Coal permeability stimulation by NaClO oxidation
Reydick Balucan A C , Zhenhua Jing A , Jim Underschultz B and Karen Steel AA School of Chemical Engineering, The University of Queensland, St Lucia, Qld 4072, Australia.
B Centre for Coal Seam Gas, The University of Queensland, St Lucia, Qld 4072, Australia.
C Corresponding author. Email: r.balucan@uq.edu.au
The APPEA Journal 59(2) 846-850 https://doi.org/10.1071/AJ18142
Accepted: 18 March 2019 Published: 17 June 2019
Abstract
Many prospective coal seams have limited permeability and are thus marginal for economic coal seam gas (CSG) extraction. To enhance seam permeability, various CSG stimulation techniques, including hydraulic fracturing, cavity well completions and horizontal wells, have been used commercially, but these techniques are not successful everywhere. Alternately, oxidant stimulation to enhance coal seam permeability may have potential benefit. In this paper, we report the oxidation of a cubic coal sample from the gas-bearing Bandanna Formation with 1% NaClO. Permeability variation were measured over time with core stimulation/flooding tests. Coal structural changes, captured via X-ray microcomputed tomography (µCT), were used to analyse and model the impact of oxidant stimulation on coal permeability. We found that NaClO stimulation was able to widen fracture aperture and generate additional cracks and/or void space. Analyses of the coal after reaction indicated improved pore connectivity. This resulted in a significantly higher permeability, as shown by both core flood tests and flow modelling/simulations using GeoDict’s FlowDict module. Although this paper confirms oxidant stimulation has the potential to improve coal seam permeability, the optimum volume and reaction time, pressure and temperature conditions and suitability for use in various coal types requires further research.
Keywords: chemical stimulation, core flooding, core stimulation, CSG stimulation, digital coal analyses, FlowDict, GeoDict, oxidant stimulation, virtual porosimetry and granulometry, X-ray µCT.
Reydick Balucan is a Postdoctoral Research Fellow at the School of Chemical Engineering at the University of Queensland. Reydick holds a BS Chemistry (Philippines) and a PhD in Chemical Engineering (The University of Newcastle). His current research interests include permeability enhancement of coal for CSG production and the development of integrated chemical process for direct CO2 capture-mineralisation and metals recovery. |
Zhenhua Jing, is a PhD candidate at the CCSG with The University of Queensland. He obtained his BS in CSG Engineering and a MS in Geological Engineering from the China University of Geosciences (Wuhan), China. His current research is centred on laboratory analysis to understand chemical oxidant stimulation of coal seams to increase permeability and potentially enhance gas production. |
Jim Undershultz is the Deputy Director and Chair in Water at the UQ CCSG. Jim holds a BS and MS in Geology from the University of Alberta and a PhD in Petroleum Engineering from Curtin University. Previously, he held the Professorial Chair of Petroleum Hydrodynamics at UQ CCSG and managed the research program for ANLEC R&D, supporting Australia’s carbon capture and storage (CCS) demonstration. He sat on the Sustainable Energy board for the Square Kilometre Array (SESKA) geothermal project control group and the Australian Standards mirror committee for international standards on CCS. Previously, Jim was the CSIRO Lead for the Unconventional Petroleum and Geothermal Energy R&D program. |
Karen Steel is an Associate Professor at the School of Chemical Engineering, The University of Queensland. Karen holds a BE and PhD in Chemical Engineering from The University of Melbourne. Her research interests are in energy and resources, including coal science, gas recovery and sustainable mineral processing, with a strong interest in developing new technologies to solve major issues. |
References
Balucan, R. D., Turner, L. G., and Steel, K. M. (2016). Acid-induced mineral alteration and its influence on the permeability and compressibility of coal. Journal of Natural Gas Science and Engineering 33, 973–987.| Acid-induced mineral alteration and its influence on the permeability and compressibility of coal.Crossref | GoogleScholarGoogle Scholar |
Balucan, R. D., Turner, L. G., and Steel, K. M. (2018). X-ray μCT investigations of the effects of cleat demineralization by HCl acidizing on coal permeability. Journal of Natural Gas Science and Engineering 55, 206–218.
| X-ray μCT investigations of the effects of cleat demineralization by HCl acidizing on coal permeability.Crossref | GoogleScholarGoogle Scholar |
Jing, Z., Balucan, R. D., Underschulz, J. R., and Steel, K. M. (2018). Oxidant stimulation for enhancing coal seam permeability: Swelling and solubilisation behaviour of unconfined coal particles in oxidants. Fuel 221, 320–328.
| Oxidant stimulation for enhancing coal seam permeability: Swelling and solubilisation behaviour of unconfined coal particles in oxidants.Crossref | GoogleScholarGoogle Scholar |
Moore, T. A. (2012). Coalbed methane: a review. International Journal of Coal Geology 101, 36–81.
| Coalbed methane: a review.Crossref | GoogleScholarGoogle Scholar |
Turner, L. G., and Steel, K. M. (2016). A study into the effect of cleat demineralisation by hydrochloric acid on the permeability of coal. Journal of Natural Gas Science and Engineering 36, 931–942.
| A study into the effect of cleat demineralisation by hydrochloric acid on the permeability of coal.Crossref | GoogleScholarGoogle Scholar |
