Physical and analytical modelling of permeability damage in bituminous coal caused by fines migration during water production

This study presents a systematic experimental methodology to investigate permeability damage caused by fines migration. The workflow starts with a thorough characterization of a bituminous coal sample by the XRD, SEM-EDX, petrographic, proximate and ultimate methods. Then, a single-phase water flow test is conducted on the coal sample whose surface is covered with Araldite resin to eliminate coal creep. The water permeability is monitored continuously and produced water samples are collected at regular intervals. The produced water samples are tested for conductivity, ionic concentration and fines concentration and sizes. Finally, the produced fines are separated from water using a membrane filter and the fines are examined using the SEM-EDX analysis. The theory of maximum retention function is used to investigate the fines release mechanism. Experimental results indicate a 35% decline in coal permeability during 33 days of water flow. The produced fines are mostly coal and coal-clay mixtures, which is different from the observation of Guo et al. (2015) for the anthracite coal where the majority of fines were clay only. Analytical modelling suggests that the major controlling parameters for fines migration during the flow test are the flow rate, interaction energy and coal characteristics. The analytical model also reveals that most of fines are mobilized in the beginning of the flow test. (C) 2016 Elsevier B.V. All rights reserved.