As coal is characterised by low mechanical strength, it generates lots of coal fines caused by erosion of the hydraulic fluids and scratch of the proppants in the fracturing process. The coal fines will settle out and accumulate in the fractures and result in a sharp increase of the injection pressure. Therefore it is more difficulty to fill sand. The propped fracture conductivity will be reduced significantly in the process of dewatering and gas production because of the accumulation of coal fines. The function of dispersant is to suspend the coal fines in the fracturing fluids or other waterbased fluids to prevent the coal fines from aggregation. In this paper, an experimental method is presented to study the effect of the dispersants and the influence of the coal fines on the propped fracture conductivity. With this methods, two anionic dispersants, lignin sulfonic acid and sodium lignosulfonate, were evaluated. Results show that sodium lignosulfonate performs better in dispersing coal fines. It can effectively delay aggregation of coal fines and significantly reduce conductivity damage of the propped fracture. With addition of this dispersant to the hydraulic fluids, coal fines can flow readily together with water-based fluid during hydro-fracturing and gas production. [Received: June 27, 2012; Accepted: July 9, 2013]
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Pan et al. (2015) studied this question.