Fracture and pore structure dynamic evolution of coals during hydraulic fracturing

Lu, Yiyu; Wang, Li; Ge, Zhaolong; Zhou, Zhe; Deng, Kai; Zuo, Shaojie

doi:10.1016/j.fuel.2019.116272

Cited by 73 publications

(39 citation statements)

References 44 publications

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“…As shown in Figure 8, the porosity in coal directly determines the gas displacement. In contrast, in the process of water injection, the porosity of coal will also be changed by the pressurized water (Lu et al, 2020). Therefore, the effect of water injection on the coal pore structure was investigated, including the pore size and its distribution.…”

Section: The Effect Of Water Injection On the Pore Structurementioning

confidence: 99%

Methane displacement characteristic of coal and its pore change in water injection

Chen

Shan

Sun

et al. 2020

Energy Exploration & Exploitation

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Coalbed methane as one type of clean energy has become an important gas resource recently. High-pressure water injection in coal seams is an effective approach for improving gas extraction efficiency, which is determined by the gas displacement characteristic and pore structure of coal. To investigate the gas displacement characteristics in coal and its pore response and influential factors, gas adsorption and water injection experiments were conducted under different conditions. The results show that the gas displacement caused by the water injection undergoes three stages: rapid increase, slow increase, and almost constant. The wetting process in water injection includes three processes: wetting, soaking, and spreading, and the wettability of coking coal is best, followed by lean coal and anthracite. The amount of gas driven by the water increases with increasing water injection pressure, and it is more favorable to increase the injection pressure to improve the gas displacement effect under the relatively low injection pressure. The lower the coal rank, the better the gas displacement effect due to the higher porosity of the coal, and the longer the early gas displacement stage. The high adsorption equilibrium pressure can improve the gas displacement effect; for the relatively high adsorption equilibrium pressure, the gas displacement effect is better. After water injection in coal, the large fractures and pores dramatically increase in size, especially for the low metamorphic coals coking coal, contributing to the majority of the increase in porosity. The results of this study can provide a theoretical foundation for the wide application of water injection technology for efficient gas drainage in coal mines.

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Section: The Effect Of Water Injection On the Pore Structurementioning

confidence: 99%

Methane displacement characteristic of coal and its pore change in water injection

Chen

Shan

Sun

et al. 2020

Energy Exploration & Exploitation

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show abstract

“…Yiyu Lu used nuclear magnetic resonance method to dynamically monitor the development of fractures during hydraulic fracturing of coal samples and observed that the pore pressure and effective stress of coal caused the pores to rupture, close, and continuously reorganize. 18 Guojian Cheng used a special device to simulate the shear behavior in the process of fracturing coal samples. Cheng's experiment showed that hydraulic tensile fractures are easy to close and inhibit the increase in permeability, while shear fractures can effectively enhance the permeability of coal.…”

Section: Introductionmentioning

confidence: 99%

Variation law of roof stress and permeability enhancement effect of repeated hydraulic fracturing in low‐permeability coal seam

Liangwei

2021

Energy Science & Engineering

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“…More research has been conducted on conventional hydraulic fracturing with a constant pumping rate. At present, a large number of engineering applications have been carried out in coal mines, including hard roof control, stress transfer for control dynamic deformation of tunnels, and permeability enhancement in the low permeability coal seam [26][27][28][29][30]. Pulse hydraulic fracturing is rarely used in coal mines.…”

Section: Introductionmentioning

confidence: 99%

Combination of Pre-Pulse and Constant Pumping Rate Hydraulic Fracturing for Weakening Hard Coal and Rock Mass

et al. 2020

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The weakening of hard coal–rock mass is the core common problem that is involved in the top coal weakening in hard and thick coal seams, the hard roof control during the initial mining stage in the longwall mining face, and the hanging roof control in the gob of non-coal mine. Based on the characteristics of pulse hydraulic fracturing and constant pumping rate hydraulic fracturing, a weakening method for hard coal–rock mass by combining pre-pulse and constant pumping rate hydraulic fracturing is proposed. A complete set of equipment for the combined pulse and constant pumping rate hydraulic fracturing construction in the underground coal mine is developed. The pulse and constant pumping rate hydraulic fracturing technology and equipment were applied in the top coal weakening of the shallow buried thick coal seam. Compared with no weakening measures for top coal, the average block size of the top coal caving was reduced by 42% after top coal hydraulic fracturing. The recovery rate of the top coal caving mining face reached 85%, and it increased by 18% after hydraulic fracturing.

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Fracture and pore structure dynamic evolution of coals during hydraulic fracturing

Cited by 73 publications

References 44 publications

Methane displacement characteristic of coal and its pore change in water injection

Methane displacement characteristic of coal and its pore change in water injection

Variation law of roof stress and permeability enhancement effect of repeated hydraulic fracturing in low‐permeability coal seam

Combination of Pre-Pulse and Constant Pumping Rate Hydraulic Fracturing for Weakening Hard Coal and Rock Mass

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