of effective desorption radius with DRPCDP, and there is also a cubic polynomial relationship between cumulative gas production and linear average DRPCDP. Furthermore, well PM01 located at southern Qinshui basin of China is selected as a case, and a commercial software is adopted to predict the gas production. Compared with the simulated and modeled cumulative gas productions, the simulated data match well with the modeled data, which indicates that the model has a good accuracy.

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

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.

Impact of Various Parameters on the Production of Coalbed Methane

SPE Journal ◽  
2013 ◽  
Vol 18 (05) ◽  
pp. 910-923 ◽  
Author(s):  
Zhongwei Chen ◽  
Jishan Liu ◽  
Akim Kabir ◽  
Jianguo Wang ◽  
Zhejun Pan
Keyword(s):  
Time Constant ◽  
Coalbed Methane ◽  
Dominant Role ◽  
Gas Production ◽  
Fracture Permeability ◽  
Permeability Model ◽  
Gas Desorption ◽  
Desorption Time ◽  
Matrix Blocks ◽  
Cbm Production

Summary Coalbed-methane (CBM) reservoirs are naturally fractured formations, comprising both permeable fractures and matrix blocks. The interaction between fractures and matrix presents a great challenge for the forecast of CBM reservoir performance. In this work, a dual-permeability model was applied to study the parameter sensitivity on the CBM production, because the dual-permeability model incorporates not only the influence from matrix and fractures but also that between adjacent matrix blocks. The mass exchange between two systems is defined as a function of desorption time constant at the standard condition, coal matrix porosity, and the difference of gas pressure between two systems. Correspondingly, gas diffusivity in matrix is considered as a variable and represented by a function of shape factor, gas desorption time, and reservoir pressure. These relations are integrated into a fully coupled numerical model of coal geomechanical deformation and gas desorption/gas flow in both systems. This numerical approach demonstrates the important nonlinear effects of the complex interaction between matrix and fractures on CBM production behaviors that cannot be recovered without rigorously incorporating geomechanical influences. This model was then used to investigate the sensitivity of CBM extraction behavior to different controlling factors, including gas desorption time constant, initial fracture permeability, fracture spacing, swelling capacity, desorption capacity, production pressure, and fracture and matrix porosities. Modeling results show that the peak magnitudes of gas-production rate increase with initial fracture permeability, sorption and swelling capacities, and matrix porosity, and decrease with gas desorption time constant and production pressure. These results also show dramatic increase in gas-production efficiency with decreasing magnitudes of fracture spacing. The comparison of the transient contributions of the desorbed gas and the free phase gas from the matrix system to gas production shows that the free phase gas plays the dominant role at the early stage, but diminishes when the adsorption phase gas takes over the dominant role, indicating the necessity of incorporating free phase gas impact in simulation models. The numerical model was also applied to match the history data from a gas-production well. A better matching result than that for the single-permeability model demonstrates the potential capability of the dual-permeability model for the forecast of CBM production.

scholarly journals Experimental study on the velocity sensitivity of coal reservoir during coalbed methane drainage in southern Qinshui Basin

2018 ◽  
Vol 36 (6) ◽  
pp. 1593-1608 ◽  
Author(s):  
Huihu Liu ◽  
Shuxun Sang ◽  
Junhua Xue ◽  
Tianhe Lan ◽  
Hongje Xu ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Coalbed Methane ◽  
Gas Production ◽  
Solid Particles ◽  
Water Production ◽  
Formation Water ◽  
Coal Permeability ◽  
Velocity Sensitivity ◽  
Coalbed Methane Reservoir ◽  
Southern Qinshui Basin

Determination of the velocity sensitivity in coal reservoirs during the different production stages of coalbed methane wells is fundamentally crucial to adopt appropriate drainage technologies. To address this need, simulation experiments of coal samples from southern Qinshui Basin in China were conducted to test the variation of coal permeability with fluid flow. The pore structures were tested before and after the simulation experiment by using mercury injections, and the pore shape was observed using scanning electron microscope (SEM). The results show that formation water with fast flow may remove solid particles and that there is no velocity sensitivity under the experimental conditions of different coal samples and formation waters during the water production and depressurization stages of the coalbed methane well. There is a trend of the velocity sensitivity in the coalbed methane reservoir showing high concentration of solid particles during the stages of water production and depressurization. Coal permeability decreases with the increase of the fluid flow, there are different levels of velocity sensitivity in the coalbed methane reservoir during gas production of the coalbed methane well. The critical drainage flow should be within 11.26 m3/d during gas production of the coalbed methane well. The generation of the velocity sensitivity will make the pore structure of the coalbed methane reservoir poorly. During the stage of gas production, the formation water produces poorly, and the solid particles adhered to the surface of coal easily fall off and are deposited in the transition pore and micropore, which further results in the decrease of coal permeability.

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