Coal fracturing through liquid nitrogen treatment: a micro-computed tomography study
Hamed Akhondzadeh A C , Alireza Keshavarz A , Faisal Ur Rahman Awan A , Ahmed Z. Al-Yaseri A , Stefan Iglauer A and Maxim Lebedev BA School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, WA 6027, Australia.
B Exploration Geophysics, Curtin University, 26 Dick Perry Avenue, Kensington, WA 6151, Australia.
C Corresponding author. Email: h.akhondzadeh@ecu.edu.au
The APPEA Journal 60(1) 67-76 https://doi.org/10.1071/AJ19105
Submitted: 17 December 2019 Accepted: 31 January 2020 Published: 15 May 2020
Abstract
Low permeability of coal has been a constant obstacle to economic production from coalbed methane reservoirs, and liquid nitrogen (LN2) treatment has been investigated as one approach to address this issue. This study examined LN2 fracturing of a bituminous coal at pore-scale through 3D X-ray micro-computed tomography. For this purpose, a cylindrical sample was immersed into LN2 for 60 min. The micro-CT results clearly showed that the rapid freezing of the coal with LN2 generated fracture planes with large apertures originating from the pre-existing cleats in the rock. This treatment also connected original cleats with originally isolated pores and micro-cleats, thereby increasing pore network connectivity. Moreover, scanning electron microscopy highlighted the appearance of continuous wide conductive fractures with a maximum opening size of 9 µm. Furthermore, a nano-indentation technique was used to test the effect of LN2 on coal mechanical properties. The indentation moduli decreased by up to 14%, which was attributed to the increase in the cracked rock compressibility, showing considerable fracturing efficiency of the LN2 treatment. Through in-situ microscopic visualisation and surface investigation, this study quantified the pore structure and connectivity evolution of the rock based on the morphological alteration, and demonstrated the promising effect of LN2 freezing on fracturing of bituminous coals, thus aiding coalbed methane production. The significance of this study was investigating the mechanisms associated with and the efficiency of LN2 treatment of a coal rock in a 3D analysis inside the rock.
Keywords: CBM, coalbed methane, enhanced recovery, liquid nitrogen fracturing, scanning electron microscopy.
Hamed Akhondzadeh completed his BSc and MSc in Petroleum Engineering. During his MSc study, he conducted numerical research on heavy oil enhanced oil recovery. He used two of the most professional petroleum simulators, CMG and Eclipse, in his studies. He changed his research field to coalbed methane in 2016 and received a scholarship for his PhD studies at Edith Cowan University (ECU), Australia. As a PhD student at ECU, he is experimentally researching on coalbed methane productivity enhancement as his priority, and also partially on enhanced oil recovery and CO2 geosequestration. He is a member of SPE. |
Alireza Keshavarz holds a PhD degree in Petroleum Engineering from the University of Adelaide, an MSc in Reservoir Engineering from the University of Tehran, Iran, and a BSc in Chemical-Petroleum Engineering from the Petroleum University of Technology, Iran. He presently serves as a Senior Lecturer at the School of Engineering at ECU. Before joining ECU, Alireza was a Research Scientist in the CSIRO-Energy Business Unit, where he researched enhancing gas production from unconventional resources and CO2 sequestration. Before pursuing his PhD study, he was a Petroleum Engineer in the National Iranian Oil Co. (NIOC) for six years. Alireza’s research interests focus on enhanced oil/gas recovery from conventional and unconventional reservoirs. He is a member of SPE. |
Faisal Ur Rahman Awan is a PhD candidate in Petroleum Engineering at ECU, Australia. His work focuses specifically on coal fines fixation using nanoparticles. Mr. Awan did his Bachelor’s and Master’s degrees in Petroleum Engineering. He has also served at Dawood University of Engineering and Technology, Karachi, as an Assistant Professor in Petroleum Engineering for the last seven years. He is a member of prestigious societies such as SPE, SEG, EI and PEC. |
Ahmed Z. Al-Yaseri is a Vice-Chancellor Research and Teaching Fellow at the School of Engineering, Edith Cowan University. He holds a PhD degree from Curtin University (Australia), MSc degree from Oklahoma University and BSc degree from Baghdad University, all in Petroleum Engineering. His research interests focus on rock wettability, formation damage, multi phase flow in porous media, carbon dioxide storage and improved hydrocarbon recovery. |
Stefan Iglauer joined ECU in 2018 as a Professor to lead the developments in the Petroleum Engineering discipline. His research interests are in petrophysics and interfacial phenomena, mainly at pore-scale with a focus on CO2 geosequestration and improved hydrocarbon recovery. Stefan has authored more than 250 technical publications; he holds a PhD in Material Science from Oxford Brookes University, UK, and an MSc from the University of Paderborn, Germany. He is a member of SPE. |
Maxim Lebedev is a Professor at Curtin University, Perth, Australia, at the Exploration Geophysics discipline. He obtained a PhD in physics in 1990 from the Moscow Institute of Physics and Technology in Russia. He worked for a decade as a physicist at the High Energy Research Centre in Russia, and for eight years as a material scientist at the National Institute of Advanced Industrial Science and Technology in Japan. In 2007 Maxim joined Curtin University and became the leader of an experimental group in rock physics. His research is focused on the properties of subsurface reservoir rocks and minerals. |
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