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Australian Energy Producers Journal Australian Energy Producers Journal Society
Journal of Australian Energy Producers
RESEARCH ARTICLE

Challenges in modelling of hydraulic fracturing in low-permeability coal seams with complex cleat networks and stress regimes

Mohammad Ali Aghighi A C , Raymond Johnson Jr. A and Chris Leonardi B
+ Author Affiliations
- Author Affiliations

A School of Chemical Engineering and UQ Centre for Coal Seam Gas, University of Queensland, Qld 4072, Australia.

B School of Mechanical and Mining Engineering, University of Queensland, Qld 4072, Australia.

C Corresponding author. Email: h.aghighi@uq.edu.au

The APPEA Journal 59(1) 166-178 https://doi.org/10.1071/AJ18140
Submitted: 7 December 2018  Accepted: 22 February 2019   Published: 17 June 2019

Abstract

Improved hydraulic fracturing models can better inform operational decisions regarding production from low-permeability coals and ultimately convert currently classified contingent resources to reserves. Improving current modelling approaches requires identification and investigation of the challenges involved in modelling hydraulic fracture stimulation in complex eastern Australian cases where permeability systems and stress regimes can vary significantly. This study investigated differences among existing and emerging advanced hydraulic fracture models and codes including numerical methods used to model fluid and rock behaviours during treatments; the ability to contextualise structure, behaviour and interaction of natural fractures with the propagating hydraulic fracture (e.g. cleat or natural fracture fabric, discrete fracture networks and pressure-dependent leak-off); and their capabilities in handling simultaneously growing or complex fracture development. One finding is that the new generation of models or codes that fully or partially use particle-based numerical methods are more capable in handling complexities associated with hydraulic stimulation of naturally fractured reservoirs. However, the computational cost and time for these models may cause concerns, particularly when modelling large reservoirs and treatments. Based on these limitations, many of the advanced, industry preferred, commercial hydraulic fracture simulators still choose to incorporate limited complexities with regard to natural fractures or represent them mathematically or implicitly. This investigation also indicates that most emerging models provide better representation of natural fractures, visualisation and integration into workflows for completion or stimulation design.

Keywords: cleats, coal seam gas, eastern Australia basins, hydraulic fracture modelling, hydraulic fracturing, low-permeability coals, natural fractures, stimulation.

Dr Mohammad Ali (Hamid) Aghighi is currently a research fellow at the University of Queensland, School of Chemical Engineering. He holds a PhD in Petroleum Engineering from the University of New South Wales and an MSc and a BSc in Mining Engineering from the University of Tehran. Hamid has over 20 years of experience in both academia and industry. Hamid has published 40+ papers in journals and proceedings in the areas of petroleum geomechanics, hydraulic fracturing, wellbore stability and numerical modelling of rock and fluid behaviour in porous media. He is a member of the SPE.

Raymond (Ray) L. Johnson, Jr. is presently Professor of Well Engineering and Production Technology at the University of Queensland, School of Chemical Engineering, and serves as Adjunct Associate Professor at the University of Adelaide. He has a PhD in Mining Engineering, an MSc in Petroleum Engineering, a Graduate Diploma in Information Technology and a BA in Chemistry. Ray has been active in SPE, past chair of the SPE Queensland Section, 2013 and 2015 co-Chair of the SPE Unconventional Reservoir Conference and Exhibition Asia Pacific, and Technical Award Recipient of SPE Regional Awards in 2011 and 2017. He has been actively involved as an author and researcher in the areas of reservoir geomechanics, hydraulic fracture design execution and evaluation, and unconventional resource development.

Dr Christopher Leonardi is a faculty member in the School of Mechanical and Mining Engineering at the University of Queensland. He holds a B.E. in Mechanical Engineering with Class I Honours from James Cook University, a PhD in Civil and Computational Engineering from Swansea University (UK), and a Research Affiliate appointment in the Department of Civil and Environmental Engineering at the Massachusetts Institute of Technology (USA). Dr Leonardi’s research is currently targeted at the development of large-scale numerical models, which can be used to provide insight into the complex characteristics of fluid–solid interaction in oil and gas reservoirs. Much of this work is undertaken in close collaboration with industry via the University of Queensland Centre for Coal Seam Gas. In addition to his academic pursuits, Christopher has over five years of consulting experience, applying both computational and analytical techniques to solve problems in the mining and mechanical engineering disciplines


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