Study on the Movement of Pulverized Coal Particles in Fractal Fracture Network.

Abstract

Coalbed methane (CBM) exploitation is a complex multiphase flow process. With the development of CBM extraction technology, it is recognized that the migration of reservoir fluid in the fracture network is affected by the matrix fracture structure, fracture width, and pulverized coal particles plugging, therefore the fluid-particle coupling problem has received increasing attention. In this paper, six groups of fracture models with different fractal dimensions are established using the Weierstrass-Mandelbrot function, and the fluid-particle coupling phenomena in fractures with different roughness and aperture are simulated using an immersed boundary-lattice Boltzmann method (IB-LBM), by comparing the numerical simulation results with the theoretical analysis, it is proved that the IB-LBM numerical method has high accuracy and effectiveness. The effects of fractal dimension, particle size, and particle concentration on the plugging effect were investigated. The results show that the plugging effect on the fracture is enhanced with the increase of the pulverized coal particles content. When the concentration and size of pulverized coal particles are the same, the migration path of pulverized coal particles in complex fractures is more tortuous and more likely to be plugged. It may lead to a shift in the main seepage network of the fracture and the formation of new seepage channels. The research in this paper provides a data basis for the formation and plugging pattern of pulverized coal particles in coal seam fractures, which can provide a basis for the control of pulverized coal particles concentration in CBM drainage.