Research on the seepage properties of coal with different particle size proppant under cyclic loading

Abstract

The selection of proppant particle size significantly impacts the gas output and gas production period of the extracting coalbed methane (CBM). This study combines theoretical analysis and experiment, based on the in-situ stress distribution characteristics of the coal seam in Wangjiazhai Coal Mine, Guizhou Province, conducted artificially-fractures permeability testing with different particle size proppant combinations during the cyclic loading and unloading. The findings indicate that the coal sample with two particle sizes of proppant has more permeability and smaller stress sensitivity coefficient than the coal sample with a single proppant as effective stress increases, the coal sample with the maximum permeability and the smallest stress sensitivity coefficient is placed with proppant ratio of 20/40 mesh to 40/70 mesh is 1 to 3. The stress sensitivity coefficient and the permeability decreases with increasing the number of confining pressure cycles. The depth of proppant embedding increases has a hysteresis phenomenon with increasing the effective stress, and the coal sample with proppant ratio of 20/40 mesh to 40/70 mesh is 1 to 3 has the smallest embedded depth. The proppant will cause damage to the fractures surface of the coal seam. This study provides technical support for efficiently extracting the CBM resources that are difficult to exploit in Guizhou Province.