Coal fines migration: A holistic review of influencing factors

To ensure the continuous and stable exhaust process of coalbed methane wells, prevent coal fines from lowering the guidance ability of seepage channel, and solve the problem of stuck pump and submerged pump caused by gathering of coal fines, taking Hancheng block as the experimental area, this paper analyses on the source of the coal fines, and divides it into two categories of original coal fines and secondary coal fines. Based on the characteristics of coal petrography, coal structure, coal seam and engineering factors, we make analysis of their factor on the output of coal fines, and we conclude that the characteristics of coal petrography are the foundation, and the engineering is the precipitating factor, but the development of deformed coal is the primary factor. The study on the division of types of coal fines and output factors can provide a guidance for reasonable coal-fines-control measures.

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

Geofluids ◽

10.1155/2020/3974790 ◽

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.

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

Energy & Fuels ◽

10.1021/acs.energyfuels.0c04418 ◽

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

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A review of factors affecting mining operation

World Journal of Engineering ◽

10.1108/wje-03-2019-0082 ◽

2020 ◽

Vol 17 (3) ◽

pp. 457-472

Author(s):

Padma Charan Mishra ◽

Manoj Kumar Mohanty

Keyword(s):

Human Resource ◽

Influencing Factors ◽

Mining Operation ◽

Content Type ◽

Factors Affecting ◽

Quantitative Studies ◽

Holistic Review ◽

Principal Factors ◽

Corporate Social ◽

Conference Papers

Purpose The purpose of this paper is to explore operation influencing factors of mining. To collect gaps of study and to form a thematic representation of principal influencing factors and their unique influencing factors. Design/methodology/approach Articles were collected from different sources from 1974 to 2019 consisting of research articles, technical papers, expert blogs, working papers and conference papers covering various disciplines from psychology, human resource, finance and economics to mining engineering. Mining operation influencing factors were noted down. Four massively deposed mines were visited to observe the sequence of mining process. The field experts were also consulted to identify factors influencing their respected industry. Gaps were observed while comparing with the reviewed articles and opinions of field experts. Finally, senior experts were consulted to identify unique factors from the final list prepared and a framework of seven thematic categories consisting of unique factors was formulated. Findings A total of 197 sub-factors were collected from literature review and 2 sub-factors from Indian Mining experts during field study. These 199 sub-factors were initially categorised as 48 factors and one more factor was collected from Indian field experts. Finally, these 49 factors were thematically represented as principal factors and termed as operation, marketing and management, human resource, finance, resource and utility, corporate affairs and corporate social responsibility and environment. Research limitations/implications This study can be very helpful in the direction of different qualitative and quantitative studies, as the factors and sub-factors groups are identified. Originality/value The paper fulfils an identified need to provide a holistic review for understanding and documenting principal factors, unique factors and sub-factors those influence mining operation, profitability or sustainability issues of mines.

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Numerical Simulation Study of Fines Migration Impacts on an Early Water Drainage Period in Undersaturated Coal Seam Gas Reservoirs

Geofluids ◽

10.1155/2019/5723694 ◽

2019 ◽

Vol 2019 ◽

pp. 1-16

Author(s):

Xiaolong Peng ◽

Suyang Zhu ◽

Zhenjiang You ◽

Zhimin Du ◽

Peng Deng ◽

...

Keyword(s):

Coal Seam ◽

History Matching ◽

Generation Model ◽

Water Drainage ◽

Coal Seam Gas ◽

Fines Migration ◽

Deviation Factor ◽

Water Rate ◽

Deposition Processes ◽

Coal Fines

Coal fines migration exerts negative impacts on early water drainage of undersaturated coal seam gas (CSG) reservoirs. The complicated migration process results in ineffective and inaccurate forecast of coal fines production. Hence, a robust modelling tool is required to include the mechanisms of fines migration and to predict their impacts on rock and production. In this paper, fines migration in coal is categorized into three stages: generation, migration, and deposition processes. The corresponding models for different stages are established, including (1) a fines generation model, (2) the maximum fines-carrying concentration model and deviation factor of the modified Darcy model, (3) a fines deposition model, and (4) a dynamic permeability and porosity model. The above models are coupled with a water flow model, solved numerically using the finite difference method. Then, two dewatering strategies, including fast and moderate depressurization, are compared using the proposed models to study their effects on coal properties and following production. Finally, the production history of a CSG well in the Qinshui Basin, China, is utilized for history matching in a field case study. The simulation results indicate that new fines will be generated in a fast depressurization process and the water rate decline reduces the cleat permeability significantly. The newly generated fines can enhance the permeability temporarily, but they will block the flow channels and bring serious damage to the permeability when the water rate declines. The moderate depressurization strategy can produce the coal fines in a continuous mode, and the formation damage induced by fines deposition can be reduced to the acceptable level, which is the more reliable way to maintain well productivity. In addition, multiple well shut-in can trigger the irreversible fines deposition, reduce the permeability, and decrease the production rate.

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

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2015.06.012 ◽

2015 ◽

Vol 26 ◽

pp. 1542-1548 ◽

Cited By ~ 13

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

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Experimental Investigation of the Impact of Coal Fines Migration on Coal Core Water Flooding

Sustainability ◽

10.3390/su10114102 ◽

2018 ◽

Vol 10 (11) ◽

pp. 4102 ◽

Cited By ~ 5

Author(s):

Dapeng Gao ◽

Yuewu Liu ◽

Tianjiao Wang ◽

Daigang Wang

Keyword(s):

Differential Pressure ◽

Water Flooding ◽

Two Phase ◽

Fines Migration ◽

Equivalent Permeability ◽

The Core ◽

Core Samples ◽

Coal Rock ◽

Phase Water ◽

Coal Fines

Coalbed Methane (CBM) has become an important gas resource in recent decades. The brittle property of coal matrix and overactive operation make the migration of coal fines inevitable. Blockage by coal fines that plugs flow paths is a non-negligible issue that results in a significant decline in gas production. By setting different experimental conditions with the following factors—coal fines concentration of the mixture displacing fluids, constant flow pump rate, inlet pressure, outlet pressure and confining pressure—six experimental schemes were designed to investigate the two-phase water and coal fines flow in natural core samples. When the differential pressure and flooding flow reach a pseudo-steady status, the equivalent permeability of coal samples can be approximately calculated considering coal fines migration. Furthermore, the influences of coal fines migration on the cleat opening and permeability variation are analyzed in the porous coal medium. The study will benefit CBM development and save pump maintenance costs. In this work, we found that maintaining the differential pressure for a longer period may result in new cleat openings and severe coal rock damage during the single-phase water flooding process. While coal fines may plug some natural cleats and pores, especially in the core samples with micro-cleats during the two-phase flooding stage, coal fines migration significantly reduces the equivalent permeability and dewatering ability of the coal rock in the earlier flooding. While enlarging the differential pressure in two-phase water and fines flooding, breakthrough of coal fines from the samples contributes to widened cleats. While coal fines are difficult to flood into the core pores for low-permeability core samples, coal fines gather in the inlet, and it is also difficult to reach the pseudo-steady status even under higher differential pressure. The damage to permeability mainly occurs in the early stage of coal fines migration, and an abrupt increase in the flow velocity can damage reservoirs and induce substantial coal fines generation. Thus, maintaining a stable effective strength and a controlled depressurization rate during drainage can effectively constrain coal fines output and decrease permeability damage within coal reservoirs.

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