The effects of particle size and inorganic mineral content on fines migration in fracturing proppant during coalbed methane production

Hydraulic fracturing is an effective way to improve the productivity of coalbed methane (CBM). But fines intrusion into fracturing proppant can result serious permeability change and gas productivity reduction. The effects of fines particle size and the inorganic mineral content of fines on fines migration and permeability changes in the proppant were investigated by physical simulation and experiments on coal and mudstone samples from the Hancheng block in the Eastern Ordos Basin. Based on analyzing the characteristics of output fines mass, size distribution, micro-morphology and mineralogy, the regularities of fines migration and the permeability affected by fines particle size and inorganic mineral content of fines were revealed. The results show that the output fines mass increases while the decreasing of the particle size of the injected fines and the inorganic mineral content of injected fines. The particle sizes of fines output get smaller with the increase of the flow velocity and the inorganic mineral content. The permeable capability of the proppant channel is influenced by particle size and inorganic mineral content as follows: (1) Proppant channels with fines of 63-125 mu m in particle size show lower permeability during water injection than the other two groups of < 63 mu m and 125-200 mu m (2) For coal-mudstone fines, the higher inorganic mineral content of the fines is, the lower permeability of the proppant channels is. This study identifies the effect patterns of fines particle sizes and inorganic mineral contents of the fines on fines migration in the proppant, and suggests improvement measures to generate less fines and improve fines migration capacity.