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 permeability testing, based on the in situ stress distribution characteristics of the coal seam in Wangjiazhai Coal Mine, Guizhou Province, conducted on artificial fractures 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 particle size proppant; as effective stress increases, the coal sample with the maximum permeability and the smallest stress sensitivity coefficient is placed with a proppant ratio of 20/40 mesh to 40/70 mesh of 1–3. The stress sensitivity coefficient and the permeability decrease with an increase in the number of confining pressure cycles. The increase in the proppant embedding depth has a hysteresis phenomenon with the increase in the effective stress, and the coal sample with a proppant ratio of 20/40 mesh to 40/70 mesh of 1–3 has the smallest embedded depth. The proppant will cause damage to the fracture surface of the coal seam. This study provides technical support for efficiently extracting the CBM resources that are difficult to exploit in Guizhou Province.