Acid-induced mineral alteration on the permeability and compressibility of coal

Balucan, Reydick D., Turner, Luc G. and Steel, Karen M. (2016) Acid-induced mineral alteration on the permeability and compressibility of coal. Journal of Natural Gas Science and Engineering, 33 973-987. doi:10.1016/j.jngse.2016.04.023

Author Balucan, Reydick D.
Turner, Luc G.
Steel, Karen M.
Title Acid-induced mineral alteration on the permeability and compressibility of coal
Journal name Journal of Natural Gas Science and Engineering   Check publisher's open access policy
ISSN 1875-5100
Publication date 2016-07
Year available 2016
Sub-type Article (original research)
DOI 10.1016/j.jngse.2016.04.023
Open Access Status Not Open Access
Volume 33
Start page 973
End page 987
Total pages 15
Place of publication Philadelphia, PA United States
Publisher Elsevier
Collection year 2017
Language eng
Formatted abstract
The natural fracture system in coal serves as the primary conduit for water and gas flow in coal seam gas fields. For low permeability coal with highly mineralised fracture systems, the dissolution and/or modification of mineral occlusions could potentially enhance permeability and improve stress resilience. This study investigated the effect of mineral alteration by hydrochloric and hydrofluoric acid (HCl–HF) on fracture compressibility and coal permeability. Coal core immersion in 15% HF- 4% KCl solution has enhanced coal permeability to brine from 0.10 to 0.45 mD and reduced fracture compressibility from 0.020 to 0.006 bar-1. Enhanced permeability and improved stress resilience were attributed to kaolinite (Al2Si2O5(OH)4) dissolution and hieratite (K2SiF6) precipitation, respectively. Geochemical speciation, simulating HF interactions with coal fracture minerals, predicted the occurrence and prevalence of both dissolution and precipitation reactions. Scanning electron microscopy-energy dispersive spectroscopy confirmed the mineral alteration phenomena. Identification of resultant structural changes and the differentiation of chemical from physical effects were elucidated using X-ray computed tomography. The overall findings show that mineral alteration by HF yielded relatively large, crystalline minerals that appeared to provide structural support to fractures, resulting in enhanced fluid flow and improved resistance to compression.
Keyword Acidising
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
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Created: Thu, 28 Apr 2016, 09:56:20 EST by Reydick Balucan on behalf of School of Chemical Engineering