Research on an evaluation method for the strength of broken coal mass reinforced by cement slurry based on digital drilling test technology

Wang, Qi; Gao, Hongke; Jiang, Bei; Liu, Bohong; Yu, Hao; Gao, Song; Zhang, Chao

doi:10.1007/s10064-018-1402-7

Cited by 14 publications

(1 citation statement)

References 19 publications

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“…The fracture system in coal is the key channel for gas flow. − To improve the efficiency of CBM recovery, scholars have conducted numerous studies on promoting fracture development in coal. Traditional physical methods, such as hydraulic fracturing, , coal flooding, , hydraulic cutting, hydraulic punching, drilling, , and blasting, , are broadly applied; however, such methods are not ideal solutions for low-permeability reservoirs. As a complex mixture, coal contains extensive organic macromolecular and micromolecular phases; hence, coal has many soluble organic micromolecules. − The removal of these soluble micromolecules using organic solvents inevitably changes the fracture and pore systems of coal, − thus providing additional channels for gas flow. − For instance, [Bmim][Cl] can dissolve and remove some active functional groups and make the microstructure more compact .…”

Section: Introductionmentioning

confidence: 99%

Fracture Development Characteristics of Coal under Organic Solvent Erosion and Its Nondestructive Testing Method

Lin

Yang

et al. 2021

Energy Fuels

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The low permeability of coalbed methane (CBM) reservoirs restricts the efficient extraction of CBM. Organic solvent erosion is a sound method to improve the permeability of coal; however, a nondestructive testing (NDT) method for identifying the effects of erosion on coal is necessary. The ultrasonic characteristics of coal can reflect the physical state of coal; therefore, ultrasonic testing is a suitable method for identifying the erosion effect. First, the characteristics of fracture development in coal were studied through surface observations and mass analysis. Organic solvent treatment is an effective means to promote the development of coal fractures, and the effects of organic solvent erosion on coal can be divided into three grades. The effects of organic solvent erosion on coal are influenced by the extraction rate of the solvent for coal. A high extraction rate can improve the degree of coal fracture development, and coal becomes susceptible to breakage. N-Methylpyrrolidone (NMP) and tetrahydrofuran (THF) have high extraction rates for coal and are suitable for solvent treatment. Subsequently, the effects of solvent erosion on the ultrasonic characteristics were comprehensively investigated. After solvent erosion, the ultrasonic characteristics of coal changed remarkably. The peak amplitude of the time-domain spectrum decreased by 13.5–56.7%, the ultrasonic velocity decreased by 39.1–70.1%, and the ultrasonic attenuation coefficient increased by 12.2–130.7 dB/m. The relationship between the degree of erosion and ultrasonic parameters was revealed, and the physical state of coal was deduced through the ultrasonic parameters. Thus, ultrasonic detection can be used as an NDT method in solvent treatment. These results provide a theoretical basis for the application of solvent treatment in the coal industry.

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