Experimental investigation on coal fines migration through proppant packs: Assessing variation of formation damage and filtration coefficients

Abstract

Coalbed methane reservoirs generate coal fines during production that cause irreversible damage to cleat conductivity. In severe scenarios, this can result in temporary closure of recovery operations from the gas well(s). In this work, we simulate the impact of coal fines on proppant conductivity. Four sets of experiments were conducted: effect of salinity – 0 to 3.5 NaCl wt.%, pH – 2 to 11, coal rank - anthracite, high volatile bituminous, and sub-bituminous; and 0.01 wt% additives – Sodium Dodecyl Benzene Sulfonate (SDBS) and Cetrimonium bromide (CTAB) and validated with established analytical models. Moreover, medical computed tomography of three extreme cases was conducted. Results showed that coal fines uniform distribution within a proppant pack does not cause greater conductivity decline than non-uniform distribution owing to clogging and straining. Additionally, results showed that anionic surfactants successfully dispersed coal fines. These research results can be applied to coalbed methane reservoirs, especially during the early water drainage phase, to optimise the impact of coal fines on proppant conductivity.