Pore pressure and stress regime in a thick extensional basin with active shale diapirism (western Mediterranean)

Fernández-Ibáñez, Fermín; Soto, Juan I.

doi:10.1306/07131615228

Cited by 15 publications

(10 citation statements)

References 81 publications

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“…When comparison is made to the sedimentation rate versus fluid retention depth relationship for silt, silty claystone and claystone from global data (Swarbrick, 2012), assuming a sedimentation rate of 278 m Myr −1 , and ‘silty’ lithology, we would expect top of overpressure to begin near the base of our P‐Q unit. This is consistent with our estimates and hydrostatic pressures maintained to 2,000 m depth below the seabed in wells like Andalucia‐G1 (Fernandez‐Ibanez & Soto, 2017). Applying the same sedimentation rate and an alternative ‘silty shale’ lithology, we would expect top of overpressure to occur at depths anywhere from ca.…”

Section: Resultssupporting

confidence: 93%

“…The PPT method was proposed by Metwally and Sondergeld (2011) based on the pulse decay method introduced by Brace et al (1968), which consists of inducing pore pressure disequilibria in the rock and determining the permeability through the evolution of pore pressure-time decay curves towards the original steady state. For further details on the SSF and PPT methods refer to, for example, Metwally andSondergeld (2011) andFernandez-Ibanez andSoto (2017).…”

Section: Porosity and Permeability Determinationmentioning

confidence: 99%

“…Arab et al., 2016; Bertoni & Cartwright, 2015), although the impact of the overpressure on the hydrodynamics of the basin has primarily been addressed in Pliocene to Pleistocene sediment or areas (e.g., West Alboran Basin) where evaporites are absent (e.g. Fernandez‐Ibanez & Soto, 2017; Lafuerza et al., 2009; Revil et al., 1999). Previous studies in the WM show that overpressure associated with the presence of methane gas can exist in unconsolidated shallow sediment (depths <350 m below seabed), with fluid overpressure observed to return towards hydrostatic below the overpressure zones (e.g.…”

Section: Introductionmentioning

confidence: 99%

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The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean

et al. 2021

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Section: Resultssupporting

confidence: 93%

Section: Porosity and Permeability Determinationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean

et al. 2021

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“…Although a decoupling exists between the Ghomaride/Basement (SU1) and the upper sedimentary units, we propose that the undercompacted Langhian shales (SU2) are the main weak layer rather than the Ghomaride/Basement (Figure 12), as a result of its ductile behavior, this unit being overpressured and undercompacted (Fernández‐Ibáñez & Soto, 2017) consistent with the tight geometries of the observed folds.…”

Section: Discussionmentioning

confidence: 99%

Polyphase Tectonic Evolution of Fore‐Arc Basin Related to STEP Fault as Revealed by Seismic Reflection Data From the Alboran Sea (W‐Mediterranean)

et al. 2020

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Since the Miocene, the thinned continental crust below the Alboran Sea and its overlying sedimentary cover have been undergoing deformation caused by both convergence of Eurasia and Africa and by deep processes related to the Tethyan slab retreat. Part of this deformation is recorded at the Xauen and Tofiño banks in the southern Alboran Sea. Using swath bathymetry and multichannel seismic reflection data, we identified different stages and styles of deformation. The South Alboran Basin is made up of Early Miocene to Pliocene sedimentary layers that correlate with the West Alboran Basin depocenter and are dominated by E-W trending folds and thrusts. The Xauen and Tofiño Banks first recorded the phase of extension and strike-slip movement during the slab retreat, followed by the phase of compressional inversion since the Tortonian and are now structured by tight folds, thrusts, and mud bodies. This study proposes that the Banks were located on the southern-inherited Subduction Tear Edge Propagator (STEP) fault related to the westward migration of the Alboran domain during the Miocene. The STEP fault zone, acting as a boundary between the African block and the Alboran block, was located along the onshore Jebha-Nekor fault and the offshore Alboran Ridge and the Yusuf fault zone. Thick-skinned and thin-skinned shortening occurred when slab retreat stopped, and inversion began. The present-day style of the deformation seems to be linked to a decollement level made of undercompacted shale on top of the Ghomaride complex.

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“…Shale rollers have been interpreted in the field and on seismic data in many basins where extension is detached above mobile shale (e.g. Blanchard et al., 2019; Cohen & McClay, 1996; Fernández‐Ibáñez & Soto, 2017; Morley, 2003; Morley et al., 1998; Morley & Guerin, 1996; Sandal, 1996; Soto et al., 2010). If, on the other hand, there is near‐equal magnitude of displacement on normal faults with opposite dips, a more symmetric structure forms (Figure 1c).…”

Section: Shale Piercement Mechanismsmentioning

confidence: 99%

Piercement mechanisms for mobile shales

Hudec

Soto

2021

Basin Research

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We have identified seven mechanisms by which mobile shales can pierce their roofs. The operative piercement mechanism depends on mobile‐shale viscosity, roof strength and stress state. For mobile shales at depths of several kilometres, three mechanisms are possible: fracture piercement, thrust piercement and ductile “piercement.” However, injection up fractures and faults appears to be the dominant mechanism by which mobile shales rise towards the surface. In this process, mobile shales behave similar to magmas rising through the Earth's crust. Nearer the surface, a wider range of piercement mechanisms becomes possible: passive piercement, reactive piercement, active piercement and erosional piercement. These mechanisms all have salt‐tectonics analogues. Although shale tectonics and salt tectonics share common piercement mechanisms, in many cases the resulting structures are different. This is because near‐surface mobile shales can have much lower viscosities than salt. Mobile shales that reach the surface extrude very rapidly, in many cases leading to caldera collapse of the underlying shale chamber. This instability in the near‐surface means that long‐term, stable growth of passive shale diapirs is unlikely, in contrast with the behaviour of salt. A key question in seismic interpretation of mobile‐shale structures is whether large‐volume mobile‐shale diapirs exist. We show that both active piercement and ductile “piercement” can create such structures. Both of these mechanisms create steeply upturned beds on diapir flanks, which are diagnostic. However, active shale diapirs appear to be rare, and ductile “piercements” are not documented. We therefore suggest that large‐volume shale diapirs should be interpreted with caution on seismic data.

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Pore pressure and stress regime in a thick extensional basin with active shale diapirism (western Mediterranean)

Cited by 15 publications

References 81 publications

The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean

The Messinian Salinity Crisis as a trigger for high pore pressure development in the Western Mediterranean

Polyphase Tectonic Evolution of Fore‐Arc Basin Related to STEP Fault as Revealed by Seismic Reflection Data From the Alboran Sea (W‐Mediterranean)

Piercement mechanisms for mobile shales

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