scholarly journals An Experimental Study on Coal Fines Migration during Single Phase Water Flow

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Wenlong Han ◽  
Yanbin Wang ◽  
Jingjing Fan ◽  
Yong Li ◽  
Xiang Wu ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Water Flow ◽  
Coalbed Methane ◽  
Confining Pressure ◽  
Fines Migration ◽  
Reservoir Permeability ◽  
Confining Pressures ◽  
Coal Fines ◽  
Flow Velocities ◽  
Loss Rates

Coal fines migration and intrusion in coal fractures affect coalbed methane (CBM) wells performance by reducing reservoir permeability and production continuity. Physical simulations are conducted to investigate the permeability variation under different diameter coal fines intrusion at various flow velocities and confining pressures. The results show that the conductivity of fractures is dramatically reduced and hardly recover to its initial condition after coal fines intrusion. The permeability after coal fines intrusion (Pcfi) has no direct correlation with the increase of flooding velocity, while decreases with the increase of confining pressures. The fractures can be totally blocked by coal fines, while penetration also happened during the flooding process, causing permeability fluctuation. The permeability loss rates value for 80-120 mesh coal fines intrusion are generally <60% compared with the initial permeability, including the flow velocity of 2, 3, 4, 6, 8, and 10 mL/min with confining pressure of 6 MPa and the confining pressure of 2, 3, 4, 5, and 6 MPa with flow velocity of 3 mL/min. However, under 120+ mesh coal fines condition, the permeability loss rates are higher than 85% under most flow velocities and confining pressures. When coal fines become smaller, the permeability loss rates decrease to be lower than 45%, and part the coal fines are discharged with the water flow. Thus, coal fines proper dischargement can partly maintain the reservoir permeability during coalbed methane production. The results would be useful in understanding coal fines intrusion behaviors and its controlling strategies during CBM drainage.

scholarly journals Quantitative optimization of drainage strategy of coalbed methane well based on the dynamic behavior of coal reservoir permeability

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xinlu Yan ◽  
Songhang Zhang ◽  
Shuheng Tang ◽  
Zhongcheng Li ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Dynamic Behavior ◽  
Water Flow ◽  
Coalbed Methane ◽  
Single Phase ◽  
Reservoir Permeability ◽  
Geological Conditions ◽  
Cbm Production ◽  
Coal Reservoir ◽  
Flow Stage

AbstractThe development of coalbed methane (CBM) is not only affected by geological factors, but also by engineering factors, such as artificial fracturing and drainage strategies. In order to optimize drainage strategies for wells in unique geological conditions, the characteristics of different stages of CBM production are accurately described based on the dynamic behavior of the pressure drop funnel and coal reservoir permeability. Effective depressurization is achieved by extending the pressure propagation radius and gas desorption radius to the well-controlled boundary, in the single-phase water flow stage and the gas–water flow stage, respectively, with inter-well pressure interference accomplished in the single-phase gas flow stage. A mathematic model was developed to quantitatively optimize drainage strategies for each stage, with the maximum bottom hole flow pressure (BHFP) drop rate and the maximum daily gas production calculated to guide the optimization of CBM production. Finally, six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were used as a case study to verify the practical applicability of the model. Calculation results clearly indicate the differences in production characteristics as a result of different drainage strategies. Overall, if the applied drainage strategies do not achieve optimal drainage results, the coal reservoir could be irreversibly damaged, which is not conducive to expansion of the pressure drop funnel. Therefore, this optimization model provides valuable guidance for rational CBM drainage strategy development and efficient CBM production.

scholarly journals Mechanism of Structural Damage in Low Permeability Coal Material of Coalbed Methane Reservoir under Cyclic Cold Loading

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 519
Author(s):  
Hewan Li ◽  
Jianping Zuo ◽  
Laigui Wang ◽  
Pengfei Li ◽  
Xiaowei Xu
Keyword(s):  
Liquid Nitrogen ◽  
Coalbed Methane ◽  
Structural Damage ◽  
Coal Sample ◽  
Gas Permeability ◽  
Confining Pressure ◽  
Damage Degree ◽  
Confining Pressures ◽  
Coalbed Methane Reservoir ◽  
The Relationship

The pore and fracture structure of coal is the main factor that affects the storage and seepage capacity of coalbed methane. The damage of coal structure can improve the gas permeability of coalbed methane. A coal sample with a drilled hole was kept inside of a custom-designed device to supply confining pressure to the coal sample. Liquid nitrogen was injected into the drilled hole of the coal sample to apply cyclic cold loading. Confining pressures varying from 0~7 MPa to the coal sample were applied to explore the relationship between the structural damage and confining pressure. The structural damage rules of coal samples under different confining pressure were revealed. The results showed that: (1) The structural damage degree of the coal sample increases with the increase of confining pressure; (2) The coal sample was broken after three cycles of cold loading under 7 MPa confining pressure; (3) Without confining pressure, the coal sample is more likely to be damaged or even destroyed by cold liquid nitrogen. (4) The fracture extends along the stratification direction of coal samples, which is significant for coal samples with original fractures, but not obvious for the coal sample without fracture. The research results provide a new method and theoretical basis for permeability improvement of the coal seam.

Coal Fines Migration, Deposition, and Output Simulation during Drainage Stage in Coalbed Methane Production

2021 ◽  
Vol 35 (6) ◽  
pp. 4901-4913
Author(s):  
Wenlong Han ◽  
Yanbin Wang ◽  
Yong Li ◽  
Xiaoming Ni ◽  
Xiang Wu ◽  
...  
Keyword(s):  
Methane Production ◽  
Coalbed Methane ◽  
Fines Migration ◽  
Coalbed Methane Production ◽  
Coal Fines

An experimental study of coal-fines migration in Coalbed-methane production wells

2015 ◽  
Vol 26 ◽  
pp. 1542-1548 ◽  
Author(s):  
Guoqing Han ◽  
Kegang Ling ◽  
Huaxiao Wu ◽  
Fei Gao ◽  
Feng Zhu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Methane Production ◽  
Coalbed Methane ◽  
Fines Migration ◽  
Production Wells ◽  
Coalbed Methane Production ◽  
Coal Fines

Generalized Prediction for Subcooled Water Flow Boiling CHFs Versus Outlet Subcoolings for Flow Velocities at Outlet Pressures in Various Tubes

2004 ◽  
Author(s):  
Akira Sakurai ◽  
Katsuya Fukuda
Keyword(s):  
Flow Velocity ◽  
Water Flow ◽  
Flow Boiling ◽  
Hydrodynamic Instability ◽  
Vertical Tube ◽  
Spontaneous Nucleation ◽  
Outlet Pressure ◽  
Subcooled Water ◽  
Inside Diameter ◽  
Flow Velocities

The mechanisms and corresponding correlations for the subcooled water flow boiling CHFs for outlet subcoolings in a vertical tube having an inside diameter, D, and length-to-diameter, L/D, ratio for a flow velocity with outlet pressure as a parameter were previously clarified by the authors based on the existing flow boiling CHF data measured using the tubes having the diameters ranging from 0.4 to 12 mm, and the L/D ratios ranging from 2.4 to 96.6 for the flow velocities ranging from 5 to 130 m/s, at the pressures ranging from 0.34 to 17.2 MPa. Namely the CHF, qcr,sub, versus outlet subcooling, Δsub,out, for a flow velocity with outlet pressure as a parameter were divided into four regions for outlet subcoolings: first the CHF decreased down to minimum one (first region), secondly it increased up to maximum one (second region), thirdly it decreased down to minimum one (third region), and finally it again increased monotonously with an increase in outlet subcooling. The CHFs belonging to third region became significant with a decrease in diameter for the smaller tubes with diameters such as around 1 mm, and on the other hand, those almost disappeared with an increase in diameter for the larger tubes with the diameters such as around 9 mm. The CHFs belonging to second region significantly depending on the pressure and tube diameter, and those belonging to fourth region being almost independent of the pressure, and tube inside diameter, D, and length-to-diameter, L/D, ratio were well expressed by the unified subcooled water flow boiling CHF correlations representing the CHF resulting from the hydrodynamic instability, HI, and those representing the CHF resulting from the heterogeneous spontaneous nucleation, HSN, on the inside surface near the exit of heated tube respectively. In the present paper, the generalized evaluation of the maximum qcr,sub of the qcr,sub data belonging to 2nd region resulting from the HI unsolved before was realized solving the simultaneous equations consisted with the unified qcr,sub correlation representing qcr,sub resulting from the HI previously derived and the generalized correlation for the Δsub,out,max at corresponding qcr,sub,max newly derived.

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

Intraoperative transesophageal assessment of coronary artery flow can predict 5 type myocardial infarction

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A Zagatina ◽  
M Novikov ◽  
N Zhuravskaya ◽  
V Balakhonov ◽  
S Efremov ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Cardiac Surgery ◽  
Coronary Artery ◽  
Flow Velocity ◽  
Coronary Flow ◽  
Index Number ◽  
Left Main ◽  
Coronary Flow Velocity ◽  
Before And After ◽  
Flow Velocities

Abstract Background Stenosis of a coronary artery results in an increase in flow velocity in the pathologic segment. Effective grafting should decrease the stenotic native coronary velocity according to hemodynamic law. The range of decreased velocity before and after cardiac surgery can hypothetically reflect the effectiveness of a graft. The aim of the study is to determine if measuring coronary flow velocity changes during coronary artery bypass grafting (CABG) can predict intraoperative myocardial infarction. Methods One hundred sixty-six (166) consecutive patients (121 men, 64±9 years old) referred for cardiac surgery, were prospectively included in the study. A standard basic perioperative transesophageal echocardiography (TEE) examination was performed with additional scans of the left main, left anterior descending (LAD), and circumflex (LCx) arteries' proximal segments. Measurements of coronary flow velocities were performed before and after grafting in the same sites of the arteries. The maximal value of cardiac troponin I (cTnI) after CABG and the additive criteria were accounted for in the analysis as it is described in the expert consensus document for Type 5 myocardial infarction (MI) definition. Results One hundred sixty-three patients (98%) had arterial hypertension, 28 patients (17%) had diabetes mellitus, 35 patients (21%) were currently smokers. The feasibility of coronary flow assessment during cardiac operations was 95%. Before grafting, the mean velocity in the left main artery was 91±49 cm/s, in LAD 101±35 cm/s, and in LCx 117±49 cm/s. There was a significant correlation between changes in coronary flow velocities during operation and the value of cTnI (R=0.34, p&lt;0.0001). Ten patients met the criteria for Type 5 MI. There were no differences in age, body mass index, number of coronary arteries with stenoses, frequency of prior MI, ejection fraction or coronary flow velocity before surgery in patients with and without Type 5 MI. The group of patients with Type 5 MI had an increase in native artery velocities during surgery in comparison with patients without MI, who had a significant decrease in coronary flow velocity after grafting (30±48 vs. −10±30 cm/s; p&lt;0.0006). Increases in native coronary velocities greater than 3 cm/s predicted Type 5 MI with 81% accuracy (sensitivity 88%, specificity 70%). Conclusion Coronary flow velocity assessment during cardiac surgery could predict an elevation of cardiac troponins and Type 5 MI. Funding Acknowledgement Type of funding source: None

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.

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