Abstract
Fracture structure characteristics are crucial for determining the fracture mechanism of coal mass and the migration law of oil and gas disasters. In this study, computed tomography (CT) scanning technology and fractal theory were used to investigate the damage process of coal mass in the common storage area of coal and oil resources under uniaxial compression as well as the degree of damage of high-pressure oil and gas diffusion to the surrounding coal and rock mass. Uniaxial compression and acoustic emission signal acquisition tests of coal mass were conducted. The relationship among the load evolution law of coal samples at different positions around the oil well and the failure mode of key failure positions were further analyzed. Finally, the formation mechanism of coal load fracture and oil and gas disaster channel in coal and oil resource costorage area was investigated. The test results showed the following: (1) High-pressure oil and gas diffusion degrades the mechanical properties of coal mass in varying degrees. The closer the coal sample to the oil well, the greater the fracture development degree, the fracture density, the fracture fractal dimension of coal sample, and the severity of the coal mass damage and the lower the compressive strength, the acoustic emission event number, and the cumulative energy. (2) The lateral diffusion of high-pressure oil and gas changes the failure mode of coal samples in the common storage area of coal and oil resources. The failure modes when the sampling location is away from the oil well are step failure, conjugate shrinkage failure, and high-frequency vibration intermittent microcrack fracture. (3) Coal mass instability and coal mine oil and gas disaster in the common storage area of coal and oil resources can easily be induced by the formation of microfracture expansion, extension, and coalescence caused by coal failure, the formation of network and macrochannels of main fracture, and the instantaneous release of accumulated stress during failure.
Highlights
Shuangma coal mine is located in the costorage area of coal and oil resources in eastern Ningxia
This study used coal sample computed tomography (CT) scanning technology and acoustic emission test to analyze the influence of fracture structure on the failure mode of coal mass. is study explored the failure mode of coal mass damaged by high-pressure oil and gas at different positions of abandoned oil wells; we further investigated the mechanism of coal mass load fracture and oil and gas disaster migration channel in the common storage area of coal and oil resources
Accurate Identification of Fracture Parameters. e CT slice thickness of the coal samples was set to 2 mm, and 50 CT slice images were obtained for a single coal sample
Summary
Shuangma coal mine is located in the costorage area of coal and oil resources in eastern Ningxia. E initiation, expansion, coalescence, expansion failure, and rapid release of accumulated stress of internal cracks in mining coal mass in this area [1] can induce dynamic disasters such as oil and gas disasters [2]. Fracture is the migration channel of oil and gas, and it is an important factor for destroying mining coal mass and migrating oil and gas. Research on the load breaking of coal mass and formation mechanism of an oil and gas disaster channel in coal and oil resource costorage area is crucial for preventing and controlling oil and gas disasters in coal mines [3–5]. Rocks have a complex internal structure, making it challenging to accurately describe the fracture structure of coal and rock mass by direct measurement. As a nondestructive detection technology, computed tomography (CT) is used to characterize rock fractures, minerals, and pore permeability [6–8], and used widely to characterize
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