The permeability structure of fault zones in sedimentary basins: a case study at the Castle Cove Fault, Otway Basin
Natalie Debenham A D , Natalie J. C. Farrell B , Simon P. Holford A , Rosalind C. King C and David Healy BA Australian School of Petroleum, Centre for Tectonics, Resources and Exploration (TRaX), The University of Adelaide, SA 5005, Australia.
B Department of Geology and Petroleum Geology, Tectonics and Geophysics Group, The University of Aberdeen, AB24 3FX, Scotland.
C Department of Earth Sciences, Centre for Tectonics, Resources and Exploration (TRaX), The University of Adelaide, SA 5005, Australia.
D Corresponding author. Email: natalie.debenham@adelaide.edu.au
The APPEA Journal 58(2) 805-808 https://doi.org/10.1071/AJ17141
Accepted: 22 February 2018 Published: 28 May 2018
Abstract
An understanding of the permeability structure and transmissibility of fault zones can have profound implications for reservoir appraisal and development within petroleum systems. Previous investigations on the permeability structure of fault zones often focus on low-porosity host rocks rather than porous sedimentary rocks which more commonly form reservoirs. We present detailed mineralogical and geomechanical data from porous Cretaceous sandstones (Eumeralla Formation) collected at the Castle Cove Fault in the Otway Basin, south-east Australia. Ten orientated sample blocks were collected in the hanging wall at distances within 0.5–225 m from the fault plane. A progressive increase in porosity (~17–24%), permeability (0.04–2.92 mD), and pore throat size and connectivity was observed as the fault plane was approached. High-resolution thin section analyses revealed an increase in grain-scale fractures and deformation of authigenic clays in sandstones adjacent to the Castle Cove Fault plane. The improvement of the permeability structure of the sandstones is attributed to the formation of grain-scale fractures and the change in clay morphology as a result of faulting. This study demonstrates the importance of detailed mineralogical and geomechanical analyses when attempting to understand the reservoir properties of high porosity, low permeability, and clay-rich sandstones.
Keywords: connectivity, permeability, pore throat size, porosity, reverse-reactivated normal fault.
Natalie Debenham is currently undertaking a PhD at the Australian School of Petroleum, the University of Adelaide. She graduated with a BSc Hons from the University of Adelaide (2014) and an MRes from Macquarie University (2015). Her current research is focused on subsurface fluid flow through natural fracture networks in Australia’s petroleum producing basins. In 2016, Natalie was awarded the APPEA Tony Noon Memorial Scholarship. Member: AAPG, ASEG, GSA, PESA, and SPE. |
Natalie Farrell is a Postdoctoral Researcher in the Department of Geology and Petroleum Geology at the University of Aberdeen. She graduated with a MESci from the University of Liverpool (2007) and a PhD from the University of Aberdeen (2016). Her research interests include brittle microstructures, petrophysics, image analysis, and experimental rock physics. |
Simon Holford is an Associate Professor at the Australian School of Petroleum, the University of Adelaide. He graduated with a BSc (Hons) from Keele University (2001) and a PhD from the University of Birmingham (2006). His research interests are in the deformation, uplift, and magmatic evolution of rifted margins, sedimentary basins, and continental interiors and their impact on hydrocarbon exploration. Member: AAPG, AGU, GSA, GSL, and PESA. |
Rosalind King is an Associate Professor in the Department of Earth Sciences at the University of Adelaide. She graduated with a BSc (Hons) and a PhD from the University of Liverpool in 2001 and 2005 respectively. Her research interests include the tectonics of deepwater fold-thrust belts, detachments, fold and thrust mechanics, and petroleum geomechanics. |
David Healy is a Reader in the Department of Geology and Petroleum Geology at the University of Aberdeen. He graduated with a BSc (Hons) from the University of Exeter (1985) and a PhD from the University of Liverpool (2004). His research interests span structural and metamorphic geology, rock physics, and geomechanics. Member: AGU and EGU. |
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