Mechanism of Loading Fracture of Coal Mass and Formation of Oil and Gas Disaster Channel in Coal and Oil Resources Costorage Area

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.