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.

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.

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

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.

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.

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

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.

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.

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

Energies ◽  
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.

scholarly journals Determination of Long Horizontal Borehole Height in Roofs and its Application to Gas Drainage

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2647
Author(s):  
Gang Wang ◽  
Cheng Fan ◽  
Hao Xu ◽  
Xuelin Liu ◽  
Rui Wang
Keyword(s):  
Numerical Simulation ◽  
Theoretical Model ◽  
Fracture Zone ◽  
Coalbed Methane ◽  
High Efficiency ◽  
Gas Drainage ◽  
Methane Drainage ◽  
Working Face ◽  
Variation Characteristics

Accurately determining the height of the gas-guiding fracture zone in the overlying strata of the goaf is the key to find the height of the long horizontal borehole in the roof. In order to determine the height, in this study we chose the 6306 working face of Tangkou Coal Mine in China as a research example and used both the theoretical model and discrete element method (DEM) numerical simulation to find the height of the gas-guiding fracture zone and applied the height to drill a long horizontal borehole in the roof of the 6303 working face. Furthermore, the borehole was utilized to deep into the roof for coalbed methane drainage and the results were compared with conventional gas drainage measures from other aspects. The height of the gas-guiding fracture zone was found to be 48.57 m in theoretical model based on the bulk coefficient and the void ratio and to be 51.19 m in the DEM numerical simulation according to the temporal and spatial variation characteristics of porosity. Taking both the results of theoretical analysis and numerical simulation into consideration, we determined that gas-guiding fracture zone is 49.88 m high and applied it to drill a long horizontal borehole deep into the roof in the 6303 working face field. Compared with conventional gas drainage measures, we found that the long horizontal borehole has the high stability, high efficiency and strong adaptability for methane drainage.

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