Study on Influencing Factors of Coal Fines Produced by CBM Wells in Hancheng Block, Shaanxi Province, China

Zhu, Xue Shen; Cao, Daiyong; Ying, Wei; Yuan, Yuan; Yao, Zheng; Zhou, Jinjun; Zhang, Xiaoyu

doi:10.4028/www.scientific.net/amm.295-298.3228

Cited by 3 publications

(5 citation statements)

References 2 publications

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“…Zhang et al developed reasonable measures to control coal fine production by analyzing the mechanism of coal fine production . Zhu et al provided guidance on coal fine control measures by dividing coal fine types and production factors . Li et al mixed calcium sulfoaluminate particles with sand to create a new fracturing proppant that improves the efficiency of CBM extraction by reducing coal fine generation and preventing coal fine migration .…”

Section: Introductionmentioning

confidence: 99%

“…15 Zhu et al provided guidance on coal fine control measures by dividing coal fine types and production factors. 18 Li et al mixed calcium sulfoaluminate particles with sand to create a new fracturing proppant that improves the efficiency of CBM extraction by reducing coal fine generation and preventing coal fine migration. 19 Shi et al found that NaHCO 3 may fix a portion of coal fines at its source through coagulation and promote the movement of another portion of fine particles by reducing the viscosity, 20 thus reducing the negative impact caused by coal fines.…”

Section: Introductionmentioning

confidence: 99%

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SDBS-Induced Dispersion Effect of High-Rank Coal Fines to Inhibit the Conductivity of Propping Fractures

Lyu

Xiong

et al. 2023

Energy Fuels

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Coal fines are commonly produced in the form of aggregates during the development of coalbed methane (CBM), which significantly restricts the well productivity. Specifically, the reunion state of coal fines plays a key role in impacting the conductivity of propping fractures after fracturing. In this work, the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) was selected to control the reunion state of coal fines. Visualized simulations of coal fines’ transport behavior in proppants with different particle sizes were carried out under low constant pressure based on sand pack experiments. Moreover, the characteristics of coal fine filling and production in propping fractures were obtained. The results indicate that SDBS has a dispersion effect on coal fine aggregates in the KCl fracturing fluid, with an average reduction of 36% in particle size. There is a positive correlation between the proppant size and the permeability coefficient of propping fractures. Coal fines reduce the permeability coefficients obviously, which first rapidly decrease and then slowly reach a stable stage. In the first stage, the changes of permeability coefficients are affected by the relative particle sizes of the proppant and the coal fine, which is consistent with the classic 1/3 sealing mechanism. In the second stage, SDBS increases the amount of coal fines between the proppant pore throats, and the thickness of the filter cake formed from coal fines at the entrance of the propping fracture increases, resulting in the inhibition of fracture conductivity. Additionally, the output of coal fines is increased dramatically induced by SDBS. Finally, the inhibitory effect of SDBS on fluid production was verified by comparing the water production and coal fine content of two field wells CW # 1 and CW # 2. This study has guiding significance for the output and control of coal fines in low-pressure production of CBM wells.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

SDBS-Induced Dispersion Effect of High-Rank Coal Fines to Inhibit the Conductivity of Propping Fractures

Lyu

Xiong

et al. 2023

Energy Fuels

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“…The issue of coal fines production has long been severely affecting the stable production of coalbed methane. During the generation and migration process, coal fines can block coal reservoir fractures, causing a decrease in reservoir permeability and blocking the bottom-hole screen pipes and pump inlets, leading to production failures. − The production of coal fines during the coalbed methane production process is controlled by engineering and geological factors, − with different production stages exhibiting varying coal fines production patterns. − The drilling process, including the grinding of coal seams by drilling tools, the erosion of coal reservoirs by water flow during drainage, and the abrasion of coal reservoirs by fracturing fluids or proppants during fracturing, can result in a large amount of coal fines. − In addition, stress changes induced by coalbed methane production can also lead to shear failure in the coal reservoir, resulting in the generation of coal fines . Geological structures and coal quality also affect the production of coal fines; , tectonic coal, which forms under tectonic deformation, has a complex pore structure and features low strength and low permeability, making it prone to damage and the production of large amounts of coal fines during the production process − and causing reservoir damage and seriously affect production.…”

Section: Introductionmentioning

confidence: 99%

“… 12 − 15 In addition, stress changes induced by coalbed methane production can also lead to shear failure in the coal reservoir, resulting in the generation of coal fines. 16 Geological structures and coal quality also affect the production of coal fines; 5 , 6 tectonic coal, which forms under tectonic deformation, has a complex pore structure and features low strength and low permeability, making it prone to damage and the production of large amounts of coal fines during the production process 17 − 20 and causing reservoir damage and seriously affect production.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Impact of Coal Fines Migration on Pores and Permeability of Cataclastic Coal

Xie,

Wei,

Liu

et al. 2023

ACS Omega

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During the production process of coalbed methane, the generation and migration of coal fines can obstruct fractures in coal reservoirs and reduce their permeability. In order to investigate the effects of coal fines migration on the porosity and permeability of coal reservoirs, we conducted core water flooding experiments, low-field nuclear magnetic resonance (NMR), and low-temperature N2 adsorption experiments to study the variations in porosity and permeability of cataclastic coal during coal fines migration and the impact of coal fines migration on porosity and permeability. The experimental results reveal that the initial porosity ratio of cataclastic coal exhibits the characteristics of micropore > macropore > transitional pore > mesopore, with the pore types being predominantly fissured. The porosity of pores larger than 1000 nm and those larger than 10,000 nm exhibit consistent trends before and after water flooding, indicating that the blockage or unblocking of pores with radius larger than 10,000 nm by coal fines can also cause blockage or unblocking of some interconnected macropore. The early stage of flooding is the main period for coal fines migration and production in cataclastic coal, during which the mass concentration of coal fines production is higher and some macropores and fractures become blocked, resulting in a larger decrease in porosity. The higher the initial permeability of cataclastic coal samples with a larger end-face fracture density, the more similar the variations in porosity and permeability of pores larger than 10,000 nm during the flooding experiment, indicating that coal fines mainly block interconnected pores and fractures with radius larger than 10,000 nm through migration, thereby reducing permeability. This study provides a theoretical basis for the efficient production of coalbed methane.

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“…If the fallen coal fine can be properly discharged, the seepage channel can be expanded, the permeability can be improved, and the gas production of a single well can be increased. On the other hand, when the detached coal fines are too large or the hydrodynamic conditions are insufficient to transport them, the precipitated coal fine will block the pores and fractures of the coal reservoir, leading to a decrease in permeability [6,7]. The impact of a large amount of coal fine production on the CBM drainage mainly includes the following aspects [8]: (1) reduced permeability, difficulty in drainage and pressure reduction, and difficulty in gas desorption; (2) coal fine can cause wear on the pump barrel and plunger, causing problems such as buried pipe columns and pump jamming due to the accumulation of coal fine; and (3) the mixture of coal fine increases the fluid concentration and the construction pressure.…”

Section: Introductionmentioning

confidence: 99%

Response and Mechanism of Coal Fine Production to Differential Fluid Action in the Baode Block, Ordos Basin

Wang,

Cui,

et al. 2023

Processes

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The Baode Block in the Ordos Basin is currently one of the most successfully developed and largest gas field of low–medium rank coal in China. However, the production of coal fine has affected the continuous and stable drainage and efficient development of this area. The special response and mechanism of differential fluid action during the drainage process is one of the scientific issues that must be faced to solve this production problem. In view of this, the evolution laws of a reservoir’s macro–micro physical characteristics under different fluid conditions (fluid pressure, salinity) have been revealed, and the response mechanism of coal fine migration-induced reservoir damage has been elucidated through a nuclear magnetic resonance online displacement system. The results indicated that pores at different scales exhibited varying patterns with increasing displacement pressure. The proportion of the mesopore and transition pore is not affected by salinity and is positively correlated with displacement pressure. When the salinity is between 3000 mg/L and 8000 mg/L, the proportion of macropore and micropore showed parabolic changes with increasing displacement pressure, and there was a lowest point. The evolution law of pore fractal dimension and permeability change rate under the action of different fluids jointly showed that there was an optimal salinity for the strongest reservoir sensitivity enhancement effect. The mechanical and chemical effects of fluid together determined the damage degree of coal reservoir induced by coal fine migration.

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Study on Influencing Factors of Coal Fines Produced by CBM Wells in Hancheng Block, Shaanxi Province, China

Cited by 3 publications

References 2 publications

SDBS-Induced Dispersion Effect of High-Rank Coal Fines to Inhibit the Conductivity of Propping Fractures

SDBS-Induced Dispersion Effect of High-Rank Coal Fines to Inhibit the Conductivity of Propping Fractures

Experimental Investigation on the Impact of Coal Fines Migration on Pores and Permeability of Cataclastic Coal

Response and Mechanism of Coal Fine Production to Differential Fluid Action in the Baode Block, Ordos Basin

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