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Type: Book chapter
Title: Pore pressure/stress coupling and its implications for rock failure
Author: Hillis, R.
Citation: Subsurface sediment mobilization, 2003 / Van Rensbergen, P., Hillis, R., Maltman, A., Morley, C. (ed./s), vol.216, pp.359-368
Publisher: Geological Society of London
Publisher Place: Unit 7, Brassmill Ent Centre, Brassmill Lane, Bath BA1 3JN
Issue Date: 2003
Series/Report no.: Geological Society Special Publication
ISBN: 1862391416
Editor: Van Rensbergen, P.
Hillis, R.
Maltman, A.
Morley, C.
Statement of
R. R. Hillis
Abstract: Clastic dykes and sills witness that subsurface sediment mobilization is often controlled by the brittle failure of units 'sealing' overpressured and liquidized sediments. Brittle failure also imposes a limit on the buoyancy pressure that can be exerted by hydrocarbon columns. Conventional understanding of brittle failure induced by increasing pore pressure (P p) assumes that total minimum horizontal stress (σ h) is unaffected by changes in pore pressure. However, total minimum horizontal stress increases from shallow, normally pressured sequences to deeper, overpressured sequences. Data from the Canadian Scotian Shelf, the North Sea and the Australian North West Shelf demonstrate such P p/σ h coupling, with the minimum horizontal stress increasing at approximately 60-80% of the rate of pore pressure (i.e., Δσ h/ΔP p = 0.6-0.8). Hence, a greater increase in pore pressure can be sustained prior to brittle failure of units sealing overpressured compartments than would be predicted by conventional, uncoupled failure models. Furthermore, because total vertical stress is not similarly coupled to pore pressure, differential stress (σ 1-σ 3) reduces as pore pressure increases in normal fault regime basins. Thus, the mode of rock failure can not be inferred from differential stress in the stable state and P p/σ h coupling promotes tensile over shear failure.
DOI: 10.1144/GSL.SP.2003.216.01.23
Appears in Collections:Aurora harvest 2
Australian School of Petroleum publications

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