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Book Chapter

Fast: A New Technique for Geomechanical Assessment of the Risk of Reactivation-related Breach of Fault Seals

By
Scott D. Mildren
Scott D. Mildren
Australian Petroleum Cooperative Research Center, Australian School of Petroleum, University of Adelaide, Australia Present address: JRS Petroleum Research, Adelaide, Australia.
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Richard R. Hillis
Richard R. Hillis
Australian Petroleum Cooperative Research Center, Australian School of Petroleum, University of Adelaide, Australia
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Paul J. Lyon
Paul J. Lyon
Australian Petroleum Cooperative Research Center, Australian School of Petroleum, University of Adelaide, Australia
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Jeremy J. Meyer
Jeremy J. Meyer
Australian Petroleum Cooperative Research Center, Australian School of Petroleum, University of Adelaide, Australia Present address: JRS Petroleum Research, Adelaide, Australia.
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David N. Dewhurst
David N. Dewhurst
Australian Petroleum Cooperative Research Center, Commonwealth Scientific and Industrial Research Organization Petroleum, Australian Resources Research Center, Perth, Western Australia
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Peter J. Boult
Peter J. Boult
Australian School of Petroleum, University of Adelaide, Australia and also Department of Primary Industries and Resources South Australia, Adelaide, Australia
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Published:
January 01, 2005

Abstract

Postcharge fault reactivation may cause fault seal breach. We present a new methodology for assessment of the risk of reactivation-related seal breach: fault analysis seal technology (FAST). The methodology is based on the brittle failure theory and, unlike other geomechanical methods, recognizes that faults may show significant cohesive strength. The likelihood of fault reactivation, which is expressed by the increase in pore pressure (ΔP) necessary for fault to reactivate, can be determined given the knowledge of the in-situ stress field, fault rock failure envelope, pore pressure, and fault geometry. The FAST methodology was applied to the fault-bound Zema structure in the Otway Basin, South Australia. Analysis of juxtaposition and fault deformation processes indicated that the fault was likely to be sealing, but the structure was found to contain a residual hydrocarbon column. The FAST analysis indicates that segments of the fault are optimally oriented for reactivation in the in-situ stress field. Microstructural evidence of open fractures in a fault zone in the subsurface in an offset well and an SP (self-potential) anomaly associated with a subseismic fault cutting the regional seal in the Zema-1 well support the interpretation that seal breach is related to fracturing.

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Figures & Tables

Contents

AAPG Hedberg Series

Evaluating Fault and Cap Rock Seals

Peter Boult
Peter Boult
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John Kaldi
John Kaldi
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American Association of Petroleum Geologists
Volume
2
ISBN electronic:
9781629810423
Publication date:
January 01, 2005

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